U.S. patent application number 10/461201 was filed with the patent office on 2004-01-29 for refrigeration system and method of operating the same.
This patent application is currently assigned to Hussmann Corporation. Invention is credited to Street, Norman E., Sunderland, Ted W..
Application Number | 20040016253 10/461201 |
Document ID | / |
Family ID | 46299422 |
Filed Date | 2004-01-29 |
United States Patent
Application |
20040016253 |
Kind Code |
A1 |
Street, Norman E. ; et
al. |
January 29, 2004 |
Refrigeration system and method of operating the same
Abstract
A refrigeration system comprises a condenser, an evaporator, and
a plurality of compressors in fluid communication. The plurality of
compressors has a current run pattern with a current run capacity.
The refrigeration system further comprises a controller operable to
control the plurality of compressors. One method of operating the
refrigeration system includes, at the controller, determining
whether to increase or decrease the current run capacity and, when
an increase or decrease in the current run capacity is required,
creating a new run pattern to replace the current run pattern.
Inventors: |
Street, Norman E.;
(O'Fallon, MO) ; Sunderland, Ted W.; (Troy,
MO) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
3773 CORPORATE PARKWAY
SUITE 360
CENTER VALLEY
PA
18034-8217
US
|
Assignee: |
Hussmann Corporation
Bridgeton
MO
|
Family ID: |
46299422 |
Appl. No.: |
10/461201 |
Filed: |
June 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10461201 |
Jun 12, 2003 |
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09849900 |
May 4, 2001 |
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6647735 |
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09849900 |
May 4, 2001 |
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PCT/US01/08072 |
Mar 14, 2001 |
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PCT/US01/08072 |
Mar 14, 2001 |
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09524939 |
Mar 14, 2000 |
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6332327 |
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Current U.S.
Class: |
62/228.5 ;
62/228.1 |
Current CPC
Class: |
F25B 49/022 20130101;
F25B 5/02 20130101; F25B 2700/1933 20130101; F25B 2700/03 20130101;
F25B 2700/1931 20130101; F25B 6/04 20130101; F25B 41/22 20210101;
F25B 2400/22 20130101; F25B 2600/07 20130101; F25B 2500/06
20130101; F25B 49/02 20130101; F25B 2600/111 20130101; F25B 25/005
20130101; Y02B 30/70 20130101; F25B 2700/21152 20130101; F25B
2400/075 20130101; F25B 2700/21157 20130101; F25B 2700/21151
20130101 |
Class at
Publication: |
62/228.5 ;
62/228.1 |
International
Class: |
F25B 001/00; F25B
049/00 |
Claims
What is claimed is:
1. A method of controlling a refrigeration system comprising a
condenser, an evaporator, and a plurality of compressors in fluid
communication, and a controller operable to control the plurality
of compressors, the method comprising the acts of: at the
controller, controlling the plurality of compressors with a current
run pattern and resulting in a current run capacity; determining
whether to increase or decrease the current run capacity; and when
an increase or decrease in the current run capacity is required,
creating a new run pattern to replace the current run pattern.
2. A method as set forth in claim 1 wherein the method further
comprises the act of monitoring run times for the plurality of
compressors, and wherein the creating a new run pattern is based in
part on the monitored run times.
3. A method as set forth in claim 1 wherein the refrigeration
system further includes a suction group and wherein the suction
group includes the plurality of compressors.
4. A method as set forth in claim 3 wherein the refrigeration
system further includes a second suction group including a second
plurality of compressors, wherein the controller is operable to
control the second plurality of compressors, and wherein the method
further comprises: controlling the second plurality of compressors
with a second current run pattern and resulting in a second current
run capacity determining whether to increase or decrease the second
current run capacity for the second suction group; and when an
increase or decrease in the second current run capacity is
required, creating a second new run pattern to replace the second
current run pattern.
5. A method as set forth in claim 4 wherein the method further
comprises the act of monitoring run times for the second plurality
of compressors, and wherein the creating a second new run pattern
is based in part on the monitored run times for the second
plurality of compressors.
6. A method as set forth in claim 1 wherein the suction group
includes a plurality of operable compressors and at least one
inoperable compressor, and wherein the new run pattern is selected
from the group of operable compressors.
7. A method as set forth in claim 1 wherein creating a new run
pattern comprises determining a total capacity for the plurality of
compressors, determining a percentage of the total capacity for
each compressor, determining a current run capacity for the
plurality of compressors, and determining a next available run
capacity percentage combination for the plurality of
compressors.
8. A method as set forth in claim 7 wherein the plurality of
compressors includes a plurality of operable compressors and at
least one inoperable compressor, and wherein the determining acts
are performed for the operable compressors.
9. A method as set forth in claim 2 wherein creating a new run
pattern comprises determining a total capacity for the plurality of
compressors, determining a percentage of the total capacity for
each compressor, determining a current run capacity for the
plurality of compressors, and determining a next available run
capacity percentage combination for the plurality of
compressors.
10. A method as set forth in claim 9 wherein creating a new run
pattern comprises prior to determining a next available run
capacity percentage combination, determining a plurality of
capacity percentage combinations; and optimizing the next run
pattern if the next available run capacity percentage combination
results in two compressor combinations having the same run capacity
percentage.
11. A method of controlling a refrigeration system comprising a
condenser, an evaporator, and a plurality of compressors in fluid
communication, and a controller operable to control the plurality
of compressors, the method comprising the acts of: at the
controller, controlling the plurality of compressors with a current
run pattern and resulting in a current run capacity; determining a
total capacity for the plurality of compressors; determining a
percentage of the total capacity for each compressor; determining a
next available run capacity percentage; and determining a new run
pattern to replace the current run pattern, the new run pattern
including the next available run capacity percentage.
12. A method as set forth in claim 11 wherein the method further
comprises determining a current run capacity percentage for the
plurality of compressors, determining whether to increase the
current run capacity, and wherein the next available run capacity
percentage is greater than the current run capacity percentage when
the current run capacity percentage is less than one hundred
percent.
13. A method as set forth in claim 11 wherein the method further
comprises determining a current run capacity percentage for the
plurality of compressors, determining whether to decrease the
current run capacity, and wherein the next available run capacity
percentage is less than the current run capacity percentage when
the current run capacity percentage is greater than zero
percent.
14. A method as set forth in claim 11 wherein the method further
comprises the act of monitoring run times for the plurality of
compressors, and wherein determining a new run pattern includes
creating a new run pattern based on the monitored run times.
15. A method as set forth in claim 11 wherein the plurality of
compressors includes a plurality of operable compressors and at
least one inoperable compressor, and wherein the determining acts
are performed for the operable compressors.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/849,900, filed on May 4,2001, entitled
"DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION";
which is a continuation-in-part of International Patent Application
No. PCT/US01/08072, filed Mar. 14, 2001, entitled "DISTRIBUTED
INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION"; which is a
continuation-in-part of U.S. patent application Ser. No.
09/524,938, filed on Mar. 14, 2000, entitled "DISTRIBUTED
INTELLIGENCE CONTROL FOR COMMERCIAL REFRIGERATION," issued as U.S.
Pat. No. 6,332,327; all of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to dynamically sequencing the staging
of compressors.
BACKGROUND
[0003] Refrigeration systems (e.g., a commercial refrigeration
system such as can be found at a supermarket) with compressors in a
parallel arrangement typically use staging of compressor ON/OFF
operation in order to match the system capacity with the attached
refrigeration load. As the refrigerated load varies, compressors
are cycled on or off to increase or reduce refrigeration capacity
accordingly. If the parallel compressors are of evenly matched
sizes, they are typically cycled in a first-on-first-off
arrangement. This distributes run time across the group of
compressors. If the parallel compressors are of differing sizes,
the staging sequence becomes particular to the differences between
individual compressor capacities. A staging sequence is manually
constructed and manually programmed into the control mechanism that
results in a step function of capacity of the desired
increment.
SUMMARY
[0004] In one configuration of a refrigeration system embodying the
invention, implementation of a distributed control methodology
places intelligence at the point of control and/or sensing (e.g.,
at the compressor control module). Division of the control tasks
and distribution of the control/monitoring devices segregates
system operating parameters. To regain system wide control and
monitoring capability, a communication network (or series of
networks) is established among subsystems and monitoring devices.
The network(s) provide(s) an infrastructure for the sharing of
operating parameters among the control/monitoring devices and a
system wide master control.
[0005] In one construction of the compressor control module, the
intelligent control/monitoring device contains the model number
information of the attached compressor. This information, when
transmitted to a system controller, is indicative of the operating
capacity of the compressor. In addition to retaining the model
number information, the compressor control module also monitors and
stores run time data for transmission. This information can be
transmitted to the system controller. In some constructions, the
system controller is capable of using the capacity data for the
attached compressors in conjunction with the individual run time
data to dynamically select the next logical sequence of operating
the compressors. The next sequence (or pattern) of operating the
compressors achieves an increase/decrease of refrigeration capacity
that meets predetermined requirements of minimum
incremental/decremental change in system capacity.
[0006] In the event a compressor cannot be operated due to a safety
limit exception or mechanical failure, the compressor controller,
in one construction, notifies the system controller. Once a
compressor(s) is recognized as non-functional, the system
controller removes the compressor from the compressor selection
process. The system controller then uses the remaining functional
compressors to form the best possible staging sequence. When the
failed compressor(s) is identified as having returned to a
functional state by the compressor controller, the system
controller is notified and the compressor(s) is again placed in the
selection process. This level of intelligent operation also allows
for mixed capacity compressor arrangements.
[0007] When an individual compressor in the parallel arrangement
fails, the programmed step function is no longer valid and system
performance is compromised. By providing a means of dynamically
determining the proper staging of the attached and functional
compressors, system performance can be maintained until the system
can be serviced. This same means of determining proper staging
eliminates the need to manually program or select compressor
staging when the system is installed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic representation of a refrigeration
system.
[0009] FIG. 1A is an schematic flow diagram of a second
refrigeration system suitable for use in connection with a
distributed intelligence control system.
[0010] FIG. 2 is a schematic representation of one construction of
a bus compatible compressor safety and control module.
[0011] FIG. 3 is a schematic representation of a compressor.
[0012] FIG. 4 is a flow diagram illustrating an exemplary operation
of the control and safety module in a standard operating mode.
[0013] FIG. 5 is a flow diagram illustrating an exemplary operation
of the control and safety module in a master controller failure
mode.
[0014] FIG. 6 is a schematic representation of aspects of a solid
state relay device.
[0015] FIG. 7 is a system block diagram illustrative of aspects of
a commercial refrigeration system.
[0016] FIG. 8 is a block diagram illustrating aspects of a
partially wireless configuration of the commercial refrigeration
system of FIG. 7.
[0017] FIG. 9 is a block diagram of a bus compatible branch control
subsystem, suitable for use with the commercial refrigeration
system of FIGS. 7 and 8.
[0018] FIG. 10 is a block diagram of a commercial refrigeration
system including bus compatible valve control.
[0019] FIG. 10A is a block diagram of an exemplary construction of
the system of FIG. 10 using valve controller to control an
evaporator valve associated with a subcooler.
[0020] FIG. 11 is a block diagram that illustrates a system using
modular case control modules to provide monitoring and control
functions for a plurality of refrigeration display cases.
[0021] FIG. 12 is a block diagram that illustrates the use of a
modular case controller configured for display case monitoring.
[0022] FIG. 13 is a block diagram that illustrates the use of a
modular case controller to provide branch control for a plurality
of display cases configured in a refrigeration branch.
[0023] FIG. 14 is a block diagram illustrating the reduced wiring
requirements associated with using a distributed intelligence
refrigeration control system.
[0024] FIG. 15 is a schematic representation of a second
construction of a bus compatible compressor safety and control
module.
[0025] FIGS. 16A-16F are flowcharts representing one method of
dynamically controlling a plurality of multiplexed compressors.
[0026] FIG. 17 is a table representing parameters identified as
rack parameters, which are communicated to and from the rack PLC in
FIG. 7.
[0027] FIG. 18 is a table representing parameters identified as
suction group parameters, which are communicated to and from the
rack PLC in FIG. 7.
[0028] FIG. 19 is a table representing parameters identified as
system data parameters, which are communicated to and from the rack
PLC in FIG. 7.
[0029] FIG. 20 is a table representing parameters identified as
suction group parameters, which are communicated to and from the
rack PLC in FIG. 7.
[0030] FIG. 21 is a table representing parameters identified as
condenser parameters, which are communicated to and from the rack
PLC in FIG. 7.
[0031] FIGS. 22A, 22B, 22C, and 22D are schematic representations
of a 256-bit memory coupled to the microprocessor 1505 in FIG.
15.
[0032] FIG. 23 is a flowchart of a read sequence for one method of
communication between the master controller 70 and the BCCSCM
1500.
[0033] FIG. 24 is a flowchart of a write sequence for one method of
communication between the master controller 70 and the BCCSCM
1500.
DETAILED DESCRIPTION
[0034] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless specified or limited otherwise,
the terms "mounted," "connected," "coupled" and "communication" and
variations thereof herein are used broadly and encompass both
direct and indirect mountings, connections, couplings and
communications. Further, "connected," "coupled," and
"communication" are not restricted to physical or mechanical
connections, couplings, or communications.
[0035] Referring now to FIG. 1, one construction of a refrigeration
system (e.g., a commercial refrigeration system for use in a food
store) is shown to comprise one or more fixtures (which are
illustrated as food display merchandisers 10A and 10B in the
shopping arena of a food store). The merchandisers 10A and 10B each
incorporate at least one evaporator coil 12A and 12B (or like heat
exchanger unit), respectively, disposed for cooling the
merchandiser. Three multiplexed compressors (designated 14A, 14B,
and 14C, respectively) are connected by way of a suction header 16
and a low side return pipe 18 in fluid communication with the low
side of the evaporators 12A and 12B for drawing refrigerant away
from the evaporators. A condenser (generally indicated at 20)
including a fan 22 and heat exchanger 24 is in fluid communication
on the high discharge side of the compressors 14A, 14B, 14C for
removing heat and condensing refrigerant pressurized by the
compressors. Although an air-cooled condenser 20 is shown, other
types of condensers, such as those liquid cooled from a ground
source water supply, may be used. Moreover, it is to be understood
that the single illustrated fan 22 represents one or more fans
typically used in a condenser for commercial refrigeration
applications.
[0036] Refrigerant from the condenser 20 is stored in a receiver 26
in communication with expansion valves 28A and 28B by way of a high
side liquid delivery line 30. The expansion valves 28A and 28B
meter refrigerant into respective evaporators 12A and 12B and
induce a pressure drop for absorbing heat, to complete the
refrigeration circuit. The compressors 14A, 14B, and 14C, and
usually also the suction header 16 and receiver 26, are mounted on
a compressor (or condensing unit) rack (not shown) prior to
shipment to the store location where the refrigeration system is to
be installed.
[0037] The food display merchandisers 10B and 10B illustrated with
the evaporators 12A and 12B can be placed in the shopping arena of
a food store. However, it is understood that other types of cooling
fixtures could be placed in other parts of the store (e.g., a
service area or backroom cooler). The liquid line 30 and suction
return line 18 have been broken to indicate connection to other
evaporators (not shown) in the system. Evaporators may be connected
to the same piping circuit between the receiver 26 and the suction
header 16, or in a different circuit or "branch" (not shown)
connected to the receiver. Further, the number of compressors 14 in
the refrigeration system can be more or less than three (including
only a single compressor). The refrigeration system typically
includes a compressor, a condenser, an expansion valve and an
evaporator. Other components can be included but are not essential,
and the precise mounting or location of the system components may
be other than described. Moreover, the same aspects of the
refrigeration system have application outside the food store
environment; for example, the invention can be used with cooling
other perishable, non-food products such as blood, plasma and
medical supplies. Also, some aspects of the communications network
(discussed below) have application in other systems.
[0038] As shown in FIG. 3 and in one construction, each compressor
14A, 14B, and 14C comprises an electric motor 32 driving a shaft 34
connected to a pressurizing unit 36. For purposes of the
description herein, compressor 14A will be referred to; the other
compressors 14B and 14C preferably having the same construction.
The pressurizing unit may take on any suitable form. In one
construction, reciprocating pistons driven by a motor constitute
the pressurizing device, but more and more, the quieter rotary
devices found in scroll compressors and screw compressors are being
employed to compress the vaporous refrigerant. A scroll compressor
is illustrated in FIG. 3. The compressor 14A has a low side suction
inlet 38 that receives the vaporous refrigerant from the
evaporators 12A and 12B and a high side discharge outlet 40 through
which hot, pressurized refrigerant is discharged from the
compressor. In one construction, the motor 32 and pressurizing unit
36 are semi-hermetically or hermetically sealed within an outer
casing or shell 42. The motors 32 of the compressors are each
connected to a respective high voltage (e.g., three phase 480 V AC
or 208 V AC) power line 44A, 44B, and 44C (FIG. 1) extending from a
power distribution center 46 within the food store. These lines are
shielded, such as by placement within a conduit, as may be required
by electrical codes.
[0039] In one construction, the compressors 14A, 14B, and 14C each
have a bus compatible compressor safety and control module 48 (also
referred to as "BCCSCM," "compressor operating unit, "compressor
control module," or "compressor controller") for monitoring at
least one, but preferably several operating conditions or
parameters of the compressor. The "operating parameters," in one
construction, include (1) control parameters providing information
used for controlling the compressor 14, and (2) safety parameters
providing information about whether the compressor 14 is operating
within its designed operational envelope or in a manner which could
damage the compressor 14. It is envisioned that any number of
parameters could be monitored, including only safety parameters or,
less likely, only control parameters. Control parameters for the
compressor 14 may include, but not limited to, suction temperature,
suction pressure, and discharge pressure. Safety parameters for the
compressor 14 can include, but not limited to, discharge pressure,
discharge temperature, oil level (or pressure), phase
loss/reversal, and motor winding temperature. As is apparent, some
of the control parameters are also classified as safety
parameters.
[0040] The bus compatible compressor safety and control module
("BCCSCM") 48 is constructed and arranged to receive and/or detect
the various operating parameters and control operation of the
compressor. In one construction, the BCCSCM comprises a processor
49 and multiple sensors in communication with the processor 49. In
the illustrated construction of FIG. 3, the compressor 14A is built
with individual continuous reading analog sensors including a
discharge pressure sensor 50, a discharge temperature sensor 52, a
suction pressure sensor 54, a suction temperature sensor 56, and a
motor winding temperature sensor 58 (FIG. 3). In one construction,
the temperature sensors 52, 56 and 58 are variable resistance,
RTD-type sensors. An oil level sensor 60 can be of the type that
changes the state of a circuit when the oil level falls below a
predetermined minimum, and does not provide a continuous reading of
the oil level. A power phase monitoring device 62 incorporated into
the BCCSCM 48 is capable of detecting both phase loss and phase
reversal on the three phase power line 44A coming into the
compressor 14A. It is to be understood that other sensors can be
used (e.g., digital sensors as discussed below).
[0041] In one construction of the commercial refrigeration system,
the sensors 50-62 are installed at the compressor assembly site and
disposed within the hermetically (or semi-hermetically) sealed
shell 42 of the compressor (FIG. 3). This construction allows the
sensors 50-62 to be protected in the shell 42 and, particularly in
the case of the suction pressure sensor 54, are located close to
the pressurizing unit 36 for more accurate readings of compressor
function. However, it is to be understood that the sensors 50-62
could be located other than in the shell 42. For instance, it is
envisioned that sensors could be replaceably received in openings
59 in the shell (schematically illustrated in phantom in FIG. 3)
accessible from the exterior, or external to the compressor shell
as in the case of a reciprocating semi-hermetic compressor, or any
other motor driven compression device.
[0042] The processor 49 of the BCCSCM 48, in one construction, is a
dual processor system, including a host controller (such as a
microcontroller, an ASIC, or a microprocessor, any of which may be
connected to a memory) and a communication slave controller. The
host controller and communication slave are not separately
represented in FIG. 2, but are collectively represented as the
processor 49. In one construction, the host controller has a 256
byte internal RAM, 8 kilobytes of flash program memory, and 16
input/output pins for control interface. The communication slave,
in one construction, is an application specific integrated circuit
(ASIC) that communicates with the field bus network (described in
one construction below as AS-Interface.RTM. network). The
communication slave translates the protocol of the field network
into a signal understood by the host controller, and vice
versa.
[0043] For an exemplary construction of the communication slave, if
the field bus network provides four data bits per message, the
communication slave can be configured to extend the data
capabilities of the field bus network by interfacing with an
intermediate memory device (an additional RAM) between the
communication slave and the host controller. In such a
construction, the communication slave and the host controller
interface with the RAM to extend the data capabilities of the field
bus network by using sequential read or write cycles of the field
bus network to build larger data sizes. In other words, rather than
limiting the data sizes to four bits, larger data sizes are
constructed by grouping multiple four-bit data transmissions. The
communication slave sequentially writes the data into (or reads the
data from) the additional RAM. The host microcontroller reads the
data from or writes the data to the additional RAM. Thus, for
example, a sixteen-bit data parameter may be constructed over the
course four successive data cycles.
[0044] Alternative structures of the BCCSCM can also be employed.
For example and as shown in FIG. 15, the BCCSCM 1500 includes a
microprocessor 1505, RAM 1510, and program memory 1515. The BCCSCM
1500 also includes a communication slave 1520, a suction sensor
1525, a discharge sensor 1520, an oil sensor 1535, a current sensor
1540, and a voltage sensor 1545. The BCCSCM 1500 also further
communicates with the compressor 14 to receive switched contact
input from a high-pressure cut out 1550 and oil level sensor 1555
and communicates with a compressor on/off control 1560.
[0045] In other constructions of the refrigeration system, a field
bus protocol having larger inherent data sizes could be
accommodated, thereby potentially eliminating the need for a
communication slave to translate the protocol. In yet another
construction, the communication slave and the host controller (or
microprocessor 1505) are combined as single controller (e.g., a
single ASIC) or as a single microprocessor and memory. Unless
specified otherwise, when referring to the construction shown in
FIG. 2, the description also applies to the construction shown in
FIG. 15.
[0046] The host controller (e.g., microprocessor 1505) is adapted
to receive signals from the sensors indicative of the values of the
sensed operating parameters. The host controller also stores safety
limit values for the measured safety parameters, respectively. The
host controller is capable of generating digital status information
indicative of the values of the operating parameters. When a safety
limit is traversed, the host controller is capable of generating a
digital status information signal including specific information as
to which safety parameter is out of specification. The signals are
translated by the communication slave for sending over the field
bus network. This will be discussed in further detail below.
[0047] In one construction, the BCCSCM 48 for each compressor 14
further includes a switch device 64. The switch device 64, in one
construction, is a three pole solid state relay such as SSRD Series
panel mount heavy duty solid state AC relay. The SSRD Series is
made by Teledyne, Inc. of Los Angeles, Calif. and available from
Allied Electronics of O'Fallon, Mo. The relay operates, upon
receiving a command from the processor 49 (or processor 1503), to
block at least two of the three phases of the electrical power to
the compressor motor 32, thereby turning the motor off. It is to be
understood that other switch devices can be used. The processor 49
is programmed to cause the relays to turn off the compressor (14)
when a safety limit value of one of the safety parameters is
traversed.
[0048] In another embodiment, the SSRD is constructed to include an
overcurrent protection capability. A current sensor (shown as
current sensor 1540 in the BCCSCM 1500), which can be associated
with the switch device, monitors the current through the SSRD. If
the sensed current exceeds a threshold (e.g., 350A for 1.5 line
cycles), the SSRD is shut off (rendered non-conducting) to protect
the compressor motor 32. Such an overcurrent condition can occur,
for example, if the rotor of the compressor motor 32 locks. Thus, a
current sensor associated with the SSRD serves as a locked rotor
detector. The sensed current information may also be used to detect
other compressor abnormalities.
[0049] A current sensor that is a self-contained part of the
compressor-controlling device provides certain benefits. For
example, current information is available on the system control bus
via the BCCSCM for use in safety and control applications, and the
value of the current can be used for energy management/monitoring
functions. The current sensor may be constructed internal to the
SSRD, or it may be a sensor external to the SSRD. For example, a
current sensing toroid could be used external to the SSRD to sense
current. Alternatively, a high power, current sensing resistor may
be included within the SSRD to sense current.
[0050] FIG. 6 is a schematic representation of another aspect of an
SSRD. A typical commercial refrigeration compressor system uses
three-phase electrical power. Thus, by controlling the SSRD, the
application of phases A, B, and C of such a three-phase power
system is also controlled.
[0051] As illustrated in the construction of FIG. 6, the SSRD
includes three opto-isolators 102, 104, and 106 that are
constructed as an integral component of the overall SSRD assembly.
Opto-isolator 102 is associated with phase A, opto-isolator 104 is
associated with phase B, and opto-isolator 106 is associated with
phase C. The opto-isolators 102, 104, and 106 detect the
zero-crossing of the respective phases with which they are
associated. Thus, when phase A crosses zero, opto-isolator 102
produces an output, via its collector, on line 108. Likewise, when
phase B crosses zero, opto-isolator 104 produces an output on line
110. Similarly, when phase C crosses zero, opto-isolator 106
produces an output on line 112. As one skilled in the art can
appreciate from the foregoing, such zero-crossing information
amounts to phase reference information, which may be compared to
determine the relationship between the power phases.
[0052] As those skilled in the art will also appreciate, if power
is applied to the compressor motor 32 when an improper phase
relationship exists, the compressor motor 32 may be damaged or
destroyed. For example, if a scroll compressor is run backwards,
for even an instant, because of an improper phase relationship, the
compressor may be seriously damaged or ruined. The zero-crossing
detection capability of the SSRD shown in FIG. 6 is integral to the
SSRD and available when the SSRD is open-circuited-when it is
non-conducting and no power is applied to the compressor motor 32.
Hence, a BCCSCM with the SSRD shown in FIG. 6 can monitor the
phases for a proper polarity relationship before applying power to
the compressor motor 32. Stated differently, a BCCSCM with the SSRD
shown in FIG. 6 can determine the presence of an improper phase
relationship by comparing the phase information to an acceptability
standard and prevent potential damage to the compressor motor 32
that would otherwise occur if power were applied to the motor. In
contrast, prior art phase polarity detection schemes rely on
devices external to the SSRD. Such prior art schemes do not detect
an improper phase relationship before applying power. Rather, such
systems check the phase relationship only after power application.
In such systems, if an improper phase relationship is detected,
power is removed. As those skilled in the art can appreciate, the
compressor motor 32 may be damaged or destroyed before power is
removed, even if it is removed relatively rapidly. Thus, the SSRD,
as shown in FIG. 6 (and as shown as 1560 in FIG. 15), provides for
phase detection prior to the application of power.
[0053] Referring again to FIG. 1, a master controller 70 (also
referred to as a system controller) for controlling all of the
compressors 14A, 14B, and 14C of the refrigeration system is in
electronic communication with all of the BCCSCMs 48 of the
refrigeration system via line 80. In one construction, the
controller 70 includes a CPU 72 (or simply a processing unit) which
coordinates data transfer among the components of the system. The
CPU 72 also processes data acquired from the BCCSCMs 48 and
determines control commands to be sent to the BCCSCMs. Other logic
devices can be used in place of the CPU 72 to perform the function
of the CPU 72.
[0054] In one specific construction, the CPU 72 includes a 16-bit
RISC processor, has 64 kilobytes of read only memory (ROM), 16
kilobytes of random access memory (RAM), a real time clock to
perform time-based control functions, and at least two interfaces
(e.g., serial interfaces) to permit connection to a local
human-machine interface (hereinafter, "HMI"), as well as a remote
interface. The local and remote interfaces may also be referred to
herein as input/output devices. The CPU 72 can also include both
digital and analog inputs and outputs, and is powered by a 24-VDC
power supply 74 transformed and rectified from a 120-VAC feed line
69.
[0055] The controller 70 further includes a communications module
76 to permit the CPU 72 to work with a field bus networking system.
The field bus networking system is designed to connect sensors,
actuators, and other control equipment (e.g., BCCSCM 48) at the
field level. An example of a suitable field bus networking system
is the AS-Interface.RTM. (or AS-i) networking system. Components
for the AS-i network are sold commercially by Siemens
Aktiengesellschaft of Germany, and available in the United States
from Siemens Energy Automation and Control, Inc. of Batavia, Ill.
The communications module 76 can be powered by the same 24-VDC
power supply 74 used by the CPU 72.
[0056] In one construction, the controller 70 includes a network
power supply 78, which provides a 24VDC to 30 VDC power supply
connected to the 120-VAC feed line 69. The network power supply 78
provides power to the field bus network via line 79 as further
discussed below.
[0057] In one construction, the field bus network includes an
unshielded two wire bus 80 connecting the communications module 76
(and hence the CPU 72) to all of the BCCSCMs (and, as discussed
below, other control modules). One wire is a ground wire and the
other is a communication and power line which carries all
communication and power for the BCCSCMs 48. Power for the BCCSCMs
is supplied from the network power supply 78 through line 79, which
has a communications decoupling feature allowing communications and
power to be supplied over the same line. The BCCSCMs 48 are each
connected to the bus 80 at nodes 82 by a respective coupling that
penetrates insulation of the bus cable and makes contact with the
wires. Each BCCSCM 48 is plugged into the coupling to connect the
control and safety module to the network.
[0058] In the construction shown in FIG. 1, the master controller
70 also controls cycling of the condenser fans 22. For example, the
master controller 70 can monitor discharge pressure and liquid
refrigerant temperature to determine when to cycle the condenser
fans 22. Similarly, the master controller 70 can monitor discharge
pressure and outdoor ambient temperature to determine whether to
split the condenser.
[0059] In the illustrated construction, the master controller 70
transmits these cycling commands from the CPU 72 to a condenser
controller 84 located close to the fans 22. The condenser
controller 84 executes the commands for shutting down or energizing
the condenser fans 22. Because the condenser is, in some
constructions, located remotely from the compressor rack, it may be
undesirable or impractical to locate the condenser controller 84 on
the same field network bus (e.g., AS-i bus) as the CPU 72. FIG. 1
illustrates such a situation, in which the condenser controller 84
has its own field bus network (e.g., another AS-i bus 85). In other
words, the condenser controller 84 can have its own field bus
network for controlling the condenser fans, just like the network
of the compressors 14A, 14B, and 14C with the master controller 70.
For example, the CPU 72 can communicate with the condenser
controller 84 over a relatively longer distance network. The
Multipoint Interface or "MPI", available from Siemens, is an
example of such a longer distance network/field bus. Another
example is the ProfiBUS standard. In this way, the condenser
controller 84 acts as a gateway to extend the range of the master
controller 70 in a situation in which the primary field bus network
associated with the compressor rack could not practically be used.
Thus, the master controller 70 provides operating and control
functions to the condenser controller 84. The condenser controller
84, via its own field bus network 85, supplies the control
information to a BCFCM 86 which drives the fans 22. Likewise, data
available at the condenser (e.g., an ambient air temperature
associated with the condenser and information regarding which
fan(s) is/are on) may be transmitted to the master controller 70.
In one construction, an air temperature sensor provides ambient air
temperature data directly to the condenser controller 84 (i.e.,
independently of any field bus network), which transmits such data
to the master controller 70.
[0060] Advantageously, if the master controller 70 ceases
communications with the condenser controller 84, the condenser
controller is preferably programmed to independently determine and
provide at least some of the control information required to drive
the fans 22 via the BCFCM. Other condenser control arrangements may
be used. For instance, the condenser controller 84 could be
eliminated and its functions programmed into the master
controller.
[0061] The BCFCM 84 includes, in one construction, a communication
slave controller and a microprocessor and memory as described in
connection with the BCCSCM 1500 of FIG. 15. However, the BCFCM
would include different inputs and outputs connected to the
microprocessor of the BCFCM than the microprocessor 1505. In other
words, the inputs and outputs connected to the microprocessor of
the BCFCM would be the inputs and outputs associated with the
condenser 20.
[0062] Referring now to FIG. 4, in one operation of the
refrigeration system, the sensors 50-62 or 1525-1545 of each BCCSCM
48 or 1505 (e.g., the BCCSCM associated with compressor 14A)
provide information regarding the operating parameters monitored by
the sensors. The information provided by the sensors 50-62 or
1525-1545 could be limited to whether or not a pre-set safety limit
value has been traversed. However, in one construction, at least
some of the sensors provide signals to the processor of each BCCSCM
48 or 1500 indicative of the actual value of the operating
parameter at the time sampled.
[0063] In one construction, the sensors for discharge pressure 50
and temperature 52, and suction pressure 54 and temperature 56
provide digital signals to the processor 49 indicative of the
actual value of the parameter measured. Thus, the sensor/transducer
converts the analog data to a digital format before providing the
information to the processor 49.
[0064] In the construction shown in FIG. 15, the sensors 1525,
1530, and 1535 are dual function pressure/temperature sensors
having an addressable, 14 bit analog to digital converter. That is,
each sensor includes a first sensing device (e.g., thermistor) that
senses a temperature and a second sensing device (e.g., a strain
gauge) that senses a pressure. Both the first and second sensing
devices are disposed within a single housing. The A/D converter is
also located within the sensor housing and converts the analog
signals from the detecting devices to a single digital signal
conveying the measured parameters. The A/D converter can include
other channels (e.g., a channel for monitoring the supply voltage
to the sensors), and the digital signal can convey information
relating to the other channels. Additionally, the digital signal
can send an error code to the processor 1503 when an error code
occurs at the sensor. For example, if the A/D converter does not
receive a signal from the temperature sensing device, it can
generate an error code that is communicated to the processor 1503.
The processor 1503 can then communicate to the system controller
that a sensor error has occurred. An example dual function
pressure/temperature sensor is a ML 200 psis per SCD1126, part no.
9310101, manufactured by Honeywell.
[0065] The motor winding temperature sensor 58, and the current and
voltage sensors 1540 and 1545 provide an analog signal to the
processor 1505 indicative of the actual value of the parameter
measured. The oil level sensor 60 (or 1555) provides a circuit open
or circuit-closed signal to the processor indicative of whether an
oil level safety limit has been traversed. The high pressure cut
out 1550 provides a circuit open or circuit-closed signal to the
processor indicative of whether a pressure limit has been
traversed.
[0066] As explained above with respect to FIG. 6, phase loss or
phase reversal can be monitored/detected by monitoring the zero
crossings of each phase with a plurality of opto-isolator devices.
An alternative, separate power phase monitoring device 62 may also
be used. Such a separate power phase monitoring device 62 would,
for example, provide a circuit open or a circuit closed signal to
the microcontroller to indicate whether a phase loss or phase
reversal has occurred.
[0067] The processor 49 or 1503 of each BCCSCM 48 or 1500 checks
the inputs from each sensor to determine whether a safety limit
value for any of the measured compressor characteristics has been
exceeded. If no safety limit values are exceeded, the processor 49
loads the sensor data for transmission to the master controller 70
when the processor is queried. The master controller 70 is the
system network controller in standard operation of the
refrigeration system shown in FIG. 1. In the illustrated
embodiments, the host controller (or the microprocessor 1505)
stacks the information to await transmission to the master
controller 70. The processor 49 (or 1503) then waits for a message
from the master controller 70 containing commands and a query for
the sensor data. As soon as the message is received, the processor
49 responds over the communication and power line of the two-wire
bus 80 to the controller 70 with the information data stored from
the sensors 50-62.
[0068] For the construction shown in FIG. 1, data from all of the
processors flows in a stream over the communication and power line
of the bus 80 to the communication module 76 and thence to the CPU
72 of the master controller 70. The communication protocol allows
the CPU 72 to associate the operating parameter information
received with particular compressors, and to discriminate between
different operating parameters for each compressor. In one
construction, more specifically, each BCCSCM is assigned a
particular address, which allows the controller 70 to communicate
individually with each of the BCCSCMs over the same line, and also
allows the BCCSCM processors to identify themselves to the master
controller.
[0069] The data is now available through interfacing with the
master controller 70, either remotely or by a local human machine
interface, to view individual compressor data. The processor 49 (or
1503) also looks for the command portion of the master controller
70 message for a command to turn the compressor (14A, 14B, or 14C)
on or off. If such a command is present, the processor 49 executes
it by operating the solid state relay (switch device 64) to turn
the compressor on or off. However, if the command is to turn the
compressor on, the processor 49 will not execute it if the
processor 49 has previously determined that a safety limit value of
one of the safety parameters has been traversed and remains in a
safety exception state. It is envisioned that other capacity
control commands could be received and executed by the processor 49
such as when the compressor was of a variable capacity type. The
software of the processor then returns to the initial step of
reading the sensor inputs.
[0070] Before proceeding further, another method of communication
between the master controller 70 and the BCCSCM 1500 (or 48) will
now be discussed. The method below will be described for the master
controller 70 in communication with the BCCSCM 1500 via an AS-i
cable (i.e., bus80); however, other networks can utilize the method
below. For example, other networks that do not utilize an AS-i bus
can implement the method.
[0071] The communication slave 1520 shown in FIG. 15 is an AS-i
compatible ASIC that is in communication with the communication
module 76 (referred to below as the master). The communication
module 76 is or includes an AS-i compatible ASIC. The communication
slave 1520 is in further communication with the microprocessor
1505. More specifically, the communication slave 1520 and the
microprocessor 1505 are electrically coupled by four "control" (or
"parameter") channels P0, P1, P2, and P3; four "output" channels
DO0, DO1, DO2, and DO3; four "input" channels DI0, DI1, DI2, and
DI3; a DSR channel; and a PST channel. Each channel P0, P1, P2, P3,
DO0, DO1, DO2, DO3, DI0, DI1, DI2, DI3, DSR, and PST is coupled to
the communication slave 1520 at a respective terminal. Other
configurations can be utilized for the communication method
described below. For example, the method is not limited to four
"input" or four "output" channels. Additionally, other devices can
be used in place of the master ASIC, slave ASIC, and the
microprocessor.
[0072] The AS-i networking solution was originally designed to
control four actuators (relays, solenoids, etc.) and/or read four
switched inputs. To control the four actuators, the AS-i master
transmits requests via the two-wire interface, which also carries
the 30 VDC power, to the AS-i slave. In response to the master
requests, the AS-i slave either switches its outputs to the state
directed by the AS-i master or responds to the master with the
current state of its inputs. In accordance with this communication
activity, four data bits representing the desired output state or
current input state are transmitted during each
master-request/slave-response communication cycle. The AS-i slave
can also use parameter bits to define or control operation of the
attached slave (e.g., to logically AND or OR with the other
inputs/outputs). A data exchange with the AS-i slave causes the
data strobe output DSR to pulse, while a parameter write to the
AS-i slave causes the parameter strobe PST to pulse.
[0073] For communication between the communication module 76 and
the BCCSCM 1500, a redefinition of the use of the inputs and
outputs of the slave 1520 allows the slave 1520 to be connected to
a microprocessor as a communication gateway via the AS-I bus. When
coupled in this fashion, the slave/microprocessor 1520/1505
combination creates an AS-i bus accessible slave device capable of
communicating variable length data elements from an addressable
array of bytes. Further, by defining some of the available
addressable bytes as pointers into the microprocessor memory space,
additional data space is available for transmission over the AS-i
bus.
[0074] The AS-i protocol calls for communication between the AS-i
master and AS-i slave to be in four-bit data packets. That is, each
request or response across the AS-i bus includes a wholly
self-contained message of four-bits. Please note, however, each
request and response can include other bits (e.g., addressing bits,
parity bit(s), etc.) for communication between devices on the
network.
[0075] Generally speaking, a master request controls the output
states of the output terminals P0-P3 or DO0-DO3 and the AS-i slave
1520 responds by including the states of the inputs DI0 and DI3.
The control (or parameter) bits P0-P4 provide additional
information to the microprocessor. The P0 and P1 bits are data
block selection bits (discussed below), the P2 bit is a read/write
selection bit, and the P3 bit is a compressor ON/OFF bit. The
microprocessor 1505 monitors activity on the communication channels
with the slave 1520 and controls the inputs to the slave 1520.
[0076] The microprocessor is coupled to a 256-bit memory. The
256-bit memory is divided into four, eight-byte blocks. When
writing to or obtaining data from the 256-bit memory, the P0 and P1
bits select one of the blocks. Therefore, the number of blocks
(2.sup.(m) blocks) can vary if the number of selection bits (m)
varies. FIGS. 22A, 22B, 22C, and 22D represent one configuration
for the four blocks 2210, 2220, 2230, and 2240.
[0077] Each block is further divided into sixteen sub-blocks. For
the construction shown in FIGS. 22A-22D, each sub-block includes
four-bits (or a nibble). The size of each sub-block (e.g., (n)
bits) is equal to the number of input/output channels (e.g., (n)
channels). The total number of sub-blocks in a block is equal to
2.sup.(n), and a binary number from 0 (e.g., 0000) to 2.sup.(n)
(e.g., 1111) identifies each sub-block. However, other
configurations are possible.
[0078] Referring to FIGS. 22A-22D, each sub-block contains one or
more pieces of information (e.g., one or more parameters), one or
more sub-blocks can be combined to form a piece of information
(e.g., form a parameter), one or more sub-blocks can be used as a
pointer, or a sub-block can be unused. For example, block 2240 uses
sixteen nibbles for storing six parameter values. More
specifically, nibbles 0000 and 0001 (byte 0) represent a value for
the "suction pressure cut in" parameter; nibbles 0010 and 0011
(byte 1) represent a value for the "suction pressure cut out"
parameter; nibbles 0100 and 0101 (byte 2) represent a value for the
"split suction assignment" parameter; nibbles 0110, 0111, 1000, and
1001 (bytes 3 and 4) represent a value for the "discharge pressure
limit" parameter; nibbles 1010, 1011, 1100, and 1101 (byte 5 and 6)
represent a value for the "discharge temperature limit" parameter;
and nibbles 1110 and 1111 (byte 7) represent a value for the "oil
pressure limit" parameter. As another example, nibbles 1110 and
1111 (byte 7) of block 2210 include values for eight parameters. As
yet another example, nibbles 1110 and 1101 (byte 6) of block 2220
is unused in the configuration shown.
[0079] In the construction shown in FIG. 22, bytes 0 and 1 of block
2230 include a 16-bit pointer. The 16-bit pointer points to data
stored in RAM 1510. The resulting value corresponding to the
pointer is stored in bytes 2 and 3 of block 2230. By using the
pointer, additional storage capabilities can by used at the
processor 1503. Other pointers, pointer sizes, and data sizes can
be used. Also, it should be noted, that the data blocks 2210 to
2250 are mirrored at the master controller 70.
[0080] Because there is only a four-bit control architecture, the
network uses an operation sequence for reading and writing data of
particular length. FIG. 23 includes a flow diagram representing a
read sequence. At 2300, the AS-i master issues a "write_parameter"
message to the AS-i slave 1520. The "write_parameter" message
includes a two-bit value for selecting a data block, a one-bit
value for informing the processor 1503 a read operation is
beginning, and a one-bit value for the current compressor state.
The "write_parameter" message is then communicated from the
communication slave 1520 to microprocessor 1505 on channels
P0-P3.
[0081] At block 2305, the master issues a "data_exchange" message
to the slave 1520. The "data-exchange" message includes a four-bit
value pointing to one of the sixteen nibbles of the selected block.
The "write_parameter" message is then communicated from the
communication slave 1520 to the microprocessor 1505 on channels DO0
to DO3.
[0082] At block 2310, the microprocessor 1505 responds by obtaining
the stored bits of the identified nibble, and communicating the
obtained bits to the slave 1520 on channels DI0 to DI3. The slave
then communicates the obtained nibble to the master in the next
state change. At block 2320, the master controller 70 stores the
obtained nibble in its mirrored 256-bit storage.
[0083] At block 2325, the master controller determines whether all
nibbles for the requested parameter have been obtained. If the
result is affirmative, the master controller combines the stored
nibbles (or divided if the parameter is less than a nibble),
resulting in the requested parameter value. If the result is not
affirmative, then the network repeats blocks 2305, 2310, 2320 and
2325. Therefore, the network decomposes, transmits, and composes
variable length data in four-bit packets.
[0084] FIG. 24 includes a flow diagram representing a write
sequence. At 2400 the master controller decomposes a message to be
communicated to the microprocessor 1505 into a plurality of nibbles
(or creates a nibble if a message is less than a nibble). At 2403,
the AS-i master issues a "write-Parameter" message to the AS-i
slave, which is then communicated to the microprocessor 1505 on
channels P0-P3. The "writeparameter" includes a two-bit value for
selecting a data block, a one-bit value for informing the processor
1503 a write operation is beginning, and a one-bit value for the
current compressor state.
[0085] At block 2405, the AS-i master issues a "data-exchange"
message to the AS-i slave 1520, which is then communicated to the
microprocessor 1505 on channels DO0 to DO3. The "data-exchange"
message includes a four-bit value pointing to one of the sixteen
nibbles of the selected block. The slave responds with a dummy
value, which is ignored (block 2405).
[0086] At block 2410, the AS-i master issues a second
"data_exchange" message to the AS-i slave 1520, which is then
communicated to the microprocessor 1505 on channels DO0 to DO3. The
second "data_exchange" message includes a four-bit value that is
written to the selected nibble. The slave responds with a dummy
value, which is ignored (block 2418). At block 2420, the master
controller determines whether all nibbles for the requested
parameter have been communicated. If the result is affirmative, the
master controller exits the write routine. If the result is not
affirmative, then the network repeats blocks 2405, 2408, 2415, 2418
and 2420. Therefore, the network decomposes, transmits, and writes
variable length data in four-bit packets.
[0087] Referring again to the constructions shown in FIGS. 1, 2,
and 15, when one or more of the inputs from the sensors 50-62 (or
1525-1555) to the processor 49 (or 1503) traverses a safety limit
value, the processor 49, for these constructions, loads a safety
exception message for the master controller 70 and immediately
shuts down the compressor (e.g., compressor 14B). The safety
exception message is loaded into the top of the stack of
information to be sent to the master controller. When the processor
49 receives a message from the master controller 70, it responds by
including the safety exception message for the master controller.
The master controller 70 knows not only that one of the safety
limit values for a particular compressor was traversed, but which
safety parameter or parameters were traversed and in most instances
the actual values of those parameters. An alarm can be activated by
the master controller 70 to alert the appropriate persons that a
problem exists. The information can be accessed by a technician via
a suitable HMI in the system (located, for example, at the
controller 70), or remotely such as through an Internet connection.
The information regarding the operating parameters of the properly
functioning compressors (e.g., 14A, 14C) can also be accessed in
this manner.
[0088] In some constructions, the BCCSCM 1503 (or 48) includes
digital sensors. If a sensor is a digital sensor, the digital
sensor can communicate a code indicating a fault has occurred at
the sensor. Alternatively, the digital value or voltage received
from the sensor can indicate faulty wiring (e.g., an open or short
circuit) or a faulty transducer. Similar to what was discussed
above, the processor 1503 (or 49) can load a message for the master
controller 70 informing the controller of the sensor error. The
message is loaded into the top of the stack of information to be
sent to the master controller 90. When the processor 1503 receives
a message from the master controller 70, it responds by including
the message for the master controller. An alarm can be activated by
the master controller 70 to alert the appropriate persons that a
problem exists. Other control modules (discussed below) can operate
similarly.
[0089] In some constructions, the compressor having a faulty sensor
may continue to operate. For example, in one construction, each
BCCSCM 1500 includes sensors that sense, among other things,
suction pressure. Theoretically, the suction pressure for each
compressor 14 attached to the same suction header should have the
same pressure (but practically, may slightly differ due to filters
and pipe length). If one of the compressors (e.g., compressor 14A)
has a faulty suction pressure sensor, the master controller 70 can
use the sensed suction pressure of the other compressors (e.g., 14B
and/or 14C) attached to the same suction header (e.g., suction
header 16) as the compressor (e.g., 14A) having the faulty sensor
to control that compressor (e.g., 14A). Alternatively, the system
can include a pressure sensor coupled to the suction header 16 (or
piping in communication with the suction header) to control
operation of a compressor having a faulty sensor. In addition to
using the redundant value at the master controller 70, the master
controller can communicate the redundant value to the BCCSCM having
the faulty suction pressure sensor. Therefore, the refrigeration
system can use the redundancy of the attached sensing devices to
continue operation of a compressor (or other subsystem) having a
faulty sensor, even though the compressor (or other subsystem)
includes the faulty sensor.
[0090] Before proceeding further, it should be noted that, although
the failed sensor was a sensor that measures suction pressure, the
system can perform similarly for other sensors (e.g., suction
temperature, discharge pressure, discharge temperature, etc.) and
for other sensors attached to other control modules (discussed
below). Additionally, the master controller 70 can compare values
acquired from sensors that should have similar or substantially
similar values to determine whether one of the sensors is faulty
(e.g., a faulty sensor due to drift). Continuing the above example,
the master controller 70 can compare the sensed suction pressure
for compressors 14A, 14B, and 14C. If one of the sensed values
(e.g., the suction pressure for compressor 14A) is significantly
different than the values of the other compressors (or different
than a sensor attached to the suction header 16), then the master
controller 70 can mark the suction pressure sensor having the
significantly different value as faulty. An alarm can be activated
by the master controller 70 to alert the appropriate persons that a
problem exists. Additionally, the master controller can communicate
the fault to the compressor having the faulty sensor.
[0091] As discussed herein, the master controller 70 receives
information concerning operation parameters of the compressors 14A,
14B, and 14C. A primary control parameter is suction pressure. The
controller 70 is programmed so that it manipulates (e.g., such as
by averaging) the suction pressure readings from the BCCSCMs 48 to
determine the refrigeration level produced by the multiplexed
compressors 14A, 14B, and 14C. The controller 70 uses this
information to strategize cycling compressors in the system to
achieve the desired refrigeration capacity level.
[0092] One exemplary method of dynamically controlling a plurality
of multiplexed compressors (e.g., compressors 14A, 14B, and 14C) is
schematically shown in FIGS. 16A-16F. The flowcharts represent one
or more software modules that are continuously called by the CPU 72
to dynamically control the multiplexed compressors. Before
proceeding further, it should be noted that the blocks of FIGS.
16A-16F represent software instructions received, interpreted, and
executed by the CPU 72, resulting in the CPU 72 (and the master
controller 70) performing the operations of the blocks. It should
also be noted that FIGS. 16A to 16F is one exemplary method. Other
acts can be included with the method shown in FIGS. 16A-16F, one or
more acts shown in FIGS. 16A-16F can be removed, and the order or
sequence of the acts shown in FIGS. 16A-16F can vary. Furthermore,
while the method shown in FIGS. 16A-16F will be described in
connection with software, the method can be implemented by other
means (e.g., an ASIC).
[0093] As discussed earlier, the refrigeration system includes one
or more multiple suction groups, where each suction group has one
or more compressors. If a suction group has a plurality of
compressors, the compressors are multiplexed in an arrangement
(typically a parallel arrangement). Referring to FIG. 16A, the
master controller 70 performs a capacity calculation for each
suction group and each compressor of each suction group. At blocks
1600, the master controller 70 initializes the loop counters. At
blocks 1605, the master controller 70 determines (e.g., calculates
by adding capacities for each compressor (as shown in FIG. 16A),
obtain previous calculations from storage, etc.) the total capacity
for the suction group at a given operating point. The master
controller 70 uses known equations for determining the capacity of
each compressor at the current operating pressures when performing
the capacity calculations. At blocks 1610, the master controller 70
determines the capacity of each individual compressor as a
percentage of the total capacity. By way of example, if a first
suction group has three compressors (e.g., 14A, 14B, and 14C), the
first compressor (e.g., 14A) may have a 50% capacity, a second
compressor (e.g., 14A) may have a 25% capacity, and a third
compressor (e.g., 14A) may have a 25% capacity. At block 1615, the
master controller determines whether the capacity calculations were
performed for all of the suction groups. If the answer is
affirmative, then the master controller proceeds to block 1620
(FIG. 16B). Otherwise, the master controller returns to block
1605.
[0094] At FIG. 16B, the master controller determines a current
compressor run pattern, current run capacity, and current % total
capacity. At blocks 1620, the software initializes the loop
counters. At blocks 1625, the master controller 70 builds a binary
image of the status of the compressors 14 and determines the
current run capacity of each suction group. More specifically, the
master controller 70 determines which compressors 14 are currently
on, and adds the capacity of each activated compressor 14 to the
current run capacity for the respective suction group(s). At block
1630, the master controller 70 determines the current run capacity
of each suction group as a percentage of the total capacity of each
suction group. Continuing the earlier example, if the second and
third compressors 14B and 14C are ON, then the current run capacity
is 50% of the total capacity. At block 1635, the master controller
determines whether the capacity calculations were performed for all
of the suction groups. If the answer is affirmative, then the
master controller proceeds to block 1640 (FIG. 16C). Otherwise, the
master controller returns to block 1620.
[0095] In FIGS. 16C-16F, the master controller 70 determines the
control pattern for the next cycle. At block 1645, the master
controller 70 determines whether an increase in run capacity is
required. If the answer is affirmative, then the master controller
proceeds to block 1650 (FIG. 16D). Otherwise, the master controller
proceeds to block 1655 (FIG. 16E).
[0096] With reference to FIG. 16D, the master controller 70
determines the next control pattern, which requires an increase in
run capacity. Increasing the run capacity of a suction group
typically requires activating an inactive compressor. At block
1650, the master controller determines whether all compressors are
ON. If the answer is affirmative, then the master controller
proceeds to block 1660 (FIG. 16C). Otherwise, the master controller
proceeds to blocks 1665 (FIG. 16E). At blocks 1665, the master
controller 70 determines each available capacity percentage
combination for each suction group. Continuing the earlier example,
the percentage combinations for compressors 14A, 14B, and 14C
include 25%, 25%, 50%, 50%, 75%, 75%, and 100%. However, if one of
the compressors has an alarm condition, that compressor is removed
from the possible combinations (block 1665E). At blocks 1670, the
master controller 70 determines the next capacity increment.
Revisiting the earlier example, the second and third compressors
14B and 14C were ON resulting in a 50% run capacity. The next
available run capacity is 75% (i.e., activating the first
compressor 14A with either the second or third compressors 14B or
14C). At block 1670F, the master controller 70 performs a "FIFO
test." The FIFO test (shown in detail in FIG. 16F) determines the
next compressor run pattern when multiple possible combinations
have an equivalent run capacity. That is, if blocks 1665 and 1670
result in multiple combinations for the next available capacity,
the FIFO test determines the next compressor run pattern.
Continuing the earlier example, the next available run capacity for
the three compressors 14A, 14B, and 14C is 75%, and there are two
combinations that result in that run capacity (i.e., compressors
14A and 14B, or compressors 14B and 14C). In the configuration
shown in FIG. 16F, the master controller 70 selects the most
optimal run pattern for the compressors 14. For example, the most
optimal run pattern can include compressor run time as a variable.
Optimizing the run pattern with compressor run time attempts to
equitably distribute compressor run time over the compressors of
the suction group. However, other tests can be included in
selecting the next compressor run pattern.
[0097] Returning to block 1645, the master controller determines
whether an increase in run capacity is required. If the answer is
negative, then the master controller 70 proceeds to block 1655
(FIG. 16E). In general, the control scheme of FIG. 16E corresponds
to FIG. 16D; however, the master controller 70 decreases the run
capacity of the suction group. Decreasing the run capacity
typically requires deactivating an active compressor.
[0098] At block 1655, the master controller 70 determines whether
all compressors 14 are OFF. If the answer is affirmative, then the
master controller 70 proceeds to block 1660 (FIG. 16C). Otherwise,
the master controller 60 proceeds to blocks 1675 (FIG. 16E). At
blocks 1675, the master controller 70 determines each available
percentage combination for each suction group. Blocks 1675
generally correspond to blocks 1665 (FIG. 16D). At blocks 1680, the
master controller determines the next capacity decrease. Revisiting
the earlier example, the first and second compressors were ON
resulting in a 50% run capacity. The next available run capacity
decrement is 25% (i.e., activating the second or third compressors
14B or 14C). Similar to 1670 discussed above, at block 1680F, the
master controller 70 performs a "FIFO test." The FIFO test (shown
in detail in FIG. 16F) determines the next compressor run pattern
when multiple possible combinations have an equivalent capacity.
That is, if blocks 1675 and 1680 result in multiple combinations
for the next available capacity, the FIFO test determines the next
compressor run pattern. Continuing the earlier example, the next
available capacity for the three compressors 14A, 14B, and 14C is
25%, and there are two combinations that result in that capacity
(i.e., activating the second or third compressors 14B or 14C). In
the configuration shown in FIG. 16E, the master controller selects
the next compressor run pattern.
[0099] Returning back to blocks 1660 (FIG. 16C), the master
controller 70 updates sequence status information in view of FIFO
calculations. More specifically, the master controller keeps a
continuous runtime for each compressor 14A, 14B, and 14C. This
information is used in the FIFO calculations when multiple
capacities are possible. At block 1685, the master controller 70
exits the software routine, resulting in a pattern for each suction
group.
[0100] In one construction, the routine shown in FIG. 16 is called
when a change in capacity for a suction group is required. More
specifically, in one construction of the refrigeration system, a
PID error signal is used for controlling the operation of the
compressors 14. If the error signal requires a change in capacity,
the CPU 72 invokes the routine in FIG. 16, resulting in a new run
pattern.
[0101] In one construction, should the master controller 70 (and in
particular the CPU 72) fail, the BCCSCMs 48 and 1500 are capable of
performing the controller functions for the compressors 14A, 14B,
and 14C. A flowchart of the one operation of the processors 49 (or
1503) in the master fail mode is shown in FIG. 5. As stated above
with reference to FIG. 4, the processor 49 of each BCCSCM 48 waits
a predetermined time period for a message from the master
controller 70. If the period times out with no message, the
processor 49 defaults to a master fail operation mode.
[0102] In the operation shown in FIG. 5, the BCCSCMs 48 (and/or
1500) communicate with each other over the communication and power
line of the bus 80, in addition to communicating with the
controller 70. In the failure mode, each processor 49 (or 1503)
determines whether it is to have primary control. One processor of
the BCCSCMs will have previously been programmed with a certain
identification or address, e.g., ID=1. Typically, this would be the
BCCSCM 48 of the first compressor 14A in the system. Any BCCSCM 48
not having this identification will continue to operate only
responsively to commands received over the field bus network (i.e.,
it resumes standard operation as a slave). It is also envisioned
that the slave processors (i.e., processors associated with
compressors 14B, 14C) would start a second timer once entering the
failure mode to look for a message from the processor of the BCCSCM
48 designated for primary system control in the failure mode (i.e.,
the processor 49 associated with compressor 14A). If the other
processors 49 do not receive such a message, a second BCCSCM 48
would be pre-selected (e.g., the BCCSCM having ID=2 associated with
compressor 14B) to control the operation of the system in the
failure mode. Thus, the system is highly granular, allowing for
multiple failures while maintaining operation.
[0103] In one method of operation, the processor 49 (or 1503) of
the BCCSCM 48 (or 1500) of compressor 14 is identified as the
primary control or master, in case of failure of the master
controller 70, and will execute a master control function involving
at least basic compressor cycling. In that regard, the primary
control processor 49 is capable of determining the collective
suction pressure of the operating compressors 14A, 14B, and 14C and
providing control commands for itself and the other slave
processors to turn compressors on and off to maintain the
refrigeration capacity requirements of the system. After performing
this function, the "primary" processor 49 resumes a slave presence
on the network which allows it to again look for a message from the
master controller 70 for a period of time before returning again to
perform a system control function. Once the master controller 70 is
detected, the primary control processor 49 returns to its standard
(slave) mode of operation.
[0104] In general, the distributed intelligence control provides
for ease of assembly and installation and enhances control. The
compressors 14A, 14B, and 14C are configured with one or more
sensors to optimize uniformity of measurement of operation
parameters and to minimize installation variances as well as
provide protection of such sensor devices. The modularity and
intelligence of the compressor controllers interface with the
master controller 70 to assure optimum compressor performance, as
well as granularity of the system.
[0105] For the constructions utilizing a two wire bus that provides
power and communication to the control modules (e.g., via an AS-i
bus), assembly of a refrigeration system is made easier by
simplification of the wiring which is normally done upon
installation. The high voltage lines 44A, 44B, and 44C are still
used to run the compressors 14A, 14B, and 14C for primary
operation. According to electrical codes, it is typically required
to shield these lines such as by placing them in conduit. However,
for the construction shown in FIG. 1, no separate power lines other
than three phase high voltage lines 44 must be run to the
compressor motors 32. Additionally, it is unnecessary to run
additional high voltage lines to the BCCSCM's. Instead, a single
high voltage feed line 69 supplies the power supply 74 for the CPU
72 and communication module 76 and also the network power supply
78.
[0106] Power for all of the BCCSCMs 48 (and/or 1500) is supplied
through the same two wire bus 80 extending from the communications
module 76 to the control and safety modules 48. The bus 80 does not
need to be shielded because it carries only 30 VDC power.
Preferably, the wiring of the BCCSCMs 48 to the master controller
70 is done at the factory where the compressors 14A, 14B, and 14C
are mounted together with the controller on a compressor rack (not
shown) so that no power wiring of any kind for the BCCSCMs is
required at the building site. The number of BCCSCMs 48 attached to
the bus 80 up to some upper limit of the controller 70 (e.g., 31)
is immaterial and requires no special re-configuration of the
controller.
[0107] As stated above, the connection of the BCCSCMs 48 (and/or
1500) to the communication bus 80 achieves not only power, but
communications for the control and safety modules. No separate
feedback wiring from the individual sensors is necessary. The
processor 49 (or 1503) of the BCCSCM executes commands from the
master controller 70 and is capable of reporting back to the
controller 70 that the command has been executed. The processor 49
reports the readings from all of the sensors 50-58 or 1525-1555,
and not only whether a safety limit value has been exceeded, but
exactly which one it is and what the exact value was. This enables
the master controller 70 to provide specific information to a
repair technician without any additional wiring between the
controller 70 and the BCCSCM 48. In addition to permitting
refrigeration level control by the controller 70, the system allows
the controller 70 to make other adjustments in the system and to
monitor trends for use in failure prediction/avoidance.
[0108] The processors 49 (and/or 1503) of the BCCSCMs also, in one
construction, have the embedded intelligence to operate the
refrigeration system in case the master controller 70 fails. In
that regard, the BCCSCMs 48 (and/or 1500) are capable of
communicating with each other as well as the master controller 70
over the two wire bus 80. In case of failure of the master
controller, one of the BCCSCMs will take over as master or
"primary" and can perform at least the function of averaging the
measured suction pressure readings from the operating compressors
to determine refrigeration level and determine how to cycle the
compressors to maintain a predetermined capacity.
[0109] Referring still to FIG. 1, the commercial refrigeration
system may also optionally include one or more liquid subcoolers 15
and an oil separation and return subsystem 17. The general
operation of liquid subcoolers is known in the art. An exemplary
embodiment of a control system for controlling such a subcooler
and/or such an oil separation and return system, in accordance with
aspects of the present invention, is described in further detail
below with respect to FIGS. 10 and 10A. Examples of oil separation
systems are included in U.S. Pat. Nos. 4,478,050, 4,503,685, and
4,506,523, which are incorporated herein by reference.
[0110] For purposes of disclosure and simplicity, the refrigeration
so far described herein has been, primarily, a vapor phase
evaporative cooling system. The invention, however, is not to be so
limited in its application. For example, FIG. 1A is a schematic
diagram of one exemplary form of a modular secondary refrigeration
system 200 which could also be modified to be implemented and
controlled by an integrated distributed intelligence control
system. Such a secondary cooling system is described in exacting
detail in U.S. Pat. No. 5,743,102, the entire disclosure of which
is incorporated herein by reference.
[0111] Referring to FIG. 1A, the refrigeration system 200 comprises
a primary vapor phase refrigeration system including a plurality of
parallel, multiplexed compressors 202. The compressors deliver
liquid refrigerant at high temperature and pressure to a first
condenser 204 and a second condenser 206 from which the liquid
refrigerant passes to an expansion valve 208 feeding the
refrigerant into an evaporator 210. Vaporous refrigerant is drawn
from the evaporator 210 back to the compressors 202 to complete a
conventional vapor phase refrigeration cycle. However, the
evaporator 210 is incorporated as part of a first heat exchanger
including a first reservoir 212 holding a coolant liquid (e.g.,
glycol). Typically, this reservoir 212 is located close to the
compressors and condensers so that the vapor phase refrigerant loop
is short, requiring minimal refrigerant. The first reservoir 212 is
part of a secondary refrigeration system including pumps 214 which
drive coolant fluid through the reservoir to second heat exchangers
216 located in respective fixtures 218, which may constitute
refrigerated merchandisers in the shopping arena of a supermarket.
The coolant liquid absorbs heat from items (not shown) in the
fixtures 218, while remaining in a liquid state, and then is forced
by the pumps 214 back to the first reservoir 212 where that heat is
removed to the vapor phase refrigeration system. The vapor phase
refrigeration system may beneficially be, but is not necessarily,
located adjacent to the fixtures 218. The temperature of the
fixtures 218 may be maintained through the use of sensors (e.g.,
sensors 220) which control valves 222 and the pumps 214. The
control system, in one construction, may be beneficially used to
control the operation of the primary vapor phase and secondary
liquid refrigeration systems according to the principles set forth
herein.
[0112] The refrigeration system 200 further includes a coolant
liquid defrost system comprising a second coolant liquid reservoir
224 that contains the first condenser 204. The coolant liquid
system pumps 214 are valved to divert some of the coolant liquid to
the reservoir 224 where it is heated by the hot refrigerant passing
through the first condenser 204. At a predetermined interval or
when it is sensed that frost has built up on the second heat
exchangers 216, valves including defrost valves 226 are controlled
to stop the flow of cold coolant liquid from the first reservoir
212 to the second heat exchangers 216 and to permit flow of heated
coolant liquid to the second heat exchangers for defrosting. Again,
the control system can be beneficially employed to control
operation of the defrost of the system 200. Additional aspects of
secondary cooling systems, including specific valving and flow
control structures, are disclosed in U.S. Pat. No. 5,743,102.
Accordingly, one skilled in the art having the benefit of the
present disclosure could adapt the teachings herein for use with
secondary cooling systems by providing similar distributed, modular
control and monitoring of the compressors, valves, set points, and
other components/sensors associated with such secondary cooling
systems.
[0113] FIG. 7 is a system block diagram illustrative of an
integrated distributed intelligence control system 700 for use in a
refrigeration application, such as a commercial refrigeration
application. As depicted therein, the system 700 preferably
includes several field bus communication networks that cooperate to
provide distributed intelligence system monitoring and control. A
local network server 702, a local workstation 704, and a remote
workstation 706 provide top-level control. In one construction, the
local network server 702 and the local workstation 704 will be
installed near the refrigeration system (e.g., inside the facility
containing the refrigeration system). In one construction, the
remote workstation 706 is constructed and configured to communicate
via a wide-area network such as the Internet 708. Other network
levels are preferably connected to the top-level via a
communications interface, such as, for example, an Ethernet hub
712.
[0114] A first field bus control network 716, which preferably
comprises an AS-i bus as previously described herein, is connected
to the Ethernet hub 712 via a gateway interface device 714 and a
rack PLC 720 (also referred to as the system controller). It is to
be understood and appreciated that the rack PLC 720 illustrated in
FIG. 7 corresponds to the CPU associated with master controller 70,
which is illustrated and described with respect to FIGS. 1 and 2
above. Accordingly, the rack PLC 720 may also be referred to as the
CPU or even as the master controller. One construction of the
gateway interface device 714 is a Siemens IPC, which is a Windows
NT.RTM. based computer. As explained in greater detail below,
gateway interface device 714 is constructed and arranged to provide
a gateway between similar and dissimilar field bus networks having
similar and dissimilar network protocols. In other constructions,
one or more operations described in connection with the remote
workstation 706, the local workstation 704, and/or the local
network server 702 can be performed by the gateway interface device
714 and vice-versa. For one exemplary construction, the device 714
can function as both the local workstation and the gateway
interface. As another example, in some constructions that are
discussed below, the device 714 includes one or more tables for use
by the rack PLC 720. However, these tables can be located at the
remote workstation 706 or the local workstation 704.
[0115] A wireless hub 713 may optionally be included to allow
access to the control network by a work station over a wireless
interface (e.g., a wireless Ethernet link), such as between a
wireless computing device 715 (e.g., a Windows CE.RTM. compatible
computer) and the Ethernet hub 712.
[0116] Local workstation 704, remote workstation 706, and wireless
computer 715 can be used to access system information such as, for
example, set points, defrost schedules, alarm logs, current system
conditions (e.g., temperatures), and other system status and set
point information. Likewise, these devices may be used to input
system information such as set points or system schedules (e.g.,
defrost schedules or maintenance schedules).
[0117] The first field bus control network 716 also includes an
AS-i master interface 722 which serves as a communication interface
between rack PLC 720 and various control modules. The AS-i master
interface 722 corresponds to the communication module 76 discussed
above with respect to FIG. 1. The devices associated with the first
field bus control network 716 may be generally referred to as "rack
devices," or as being "located at the rack." This nomenclature is
used because in the embodiment illustrated in FIG. 7, rack PLC 720
is installed at or near the rack of compressors for which it
provides system integration and control. For example, a rack will
typically include between two and thirty-one compressors, and a
given installation may include multiple racks. Thus, a large system
might have thirty-two racks of compressors, each controlled by a
separate rack PLC that interfaces with a common processor or
gateway device. In one construction, each rack PLC interfaces with
computer/gateway interface device 714. The gateway device 714
accommodates for set point control, status monitoring, fault
logging, data storage, and the like for each rack PLC (and the
devices integrated by such rack PLC) in the system. For simplicity,
FIG. 7 depicts an installation having only a single rack, and,
accordingly, a single rack PLC 720.
[0118] Before proceeding further, it should be noted that aspects
of the refrigeration system discussed herein are not limited to a
refrigeration system having compressors located on a rack. Rather,
one or more aspects discussed herein can be applied to systems
having a single compressor unit and to systems having multiple
single compressor units not located on a rack.
[0119] The control modules illustrated in FIG. 7 preferably include
one or more compressor controllers (e.g., Bus Compatible Compressor
Safety and Control Modules or BCCSCMs 48 or 1500), one or more
branch controllers 724 (also referred to herein as Bus Compatible
System Branch Modules 724 or BCSBMs), and one or more valve
controllers 726 (also referred to herein as Bus Compatible Valve
Control Modules or BCVCMs). The one or more compressor controllers
48 (or 1500), one or more branch controllers 724, and the one or
more valve controllers 726 will also be generically referred to
herein as device controllers and subsystem controllers. When
connected to the first field bus control network 716, each of these
modules 48, 724, and 726 communicates with rack PLC 720, via an
AS-i compatible bus 728 and AS-i master 722. The operation of
BCCSCM 48 has previously been described. The operational aspects of
the BCSBM 724 and the BCVCM 726 are described in greater detail
below. Of course, other constructions for the first field bus
control network 716 can by used with the refrigeration system. For
example, other field bus types can be used in place of the AS-i
compatible bus 728.
[0120] A second field bus control network 730, which can also
comprise another AS-i bus as previously described herein, is
connected to gateway interface 714 and the master controller (rack
PLC 720) over a relatively longer distance network 731 (e.g., a
twisted pair network, such as, for example, a Siemens' MPI
compatible interface or ProfiBUS). In one construction, the second
field bus control network 730 is slaved to the rack PLC 720.
However, other configurations are possible. Second field bus
control network 730 includes a condenser PLC 732 (also referred to
as condenser controller), another AS-i master 734, and one or more
fan control modules 736 (also referred to as Bus Compatible Fan
Control Modules or BCFCMs). For FIG. 1, the condenser PLC 732
corresponds to condenser controller 84, and may also be referred to
as providing a network gateway between BCFCM 736 and rack PLC 720.
Operational aspects of the condenser PLC 732, AS-i master 734, and
BCFCM 736 were also described above with regard to FIG. 1. Of
course, other constructions for the second field bus control
network 730 can by used with the refrigeration system. For example,
other field bus types can be used in place of the AS-i compatible
bus.
[0121] A third field bus control network 740 communicates with rack
PLC 720 over another relatively longer distance communication bus
741, such as, for example, a LonWorks.RTM. network (also referred
to as a LonWorks.RTM. bus or an Echelon network). LonWorks.RTM.
information and network components are available from the Echelon
Corporation of Palo Alto, Calif. The third field bus control
network 740 is used to facilitate communications between the master
controller (rack PLC 720) and one or more refrigeration cases,
which are controlled by one or more case/fixture controllers 744
(also referred to as Bus Compatible Modular Case Controls, BCMCCs,
case controllers, or display case controllers), the operation of
which is described below. Similar to the other device controller
introduced earlier, the one or more case/fixture controllers 744
will also be generically referred to herein as device controllers
and subsystem controllers. Communications between the BCMCC 744 and
rack PLC 720 occurs via interface gateway 714 and the communication
bus 741. The type of gateway device used will typically depend upon
the bus/communication protocols employed. In the system illustrated
in FIG. 7, BCMCC 744 operates on a LonWorks.RTM./Echelon compatible
bus, thus interface gateway 714 is constructed and arranged to
integrate communications between such a bus and rack PLC 720. Of
course, other constructions for the third field bus control network
740 can by used with the refrigeration system.
[0122] Also, as illustrated in FIG. 7, third party controls 746 and
748 (e.g., HVAC, fire, and rack/case controls) can optionally
interface to, and become part of, system 700, via communication bus
741. Thus, the system facilitates interoperability between control
systems from different sources that are compatible with the gateway
and communication standard used for the associated communication
bus (e.g., AS-i, ProfiBus, LonWorks.RTM./Echelon or Ethernet).
Using distributed intelligence control system 700, for example,
third party controls 746 and 748 can be integrated and used if such
controls are compatible with LonWorks.RTM./Echelon interface
standards and protocols. A third party fixture/case controller that
is compatible with communication bus 741 and interface gateway 714
can be used to interface with and control one or more refrigerated
fixtures (not shown) via a case/fixture controller (e.g., BCMCC
744). In one construction, the rack PLC 720 can advantageously
continue to maintain integrative control over the entire system by
retaining knowledge over the operation of BCMCC 744. Accordingly,
even when third party controls are desired or required for a part
of the overall refrigeration system, the advantages of modularity
and distributed control made possible by the disclosed
refrigeration system are not lost.
[0123] BCMCC 744 and the third party controls 746 and 748 may be
collectively referred to as remote terminals associated with third
field bus control network 740. In one construction, the
communication bus 741 comprises a wireless RF interface (also
referred to as an RF link) such that no wiring is required between
the remote terminals and the interface gateway 714. Using a
wireless RF interface provides substantial advantages, including
reducing the amount and complexity of field wiring needed to
install the system, and greatly reducing the risk of damage due to
external influences such as lightening strikes, high voltage
arcing, or high current transmissions in adjoining
equipment/wiring. Such external influences are common in some
geographic regions and can result in considerable system downtime
and/or service expense. RF interfaces may be implemented using
broad band spread spectrum (BBSS) transmission systems or narrow
band on/off keyed (OOK) transmission systems. BBSS systems provide
improved data integrity performance with respect to data
transmitted in harsh electrical environments, and often provide
higher data throughput rates. OOK systems, on the other hand, are
typically less expensive to implement. It should be understood,
however, that the third field bus control network 740 may be
completely "hard wired" or partially wireless and partially hard
wired.
[0124] A remote, wireless interface device 750 can be used by
system operators, maintenance personnel, and the like to
communicate directly with one or more case controllers such as
BCMCC 744. In one construction, the interface device 750 comprises
an infrared transceiver that operates as a remote keypad for a
display module associated with the case controller. Thus, interface
device 750 can be used to query case controllers to determine
information such as current temperature or set point information
or, optionally, to input set point data into case controllers. Such
set point data can include, among other items, defrost schedules or
temperature set point data. In the construction illustrated in FIG.
7, however, BCMCC 744 receives its primary control inputs from rack
PLC 720.
[0125] In addition to the three field bus networks already
described with respect to FIG. 7, the distributed intelligence
control system 700 also includes local and remote human-machine
interface (HMI) devices. A remote HMI device 752 provides user
access to system status information, which is transmitted to the
remote HMI device via network 731. In one construction, the remote
HMI device 752 comprises a touch screen device, such as a TP 170A
device, available from Siemens (part no. 6AV6545-OBA15-2AX0).
Similarly, a local HMI device 754 provides user access to system
configuration data, system status data, diagnostic data, and the
like. The local HMI device 754 communicates with rack PLC 720, via
network 731. In the construction illustrated in FIG. 7, the local
HMI device 754 comprises an LCD display with a membrane keyboard,
such as an OP3 device, which is available from Siemens (part no.
6AV3503-1DB10). Additional details regarding constructions of
remote HMI device 752 and local HMI device 754 are provided in the
Appendix.
[0126] One of the advantages of using a distributed intelligence
control system, such as the system of FIG. 7, is that such a system
is generally easier to install than conventional systems, which
typically require multiple runs of high power wiring between the
rack and each remotely located controlled device, such as display
cases, as well as separate wiring to/from each system sensor. For
example, prior art systems typically require at least one
additional separate wire, often a high power wire requiring
compliance with particular standards, for each system element being
controlled.
[0127] In addition, the distributed intelligence control system is,
in one construction, at least partially self-configuring. For
example, each AS-i bus compatible device can generate its own
unique identification (ID)/address. An AS-i master queries each
device on the system, and that device tells the AS-i master its
ID/address. For one example method of operation, each BCCSCM on
control network 716 would indicate to rack PLC 720 that it is a
compressor control module as well as its ID/address. In the event
that a duplicate ID/address is generated, the AS-i master instructs
the device to pick another value. Thus, as can now be appreciated,
a complicated refrigeration control system can be installed with a
reduced complexity in the installation process because persons
installing the system need not concern themselves with all of the
details associated with identifying and addressing each control
module in the system.
[0128] Likewise and in another construction, each distributed
control module in system 700 (e.g., BCCSCM 48, BCSBM 724, BCVCM
726, BCFCM 736, and BCMCC 744) includes processing capability, data
storage capability, and provides configuration/set point mirroring,
whereby the most recent system configuration and set point data for
each module is stored in that module. Such configuration and set
point data includes, for example, module ID/address information,
control system set points (e.g., case temperature), defrost cycles,
alarm history, and the like. Thus, if rack PLC 720 fails and needs
to be reprogrammed or replaced, the entire system partially
reconfigures itself and supplies the most recent configuration and
set point data to the new/repaired rack PLC. Similarly, if
communication with rack PLC 720 is lost, each control module in
system 70 can continue to attempt to maintain control by adhering
to the most recent set points/schedules provided by rack PLC 720.
In this way, the integrity and history associated with system 700
is maintained even when rack PLC 720 is replaced.
[0129] More detailed methods of operation for configuring a
refrigeration system 700 will now be described in connection with
FIGS. 7 and 17-22. When manufacturing or assembling a device or
subsystem (e.g., an evaporator, a compressor, a condenser, a
refrigeration case, a system branch, etc.) the device manufacturer
or assembler (collectively referred to below as manufacturer)
couples the device or subsystem controller (e.g., the BCVCM(s) 726,
BCSBM(s) 724, BCCSCM(s) 48 and/or 1500, BCFCM(s) 736, BCMCC 744,
condenser PLC 732) to the related device or subsystem. In addition,
the device manufacture stores an identification code (e.g., model
number, serial number, device type, etc.) for the device or
subsystem (collectively referred to below as device) in the related
device controller. As discussed in connection with FIG. 7, the
device controllers are connected (either directly or indirectly)
with the rack PLC 720 (which is also referred to as the system
controller). Before proceeding further, it should be noted that the
rack PLC may also be referred to as the system controller 720.
However, unless specifically limited otherwise, other processing
units can be used in place of or in combination with the rack PLC
to perform one or more operations disclosed below.
[0130] With reference to FIG. 7, the one or more technicians
assemble the physical structure of the refrigeration system. After
or concurrent with assembling the physical structure, the one or
more technicians activate the rack PLC 720 and the computer 714.
Among other initial operations performed by the rack PLC 720 and
the computer 714, the rack PLC 720 establishes a communication
network with the devices of the refrigeration system and determines
what devices are included with the refrigeration system. In
general, the rack PLC 720 initiates one or more signals requesting
the device controllers to identify themselves, and identify what
devices are coupled to the device controllers (e.g., via the
identification codes). Further, the rack PLC 720, with the help of
the communication modules (e.g., the gateway interface 714, AS-i
masters 722, 734, etc.), establishes the protocols and addresses
for communication in the refrigeration system.
[0131] After establishing the communication network and the
elements of the refrigeration system, the rack PLC 720, with the
assistance of the PC interface 714, configures the refrigeration
system by providing information (e.g., control and safety
parameters, schedules, signals, etc.) to the device controllers.
For example, the rack PLC 720 and/or the PC interface 714 includes
in memory the identification codes for various devices that can be
attached to the refrigeration system. As a specific example,
hundreds of compressor models can be used in the refrigeration
system and, consequently, the rack PLC 720 and/or the PC interface
includes in memory an identification code (e.g., model number) for
each possible compressor. Associated with each identification code
in memory are limits, equations, values, and other information used
by the refrigeration system for operation. Further, databases may
also be used for obtaining information based on combination of
identification codes. Using the identification codes, the rack PLC
acquire values, parameters (control and safety parameters),
equations, limits, etc. from memory; perform calculations using the
acquired information (e.g., calculate values or limits for the one
or more parameters, create schedules, etc.); and acquire similar
information from other processing units. The information received
at the device controllers is used by the device controllers to
locally operate (or control) the devices.
[0132] The device controllers (e.g., the BCCSCM described earlier)
can include one or more sensors that sense parameters identified by
the rack PLC 720. The sensed values are communicated via the
established communication network to the rack PLC 720. The rack PLC
uses the sensed parameters, stored information/data regarding the
refrigeration system, and information stored at the rack PLC (or at
other processing units such as the PC interface 714) to operate (or
control) the refrigeration system. Controlling the refrigeration
system includes providing control signals and information to the
device controllers for operating the devices.
[0133] Referring now to Tables 1-4, the tables disclose what
parameters are maintained at each module for one construction of
the refrigeration system. Table 1 discloses the parameters
maintained at the compressor control module.
1 Compressor Module (BCCSCM) Configuration Data Operating Parameter
Source Compressor Model Number Manufacture (User Input) Suction
Pressure Cut-In System Controller Suction Pressure Cut-Out System
Controller Split Suction Assignment System Controller Discharge
Pressure High Limit System Controller Discharge Temperature High
Limit System Controller Motor Current Limit System Controller AS-i
Address Manufacture (User Input) Compressor Type System Controller
Number of Sensors Internal Determination Operating Voltage System
Controller Oil Pressure Limit System Controller Oil Level Switch
Enabled Internal Determination Motor Temp Limit System
Controller
[0134] With reference to Table 1, the manufacturer of each
compressor enters a compressor model number into the compressor
control module. The compressor model number, when retrieved by the
rack PLC 720, identifies the respective compressor. Using the
compressor model number, the rack PLC 720 can obtain related data
for the compressor. For example, based on the compressor model
number, the rack PLC 720 can obtain the specifications for the
compressor, such as compressor manufacture, compressor type (e.g.,
scroll, screw, reciprocating, etc.), capacity, safety limits, etc.
Also, as discussed above, the rack PLC 720 communicates one or more
operating parameters to the compressor control module. The
parameters provided from the rack PLC 720 to the compressor control
module are identified in column two of Table 1 as "System
Controller." Other parameters may be communicated from the system
controller to the control module and not all parameters are
required for the control module in all constructions.
[0135] Referring again to Table 1, some of the parameters are
established or calculated by the compressor control module. For
example, the "number of sensors" parameter is an internal
calculation performed by the compressor control module. For example
and in one construction, the compressor control module polls for
sensors connected to the module. Based on the response, the
compressor module can determine how many sensors are connected to
the module.
[0136] The oil level switch enabled parameter is also an internal
determination for the construction shown in Table 1. For some
compressor types (e.g., scroll compressors), an oil level switch is
used to control the oil level of the compressor. The compressor
module performs an internal determination whether an oil level
switch is attached and enabled.
[0137] Referring again to Table 1, the parameter "AS-i Address" is
identified as a manufacturer or user input. The AS-i address
parameter is used by the network for promoting communication
between the system controller and the respective compressor module.
The system controller can subsequently modify the AS-i address
parameter to allow for automatic addressing of the attached
device.
2 Table 2, System Module (BCSBM) Configuration Data, discloses the
parameters maintained at the system branch control module for one
construction of the refrigeration system. System Branch Module
(BCSBM) Configuration Data Operating Parameter Source Case Model
Number Manufacture (User Input) Defrost Schedule System Controller
Discharge Air Temp Set Point System Controller Defrost Type System
Controller Number of Defrosts per Day System Controller Discharge
Air Temperature High Limit System Controller Defrost Termination
Temperature System Controller AS-i Address Manufacture (User Input)
Time and Date System Controller
[0138] Similar to what was discussed above for the compressor
control module, the manufacture of each system branch control
module enters a case model number into the control module. The case
module number identifies the respective case model to the rack PLC
720. Using the case model number, the rack PLC 720 obtains
information relating to the case and the system branch. Also, as
discussed earlier, the rack PLC 720 communicates one or more
operating parameters to the system branch control module. The
parameters provided from the rack PLC 720 to the system branch
control module are identified in column two of Table 2 as "System
Controller." This information can be maintained at the system
controller and at the individual modules. Other parameters may be
communicated from the rack PLC 720 to the system branch control
module and not all parameters are required for the system branch
control module in all constructions. It is also envisioned that the
identifying model number can be assigned by installation or service
personnel via the system controller for field replacement of a
failed device.
[0139] Referring again to Table 2, the parameter "AS-i Address" is
identified as a manufacturer or user input. The AS-i address
parameter is used by the network for promoting communication
between the system controller and the respective system branch
control module. The system controller can subsequently modify the
AS-i address parameter to allow for automatic addressing of the
attached device.
3 Table 3, Valve Module (BCVCM) Configuration Data, discloses the
parameters maintained at the valve control module for one
construction of the refrigeration system. Valve Module (BCVCM)
Configuration Data Operating Parameter Source Valve Model
Number/Application Code Manufacture (User Input) Number of Steps
Internal Determination Failsafe Position System Controller AS-i
Address Manufacture (User Input)
[0140] The manufacture of each valve enters a valve model
number/application code into the valve control module. The valve
model number identifies the respective valve attached to the valve
control module. Using the valve model number, the system controller
can obtain information relating to the valve. The parameter(s)
provided from the system controller to the valve control module
includes the failsafe position parameter for the valve. This
parameter can be maintained at the system controller and at the
individual modules. Other parameters may be communicated from the
rack PLC 720 to the valve control module and not all parameters are
required for the valve control module in all constructions.
[0141] Referring again to Table 3, the parameter "AS-i Address" is
identified as a manufacturer or user input. The AS-i address
parameter is used by the network for promoting communication
between the system controller and the respective system branch
control module. The system controller can subsequently modify the
AS-i address parameter to allow for automatic addressing of the
attached device.
[0142] Additionally, the "number of steps" parameter is a parameter
established by the valve control module. For example, the "number
of steps" parameter is an internal calculation performed by
operating a stepper motor attached to the valve and determining the
number of steps performed by the stepper motor.
4 Table 4, Case Control Module (BCMCC) Configuration Data,
discloses the parameters maintained at the system branch control
module for one construction of the refrigeration system. Case
Control Module (BCMCC) Configuration Data Operating Parameter
Source Case Model Number Manufacture (User Input) Defrost Schedule
System Controller Discharge Air Temp Set Point System Controller
Defrost Type System Controller Number of Defrosts per Day System
Controller Discharge Air Temperature High Limit System Controller
Defrost Termination Temp System Controller Network Address
Manufacture (User Input) Number of Sensors Internal Determination
EEPR Attached Y/N Internal Determination Number of Steps Internal
Determination Failsafe EEPR Position System Controller Time and
Date System Controller
[0143] The manufacture of each case enters a case model number into
the respective BCMCC. The case module number identifies the case
model attached to the case control module. Using the case model
number, the rack PLC 720 can obtain information relating to the
case. For example, based on the case module number, the system
controller can obtain the specifications for the case. The rack PLC
720 communicates one or more operating parameters to the case
control module. Additionally, the rack PLC 720 can create and
provide one or more schedules to the case control module. The
parameters provided from the rack PLC 720 to the case control
module are identified in column two as "System Controller." Other
parameters may be communicated from the rack PLC 720 to the case
control module and not all parameters are required for the case
control module in all constructions.
[0144] Referring again to Table 4, some of the parameters are
established or calculated by the case control module. For example,
the "number of sensors" parameter is an internal calculation
performed by the case control module. For example and in one
construction, the case control module polls for sensors connected
to the module. Based on the response, the case control module can
determine how many sensors are connected to the module. Other
parameters determined internally at the control module include the
parameters: "EEPR attached Y/N" and "number of steps." For the
"EEPR Attached Y/N" parameter, the case control module polls
whether an EEPR is attached to the case control module. The "number
of steps" parameter is an internal calculation to determine the
number of steps an attached stepper motor includes. This
calculation is performed if the case includes an EEPR.
[0145] Referring again to Table 4, the parameter "Network Address"
is identified as a manufacturer or user input. It should be noted
that, for the construction shown in FIG. 7, the case control module
communicates with the system controller, via the PC interface, on a
RS-485 network using a modbus protocol. Therefore the network
address is not an AS-i address.
[0146] With reference to FIG. 7, the fan control module (BCFCM) is
a controller that activates/deactivates an attached fan. A table of
the parameters for the fan control module is not provided because,
for the construction shown, the BCFCM only activates or deactivates
the fan. However, the rack PLC 720 communicates with the fan
control module via the condenser slave module and AS-i master as
shown in FIG. 7 and as described above. Therefore, address
information is still communicated with the rack PLC 720 based on
the principals described herein.
[0147] FIGS. 17-21 include five tables that represent the
information communicated to and from the rack PLC 720. The table
1700 (FIG. 17) includes parameters associated with rack data. The
table 1800 (FIG. 18) includes parameters associated with suction
group data. The table 1900 (FIG. 19) includes parameters associated
with compressor data. The parameters in table 1900 are repeated for
each compressor of the refrigeration system. The table 2000 (FIG.
20) includes parameters associated with system data. The parameters
in table 2000 are repeated for each system branch of the
refrigeration system. The table in FIG. 2100 (FIG. 21) includes
parameters associated with condenser data.
[0148] As discussed earlier, before the refrigeration system (e.g.,
system 700) can operate, the network needs to map (or identify) the
components of the system before the components can communicate
among themselves. That is, the addressing system for the components
of the network needs to be in place before communication among the
network can occur. The rack PLC 720 and/or the PC interface 714
initiate call signals or requests to determine what elements make
up the communication network.
[0149] For example, the rack PLC 720 commands the attached AS-i
master 722 to scan what is attached to the AS-i master 722. In
response to call signals initiated by the AS-i master, each
compressor control module 48 (or 1500), system branch module 724,
and valve module 726 responds by communicating respective addresses
to the AS-i master. Based on the result, the AS-i master 722
informs the rack PLC 720 how many modules are attached to the AS-i
master 722 and provides addresses to the rack PLC 720 allowing the
rack PLC 720 to communicate with the control modules via the AS-i
master 722. Similarly, the rack PLC 720 and/or PC interface 714
obtains addressing information from the condenser slave controller
732, and third party controls 724 and 748. Additionally, the rack
PLC 720 and/or PC interface 714 can obtain addressing information
from the local HMI 754, remote HMI 752, wireless hub 713, local
workstation 704, local network server 702, remote workstation 706,
etc. The rack PLC 720 can then build a map of the refrigeration
system 700 as a result of this information.
[0150] Once the communications network is established, the rack PLC
720 begins developing refrigeration system 700. In general,
parameter information is communicated among components of the
system, resulting in the rack PLC 720 configuring the system. The
rack PLC 720 requests a module to identify the component (e.g.,
compressor, case, valve, condenser) attached to the module. For
example, each component can provide a model or ID number identify
the respective component. In response to receiving the information,
the rack PLC 720 obtains information stored from memory. The
information includes safety information, which is selectively
shared with the appropriate module(s). The information also
includes operation information (control parameters, schedules,
etc.), which is also selectively communicated to the appropriate
module(s). Further discussion about what how information is
obtained, where information is communicated, and where information
is stored is discussed in connection with FIG. 17-21.
[0151] With reference to tables 1700, 1800, 1900, 2000, and 2100,
the first column in each table 1700-2100 relates the parameters
associated with each data group. The second column of each tables
1700-2100 indicates the original source of the related parameter.
The different types of original sources include an operator
entering the data for the associated parameter (referred to as
"operator input"), a network query from the system controller to a
networked device (referred to as "network query"), a parameter
received from a control module (referred to as "BCVCM," "BCSBM,"
"BCCSCM," "BCMCC," or "BCFCM"), a parameter calculated using one or
more pieces of information already obtained (referred to as
"calculated"), and a parameter obtained from memory (referred to as
"case database" or a variation thereof). For example, the "rack
name" parameter of the rack data table 1700 identifies the operator
as providing the necessary information. The "number of systems (n)"
parameter of the rack data table 1700 is obtained by the rack PLC
720 performing a network query to determine the number of branch
systems attached to the rack PLC 720. The "main liquid valve type"
parameter of the rack data table 1700 is obtained from the valve
control module 726. The "suction pressure set point" parameter of
the suction group data table 1800 is a calculated parameter based
on refrigerant type and case discharge air set point. Equations
known to one skilled in the art can be used to calculate the
suction pressure set point. The "operating current data" parameter
of the compressor data table 1900 is obtained from a database
stored at the PC interface 714. Other parameters within the tables
1700-2100 are obtained using similar methods.
[0152] The data and/or information for each parameter is obtained
sequentially and is obtained in approximately the order as shown in
FIGS. 17-21. However, as also discussed, the order of obtaining the
information can vary. Regardless of the order, tables 1700-2100
identify the parameters communicated to and from the rack PLC 720
for one configuration of the refrigeration system 700.
[0153] The third and fourth columns 1700-2100 identify whether the
parameter is manually entered or automatically obtained.
[0154] The fifth column identifies where each parameter is stored,
and identifies from where the parameter is initiated and to where
the parameter is communicated. As used within tables 1700-2100, the
symbol "C" identifies the parameter being stored at the PC
interface 714. The symbol "P" identifies the parameter being stored
at the rack PLC 720. The symbol "M" identifies the letter being
stored at a device control module. The symbol "AM" identifies the
parameter being stored at the AS-i master 722. The symbols ">"
and "<" identify the flow of the communication (i.e., "source
>destination" and from "destination<source").
[0155] For example, the "rack name" parameter of table 1700 is
maintained at both the PC interface 714 and the rack PLC 720.
Additionally, the rack name is originally entered at either the PC
interface 714 or the system controller 720, and is subsequently
communicated to the other processing units.
[0156] For another example, the "compressor model number" parameter
originates at the compressor control module 48 (or 1500) and is
communicated to the rack PLC 720. From the rack PLC, the compressor
model number is communicated from the rack PLC 720 to the PC
interface 714.
[0157] For yet another example, the "number of systems (n)
parameter" parameter is obtained during a network query, and is
communicated from the AS-i master 722 to either the PC interface
714 or the rack PLC 720 and then is shared to both the PC interface
714 and the rack PLC 720. Other parameters of tables 1700-2100 are
communicated similarly. Before proceeding further, it should be
noted that the tables 1700-2100 present one construction for the
refrigeration system. The parameters used, the source of the
parameters, how the information is obtained for each parameter, the
storage location for each parameter, and how a parameter is
calculated (if necessary) can vary for other constructions.
Moreover, it is envisioned that not all of the parameter shown in
tables 1700-2100 may be used and other parameters can be added.
Also and as discussed earlier, while the rack PLC 720 and PC
interface 714 are shown as separate components, it is envisioned
that these components and/or functions performed by these
components can be combined or divided differently. Therefore, other
constructions of the refrigeration system can affect the tables
1700-2100.
[0158] The last column of each table 1700-2100 identifies the
parameters necessary for calculating a value or limit.
[0159] Once the refrigeration system 700 is configured, the system
can begin operation. Of course, one or more subsystems can begin
operation (before operation of the refrigeration system as a whole)
as the necessary information for operating the subsystem(s) is
obtained at the subsystem(s). Once operation of the refrigeration
system 700 begins, the system can perform a subsequent
configuration. Reasons for a subsequent configuration include an
alarm resulting in the deactivation of a device or subsystem, the
operator changing the refrigeration system (e.g., adding a
component such as adding a compressor), and the refrigeration
performing a periodic update or review.
[0160] For example, if a compressor 14 is added or removed from the
system 700, the operator can inform the rack PLC (e.g., via the PC
interface 714) to perform a new configuration for the whole system.
Alternatively, the operator can have the system controller update
the existing configuration in view of the added component. As
another example, the system can perform all of or a portion of the
configuration process as part of a periodic maintenance
program.
[0161] As yet another example, the system can perform all of or a
portion of the configuration process when an alarm is detected at
the component level. For example, the device controllers receive
the safety parameters for the device. When a sensed value of a
safety parameter is outside of a sensed limit, the device
controller generates an alarm and deactivates the device. The
alarm, the parameter causing the alarm, the value of the parameter,
and the time and date of the alarm is communicated to the rack PLC.
Upon receiving the alarm, the rack PLC 720 can perform all or a
portion of the configuration process to update the system in view
of the alarm. For example, if a compressor control module 48 (or
1500) detects an alarm condition, the rack PLC 720 can reconfigure
the run pattern of the compressors 14 (discussed earlier) in view
of the deactivation of the faulty compressor. Other aspects of the
refrigeration system can be reconfigured when an alarm is generated
by a device. That is, depending on the location of the error, the
rack PLC 720 will reconfigure the appropriate operation for the
component, related components, and/or related subsystems (generally
referred to as applicable components), which relate to the
alarm.
[0162] In another example, when a component does fail and require
replacement, the replacement of the component may result in a new
or different device controller being added to the system. The
system controller identifies that a device controller has been
removed and identifies a new controller has been installed. The new
device controller may be the same type as the replaced controller.
If the new component/controller is the same as the replaced
component/controller, then the new device controller can be
configured the same as the old controller. If the new/component
controller is different than the replaced/component controller,
then the system controller can reconfigure the portion of the
refrigeration system including the new device controller.
Additionally, the system controller can modify the control
parameters of other modules/components to preempt a trending
condition that could cause alarm in a single offending module.
[0163] Before proceeding further, it is envisioned that in one
construction of the refrigeration system, the rack PLC 720 can
detect the likelihood of an alarm not yet detected at the component
level using data acquired from multiple systems. More specifically,
the rack PLC 720 obtains acquired data from multiple devices. Based
on acquired data from a first device, the rack PLC 720 can
speculate eventual damage to a second device. The rack PLC 720 can
generate an alarm condition resulting in the deactivation of the
first and/or second device, reconfigure the refrigeration system,
and communicate the alarm to the high-level devices.
[0164] It should also be noted that while operations of the system
are described above, the order of operation could vary. That is,
the refrigeration system is a complex system having many parameters
(or variables), components, subsystems, etc. Because of the
flexibility of the distributed system, a skilled artisan in the
field of refrigeration can vary when various operations discussed
herein are performed. Therefore, the invention is not limited to
the order of operations discussed herein.
[0165] FIG. 8 is a block diagram of aspects of the integrated
distributed intelligence control system of FIG. 7. FIG. 8
illustrates the use of wireless interfaces between the first field
bus control network 716, the second field bus control network 730,
and the third field bus control network 740. Further, FIG. 8
illustrates locating one or more case controllers (e.g., BCMCC 802)
remote from communication bus 741. Finally, FIG. 8 also illustrates
locating additional valve controllers (e.g., BCVCM 804, 806) on
communication bus 741 and remotely.
[0166] In the partially wireless system depicted in FIG. 8, an MPI
compatible RF interface is used to facilitate communications
between rack PLC 720 and condenser PLC 732, and between rack PLC
720 and remote HMI 752. More particularly, rack PLC 720
communicates via a wire-based MPI interface 731 with a first MPI
compatible RF transceiver 810. It is believed that DECT compliant
devices (e.g., DECT Engine MD 32), available from Siemens, can be
used to facilitate an MPI compatible wireless interface. A second
MPI compatible RF transceiver 812 is associated with condenser PLC
732. Similarly, a third MPI compatible RF transceiver 814 is
associated with remote HMI 752.
[0167] As explained above with regard to FIG. 7, it is preferable
in some constructions to use a LonWorks.RTM. compatible bus system
for the third field bus network 740. This is because such
compatibility is believed to facilitate connectivity and
interoperability with third party controls 746 and 748. Further,
such a bus typically enjoys a range (i.e., the reliable length of
the bus) that exceeds the recommended range of the AS-i standard.
Accordingly, in the construction illustrated in FIG. 8,
LonWorks.RTM. compatible RF interfaces 818, 820, and 822 are used
for communications between rack PLC 720, remote case controller 802
(BCMCC 802) and remote valve controller 806 (BCVCM 806). More
particularly, the RF interfaces 818, 820, and 822 comprise narrow
band RF transceivers, such as RF to Twisted Pair Routers for
LonWorks.RTM. (also referred to as an RF/TP-49 Router).
[0168] As can now be appreciated from the constructions illustrated
in FIGS. 7 and 8, rack PLC 720 operates as a master device and
communicates with various slave control devices via a plurality of
network interfaces. For example, rack PLC 720 communicates with
local device-level controllers (BCSBM 724, BCCSCM 48 (or 1500), and
BCVCM 726) via local AS-i bus 728. Rack PLC 720 communicates with
condenser PLC 732 to control fan controller (BCFCM 736) and fan(s)
830 via an MPI compatible RF interface comprising a hard wired MPI
interface 731 between rack PLC 720, local RF interface 810, and
remote RF interface 812. Rack PLC 720 communicates with case
controllers BCMCC 744 and 802 via communication bus 741, and a
wireless link established between RF interfaces 818 and 820.
Likewise, rack PLC 720 communicates with valve controllers BCVCM
804 and 806 via communication bus 741, and a wireless link
established between RF interfaces 818 and 822.
[0169] FIG. 9 is a block diagram of a bus compatible refrigeration
branch control system 900, suitable for use as part of a
refrigeration system, including the systems depicted in FIGS. 7 and
8. A refrigeration branch includes a number of refrigeration units
(e.g., display cases, cold storage rooms, and the like) sharing a
common closed-loop refrigeration control path. As illustrated
construction of FIG. 9, the refrigeration branch control system 900
includes a Bus Compatible System Branch Module BCSBM 724, which is
constructed and arranged for communication with rack PLC 720 via
field bus control network 728 (e.g., a local AS-i bus). It should
be understood that multiple BCSBMs could be employed in a
refrigeration system having multiple refrigeration branches. For
convenience, the operation of one construction of a bus compatible
refrigeration branch control system (e.g., system 900) will be
described with respect to a system having only a single
refrigeration branch. It is also to be understood that the
disclosure herein may be scaled to accommodate systems employing
multiple refrigeration branches. The Appendix hereto identifies one
hardware configuration for a BCSBM. Briefly stated, for the
construction shown, the BCSBM comprises a processing capability and
a data storage capability.
[0170] BCSBM 724 effects branch control by controlling the
operation of a plurality of solid-state relay devices (SSRs). Such
SSRs may include, for example, a suction stop SSR 902, a liquid
line SSR 904, and a gas defrost SSR 906. In the construction
illustrated in FIG. 9, BCSBM 724 individually controls each of the
SSRs 902, 904, and 906. For example, BCSBM 724 controls the suction
stop SSR 902 via a first defrost control signal 910. Similarly,
BCSBM 724 controls the liquid line SSR 904 via a
temperature/refrigeration control signal 912. BCSBM 724 also
controls the defrost SSR 906 via a second defrost control signal
914. In one construction, each of these control signals 910, 912,
and 914 comprises an on/off signal, directing the associated SSR to
be either open circuited (non-conducting) or close circuited
(conducting). It should be understood that each of the SSRs 902,
904, and 906 is connected to an associated control valve (valves
not shown) such that when the corresponding control signal 910,
912, or 914 is asserted, the SSR conducts and the associated
control valve is opened or closed, as appropriate. Finally, BCSBM
724 controls an electronic evaporator pressure regulator valve
(EEPR valve) 920 associated with the refrigeration branch via a
control line 922. Of course, other devices can be used in place of
the SSRs.
[0171] Advantageously, the BCSBM 724 provides for distributed
control of refrigeration and defrost cycles of an associated
refrigeration branch. For example, in one construction, temperature
control for a branch is achieved by positioning the associated EEPR
valve 920. Case/fixture temperature(s) (e.g., discharge air
temperature) is/are provided to rack PLC 720 by a bus compatible
modular case control subsystem (e.g., BCMCC 744, which is described
in greater detail below with respect to FIGS. 11-13). As such, the
system does not require wiring a separate, additional temperature
sensor for branch control because existing temperature data is made
available to BCSBM 724 via BCMCC 744 and rack PLC 720. Based on the
provided temperature information, rack PLC 720 transmits the
desired set point to BCSBM 724 over local field bus network 728.
BCSBM 724 then drives EEPR valve 920 to the desired setting via
control line 922. In another construction, case temperature, door
open/close, and defrost termination inputs are added to the BCSBM
724. This allows for operation of branch systems without the need
of feedback from the BCMCC 744.
[0172] BCSBM 724 can also affect a degree of temperature control by
cycling the liquid line solenoid via the liquid line SSR 904. In
this regard, rack PLC 720, in one construction, receives discharge
air temperature readings from one or more display cases being
cooled by the refrigeration branch. Such temperature information
originates from one or more bus compatible modular case
controllers, as described below. Based on the received temperature
information, rack PLC 720 provides liquid line commands to BCSBM
724 over local field bus network 728. BCSBM 724 thereafter cycles
liquid line SSR 906 via temperature/refrigeration control line
912.
[0173] In another construction, case temperature, door open/close,
and defrost termination inputs are added to the BCSBM 724. This
allows for operation of branch systems without the need of feedback
from the BCMCC.
[0174] Referring still to FIG. 9, BCSBM 724 can also be used for
defrosting an evaporator coil associated with the refrigeration
branch. For example, in one construction, rack PLC 720 determines
the defrost scheduling for each branch. When a particular branch is
scheduled to commence a defrost cycle, rack PLC 720 instructs BCSBM
724 to begin the defrost cycle. BCSBM 724 thereafter drives the
first defrost control line 910 to cause the suction stop SSR 902 to
operate the suction stop solenoid so as to cut off the
refrigeration cycle. At or about the same time, BCSBM 724 also
drives the second defrost control line 914 to cause the gas defrost
SSR 906 to open a gas defrost solenoid that allows a gas (e.g., hot
gas) to flow through the evaporator coil and through a check valve
associated with the liquid line solenoid--in effect, operating the
system in reverse. It is to be understood that the use of a hot gas
defrost cycle reflects an exemplary construction only; the system
can be employed with cool gas defrosting, electric defrosting, and
other known methods of defrosting. When the defrost cycle is
complete (which may be determined on the basis of time or
temperature or other criteria), rack PLC 720 sends an appropriate
message to BCSBM 724 to terminate the defrost cycle and begin a new
refrigeration cycle.
[0175] At the end of a defrost cycle, it may be desirable to
initiate a drip cycle in which condensate on the coil is allowed to
drip off and flow out through a drain. If a drip cycle desired,
rack PLC 720 sends an appropriate command to BCSBM 724 at the end
of the defrost cycle. Rather than start a new refrigeration cycle,
however, BCSBM 724 removes the second defrost control signal 914
thereby causing the gas defrost SSR 902 to open the gas defrost
solenoid, while BCSBM 724 continues to apply the first defrost
control signal 910 and maintain the suction stop solenoid in the
closed position, via suction stop SSR 902. This continues until the
drip cycle terminates.
[0176] Similarly, when a fixture/case associated with the
refrigeration branch is being cleaned or subject to a maintenance
action, it is not normally desirable to operate a refrigeration
cycle. Therefore, in such a mode, rack PLC 720 sends a command to
BCSBM 724, which causes suction stop SSR 902 to close the suction
stop solenoid.
[0177] Referring still to FIG. 9, modular branch control system 900
provides, in one construction, a degree of back-up capability,
thereby improving overall system robustness, should one or more
components fail. For example, if communication with rack PLC 720 is
lost, BCSBM 724 is constructed and configured so that it maintains
the recent refrigeration and defrost set point and cycle
information. Thus, the refrigeration branch remains operable
despite the loss of communications with rack PLC 720. Also, when
multiple branch control modules are employed to control multiple
refrigeration branches, it is preferable that only one branch be in
a defrost cycle at any given time. Normally, this scheduling is
coordinated by rack PLC 720. In the event that communications with
rack PLC 720 are lost, however, each branch controller preferably
continue to operate on its prior schedule so that the defrost
cycles continue to run at non-overlapping times, despite the loss
of communications with rack PLC 720.
[0178] Similarly, if the temperature associated with one or more
display cases in the branch is being controlled by a local case
controller (e.g., a BCMCC as illustrated in FIG. 11) and that local
case controller fails, BCSBM 724 can maintain a degree of
temperature control by cycling liquid line SSR 904, in a manner
similar to that described above.
[0179] FIG. 10 is a block diagram of a commercial refrigeration
system that is compatible with the systems depicted in FIGS. 7 and
8, including multiple bus compatible valve controllers. The
commercial refrigeration system illustrated in FIG. 10 includes one
or more Bus Compatible Valve Control Modules (BCVCMs) 726, 804, and
806.
[0180] Each of the BCVCMs 726, 804, and 806 is constructed and
arranged, in one configuration, to control an electronically
controlled valve associated with the commercial refrigeration
system. For a more specific construction, each BCVCM is constructed
to receive at least one valve position signal and provide at least
one valve drive signal. In one construction, each BCVCM provides a
stepper drive output for driving a stepper-motor controlled valve.
It is to be understood, however, that the system can be modified
for use with other types of valves, such as solenoid controlled
valves. A non-exhaustive list of the types of refrigeration system
valves that may be controlled in accordance with the distributed
intelligence control system include, for example, heat reclaim
valves, electronic evaporator pressure regulator valves (e.g., EEPR
valves using a stepper-motor rather than a solenoid valve),
flooding valves, main liquid pressure reduction valves, receiver
pressure regulator valves, surge receiver control valves, split
condenser valves, defrost control valves, secondary cooling control
valves, oil control and separation valves, and electronic expansion
valves (e.g., in a display fixture or a subcooler). Other examples
of systems and valves adapted to be controlled by the system may be
found in U.S. Pat. Nos. 3,343,375, 4,478,050, 4,503,685, 4,506,523,
5,440,894, 5,743,102, 5,921,092, and 6,067,482, each of which is
incorporated herein by reference. The Appendix hereto identifies
one hardware configuration for a BCVCM.
[0181] The first BCVCM 726 will be used here as an example. As
illustrated in FIG. 10, BCVCM 726 is configured to control an
electronic expansion valve associated with a subcooler in a low
temperature refrigeration branch. Those skilled in the art will
recognize that subcoolers may be used to improve system efficiency
by helping to shift some of the total system load from low
temperature branches to medium or high temperature compressors.
First BCVCM 726 communicates directly with rack PLC 720 via field
bus control network 728 (e.g., a local AS-i bus) to control the
operation of a first electronically controlled valve 1002. The
first BCVCM 726 determines the position of the first electronically
controlled valve 1002. This step is illustrated schematically as a
line 1004 (see also lines 1014 and 1024). In one construction, no
physical valve position feedback lines are required. Rather, each
electronically controlled valve (e.g., valve 1002) is a
stepper-motor controlled valve. The associated BCVCM determines
valve position by keeping track of the number of steps the stepper
motor has moved relative to a known reference point (i.e., zero
point). In order to maintain control, the BCVCM periodically
calibrates the valve position by temporarily returning to the
reference point and moves the valve to the last commanded position
(step) relative to the reference point. With the current position
of the valve known, first BCVCM 726 provides the valve position
information to rack PLC 720 via control network 728. Similarly,
rack PLC 720 provides a desired valve position signal to first
BCVCM 726 via control network 728. Upon receipt of the desired
position information, first BCVCM 726 provides a valve drive signal
to the first electronically controlled valve 1002, via line 1006,
to position the valve in the desired position.
[0182] The operation and control of the second BCVCM 804, a second
valve 1012, and lines 1014 and 1016 is substantially similar to the
operation of the first BCVCM 726. The second BCVCM 804 illustrated
in FIG. 10, however, is not located on field bus control network
728. Rather, BCVCM 804 is located at a position sufficiently remote
from rack PLC 720 to require a different bus, such as field control
bus 741 (e.g., a LonWorks.RTM./Echelon bus). Likewise, the third
BCVCM 806 operates substantially similarly to the first and second
BCVCMs 726 and 804, except that BCVCM 806 communicates with rack
PLC 720 via a wireless RF interface (as also illustrated in FIG.
8).
[0183] As can now be appreciated, employing valve controllers such
as BCVCMs 726, 804, and 806 facilitates distributed control of the
total refrigeration system and minimizes the amount of high power
wiring required to provide integrated control of a plurality of
system valves.
[0184] It should be understood that while FIG. 10 illustrates a
system having three BCVCMs-BCVCM 726 located on a local AS-i bus,
BCVCM 804 located on bus having a relatively longer distance
capability (e.g., control bus 741), and BCVCM 806 located on an RF
compatible bus-the system is not limited to such an arrangement.
Rather, a BCVCM may be used with each motor-driven valve requiring
independent monitoring and control. Examples of such motor driven
valves are provided in the Appendix.
[0185] FIG. 10A is an exemplary schematic of a construction related
to peer-to-peer control/communication. More particularly, FIG. 10A
illustrates peer-to-peer communications between a case controller
configured as a fixture/display monitor (e.g., BCMCC 744; see also
FIGS. 11-13) and a valve controller configured to control an
evaporator valve associated with a subcooler on a low temperature
refrigeration branch. A liquid temperature probe (e.g., digital
case sensor 1102) is installed at the inlet to each expansion valve
or, alternatively, at the liquid line inlet to each case/fixture
lineup (not shown). The liquid line probe provides digital
temperature data to the case controller (BCMCC 744), which provides
the temperature data to rack PLC 720. Rack PLC 720 supplies an
evaporator valve control command to the valve controller (BCVCM
726) which causes the valve controller to drive valve 1002 to the
desired position. Alternatively, the valve controller can be
programmed to determine the correct position of valve 1002 based on
temperature data passed to it by case controller 744, via rack PLC
720.
[0186] FIGS. 11-13 are block diagrams of aspects of a commercial
refrigeration system according to FIGS. 7 and 8, including various
system configurations providing bus compatible modular case
monitoring and/or control. Briefly stated, FIG. 11 illustrates a
system using bus compatible modular case controller (e.g., BCMCCs
744 and 802) to provide case monitoring and control functions for a
plurality of refrigeration display cases (not shown in FIG. 11).
Similarly, FIG. 12 illustrates a modular case control system 1200
configured to provide case monitoring information for use by a
system controller, such as, rack PLC 720, or third party controller
746 (FIG. 7). Finally, FIG. 13 illustrates the use of a modular
case control system 1300 to provide branch control for a plurality
of display cases comprising a refrigeration branch.
[0187] Referring now to FIG. 11, a first BCMCC 744 is constructed
and arranged to communicate with rack PLC 720 via control bus 741
(e.g., a LonWorks.RTM./Echelon bus as shown in FIG. 7). A second
BCMCC 802 is constructed and arranged to communicate with rack PLC
720 via a wireless RF interface (see also FIG. 8). It should be
understood that FIG. 11 is provided for exemplary purposes only; a
given commercial refrigeration installation may include one or a
plurality of BCMCCs, each having either a hard wired or wireless
interface with a controller such as rack PLC 720 or third party
controller 746.
[0188] Each BCMCC, in one construction, comprises a control unit
(also referred to as a control module) and, possibly, one or more
display units (also referred to as display modules). The control
unit is responsible for network communications (e.g., control unit
744A communicates with rack PLC 720 via control bus 741). The
control unit also includes a stepper drive output for controlling
an EEPR valve. The display unit receives sensor data from one or
more associated sensors and controls the power switching of various
fans, anti-sweat heaters, lights, and defrost heaters via an
associated power switching module. As will be made clear by
reference to FIGS. 12 and 13 below, one control unit can control
multiple display units via a serial link. For example, in one
construction, one control unit is capable of interfacing with up to
eight distinct display units. Thus, although FIG. 11 illustrates a
configuration having one display unit per control unit, such a
configuration is not required by the refrigeration system. Each
control unit and display unit, in one construction, includes a data
processing capability, as well as a data storage capability.
[0189] Using BCMCC 744 as an example, a display unit 744A receives
temperature information from one or more digital case sensors 1102.
In one construction, the digital case sensors 1102 are constructed
such that they are individually addressed and provide case
temperature data to BCMCC 744 in digital form over a single wire
harness 1103. For example, a plurality of digital case sensors 1102
provide digital temperature data with respect to each display case
controlled by BCMCC 744. It is to be appreciated that one or more
digital case sensors 1102 may be used with each case. Display unit
744B provides the digital temperature data to control unit 744A.
Control unit 744A supplies the temperature data to rack PLC 720 via
control bus 741. Rack PLC 720 uses the temperature data, along with
other system information, to determine appropriate display case
control activities. Further, based on system data, including this
temperature data, rack PLC 720 determines an appropriate set point.
The desired set point is transmitted to control unit 744A, which
adjusts the EEPR valve 1104 accordingly. Rack PLC 720 also
determines when a particular case requires a defrost action, fan
control action, or lighting action. Using case lighting as an
example, rack PLC 720 preferably determines when a particular case
is to be illuminated and provides an appropriate command to control
unit 744A, which relays the command to display unit 744B. Display
unit 744B asserts a signal on line 1116 to cause a power switching
module 1106 (also referred to as a power module) to activate the
light(s) of the associated case(s). Similar control actions are
taken for defrost cycling (via line 1112) and fan control (via line
1114). Anti-sweat control actions (e.g., for anti-sweat heaters
associated with display fixtures having reach-in doors) are also
accommodated by the display unit and power switching module. It is
noted, however, that many newer display fixtures do not require
complicated anti-sweat controls.
[0190] Advantageously, each power module (e.g., power module 1106)
can also serve as a local source of power for each BCMCC (including
both the control module and the display module). For example, local
AC power (not shown) is supplied to BCMCC 744. Power module 1106
converts the local AC power to DC power for use by BCMCC 744.
Accordingly, the only wiring used to interface between a BCMCC with
other devices in the control system (e.g., rack PLC 720) is
relatively low power signal wire, some of which may be replaced by
wireless interfaces, as explained herein.
[0191] When a BCMCC (e.g., BCMCC 744) is configured to control the
power switching of display case activities (e.g., anti-sweat,
defrost, fan, or lights), a separate power module (e.g., power
module 1106) is, in one construction, provided with each display
unit, as shown in FIG. 11. If, however, a BCMCC is not used to
control power switching of display case activities, only a single
power module is used for each control unit associated with the
particular BCMCC. This aspect of the system is illustrated in
greater detail with respect to FIGS. 12 and 13 below.
[0192] Although in the constructions illustrated in FIGS. 7, 8, and
11 each BCMCC is ultimately controlled by a master controller
(e.g., rack PLC 720), one or more BCMCCs in a given refrigeration
control system can optionally be configured for peer-to-peer
control/communication. Hence, multiple BCMCCs can share temperature
data, time data, defrost scheduling data, and the like to improve
system efficiency. For example, by sharing information regarding
defrost timing, each BCMCC on a given circuit can wait until all
displays finish defrosting before starting a refrigeration cycle.
By sharing information, such as current defrost status information,
each BCMCC is capable of initiating coordinated defrost cycles to
maintain minimum refrigeration load requirements and/or ensure
sufficient defrost gas (for gas defrost systems).
[0193] Advantageously, using the present modular case control
system also improves total system fault tolerance. In the event of
a network failure, such as the loss of communications with rack PLC
720, each BCMCC is, in one construction, configured to revert to an
internal schedule and attempt to provide temperature control by
determining the appropriate setting of its corresponding EEPR
valve. Using BCMCC 744 of FIG. 11 to illustrate this aspect, if
communication with rack PLC 720 is lost, BCMCC 744 attempts to
maintain display case(s) temperature at the most recent set point
by internally determining a desired setting for EEPR valve 1104.
Similarly, display unit 744B continues to provide power switching
control for display case activities on an internally derived
schedule.
[0194] An interface device 750 (e.g., a wireless device using an IR
interface) supplies a capability to read and set case/fixture
specific data. As described above with respect to FIG. 7, interface
device 750 comprises a remote keypad for use with display unit 744B
to access temperature data and/or to input set point data. Thus, it
is possible to input and monitor set point data and other data
associated with a display case using a BCMCC without the use of a
master system controller, such as rack PLC 720. It should be
understood, however, that when a master controller is present, such
controller would preferably override any user set points entered
via interface device 750.
[0195] Optionally, each display unit (e.g., display unit 744B) can
receive one or more general purpose switch inputs. For example, a
door open/closed input 1150 can be supplied to display unit 744B
when the display unit is used with a walk-in freezer. Display unit
744B could use the door open/closed input 1150 as an indication to
turn off the fan(s) (via line 1114 and power switching module 1106)
whenever the door is open. Likewise, if door open/closed input 1150
may be used to set an alarm condition, including an audible alarm,
if a door is left open longer than a threshold time (e.g., 5
minutes). Other possible switch inputs include a defrost
temperature probe (not shown) that provides a discrete switch
signal at a preset temperature, indicating that a defrost cycle may
be terminated.
[0196] Referring still to FIG. 11, the operation of BCMCC 802 is
substantially similar to that of BCMCC 744. The primary difference
between BCMCC 744 and BCMCC 802 is that the latter illustrates the
possibility of using a wireless RF interface for communications
between rack PLC 720 and BCMCC 802.
[0197] FIG. 12 illustrates the use of a modular case control system
(BCMCC 1200) configured to provide fixture/case monitoring
capabilities, but not case control capabilities. In describing FIG.
12, other advantageous aspects of modular case monitoring and
control using a BCMCC will become apparent. The BCMCC 1200 is
arranged to receive sensor data from a plurality of digital case
sensors (1205, 1207, and 1209) via a plurality of display units
(e.g., display units 1204, 1206, and 1208) over a common digital
data transmission channel/line 1212. Such sensor data, in one
construction, comprises digital temperature data, as described
above with regard to FIG. 11. A single power module 1210, provides
power to a single control unit 1202, as well as to all associated
display units (1204, 1206, and 1208) and the sensors (1205, 1207,
and 1209). Each display unit associated with BCMCC 1200 provides
the sensor data to the control unit 1202. Thus, only one control
unit is needed to interface with a plurality of display units in
the configuration illustrated in FIG. 11. The control unit 1202
supplies the sensor data received from the display units to rack
PLC 720 or, alternatively, a third party controller (e.g., third
party control 746 of FIG. 7). Rack PLC 720 can use this information
to control, among other things, a compressor (e.g., using BCCSCM
48), a branch valve (e.g., using BCSBM 724), another system valve
such as an EEPR valve (e.g., using BCVCM 726), or a condenser
(e.g., using BCFCM 736), to achieve temperature control of the
cases associated with system 1200.
[0198] The configuration illustrated in FIG. 12 can also be used to
illustrate another example of how peer-to-peer communication and
control are made possible by the use of the distributed
intelligence control system. An associated digital case sensor can
determine the discharge air temperature of each case being
monitored by BCMCC 1200. In other words, the discharge air
temperature of a first display case in a fixture lineup is
monitored by a first digital case sensor (e.g., one of sensors
1205) and provided to control unit 1202 by the first display unit
1204. Differences between control units and display units are
discussed above with respect to FIG. 11. Similarly, the discharge
air temperature of the second display case is monitored by a second
digital case sensor (e.g., one of sensors 1207) and provided to
control unit 1202 by the second display unit 1206. This process is
repeated for each display unit in the lineup. Control unit 1202
provides the discharge air temperature data to rack PLC 720 over
the control network. Rack PLC 720 uses this temperature data to
control a liquid line solenoid, via a branch control module (e.g.,
BCSBM 724) as described above with respect to FIG. 9 to achieve
temperature control for the case lineup associated with system
1200.
[0199] Another of the many advantages of the distributed
intelligence control system can be appreciated by reference to the
modular case monitoring system illustrated in FIG. 12. A single
control unit 1202 can be used to monitor a plurality of display
units (e.g., display units 1204, 1206, and 1208), but each of the
displays/fixtures associated with such display units need not
necessarily be on the same refrigeration branch. For instance, if
display units 1204 and 1206 are associated with fixtures on a low
temperature branch and display unit 1208 is associated with a
fixture on another branch, each branch can operate on separate
(preferably non-overlapping) defrost schedules (which in the case
monitoring configuration illustrated in FIG. 12 can be controlled
at the rack by a branch control module or a valve control module).
Because the system uses distributed intelligence, control unit 1202
receives information from rack PLC 720 to allow each display to
correctly reflect the defrost status of the branch with which it is
associated. Thus, using the example above, if the low temperature
branch were in a defrost cycle, display units 1204 and 1206 would
display a status message indicating as such, while display unit
1208 would continue to display present case temperature
information. Accordingly, high degrees of case monitoring and
display granularity are maintained despite the fact that only one
control unit is used.
[0200] FIG. 13 is a block diagram that illustrates a branch control
system using a modular case control system 1300 for branch control
functions. As illustrated in FIG. 13, the BCMCC 1300 includes a
control unit 1302 controlling a plurality of display units 1306,
1308, and 1310. A power module 1316 provides a local source of
power for BCMCC 1300. The control unit 1302 receives control
commands from rack PLC 720 or, alternatively, a third party
controller. Control unit 1302 also determines valve position
information from an EEPR valve 1304 and provides stepper motor
commands to position the EEPR valve 1304 in accordance with
commands from rack PLC 720 (or third party controller). In one
construction, control unit 1302 determines the valve position of
EEPR valve 1304 by monitoring the number of steps applied and
comparing that number to a known starting reference. Periodically,
the stepper motor may be "re-zeroed" to ensure proper control. When
using a BCMCC to provide branch control, the EEPR valve is, in one
construction, located with the display case(s) rather than at the
main rack with the rack PLC 720. Conversely, when branch control is
achieved using a branch control module (e.g., BCSBM 724 of FIG. 9)
or a valve control module (e.g., BCVCM 726 of FIG. 10), the EEPR
valve is, in one construction, located at the main rack with rack
PLC 720.
[0201] Referring still to FIG. 13, a commercial refrigeration
branch can include one or more display cases associated with the
display units 1306, 1308, and 1310. A central controller, such as
rack PLC 720, maintains branch control by monitoring various
parameters associated with the refrigeration system. Such
parameters can include, for example, temperature data, compressor
data, suction data, and the like. In the branch control system 1300
of FIG. 13, branch control is maintained by controlling the
position of EEPR valve 1304. More particularly, rack PLC 720
determines desired set points (e.g., discharge temperature) for the
case lineup associated with BCMCC 1300. Control unit 1302 receives
the set point information over the control network and determines
the appropriate position for EEPR valve 1304 to achieve the desired
set point(s). In particular, control unit 1302 includes a stepper
motor drive output connected to EEPR valve 1304 via line 1320.
Hence, upon receipt of the desired set point from rack PLC 720,
control unit 1302 determines the correct valve position and drives
EEPR valve 1304 to the desired position, thereby achieving the
desired branch control function.
[0202] FIG. 13 can also be used to illustrate another example of
how peer-to-peer control/communication is available with the
distributed intelligence refrigeration control system. If the
discharge, suction, or motor temperatures are high in every
compressor and the valve open positions according to the modular
case controllers in the system (e.g., BCMCC 1300) are not fully
opened, the compressor controller (e.g., BCCSCM of FIG. 7) sends a
signal to the respective control units (e.g., control unit 1302),
via rack PLC 720, to open the valves (e.g., EEPR valve 1304). If
successful, such control action(s) reduce internal compressor
temperatures and improve efficiency and compressor life expectancy.
Similarly, if compressor temperatures are lower than expected
(indicating, perhaps, a potential flood back condition that could
damage or ruin a compressor), the compressor controller will search
the system, via rack PLC 720, to determine which EEPR valves may be
open too far. Thereafter, the valves can be sequentially closed by
sending commands to the respective control units (e.g., control
unit 1302), via rack PLC 720.
[0203] It should be understood, that the BCMCC 1300 illustrated in
FIG. 13 could be modified to provide single case control as well.
In other words, BCMCC 1300 could be configured to provide complete
branch control, or single case control. It should further be
understood that one or more of the display units 1306, 1308, or
1310 can be configured to provide power switching control in a
manner described above with respect to FIG. 11. In such a
configuration, a power module would be required for each display
unit that provides power switching control (see FIG. 11).
[0204] As has been explained above, one of the advantages of the
distributed intelligence control system is the ease with which such
system is installed at a user site. The modular case control
concept, exemplary configurations of which are depicted in FIGS.
11-13, illustrates this point further. For example, each display
unit (e.g., display units 1204, 1206, 1208 of FIG. 12 or 1306,
1308, 1310 of FIG. 13) is, in some constructions, automatically
addressed by its associated control unit (e.g., control unit 1202
in FIG. 12 or control unit 1302 in FIG. 13). In other words, upon
installation of the system, the control unit automatically
determines how many display units are present, as well as their
address/location. More specifically, the control unit automatically
determines how many display units are attached. The display units
are, in one construction, connected in serial fashion (a serial
communication link from the control unit to the first display unit,
and then out of the first display unit and into the second display
unit, and so on).
[0205] In one construction, each display unit has the ability to
disable communications with all other display units that are
"downstream" of it on the serial communication channel/link. After
power up, all of the display units on a particular link are sent a
command to disable their individual communications outputs. At this
point, only the control unit and the first display unit are
communicating; remaining display units are "cut off." In this way,
the control module (e.g., control unit 1202 in FIG. 12) can now
uniquely associate a first address with the first display unit
(e.g., display unit 1204 in FIG. 12). After the first display unit
is addressed, the control unit instructs this first addressed
display unit to turn on its communications output, thereby
re-connecting the second display unit (e.g., display unit 1206 in
FIG. 12) to the link. Now the control module can uniquely associate
an address with the second display unit. This process is repeated
until all display units are addressed (e.g., until a communications
failure occurs indicating no more displays are present).
[0206] Further, each display unit, in one construction, polls each
digital case sensor (e.g., sensor 1102 of FIG. 11) associated with
that display unit to determine the location of the sensors and
type, thereby associating a unique identification/address for each
such sensor. The sensor location and type information is forwarded
to the control unit associated with that display unit. In one
construction, each digital case sensor to be used in a given
case/fixture is configured in a wire harness prior to installation.
Each sensor, in one construction, includes a memory (e.g., an
EEPROM) that is preprogrammed with a number that uniquely
identifies the type of sensor (e.g., discharge air temperature,
return air temperature, inlet temperature, outlet temperature,
product temperature, and so on), as well as the location in the
case in which it will be installed (e.g., left side, center, right
side). In this way, the system is automatically configured upon
installation, and end users and'system installers are not presented
with the complexity of programming/addressing the system at
installation time. The digital case sensors are preferably located
to provide temperature information that facilitate specific control
functions. Such sensors include, for example, discharge air
temperature sensors, return air temperature sensors, product
temperature sensors, inlet and outlet refrigeration line
temperature sensors, and defrost terminate sensors (e.g., sensors
located on the evaporator or in the airstream).
[0207] FIG. 14 is a block diagram that helps to illustrate several
of the many advantages of using a distributed intelligence
refrigeration control system. FIG. 14 is described by way of a
specific example including a fixture using modular case control
(see FIGS. 11-13). This description is for illustrative purposes
only, and should not be construed as limiting the scope of the
invention.
[0208] A master controller 1402 (e.g., rack PLC 720) communicates
with a subsystem controller 1406 (e.g., BCMCC 744) over a
communication channel 1404. For one construction, the only wiring
between the master controller 1402 and the subsystem controller
1406 is the communication channel 1404; no separate power wiring
between them is required. Hence, master controller 1402 and
subsystem controller 1406 receive power locally, thereby reducing
the installation complexity of the system. Indeed, if communication
channel 1404 is a wireless channel, no wiring is required between
master controller 1402 and subsystem controller 1406.
[0209] Each subsystem controller 1406 in the system is, in one
configuration, constructed and arranged to operate one or more
subsystem controlled devices 1408 (e.g., an EEPR valve, a solenoid
valve, a solid state relay, a power switch, and the like) over one
or more control lines 1410. Thus, where multiple wiring runs may be
necessary to provide specific control actions, only local wiring is
required. In other words, long runs of control wiring are not
required between the master controller and the subsystem control
device. For example, an EEPR valve associated with a fixture line
up is controlled locally; there is no direct control wiring between
the EEPR control valve and the master controller.
[0210] Similarly, some subsystem controllers in the system are
constructed and arranged to receive sensor input data, at a local
level, from subsystem sensors 1412 over one or more sensor data
busses 1414. For example, a plurality of subsystem sensors 1412
(e.g., digital case sensors 1307 of FIG. 13) provide case
temperature data with respect to a plurality of case monitoring
locations. In this example, subsystem sensors 1412 are constructed
and arranged to communicate with subsystem controller 1406 (e.g.,
display unit 1306) over a sensor data bus 1414 (e.g., a single
twisted pair communication bus). Subsystem controller 1406
transmits the sensor data to master controller 1402 over
communication channel 1404 (e.g., display unit 1306 transmits the
data to control unit 1302, which transmits the data to rack PLC
720). Thus, master controller 1402 receives remote sensor data
without the need for installing complicated and lengthy wiring
between master controller 1402 and the remotely located subsystem
sensors 1412.
[0211] An Appendix hereto includes a series of tables that provide
additional information regarding specific aspects of one
construction of a commercial refrigeration control.
[0212] It is to be understood that the foregoing description, the
accompanying figures, and the Appendix have been given only by way
of illustration and example, and that changes and modifications in
the present disclosure, which will be readily apparent to all
skilled in the art, are contemplated as within the scope of the
invention, which is limited only by the scope of the appended
claims. For example, as explained herein, certain constructions are
described with respect to a multiport (MPI) interface for use with
serial, digital communications. Those skilled in the art having the
benefit of the present disclosure should understand that other
field bus configurations may be used, such as ProfiBUS. ProfiBUS is
a published standard, and MPI uses RS-485 at the hardware level but
uses a proprietary data protocol from Siemens. Both MPI and
ProfiBUS can be implemented in hard wired, wireless, or partially
wireless configurations. The use of the term hardwired is intended
to include fiber optic systems. Furthermore, although multiple
constructions have been described, in part, in terms of bus systems
using serial communication standards, the invention can be enjoyed
using serial and/or parallel bus structures.
[0213] It should also be understood that while aspects of the
invention are disclosed in terms of commercial refrigeration
display cases, the invention is not so limited. For example, the
embodiments disclosed and described herein may be used in other
commercial refrigeration applications such as, for example, cold
storage rooms (e.g., meat lockers) and the like, as well as
industrial, institutional, and transportational refrigeration
systems and the like. Accordingly, the specific structural and
functional details disclosed and described herein are provided for
representative purposes and represent the preferred
embodiments.
[0214] Further, for purposes of disclosing the numerous
constructions, various features have been described by reference to
specific terms, such as BCCSCM, BCSBM, BCVCM, and BCMCC. While
these terms have been used to ensure disclosure of the numerous
constructions, they are the exclusive intellectual property of the
assignee of the present application.
[0215] In view of the above, it will be seen that the above
constructions provide a wide variety of features and results.
Manufacturing costs are reduced due to the use of fewer materials
and components, as compared to non-networked refrigeration systems.
Similarly, fabrication and installation is simplified due to the
elimination of high voltage wiring, typically required by prior art
systems. The use of modularity allows for standardized
manufacturing techniques, while still accommodating customer
requirements, such as interfacing with third party control and
monitoring devices over standardized communication interfaces. Such
improvements in manufacturing, fabrication, and installation also
translate into improved system serviceability. The increased
granularity of the system resulting from using a distributed
control architecture increases the fault tolerance of the system.
Implementing the system using optional wireless communication links
(e.g., via RF links) where relatively large distances exist between
networked components eliminates the cost for installing hardwired
links. Such optional wireless links, by their nature, provide
improved damage resistance from external problems such as
lightening strikes, high voltage arcing, or high current
transmission in adjoining equipment and wiring.
[0216] Appendix
5 Table 5 provides an overview of an exemplary preferred hardware
and network connection set for several components of a
refrigeration system suitable for use according to the invention
illustrated and discussion herein. Device Target Platform Network
Connections Rack PLC Siemens S7-300 CPU314 AS-i; LonWorks .RTM./
Echelon; TCP/IP; MPI Condenser PLC Siemens S7-300 CPU314 MPI; AS-i
Remote HMI Siemens TP170A MPI Local HMI Siemens OP3 MPI BCCSCM
Atmel AT9052813 AS-i BCSBM Siemens 4 Out AS-i Module AS-i BCVCM
Atmel AT9052813 AS-i; LonWorks .RTM./ Echelon BCFCM AMI S4 AS-i
ASIC AS-i BCMCC Echelon Neuron LonWorks .RTM./Echelon Local Windows
NT TCP/IP Workstation
[0217]
6 Table 6 provides an overview of an exemplary set of preferred
input/output (I/O) devices controlled by rack PLC 720 according to
the present invention. I/O Specifications Controlled Devices Max.
Network I/O Device Compressors 16 AS-i BCCSCM System Valves 256
LonWorks .RTM./Echelon BCVCM (Motor Actuated) System Valves 64 AS-i
BCSBM (Solenoid Actuated) Case Lighting Circuits 32 AS-i AS-i 4 Out
Condenser Fans 16 MPI Condenser PLC Satellite Compressor 2 AS-i
BCCSCM Suction Groups 4 N/A N/A
[0218]
7 Table 7 identifies a preferred set of analog inputs, with
exemplary ranges, for use by rack PLC 720 to provide refrigeration
control in accordance with the invention. Analog Inputs Input Range
Max. Network I/O Device Ambient -40.degree.-120.degree. 1 MPI
Condenser PLC Temperature Liquid Line -40.degree.-120.degree. 1
Local S7 Analog I/O Temperature Heat Reclaim 0-500 PSI 2 Local S7
Analog I/O Pressure Receiver Level 0%-100% 1 Local S7 Analog I/O
System Case -40.degree.-120.degree. 256 LonWorks/ BCMCC Temperature
Echelon Suction 0-200 PSI 32 AS-i BCCSCM Pressure Suction
-40.degree.-120.degree. 32 AS-i BCCSCM Temperature Discharge 0-500
PSI 32 AS-i BCCSCM Pressure Discharge 0.degree.-275.degree. AS-i
BCCSCM Temperature Compressor 2-100 1 per AS-i BCCSCM Motor Current
compressor
[0219]
8 Table 8 identifies a preferred set of analog inputs, with
exemplary ranges, for use by rack PLC 720 to provide refrigeration
control in accordance with the invention. Digital Inputs Input
Range Max. Network I/O Device System Defrost True/False 32 AS-i
BCSBM Termination Bi-Metal Thermostat Heat Reclaim Status
True/False 1 Local S7 Digital I/O Compressor Phase True/False 32
AS-i BCCSCM Reversal Compressor Phase True/False 32 AS-i BCCSCM
Loss Compressor Internal True/False 32 AS-i BCCSCM Protect Fail
Compressor Run Time 0-99999 32 AS-i BCCSCM Compressor Oil Fail
True/False 32 AS-i BCCSCM EEPR Valve Position 0%-100% 256 LonWorks/
BCVCM Echelon
[0220]
9 Table 9 identifies a preferred set of capacity-related control
functions associated with rack PLC 720. Capacity Control Compressor
Cycling Methods Control Parameter First On First Off Suction
Pressure Suction Pressure Reset Programmed Sequence (Uneven Comp.
capacity) Real Time Sequence Reconstruction Other Capacity Control
PWM Control Pressure/Temperature Unloader support
Pressure/Temperature Variable Speed Drive control
Pressure/Temperature Satellite Control Pressure/Temperature
[0221]
10 Table 10 identifies a preferred set of system branch control
functions associated with rack PLC 720. System Branch Control
Defrost Case Temperature Control Scheduling/ TOD Clock Liquid Line
Solenoid EEPR Suction Ctrl Initiation Ctrl Termination Time
Temperature/ Bimetal Thermostat Drip Cycle (User selectable
duration) Defrost Types Case Lighting Electric Heater Ctrl TOD
Control Branch Liquid Line Ctrl Gas Liquid Line Ctrl Off Time
Branch Liquid Line Ctrl EEPR = Electronic Evaporator Pressure
Regulator
[0222]
11 Table 11 identifies a preferred set of refrigeration system
valve and condenser control functions associated with rack PLC 720.
Valve Control Control Parameter Flooding Valve Control Motor Driven
Receiver Level Discharge Pressure Solenoid Actuated Receiver Level
Discharge Pressure Heat Reclaim Lockout control Solenoid Actuated
Main Discharge Pressure H.R. Coil Pressure Liquid Valve Motor
Driven Discharge Pressure Receiver Pressure Solenoid Actuated
Receiver Pressure/ Temperature Pressure Regulator Motor Driven Auto
Surge Discharge Pressure Receiver Pressure Valve Motor Driven Split
Condenser Discharge Pressure/Condenser Fan History Valve Solenoid
Actuated/Motor Driven Function Condenser Control Fan Cycling
Discharge Pressure/Liquid Refrigerant Temp. Condenser Split
Discharge Pressure/Outdoor Ambient Temp.
[0223] Tables 12 and 13 identify a preferred set of alarm
conditions for the refrigeration system controlled by rack PLC 720.
Table VIIIA identifies conditions having separate alarms associated
with hi conditions and low conditions. Table VIIIB identifies
conditions having a single system alarm. Both Table VIIIA and VIIIB
identify, whether the condition is logged, whether the condition is
displayed in real time, a preferred minimum update interval (MUI),
and the accuracy of the measured condition.
12 [t12] Monitoring and Alarm Label Source Hi Alarm Lo Alarm Data
Log RT Disp MUI Ace. Suction BCCSCM Yes Yes Yes Yes .5 sec .1 PSI
Pressure Suction BCCSCM Yes Yes Yes Yes .5 sec .5.degree. Temp
Discharge BCCSCM Yes Yes Yes Yes .5 sec 1 PSI Pressure Discharge
BCCSCM Yes Yes Yes Yes .5 sec 1.degree. Temp Case BCMCC/ Yes Yes
Yes Yes .5 sec .5.degree. Temp Local I/O Ambient Condenser N/A N/A
Yes Yes .5 sec .5.degree. Temp PLC Liquid Local I/O N/A N/A Yes Yes
.5 sec 1.degree. Line Temp Receiver Local I/O N/A N/A Yes Yes .5
sec 1 PSI Pres. Receiver Local I/O Yes Yes Yes Yes .5 sec 1% Level
Liquid Local I/O N/A Yes Yes .5 sec 1 PSI Pres. Motor BCCSCM Yes
Yes Yes Yes .5 sec .+-.2A Current [t13] Monitoring and Alarm
(cont.) Label Source System Alarm Data Log RT Disp MUI Acc. Def/Ref
Internal N/A Yes Yes N/A N/A Status Clock Oil Fail BCCSCM Yes Yes
N/A .5 sec N/A Phase Loss BCCSCM Yes Yes N/A .5 sec N/A Phase
BCCSCM Yes No N/A .5 sec N/A Reversal Comp BCCSCM Yes Yes N/A .5
sec N/A Internal Heat Local I/O N/A N/A Yes .5 sec N/A Reclaim I.O.
Heat HVAC N/A Yes Yes .5 sec N/A Reclaim Input Stat. Auto Surge
BCVCM N/A Yes Yes .5 sec .1% Valve Stat* Main Liq. BCVCM N/A Yes
Yes .5 sec Line Pres. Differential % Pos % Pos Valve Split Cond
Internal N/A Yes Yes .5 sec N/A Stat Flooding BCVCM N/A Yes Yes .5
sec .1% Valve Stat % Pos % Pos Receiver BCVCM N/A Yes Yes .5 sec
.1% Pres Reg. All Comp Internal Yes N/A N/A N/A N/A Off Cond Fan
Internal N/A Yes Yes .5 sec N/A Status
[0224]
13 Table 14 illustrates aspects of a preferred embodiment of a
local HMI device 754, suitable for use in the commercial
refrigeration systems depicted in FIGS. 7 and 8. Hardware Detail
Siemens TP 170A Siemens Part No. TP 170A 6AV6545-0BA15-2AX0 I/O
Specifications Controlled Devices Range Max. Network I/O Device
Alarm Output N/A 1 N/A N.O. Relay Functions System Configuration
Status Display Site Layout Refrigeration Status Branch System
Configuration Branch System Status Refrigeration Configuration
Alarm Status Alarm Configuration Condenser Status Data Logging
Configuration Site Status Diagnostic Display Maintenance Display
Historical Graphing I/O Forcing Real Time Graphing Run Time Meter
Maintenance Alarm History Set Clocks User Logs Clear History
[0225]
14 Table 15 illustrates aspects of a preferred embodiment of a
remote HMI device 752, suitable for use in the commercial
refrigeration systems depicted in FIGS. 7 and 8. Hardware Detail
Siemens OP3 Siemens Part No. TP 170A 6AV6545-0BA15-2AX0 I/O
Specifications Controlled Devices Range Max. Network I/O Device
Alarm Output N/A 0 N/A N.O. Relay Functions System Configuration
Status Display Local Branch System Configuration Refrigeration
Status Local Refrigeration Configitration Branch System Status Rack
Alarm Configuration Alarm Status Condenser Status Diagnostic
Display Maintenance Display Alarm History I/O Forcing Run Time
Meter Maintenance Set Clock Clear History
[0226] Various features and advantages of the invention are set
forth in the following claims.
* * * * *