U.S. patent application number 11/749503 was filed with the patent office on 2007-09-13 for pressure controller for a mechanical draft system.
This patent application is currently assigned to EXHAUSTO, INC.. Invention is credited to Michael Beisheim, Steen Hagensen.
Application Number | 20070209653 11/749503 |
Document ID | / |
Family ID | 46327897 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070209653 |
Kind Code |
A1 |
Beisheim; Michael ; et
al. |
September 13, 2007 |
Pressure Controller for a Mechanical Draft System
Abstract
Systems and method for controlling the flow of air through a
mechanical draft system are disclosed herein. A pressure controller
for controlling air pressure comprises an appliance controller
configured to control the operation of a plurality of appliances,
an intake fan controller configured to control the speed of an
intake fan, and an exhaust fan controller configured to control the
speed of an exhaust fan. The pressure controller also includes a
processor configured to receive a differential pressure signal and
to control the operation of the appliances, the speed of the intake
fan, and the speed of the exhaust fan in response to the
differential pressure signal.
Inventors: |
Beisheim; Michael; (Atlanta,
GA) ; Hagensen; Steen; (Atlanta, GA) |
Correspondence
Address: |
THOMAS, KAYDEN, HORSTEMEYER & RISLEY, LLP
100 GALLERIA PARKWAY, NW
STE 1750
ATLANTA
GA
30339-5948
US
|
Assignee: |
EXHAUSTO, INC.
Roswell
GA
|
Family ID: |
46327897 |
Appl. No.: |
11/749503 |
Filed: |
May 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10712516 |
Nov 13, 2003 |
|
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11749503 |
May 16, 2007 |
|
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60453086 |
Mar 6, 2003 |
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Current U.S.
Class: |
126/80 |
Current CPC
Class: |
F23N 3/002 20130101;
F23N 2233/08 20200101; F24F 11/0001 20130101; F24F 13/14 20130101;
F23N 5/203 20130101; F23N 2225/06 20200101; F24F 2011/0002
20130101; F23N 5/242 20130101; F24F 11/77 20180101; F23N 5/18
20130101; F23N 2233/04 20200101; F23N 2235/04 20200101; F23N
2231/28 20200101; Y02B 30/70 20130101; F24F 2110/40 20180101; F23N
2235/06 20200101 |
Class at
Publication: |
126/080 |
International
Class: |
F24C 1/14 20060101
F24C001/14 |
Claims
1. At least the following is claimed: 1. A mechanical draft system
comprising: a pressure controller including a wireless interface
for communicating to at least one pressure sensor, a plurality of
exhaust producing appliances, and an exhaust fan, the pressure
controller configured to: control the speed of the exhaust fan to
draw air from an exhaust duct of each of the appliances in response
to a pressure reading provided by the at least one pressure sensor;
control the operation of each of the plurality of appliances, the
operation providing programmable sequenced operation; and an
auxiliary computing device in communication with the pressure
controller.
2. The system of claim 1, wherein the auxiliary computing device is
further configured to: receive operational data transmitted from
the pressure controller; indicate a system condition by comparing
the operational data to a predefined threshold; and provide remote
access to the pressure controller.
3. The system of claim 1, wherein the auxiliary computing device
transmits remote configuration settings of the pressure controller
over the communication interface.
4. The system of claim 1, wherein the auxiliary computing device is
configured to receive operational data transmitted from the
pressure controller and indicate an alarm condition by comparing
the operational data to a predefined threshold.
5. The system of claim 1, wherein the pressure controller is
configured to transmit operational data to the auxiliary computing
device.
6. The system of claim 1, wherein the operational data is at least
one of an alarm, a fan speed, or the pressure reading.
7. The system of claim 1, wherein the auxiliary computer is
configured to provide remote access to the pressure controller.
8. The system of claim 1, wherein the wireless interface comprises
at least one wireless transceiver.
9. The system of claim 1, wherein the programmable sequenced
operation includes specifying a quantity of the plurality of
appliances to be operational based on predetermined conditions.
10. The system of claim 1, wherein the programmable sequenced
operation includes selectively identifying the appliances to be
activated or deactivated.
11. A mechanical draft system comprising: a pressure controller for
controlling the flow of air through an exhaust duct, the pressure
controller comprising: a processor configured to control the
operation of a plurality of appliances, the speed of an intake fan,
and the speed of an exhaust fan in response to a differential
pressure signal.
12. The mechanical draft system of claim 11, wherein the pressure
controller further comprises a communication interface for
communication with an auxiliary computing device.
13. The mechanical draft system of claim 11 further comprising: a
first pressure sensor located inside an enclosed area configured to
wirelessly transmit a first pressure reading of the enclosed area;
and a second pressure sensor located outside of the enclosed area
configured to wirelessly transmit a second pressure reading;
wherein the pressure controller is configured to wirelessly receive
the first and second pressure readings and the processor determines
the differential pressure signal from the first and second pressure
readings.
14. The mechanical draft system of claim 11 further comprising: an
intake fan configured to wirelessly receive a first fan rotation
setting transmitted from the pressure controller; and an exhaust
fan configured to wirelessly receive a second fan rotation setting
transmitted from the pressure controller.
15. The mechanical draft system of claim 11, wherein the processor
is further configured to provide programmable sequenced operation
by selectively identifying the appliances to be activated or
deactivated based on programmable conditions.
16. The mechanical draft system of claim 11, further comprising an
auxiliary computing device in communication with the pressure
controller, the auxiliary computing device configured to receive
operational data transmitted from the pressure controller.
17. The mechanical draft system of claim 15, wherein the auxiliary
computing device is further configured to indicate a system
condition by comparing the operational data to a predefined
threshold.
18. The mechanical draft system of claim 11, further comprising: an
auxiliary computing device in communication with the pressure
controller, the auxiliary computing device configured to remotely
transmit pressure controller configuration settings to the pressure
controller.
19. A method for controlling the operation of a plurality of
combustion appliances, the combustion appliances capable of being
independently operated to meet an exhaust system objective:
receiving a signal from a remote device; determining that less than
each of the plurality of combustion appliances are required to meet
the system objective based on the signal; identifying at least one
of the plurality of combustion appliances to be operated to meet
the system objective; activating the identified at least one
combustion appliance; adjusting the flow of exhaust drawn from
ducts connected to each of the activated appliances by controlling
the rotational speed of an exhaust fan.
20. The method of claim 19, wherein the step of selecting the
plurality of appliances comprises: selectively identifying the
appliances to be activated or deactivated based on a programmed
setting, appliance specifications, or historical appliance
operational data.
21. The method of claim 19, wherein the step of receiving a signal
from the remote device includes: receiving the signal from a
sensor; or receiving the signal from a building management
computer.
22. A mechanical draft system comprising: a controller for
controlling the flow of air through an exhaust duct, the controller
comprising: a processor configured to control the operation of a
plurality of appliances and to control the flow of air through the
exhaust duct in response to a measurement of the amount of oxygen
in the air in the exhaust duct.
23. The mechanical draft system of claim 22, wherein the controller
is configured to modulate at least one of a damper position and a
fan speed to control the flow of air through the exhaust duct based
on the measurement of the amount of oxygen in the air in the
exhaust duct.
24. The mechanical draft system of claim 23, wherein the amount of
oxygen is measured by an oxygen sensor located in a respective
exhaust duct of each of a plurality of appliances.
25. The mechanical draft system of claim 24, further comprising a
damper in the exhaust duct of each of the plurality of
appliances.
26. The mechanical draft system of claim 25, wherein the processor
modulates a damper position of each of the dampers in response to a
measurement of the amount of oxygen in the air of each of the
exhaust ducts of the plurality of appliances.
27. The mechanical draft system of claim 22, wherein the amount of
oxygen is measured by an oxygen sensor located in an exhaust duct
common to each of a plurality of appliances.
28. The mechanical draft system of claim 22, wherein the amount of
oxygen is measured by an oxygen sensor located in a respective
exhaust duct of each of a plurality of appliances.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
co-pending U.S. patent application Ser. No. 10/712,516, filed Nov.
13, 2003, and entitled "Pressure Controller for a Mechanical Draft
System," which claims the benefit of U.S. provisional application
No. 60/453,086, filed on Mar. 6, 2003, and entitled "Systems and
Methods Involving Modulating Pressure Controls," both of which are
incorporated by reference in their entirety into the present
disclosure.
TECHNICAL FIELD
[0002] The present disclosure generally relates to exhaust systems
or mechanical draft systems. More particularly, the disclosure
relates to controllers for exhaust systems or mechanical draft
systems.
DESCRIPTION OF THE RELATED ART
[0003] The boiler rooms, or mechanical rooms, of a building can
house a number of combustion appliances, such as water heaters,
furnaces, and boilers, which are used for heating purposes within
the building. Within conventional mechanical rooms, many control
devices are used for controlling the different components therein.
For example, each individual furnace or boiler may be connected to
a respective control device that controls the flow of combustion
air and exhaust air through that furnace alone. The control device
may also effect a furnace shut down procedure during unstable
conditions. Mechanical rooms can also house one or more control
devices for controlling a ventilating blower and one or more
control devices for controlling an induction draft blower. With the
large number of control devices in the mechanical room providing
various functions, coordination among the various controllers can
be quite complex. Furthermore, in this regard, components and
functions can be unnecessarily duplicated.
[0004] It has been contemplated to coordinate the control of the
ventilating blower and induction draft blower to regulate the air
flow through the mechanical room. However, until now, greater
processor functionality has yet to be achieved for simplifying the
installation and control of mechanical draft systems.
[0005] During installation of a conventional mechanical draft
system, very little feedback is provided to the installers to
indicate whether or not the components are properly connected in
the system. Because of this deficiency, correcting any problems
after installation becomes much more difficult. It would be
beneficial to the installers to receive positive feedback to
determine whether or not corrections should be made during
installation.
[0006] One concern that has been identified regarding conventional
mechanical draft systems is their lack of intelligent processing
functionality for controlling furnaces or boilers during less than
optimal conditions. In those systems, furnaces or boilers are
typically shut down and prevented from operating until an error or
problem in the system is corrected. This all-or-nothing approach
can result in a number of machines sitting idly during times of
great need. Therefore, a void exists in the prior art for allowing
a system to operate in a low output state during less than optimal
conditions and to operate in such conditions without compromising
safety and efficiency.
[0007] Conventional mechanical draft systems may also present
challenging installation and/or reconfiguration scenarios. For
example, some mechanical rooms may be large, requiring long
distances of cabling be run between a controller and related
equipment such as, but not limited to, the appliances, sensors,
actuators, etc. Additionally, such systems may be installed after a
mechanical room has already been in operation for a number of
years. Thus, physical obstructions may exist requiring cabling
between the controller and related equipment be run for even longer
distances or in inconvenient locations. Additionally, as system
objectives and/or demands change, appliances and/or related
equipment may be added to the system, requiring additional cabling.
Therefore a need exists for a system having improved installation
and/or reconfiguration requirements to allow for the communication
between the controller and related equipment without the need for
running long distances of wire between the two.
[0008] Another concern with conventional mechanical draft systems
is the lack of remote access to the pressure controller.
Specifically, conventional controllers are located in areas that
are easily accessible by support staff such that the controllers
may be physically accessed for the purpose of programming and
troubleshooting. However, a need exists for providing remote
connectivity to the controller of a mechanical draft system such
that the controllers may be installed in a location without regard
to continuous physical access. Such remote connectivity may also
enable a number of troubleshooting and notification capabilities
not previously provided by stand-alone mechanical draft
systems.
[0009] Yet another problem not addressed by conventional mechanical
draft systems is the lack of programmable appliance sequencing. For
example, conventional draft systems are not programmable to
prioritize the use of specific appliances to meet a demand based on
predefined, and programmable, conditions.
SUMMARY
[0010] Methods and systems for controlling the flow of air through
a mechanical draft system are disclosed. One embodiment of a
mechanical draft system includes a pressure controller having a
wireless interface for communicating to at least one pressure
sensor, a plurality of exhaust producing appliances, and an exhaust
fan. The pressure controller is configured to: control the speed of
the exhaust fan to draw air from an exhaust duct of each of the
appliances in response to a pressure reading provided by the at
least one pressure sensor, and control the operation of each of the
plurality of appliances, the operation providing programmable
sequenced operation. The mechanical draft system also includes an
auxiliary computing device in communication with the pressure
controller.
[0011] Another embodiment of a mechanical draft system includes a
pressure controller for controlling the flow of air through an
exhaust duct, the pressure controller comprising a processor
configured to control the operation of a plurality of appliances,
the speed of an intake fan, and the speed of an exhaust fan in
response to a differential pressure signal.
[0012] Yet another embodiment is directed to a method for
controlling the operation of a plurality of combustion appliances,
the combustion appliances capable of being independently operated
to meet an exhaust system objective. The method includes receiving
a signal from a remote device and determining that less than each
of the plurality of combustion appliances are required to meet the
system objective based on the signal. The method further includes
identifying at least one of the plurality of combustion appliances
to be operated to meet the system objective and activating the
identified at least one combustion appliance. The method further
includes
[0013] adjusting the flow of exhaust drawn from ducts connected to
each of the activated appliances by controlling the rotational
speed of an exhaust fan.
[0014] Another embodiment of a mechanical draft system includes a
controller for controlling the flow of air through an exhaust duct.
The controller includes a processor configured to control the
operation of a plurality of appliances and a modulation of a damper
position in response to a measurement of the amount of oxygen in
the air in the exhaust duct.
[0015] Other systems, methods, features, and advantages of the
present disclosure will be apparent to one having skill in the art
upon examination of the following drawings and detailed
description. It is intended that all such additional systems,
methods, features, and advantages be included within this
description and protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Many aspects of the embodiments disclosed herein can be
better understood with reference to the following drawings. The
components in the drawings are not necessarily to scale, emphasis
instead being placed upon clearly illustrating the principles of
the present disclosure. Like reference numerals designate
corresponding parts throughout the several views.
[0017] FIG. 1 is a partial block diagram illustrating an embodiment
of a mechanical draft system.
[0018] FIG. 2A is a block diagram of an embodiment of the pressure
and combustion controller shown in FIG. 1.
[0019] FIG. 2B depicts a block diagram of an exemplary auxiliary
computing device capable of providing a number of supplemental
services to the pressure and combustion controller of FIG. 2A.
[0020] FIGS. 3A and 3B are front and bottom views illustrating an
embodiment of a housing for a pressure and combustion
controller.
[0021] FIG. 4 is a flow chart of an embodiment of a set-up routine
for a mechanical draft system.
[0022] FIG. 5 is a flow chart of an embodiment of a
fan-rotation-check routine for a mechanical draft system.
[0023] FIG. 6 is a flow chart of an embodiment of a routine for
monitoring and controlling air pressure in a mechanical draft
system.
[0024] FIG. 7 is a flow chart of an embodiment of a priority
sub-routine for a mechanical draft system.
[0025] FIG. 8 is a flow chart of an embodiment of a routine for
running a bearing cycle in a mechanical draft system.
[0026] FIG. 9 is a flow chart of an embodiment of a routine for
sequencing a number of appliances using a mechanical draft
system.
DETAILED DESCRIPTION
[0027] Disclosed herein are embodiments of systems and methods for
controlling components in an exhaust system or mechanical draft
system in which combustion air is drawn into a mechanical room and
supplied to combustion or heating devices and air exhausted from
the combustion or heating devices is vented from the mechanical
room into the atmosphere. The controllers of the present disclosure
are capable of controlling the on/off state and speed of intake
fans and exhaust fans and can also control any number of
appliances, such as furnaces or boilers, within the system. The
unitary controllers disclosed herein may be configured using
microprocessor elements or other suitable electrical components for
providing greater functionality than conventional exhaust system
controllers. Also, the controllers can be programmed in the field
and reprogrammed as desired allowing greater flexibility.
[0028] The controllers can be initialized during the installation
or set-up of the mechanical draft system. The initialization
process involves entering information about the equipment and
determining whether the equipment may require additional components
to run properly. The controllers may provide installation
instructions for the additional components as needed. The
initialization process also involves setting maximum and minimum
fan speeds and setting pre-purge and post-purge parameters.
Initialization also involves determining the number of appliances
connected in the system and setting a priority list of the
appliances for use when adequate draft cannot be maintained with
all appliances running. Also established during installation or
set-up is the proper positions of adjustable dampers or baffles for
optimal air flow from the individual appliances. The position of a
modulating damper is also adjusted to control air flow from
cumulative appliances. Moreover, a fan-rotation-check procedure may
be run to determine whether or not the fans are rotating in the
correct direction.
[0029] After set-up and during system operation, the controllers
disclosed herein are capable of carrying out a process of operating
the fans during long periods of inactivity. This process, referred
to herein as a "bearing cycle," allows the fans to run for a short
amount of time, such as during off-season times, to exercise the
bearing. Reference is now made to the drawings illustrating the
embodiments of the mechanical draft system, pressure and combustion
controllers, and methods of operation.
[0030] FIG. 1 shows an embodiment of a mechanical draft system 100,
having components located both inside and outside of a mechanical
room 102. The mechanical room 102 may be a boiler room, laundry
facility, or other room or enclosed area where a plurality of
electrical or mechanical heat generating machines or appliances 104
are used. The appliances 104 may include boilers, modulating
boilers, furnaces, water heaters, gas or electric laundry dryers,
wood-burning devices, heating devices, etc.
[0031] An intake fan 106 draws air from outside the mechanical room
102 into the mechanical room 102 to provide combustible air for the
appliances 104. The intake fan 106 may be programmed to increase
its speed of rotation when the appliances are fired in order to
provide sufficient combustion air. It should be noted that the
intake fan 106 may include any well-known type of fan, such as a
single-phase fan or three-phase fan. The intake fan 106 cooperates
with input ducts that penetrate the walls or ceiling of the
mechanical room 102 and lead outside the building. The intake fan
106 and corresponding ducts may have any suitable configuration and
may be supported or directed in any suitable manner. The ducts at
the output of the intake fan 106 may lead directly to the
appliances 104 in a direct venting configuration. Also, the ducts,
if desired, may include diffusers leading to the interior of the
mechanical room 102.
[0032] The appliances 104 draw air from inside the mechanical room
102 or directly from the intake fan 106 for combustion with a
gas-based, oil-based, or wood-based fuel. Exhaust from the
appliances 104, in the form of heated gases, smoke, or the like,
travels through an air exhaust duct 108, which contains an
adjustable baffle or damper 110 for controlling the draft into
ducts 112. The damper 110, which may be a modulating damper, may
have an open position for allowing exhaust to pass through
virtually unhindered, a closed position for preventing exhaust from
passing, and one or more intermediate positions for balancing the
air flow with respect to the exhaust from other appliances 104 in
the system.
[0033] Air exhausted into the ducts 112 travels through a
modulating damper 113, which controls and maintains draft for
single or multiple appliances 104. The modulating damper 113 may
include multiple blades for controlling the draft. The modulating
damper 113 can be used within ducts 112 or within any other type of
vent or stack. The modulating damper 113 may be attached to one or
more actuators, controllers, pressure sensors, draft probes, and
over-pressure safety switches for controlling and maintaining
draft. The modulating damper 113 is used when the mechanical draft
system 100 generates more draft than the appliances 104 can handle.
By modulating the position of the modulating damper 113, a constant
draft for the appliances 104 can be maintained.
[0034] Upon a call for heat, the modulating damper 113 can be
opened completely during a predetermined pre-purge time. When one
or more of the appliances 104 are fired and the draft reaches a
predetermined draft set-point, the modulating damper 113 modulates
to maintain a constant draft. This sequence is repeated every time
another of the appliances 104 is fired. When one or more appliances
104 shut down, the modulating damper 113 closes slightly while
maintaining the predetermined draft set-point. When the last
appliance is shut down, the modulating damper 113 stays open in
accordance with any post-purge settings.
[0035] The mechanical draft system 100 includes over-pressure
protection for a situation where excessive pressure builds up
between the outlet of the appliances 104 and the modulating damper
113. When this over-pressure situation occurs, one or more of the
appliances 104 are shut down and the modulating damper 113 is
opened completely to relieve the pressure within the ducts 112.
[0036] The ducts 112 include an end 114 that may include a closed
header or an opened barometric damper to balance the system.
Exhaust travels through the ducts 112 to another end 116 that is
open to a vertical stack or chimney 118. The chimney 118, which may
be closed at one end 120, leads the exhaust outside the mechanical
room 102 through an exhaust fan 122 at the other end. The exhaust
fan 122 draws the exhaust from inside the ducts 112 and chimney 118
into the atmosphere.
[0037] The mechanical draft system 100 further includes a pressure
and combustion controller 124 for maintaining an acceptable air
pressure inside the mechanical room 102. The pressure and
combustion controller 124 controls the speeds of the intake fan 106
and exhaust fan 122 in order to provide an adequate draft through
the mechanical draft system 100. By regulating the supply of air to
the appliances 104, the energy efficiency of the appliances 104 is
greatly improved. Maintaining an equalized air pressure between the
atmosphere and the interior of the mechanical room 102 further
avoids dangerous operating conditions.
[0038] According to some embodiments, the pressure and combustion
controller 124 monitors the differential pressure that is
calculated from the difference in air pressure between the inside
of the mechanical room 102 and the atmosphere. If a positive
differential pressure is calculated, indicating excess air pumped
into the mechanical room 102 relative to the atmosphere, sometimes
referred to as overdraft, then the pressure and combustion
controller 124 slows down or shuts off the intake fan 106 and/or
speeds up the exhaust fan 122 if possible. If a negative
differential pressure is calculated based on a lack of adequate air
inside the mechanical room 102 relative to the atmosphere, then the
pressure and combustion controller 124 speeds up the intake fan 106
if possible and/or slows down or shuts off the exhaust fan 122.
When a negative differential pressure exists, the pressure and
combustion controller 124 may additionally adjust the dampers 110
or modulating damper 113 to more greatly restrict the exhaust from
the appliances 104. These actions will serve to avoid overdraft,
especially during times when the appliances are running at less
than full capacity.
[0039] If the differential pressure exceeds a predetermined
threshold, indicating an excessive difference between the pressure
inside the mechanical room 102 relative to the atmosphere, then the
pressure and combustion controller 124 shuts down the appliances
104. For instance, if the pressure in the mechanical room 102 is
40% above or below a normalized atmospheric pressure, representing
a potentially dangerous situation, then the appliances 104 are shut
down. The pressure and combustion controller 124 may additionally
reset the appliances automatically when the differential pressure
returns to an acceptable level, thereby avoiding lapses of service,
which can result from the use of manual reset switches.
[0040] The pressure and combustion controller 124 of the present
disclosure can be implemented in hardware, software, firmware, or a
combination thereof. In the disclosed embodiments, the pressure and
combustion controller 124 can be implemented in software or
firmware that is stored in a memory and that is executed by a
suitable instruction execution system. If implemented in hardware,
as in an alternative embodiment, the pressure and combustion
controller 124 can be implemented with any combination of the
following technologies, which are all well known in the art: one or
more discrete logic circuits having logic gates for implementing
logic functions upon data signals, one or more application specific
integrated circuits (ASICs) having appropriate logic gates, a
programmable gate array (PGA), a field programmable gate array
(FPGA), etc.
[0041] According to some embodiments, the pressure and combustion
controller 124 receives a differential pressure signal from a
differential transducer 126. The differential transducer 126
calculates the differential pressure based on a first pressure
reading from inside the mechanical room 102 and a second pressure
reading from outside the mechanical room 102, preferably from the
atmosphere. The first pressure reading may be taken from an open
port in the differential transducer 126 or may optionally be taken
from a first pressure sensor 128. The first pressure sensor 128 may
be attached to an interior wall of the mechanical room 102 or may
be secured inside the ducts 112 or chimney 118. The second pressure
reading may be taken from a second pressure sensor 130, preferably
located on a roof top of the building.
[0042] According to some embodiments, a second differential
transducer 138 provides pressure and combustion controller 124 with
a differential pressure between the inside of the mechanical room
102 (e.g. with pressure sensor 142) and a second pressure inside of
the chimney 122 and/or ducts 112 (e.g. with pressure sensor 140). A
measurement of the differential in pressure between the mechanical
room 102 and the ducts 112 and/or chimney 118 provides pressure and
combustion controller 124 with yet another indication of the flow
of air passing through chimney 122. The measurements provided by
differential transducers 126 and 138 can be used independently, or
together, by pressure and combustion controller 124 to control the
proper draft through duct 112 and chimney 118 (e.g. through
modulating the speed of fans and/or dampers).
[0043] According to some Some embodiments of mechanical draft
system 100 can also use one or more oxygen sensors, sometimes known
as lambda sensors, to monitor the oxygen level in the exhaust of
appliances 104. Heating appliances operate on the basis of a
stoichiometric combustion process, which is perfect combustion.
Thus, a stoichiometric combustion process uses a perfect
combination of fuel and oxygen with no other liquids or gases.
However, in reality, perfect combustion is not generally possible
because atmospheric air has only a certain amount of oxygen and
atmospheric air contains other gases and liquids that are not used
in the combustion process, but still become part of the products of
combustion that are being exhausted via the duct 112 and chimney
118. However, oxygen sensors can be used to monitor the oxygen
level in the air after the combustion process (e.g. the exhaust),
and can send a signal to the controller when the oxygen level
exceeds and/or falls below specified thresholds. Such thresholds
will vary by the specific appliance and environmental conditions.
Incorporating oxygen sensors into mechanical draft system 100 can
provide not only proper draft, but can be used to accurately
monitor and control the oxygen content in the exhausted flue gases.
This allows the appliances 104 to operate as efficient as possible
while minimizing harmful emissions.
[0044] For example, oxygen sensor 144 can be located in the chimney
118 and/or ducts 112 to monitor the oxygen level in the exhaust
duct common to all of the appliances 104. However, in some
embodiments, oxygen sensors 144a-144c can be placed in the exhaust
ducts 108 of each appliance 104 in order to monitor the exhaust of
each appliance 104 individually. Each of sensors 144a-144c are
communicatively coupled to provide oxygen readings to pressure and
combustion controller 124. Damper 110, which can be a modulating
damper, can be installed in-line downstream of the exhaust flow
from the oxygen sensors 144a-144c. Each interface of the damper 110
is also connected to the pressure and combustion controller
124.
[0045] In use, the pressure and combustion controller 124 can
receive a signal (e.g. "call for heat") from an appliance 104
thermostat or other switch or monitor. The pressure and combustion
controller 124 can then cause the damper 110 in the respective
appliance's exhaust duct 108 to open and can also activate the
exhaust fan 122 (and intake fan 106, if installed and needed). The
fan(s) can be set to reach a preset draft set point. When this
draft set point is proven, the appliance 104 is released by the
pressure and combustion controller 124. Once the appliance 104
fires, the pressure and combustion controller 124 can monitor the
oxygen levels in the exhaust gas via the respective oxygen sensor
104a-104c. If the oxygen level is too high, pressure and combustion
controller 124 controls damper 110 to move towards a more closed
position until the proper oxygen level is reached. If the oxygen
level is too low, pressure and combustion controller 124 controls
damper 110 to move towards a more open position until the proper
oxygen level is reached. The damper can regulate on predefined
intervals, or continuously, to maintain the proper oxygen
level.
[0046] Embodiments using oxygen sensors 144 and/or 144a-144c add
the ability to control an appliance's combustion by measuring the
oxygen level-rather than, or in conjunction with, the draft
pressure. Thus, the exhaust fan 122 and/or the intake fan 106
combined with the modulating damper 110 can make the necessary fan
speed and damper adjustments to maintain the specified oxygen
content in the flue gases. According to some embodiments, if the
oxygen level is outside a specified level by a preset threshold,
the pressure and combustion controller 124 can provide an alarm
signal and/or shut down one or more appliances 104.
[0047] Thus, regardless of the types of sensors installed, the
pressure and combustion controller 124 ensures that a proper draft
is maintained through the mechanical draft system 100 by
transmitting signals to various components via interface devices.
For example, an intake fan interface 132 is positioned between the
pressure and combustion controller 124 and the intake fan 106. An
exhaust fan interface 134 is positioned between the pressure and
combustion controller 124 and the exhaust fan 122. Appliance
interfaces 136 are positioned between the pressure and combustion
controller 124 and each respective appliance 104.
[0048] The intake fan interface 132 and exhaust fan interface 134
may include a power source (not shown), such as a variable
frequency drive (VFD), for supplying three phase power signals when
the fans are three-phase fans. The intake fan interface 132 and
exhaust fan interface 134 may also monitor characteristics of the
fans and indicate various information to the pressure and
combustion controller 124. For instance, the interfaces 132 and 134
may indicate to the pressure and combustion controller 124 the
existence of the fans. If a fan does not exist on the intake or
exhaust side, then the pressure and combustion controller 124 can
bypass any control functions intended for the missing fan. The
interfaces 132 and 134 may also indicate whether the fans are
operating properly and if the fans are malfunctioning. The
interfaces 132 and 134 also sense the speed of the respective fans
and indicate the speeds to the pressure and combustion controller
124. Furthermore, the interfaces 132 and 134 receive control
signals from the pressure and combustion controller 124 for
adjusting the speeds of the respective fans.
[0049] The appliance interfaces 136 may contain a proven draft
switch (not shown) which receives a signal from the pressure and
combustion controller 124 to shut down the appliances when
insufficient draft is detected. The appliance interfaces 136 may
also receive signals from the pressure and combustion controller
124 to adjust the position of the dampers 110, thereby controlling
the exhaust from individual appliances 104. The modulating damper
113 may optionally be configured to be controlled by the appliance
interfaces 136. The appliance interfaces 136 may also transmit
signals to the pressure and combustion controller 124 to indicate
various information about the appliances 104 and dampers 110. For
example, the appliance interfaces 136 may inform the pressure and
combustion controller 124 of the presence of the respective
appliances 104 so that the number of appliances 104 connected in
the mechanical draft system 100 can be determined. The appliance
interfaces 136 may also indicate whether or not the appliances 104
are currently running for monitoring periods of inactivity. The
appliance interfaces 136 may also indicate the presence and
position of the dampers 110.
[0050] The connections between pressure and combustion controller
124 and its associated input/output devices, such as differential
transducer 126, pressure sensor 128, pressure sensor 130, intake
fan interface 132, exhaust fan interface 134, and appliance
interfaces 136 may be any wired or wireless connection. In addition
to the pressure sensors, any other sensors located remote from
pressure and combustion controller 124 (e.g. those determined
useful for the purpose of data collection) may also be similarly
interfaced to controller 124. In an embodiment using a wired
interface, any of a number of appropriate signals are used for
sending and or receiving signals to and/or from the attached
devices. For example, a 0-10 v control signal supplied to exhaust
fan interface 134 from pressure and combustion controller 124 may
control the speed of the variable speed motor, while a simple
high/low signal may be transmitted to an appliance for the purpose
of signaling the activation or deactivation of the appliance.
[0051] Although embodiments having wired connections between the
input/output devices provide exceptional reliability, embodiments
using wireless interfaces are advantageous for simplifying
installation. Accordingly, in some embodiments, the connections
between pressure and combustion controller 124 and any associated
remote devices (e.g. differential transducer 126, pressure sensor
128, pressure sensor 130, intake fan interface 132, exhaust fan
interface 134, and appliance interfaces 136) may include any number
of wireless connections capable of providing appropriate signals
between the respective remote device and pressure and combustion
controller 124.
[0052] One such popular wireless protocol and transceiver is based
the Z-Wave.TM. system offered by Zensys, Inc. of Upper Saddle
River, N.J., the protocol of which is described in U.S. Pat. No.
6,879,806, which is hereby incorporated by reference in its
entirety. Another such wireless standard, including a suitable
protocol and transceiver, is the Zigbee.TM. protocol based on the
Institute of Electrical and Electronics Engineers (IEEE) 802.15
standard, which is also incorporated by reference in its
entirety.
[0053] In embodiments using wireless interfaces, each of controller
124 and any associated remote devices (e.g. differential transducer
126, pressure sensor 128, pressure sensor 130, intake fan interface
132, exhaust fan interface 134, and appliance interfaces 136) may
be outfitted with an appropriate electronic transceiver. Each
transceiver may be uniquely addressed and the transceiver
associated with controller 124 is programmed to be capable of
uniquely identifying each input/output device by each device's
unique address.
[0054] To increase communication reliability between the controller
and the input/output devices, it may be desirable to associate more
than one transceiver for each device in the case of failure of the
transceiver. For example, in such an embodiment, if a destination
transceiver did not transmit an acknowledgement, the sending
transceiver may send the signal to a backup transceiver associated
with the device. In some embodiments, as used in the Z-wave system,
a number of repeaters and alternate routes may be used to provide
reliable transmissions around dead zones and across long
distances.
[0055] FIG. 2A is a block diagram of an embodiment of the pressure
and combustion controller 124 shown in FIG. 1. In this embodiment,
the pressure and combustion controller 124 includes a processor
200, such as a microprocessor or the like. The processor 200
preferably contains electrically erasable programmable read only
memory (EEPROM) or other suitable memory device for storing
settings and parameters established during set-up of the mechanical
draft system 100. When the processor 200 is configured with a
memory device such as EEPROM, an advantage can be realized in that
the software of the processor 200 can be upgraded in the field
during set-up or during normal system operation to include new
controller functions for controlling mechanical draft systems.
[0056] The pressure and combustion controller 124 of FIG. 2A
contains input devices 202 for receiving inputs from an installer,
programmer, and/or technician. The input devices 202 may be
configured as input buttons, keypads, keyboards, or other suitable
input mechanisms. The pressure and combustion controller 124 also
contains display devices 204, such as liquid crystal display (LCD)
and light emitting diode (LED) components, for displaying various
information about the condition of the mechanical draft system 100.
For example, the display devices 204 may show the differential
pressure, actual pressure in the mechanical room 102, alarm
conditions, etc., and may indicate whether or not the intake fan
106 and exhaust fan 122 are functioning properly. The display
devices 204 may also show information as it is being entered in the
input devices 202.
[0057] The input devices 202 may include means for overriding
automatic control of the processor 200 and for allowing manual
control. During set-up of the mechanical draft system 100, the
input devices 202 may be used for entering various information. For
example, during set-up, the maximum and minimum fan speeds may be
entered. Also, an input may be entered notifying the processor 200
how many appliances 104 are to be connected in the mechanical draft
system 100. Also, with a plurality of appliances 104 in the system,
priority information can be entered to establish a priority list
dictating which appliances 104 should be allowed to run during a
condition in which the exhaust fan 122 is malfunctioning or when
the exhaust fan 122 has reached its maximum speed and cannot
provide adequate draft. This priority mode is described in more
detail below.
[0058] The pressure and combustion controller 124 further includes
an intake fan controller 206 and an exhaust fan controller 208. The
intake fan controller 206 receives information from the intake fan
interface 132 (FIG. 1) for analysis by the processor 200. When the
processor 200 detects a differential pressure that exceeds a
predetermined threshold, the processor 200 may increase, decrease,
or shut off the intake fan 106 via the intake fan controller 206.
If the intake fan 106 is a single-phase fan, the intake fan
controller 206 may contain a triac board, which may be configured
to supply a 10-volt signal to the intake fan 106. Likewise, the
exhaust fan controller 208 receives information from the exhaust
fan interface 134 and adjusts the speed of the exhaust fan 122. The
exhaust fan controller 208 may also contain a triac board if
necessary. If one or the other fan is not connected to the
mechanical draft system 100, the pressure and combustion controller
124 bypasses the respective controller 206 and 208 and compensates
for the absence of the fan.
[0059] FIG. 2A further illustrates the pressure and combustion
controller 124 having an appliance controller 210 that can shut
down or restart the appliances 104 when necessary. The appliance
controller 210 includes six outputs for controlling up to six
appliances 104. The appliance controller 210 may also control the
position of the dampers 110 located at the exhaust ducts 108 of
each appliance 104 and/or the position of the modulating damper
113. In this regard, the position of the dampers 110 and 113 may be
completely open, completely closed, or adjusted to a desirable
intermediate position.
[0060] The pressure and combustion controller 124 may optionally
contain a relay board 212 when more than six appliances 104 are
connected in the mechanical draft system 100. The relay board 212
includes four terminals shutting down or restarting four additional
appliances 104, thereby increasing the possible number of
appliances that can be controlled by the pressure and combustion
controller 124 up to ten. The pressure and combustion controller
124 further includes one or more external communication links 214.
The external communication links 214 may also include connections
to one or more external relay boards (not shown) when more than ten
appliances are installed in the mechanical draft system 100. The
external relay boards may be incorporated within relay boxes (not
shown) that can be connected in a daisy chain fashion. Using the
relay boxes, the pressure and combustion controller 124 may be
configured to control an unlimited number of appliances 104.
[0061] External communication links 214 may also include an RS-232
(serial) port, RJ-45 (Ethernet) port, wireless port (e.g. IEEE
802.11), or RJ-11 (telephone) port for communicating with other
auxiliary computing devices or peripherals capable of providing
supplementary services. For example, such computing devices may
include a computer used in a building management system.
[0062] FIG. 2B depicts a block diagram of an exemplary auxiliary
computing device 216 capable of providing a number of supplemental
services to pressure and combustion controller 124. Although
auxiliary computing device 216 may essentially be physically
located local to the controller itself, in some embodiments the
computing devices may be located remotely, such as in a corporate
data center, for example. Indeed, the functional and physical
features of auxiliary computing device 216 could be integrated into
pressure and combustion controller 214.
[0063] Regardless of the physical location, auxiliary computing
device 216 may perform a number of supplementary functions such as
providing alarm notification, data logging, and remote access and
control to pressure and combustion controller 124. Auxiliary
computing device 216 may also supply software updates over
communication link 214 for reprogramming the processor 200 in the
field according to any mechanical draft system pressure control
advances that may be developed in the future.
[0064] According to some Generally speaking, auxiliary computing
device 216 may be one of a wide variety of wired and/or wireless
computing devices, such as a laptop computer, PDA, handheld or pen
based computer, desktop computer, dedicated server computer,
multiprocessor computing device, cellular telephone, embedded
appliance and so forth. Irrespective of its specific arrangement,
portable computer system 28 can, for instance, comprise a bus 218
which may connect a processing device 222, memory 224, and an
input/output interface 220. Although not depicted, it should be
understood that auxiliary computing device 216 may also include a
number of other computing devices such as, but not limited to, a
display, user input devices, and/or a network interface.
[0065] According to some Processing device 222 can include any
custom made or commercially available processor, a central
processing unit (CPU) or an auxiliary processor, among several
processors associated with the auxiliary computing device 216, a
semiconductor based microprocessor (in the form of a microchip), a
macroprocessor, one or more application specific integrated
circuits (ASICs), a plurality of suitably configured digital logic
gates, and other well known electrical configurations comprising
discrete elements both individually, and in various combinations,
to coordinate the overall operation of the computing system.
[0066] According to some Input/output interfaces 220 provide any
number of interfaces for the input and output of data. For example,
where the auxiliary computing device 216 comprises a personal
computer, these components may interface with a user input device
(not shown), which may be a keyboard or a mouse. Where the
auxiliary computing device 216 comprises a handheld device (e.g.,
PDA, mobile telephone, etc.), these components may interface with
function keys or buttons, a touch sensitive screen, a stylus, etc.
Input/output interfaces 220 may also provide the capability to send
and receive data from other computing devices (including pressure
and combustion controller 124) and receive data and/or signals from
measurement devices (e.g. sensors, etc.).
[0067] Memory can include any one of a combination of volatile
memory elements (e.g., random-access memory (RAM, such as DRAM, and
SRAM, etc.)) and nonvolatile memory elements (e.g., ROM, hard
drive, tape, CDROM, etc.). The memory typically comprises a native
operating system, one or more native applications, emulation
systems, or emulated applications for any of a variety of operating
systems and/or emulated hardware platforms, emulated operating
systems, etc.
[0068] With respect to data logging, pressure and combustion
controller 124 may be configured to send any available operational
data to auxiliary computing device 216 over communication link 214.
Auxiliary computing device 216 may be configured to receive and
store the data within memory 224. For example, the data may be
stored and arranged within a database or within logs which may be
accessed for a number of purposes such as troubleshooting and
providing reports and statistics. For example, such reports could
be used for the purpose of providing government required emissions
data. Customized reports may be generated to view statistics
related to the control system, the appliances, and the building
itself. These reports may, for example, assist an owner in
determining available performance capacity of the appliances, usage
trends, and the prediction of system failures.
[0069] According to some In addition to receiving operational data
available to pressure and combustion controller 124 over
communication link 214, the computing devices may be configured to
receive any number of other inputs from sensors or building control
systems through input/output interface 220. For example,
measurement devices external to the auxiliary computing device 216
and/or a building control system may supply auxiliary computing
device 216 with the temperature or humidity of the mechanical room
102 as well as the status of any other building system alarms (e.g.
fire alarms, etc.).
[0070] According to some Data received by auxiliary computing
device 216 may include data recorded on a periodic basis or may
record instances of measured values that have exceeded a specified
range. For example, the types of operational data recorded on a
periodic basis may include, but is not limited to: the draft,
current used by fans 106 and/or 122, thermal data related to fans
106 and 122, the positions of dampers 110, the pressure
differential between pressure sensors 128 and 130, the pressure
differential between pressure sensors 140 and 142, the amount of
oxygen detected by oxygen sensors 144/144a-144c, the on/off status
of appliances 104, any alarms occurring on the controller or
appliances. Auxiliary computing device 216 may be configured to
monitor received data in real time and log an event occurrence if
predetermined settings are tripped. For example, if the pressure
differential exceeds a threshold value for more than thirty
seconds, an occurrence may be logged by auxiliary computing device
216.
[0071] According to some Even further, operational data received by
auxiliary computing device 216 may be used for real-time
notification, interdiction, and/or control. For example, auxiliary
computing device 216 may be configured to notify personnel via
email, phone, pager, system alarms, visible lights, etc. upon the
occurrence of a specified event. Statistical information can be
kept which can be used to predict system performance, including
system failure. By monitoring this data, system failures can be
predicted before they occur, providing for the ability to schedule
needed maintenance or down time.
[0072] According to some In addition to merely receiving data for
analysis and storage, auxiliary computing device 216 may be further
configured to provide feedback to pressure and combustion
controller 124 for the purpose of controlling appliances, fans,
dampers, etc. For example, nitrogen oxide (NOx) readings provided
by an optional NOx particle sensor may be collected by auxiliary
computing device 216. Because the draft of the exhaust system can
effect the amount of NOx particles emitted from the system, the
data may be used by pressure and combustion controller 124 to start
or shut down appliances and/or adjust fan speeds and/or damper
positions to keep NOx levels within predefined thresholds.
[0073] According to some Auxiliary computing device 216 may also
provide remote access to pressure and combustion controller 124 for
ease in performing a number of administrative functions. For
example, auxiliary computing device 216 may provide such access
through RS-232 (e.g. Hyperterminal), through a dial-up modem, or
over a network such as the Internet. Such a feature is advantageous
in that it can provide ease in the configuration and use of the
controller without the need for an extensive user interface (e.g.
display, keyboard, and/or touch-screen) associated with pressure
and combustion controller 124 itself.
[0074] According to some The remote access feature may provide the
capability to configure alarm set points, view and download any
logged data, create reports, view real-time data, and customize any
configurable aspect of the controller (e.g. control and alarm set
points, alarm text, appliance configuration, etc.) In the case that
the auxiliary computing device 216 provides such access from remote
locations (e.g. via the Internet or via dial-up access), the
feature may be helpful for troubleshooting and configuration by
expert personnel located remote from the actual controller. Such a
feature can used by the vendor to provide real-time, remote
troubleshooting and configuration assistance, or could be used by
the user of the control system to provide remote troubleshooting
where physical access to the pressure and combustion controller 124
is controlled and/or difficult. By providing remote access, the
physical controller location may be selected with less emphasis on
the ability for physical access.
[0075] According to some In addition to providing remote access to
pressure and combustion controller 124, remote access to any
auxiliary computing devices 216 may be provided to view and/or
download logged data and/or reports. Accordingly, in addition to a
user having direct access to pressure and combustion controller
124, access from other computing devices may be provided through
auxiliary computing device 216.
[0076] According to some According to the embodiment of the
pressure and combustion controller 124 shown in FIG. 2A and
according to other various embodiments that may be contemplated
based on the teachings herein, the processor 200 can perform a
number of functions that have not been performed in previous
exhaust systems and mechanical draft systems. For example, typical
exhaust system processors may control either an intake fan or an
exhaust fan, but usually do not control both intake fans and
exhaust fans. Furthermore, typical exhaust system processors are
not capable of controlling up to six appliances as is possible with
the processor 200. The expandability of the system to manage an
unlimited number of appliances with one processor is also an
advantage that the processor 200 has over typical processors. In
additional to these advantages, the processor 200 can perform other
functions as well, as is explained below.
[0077] When a three-phase fan is installed in the mechanical draft
system 100, the processor 200 may include an option to run the
mechanical draft system 100 in a rotation check mode, which
involves powering three-phase intake and/or exhaust fans at a low
level when the fans are first installed. Since the direction of fan
rotation is difficult to observe when a fan is rotating at typical
operating speeds, sometimes creating a strobe effect that increases
the difficulty, installers can benefit from the rotation check mode
to avoid mistakenly determining fan rotation.
[0078] When a specific fan-intake-check input is received by the
input devices 202, the input devices 202 signal the processor 200
to run the rotation check mode. In the rotation check mode, the
processor 200 signals the intake fan controller 206 and/or the
exhaust fan controller 208 to provide a low power signal to the
respective fans. With low power applied thereto, the fans will
rotate at a very slow speed, which may not be particularly useful
for moving air but can clearly demonstrate to an observer the
direction of rotation of the fan. The installer can observe the
rotation of the newly installed fan in the rotation check mode to
see whether or not the fan is rotating in the correct direction. If
not, then it will be known that the terminals from the power source
to the three-phase fan have been reversed. If reversed, the
installer can correct the power connections so that the fan will
rotate in the correct direction to force air appropriately. FIG. 5
illustrates an embodiment for checking fan rotation and is
described in more detail below.
[0079] The processor 200 may also contain a memory device for
storing a priority list that may be entered during the set-up of
the mechanical draft system 100. Utilizing the priority list, the
processor 200 can run a priority control procedure during less than
optimal operating conditions. For instance, when the exhaust fan
122 is malfunctioning, or if it has reached its maximum speed and
cannot provide sufficient draft to relieve a pressure build-up in
the chimney 118 or mechanical room 102, then the priority control
procedure is performed.
[0080] When one of the above conditions is detected, the priority
control procedure is initiated. First, the processor 200 shuts down
all the appliances via the appliance controller 210, the relay
board 212, and/or the external communication link 214 and relay
boxes. The processor 200 continues to check the differential
pressure periodically and starts up the first appliance on the
priority list. If a natural draft can be maintained with the one
appliance added, then a second and subsequent appliances can be
added until the differential pressure becomes unacceptable. At this
level, the last added appliance is shut off to keep the pressure
within acceptable tolerances. Additionally, the processor 200
continues to check the condition of the exhaust fan 122 to
determine when it can operate properly again. Once the exhaust fan
122 is determined to be functional, the processor 200 resets or
restarts the appliances 104 to their previous operating condition
by signals through the appliance controller 210, relay board 212,
and/or relay boxes.
[0081] The processor 200 may additionally be configured, based on
installation instructions, to run in a continuous mode. In the
continuous mode, the fans run continuously, even when the
appliances 104 are shut down. When the appliances are running, the
fans may be set to any level up to their maximum levels. When the
appliances are off, the fans may be set to their minimum speed
level.
[0082] Alternative to the continuous mode, the processor 200 may be
configured to shut the fans off during periods of appliance
inactivity. In this discontinuous mode, the processor 200 may
initiate a pre-purge mode and/or a post-purge mode during
transition periods between an appliance on-state and an appliance
off-state. In this mode, when the appliances are off and a request
for appliance operation is made, the processor 200 initiates the
pre-purge mode in which the fans are turned on for a predetermined
time before the appliances are actually fired. When the appliances
are on and a request is made to shut the appliances off, the
processor 200 shuts the appliances down and allows the fans to
continue running for a predetermined time. During set-up of the
mechanical draft system 100, an installer may input parameters
concerning the minimum and maximum speeds of the fans, whether the
system will run in a continuous mode or a discontinuous mode,
pre-purge and post-purge parameters (when in the discontinuous
mode), etc.
[0083] Furthermore, the processor 200 may be configured to maintain
an error log of errors detected in the mechanical draft system 100.
For instance, when a fan is indicated as being faulty, the
processor 200 may save a record of the time and duration that the
fan is out of service. The processor 200 may also indicate errors
by a warning or alarm signal on the display devices 204. The
tolerances within which the mechanical draft system 100 operates
can be entered during system set-up, thereby determining the
criteria by which the processor 200 detects errors, indicates alarm
conditions, and/or controls fans and appliances.
[0084] Another feature that the processor 200 may possess is a
procedure for running the fans in a discontinuous mode during long
periods of inactivity, referred to herein as a bearing cycle. The
bearing cycle runs the fans when they have not been running for a
long time in order to work the bearings of the fans and to help
lubricate the fans, thereby potentially extending the life span of
the fans. The bearing cycle involves timing the periods of system
inactivity with a timing device (not shown), such as, for example,
a timer or clock within the processor 200. The processor 200
continuously monitors whether or not the appliances are operating
and determines continuous stretches of time when the appliances are
off. When the timing device determines that a predetermined period
of inactivity has elapsed, the processor 200 signals the intake fan
controller 206 and exhaust fan controller 208 to run the fans at a
low speed for a short amount of time. The timing device is reset
whenever the appliances are turned on or whenever the bearing cycle
completes. This bearing cycle may then be repeated intermittently
when needed.
[0085] In addition to features such as the described bearing cycle
subroutine, processor 200 may also provide the ability to sequence
the activation or deactivation of appliances 104. The general
concept of appliance sequencing has been practiced for a number of
years, and the advantages of appliance sequencing are well known.
However, until now, such sequencing features have not been
advantageously integrated with a pressure control system, enabling
a number of improvements over prior art systems. A number of
exemplary sequencing approaches are described in U.S. Pat. Nos.
3,387,589; 4,598,668; 4,860,696 and 5,042,431, each of which are
hereby incorporated by reference.
[0086] Generally, the total demand of a multiple appliance system
may be divided up among two or more appliances and the number,
identity, and/or output setting of the appliances that are fired to
meet this demand at particular time can be controlled through the
sequencing feature of processor 200. For example, in a multiple
boiler system only the boilers that are needed to closely match the
heating load at any given time are fired. The output of each
individual boiler may also be modulated to operate at some fraction
of the boiler's total capacity. Controlling the number of boilers
and their output may advantageously cause boilers that are being
fired to continuously operate for longer periods of time. This is
advantageous because, for a number of reasons, the efficiency of an
appliance may increase by extending the period of time the
appliances operate continuously, much like the average miles per
gallon of a car increases when most of the driving is highway
mileage rather than stop-and-go driving. Additionally, the
efficiency of an appliance may change depending on the fraction of
the boiler's total capacity being used. Accordingly, processor 200
can be preprogrammed to operate the proper number of boilers at
their most efficient settings based on the total system demand.
[0087] Processor 200 may also take a number of other factors into
account in selecting which appliances to operate (and at what
capacity) under the specified conditions to meet an exhaust system
objective. For example, processor 200 may be programmed to operate
each appliance for a substantially equal time over an extended time
period, thereby providing an equal distribution of the use of the
appliances 104. However, in other situations, it may be
advantageous to prioritize the use (or non-use) of an appliance
having desired characteristics for a particular situation. For
example, one appliance may be able to heat water more quickly at
the expense of efficiency while other appliances may operate at a
more desirable efficiency or environmental impact. Accordingly,
processor 200 may be configured to sequence the appliances based on
an environmental condition, appliance usage, appliance
characteristic, fuel costs, or other user-desired parameters to
meet the exhaust system objective. Thus, it should be understood
that the programmed sequence for appliance activation may change
over time based on any number of desired factors.
[0088] According to one exemplary embodiment, assuming that
adequate draft can be maintained, the controller may be configured
to specify the number and/or identity of the available appliances
to be activated or deactivated based on the needs of the system
(e.g. a call for heat, or a release of an appliance). Notably, this
feature is distinguished from the priority function described
above, which may be used to prioritize the appliances activated in
the event that inadequate draft can be maintained for a desired
system need.
[0089] In one embodiment, a specified number of appliances may be
sequentially activated based on predetermined conditions. For
example, in the case that appliances 104 are boilers for heating a
water tank, a first boiler may be activated when the water
temperature in the tank drops five degrees below a set point. A
second boiler may be activated when the temperature drops ten
degrees below the set point. Likewise, a third boiler may be
activated when the temperature drops fifteen degrees below the set
point. Although temperature has been used as an example, any
measurable condition and associated set points could be used. In
some embodiments the condition for activating or deactivating an
appliance could originate from an external source, such as a
building management system.
[0090] In addition to designating a number of appliances to be
operational under the predetermined conditions, it is may also be
advantageous for the sequencing function of processor 200 to
identify the appliances 104 that are to be activated at a
particular time. Although the programmable sequencing feature has
been generally described, an exemplary sequencing subroutine is
explained in more detail with respect to FIG. 9.
[0091] Looking now to FIG. 3A, a front view of an embodiment of a
housing 300 that contains the pressure and combustion controller
124 is depicted. The front of the housing 300 includes a display
screen 302, such as an LCD window, for showing information about
the mechanical draft system 100. The housing 300 also includes
program buttons 304 for entering system set-up parameters and for
manually controlling the mechanical draft system 100. The program
buttons 304, for instance, may include buttons for scrolling
through options displayed on the display screen 302, buttons for
proceeding through and selecting program functions, and buttons for
setting or entering values. The housing 300 further includes LEDs
306 for visually indicating specific conditions of the mechanical
draft system 100.
[0092] FIG. 3B is a bottom view of the embodiment of the housing
300. The bottom of the housing 300 includes ports 308 for
connection to appliances, fans, differential transducers, etc. The
housing 300 may also include a communication terminal 304 for
connection to an external computer. For example, the communication
terminal 310 may be an RS-232 port for communicating with a
computer of a building management system. The communication
terminal 310 may be used to receive program updates for
re-programming or reconfiguring the processor 200 of the pressure
and combustion controller 124. Furthermore, system parameters may
be transmitted to an external computer via a communication network
such as the Internet.
[0093] Methods of operating a mechanical draft system are now
described with respect to FIGS. 4-8. These methods may include
functions of a number of the elements described above with respect
to FIGS. 1 and 2, including the pressure and combustion controller
124 and processor 200. Alternatively, the methods of FIGS. 4-8 may
be incorporated as programs stored on the processor 200 or other
suitable processor in a mechanical draft system.
[0094] FIG. 4 is a flow chart of an embodiment of a system set-up
routine that may be performed when an exhaust system or mechanical
draft system is being set up or installed in a building. Block 400
includes detecting the presence of an intake fan and an exhaust fan
to determine what fans will be controlled during system operation.
In block 402, the routine determines the types of fans that are
present. In decision block 404, it is determined whether each fan
is a single phase fan or a three phase fan. If a fan is a single
phase fan, flow proceeds to block 406, in which the routine
instructs or prompts the installer to install a triac board in a
pressure and combustion controller so that the proper signal level
may be delivered to the fan. If it is determined in decision block
404 that the fan is a three phase fan, then flow proceeds to block
408. In block 408, the routine instructs or prompts the installer
to install a variable frequency driver (VFD) in the exhaust system
or mechanical draft system so that three phase power signals may be
delivered to the fan. It should be noted that blocks 404, 406, and
408 may be repeated for both the intake fan and exhaust fan.
[0095] The set-up routine of FIG. 4 next allows the installer to
set maximum and minimum fan speeds for the intake fan and the
exhaust fan, as indicated in block 410. These limits are set based
on schematic and/or physical specifications and/or power
capabilities of the respective fans. A minimum fan speed, or idling
speed, is set when the mechanical draft system 100 is arranged for
continuous use. If the system is configured in a mode where the
fans are shut down when the appliances are not in use, referred to
as a discontinuous mode, then block 410 may include setting the fan
speeds during pre-purge and/or post-purge procedures.
[0096] In block 412, the system set-up routine may then run a
routine for checking the rotation of three-phase fans to ensure
that the power terminals connected to the fans are not wired
incorrectly thereby resulting in a fan rotating the wrong way. One
embodiment of the fan-rotation-check routine is described in more
detail below with respect to FIG. 5. Block 414 includes setting
pre-purge and post-purge parameters, such as the length of time
that the fans will run after a call for heat has been requested and
the length of time that the fans will run after the appliances are
turned off. In block 416, the installer is prompted to input
information to set alarm limits and delays according to user
preferences and/or system design.
[0097] In block 418, the number of appliances to be connected in
the exhaust system is determined. In decision block 420, it is
determined whether or not the number of appliances is six or fewer.
If so, then the pressure and combustion controller does not need to
be altered in any way, since it is capable of handling this number
of appliances without additional circuitry, and the routine
proceeds to block 428. If there are more than six appliances
connected in the exhaust system, then flow proceeds to decision
block 422, where it is determined whether or not there are ten or
fewer appliances. If there are seven to ten appliances in the
system, then flow proceeds to block 426 where the installer is
instructed or prompted to install an optional relay board in the
pressure and combustion controller. With the relay board, the
pressure and combustion controller may be capable of controlling up
to ten appliances. If it is determined in decision block 422 that
more than ten appliances are connected in the exhaust system, then
flow proceeds to block 424. In block 424, the installer is
instructed or prompted to install at least one relay box external
to the pressure and combustion controller and connect the relay box
or boxes to the pressure and combustion controller in a daisy chain
fashion if necessary. Each relay box allows up to six additional
appliances to be controlled. An unlimited number of relay boxes may
be connected to allow for controlling any number of a plurality of
appliances.
[0098] In block 428, the set-up routine of FIG. 4 detects the
presence of the appliances and dampers. In block 430, an appliance
priority list is set. Typically, appliances high on the priority
list are those appliances that are located closest to the vertical
stack or chimney. Alternatively, the type of appliance (boiler
versus water heater, for example) may dictate which appliances are
higher on the priority list. Other priority factor may be
considered as well, such as appliances that are larger, newer, or
more critical. In block 432, the blade positions of adjustable
dampers in the exhaust ducts from each appliance are set in order
to adjust the draft from individual appliances. Typically,
appliances located closer to a vertical stack or chimney experience
greater draft. Therefore, the dampers connected to the appliances
in these locations may be adjusted by more greatly restricting
exhaust flow from the appliances to account for this phenomenon.
Also, block 432 may further include setting the blade position of a
modulating damper in ducts receiving the air from the exhaust ducts
in order to adjust the draft from all appliances.
[0099] FIG. 5 is a flow chart of an embodiment of a
fan-rotation-check routine. The rotation of three phase fans may be
checked during set-up of the exhaust system or mechanical draft
system in order to ensure that the fans are wired to the power
source correctly. If the terminals from the power source are
reversed, the fan will rotate in a direction opposite from the
desired direction, causing the flow of air to be forced in an
undesirable manner. When the pressure and combustion controller
receives a signal to initiate the fan-rotation-check routine, then
the procedure, such as the one shown in FIG. 5, is executed.
[0100] The procedure for checking the rotation of the fans includes
connecting the fans to the power source, as indicated in block 500.
After the connections are made, block 502 includes supplying a low
power signal to the fans to cause the fans to rotate at a very slow
speed. In block 504, the installer may visually inspect the fans to
see the direction of rotation. In decision block 506, the installer
determines whether or not the direction of rotation is correct. If
not, then flow proceeds to block 508, which involves instructing or
prompting the installer to change the power source connections
leading to the fans. After changing the power terminals, the
procedure may end or alternatively may return back to block 502 for
rechecking. If it is determined in decision block 506 that the fans
are rotating correctly, then the fan rotation check routine ends.
Another advantage of running the fan-rotation-check routine during
set-up is that the slower fan speeds are safer for the
installers.
[0101] FIG. 6 is a flow chart illustrating an embodiment of a
routine performed by the pressure and combustion controller after
set-up and during normal operation of the exhaust system or
mechanical draft system. Block 600 indicates that the differential
pressure is checked intermittently and the operation of the fans is
also checked. In decision block 602, it is determined whether or
not the differential pressure is within an adequate range and
whether or not the fans are operating properly. If so, the routine
is directed to block 604 in which the speed of the fans is
maintained. With the fan speeds maintained, flow returns to block
600 for intermittent checking. If it is determined in decision
block 602 that the differential pressure exceeds a predetermined
threshold or the fans are not operating acceptably, then flow
proceeds to decision block 606.
[0102] In decision block 606, the specific problem is identified by
determining whether the exhaust fan is fine. If not, block 608 is
conducted in which a priority sub-routine, such as the routine
defined in FIG. 7, is run. Flow then returns to block 600 for
continued monitoring. If the problem identified in block 606 is not
the fans, then it is determined that the differential pressure is
actually the problem. At this point, flow proceeds to decision
block 610 for determining whether the out-of-range differential
pressure is an excessive positive differential pressure or an
excessive negative differential pressure. It should be noted that,
in this embodiment, the pressure measured inside the mechanical
room is connected to a negative terminal (or reference terminal) of
a transducer and the pressure measured in the atmosphere is
connected to a positive terminal of the transducer. However, the
connections of the pressure measurements to the terminals of the
transducer may be reversed if desired, and the proper response
according to this routine is carried out.
[0103] If it is determined in block 610 that a positive
differential pressure is present, thereby indicating that the
pressure inside the mechanical room is significantly greater than
the atmospheric pressure, then flow proceed to block 612. In block
612, the speed of the exhaust fan is increased and/or the speed of
the intake fan is decreased in an attempt to equalize the pressure
in the mechanical room. From this point, flow returns to block 600
for again intermittently monitoring the exhaust system. If it is
determined in block 610 that a negative differential pressure
exists, indicating a pressure inside the mechanical room
significantly less than the atmospheric pressure, then the
procedure flows to block 614. In block 614, the speed of the
exhaust fan is decreased and/or the speed of the intake fan is
increased. Furthermore, block 614 may include adjusting the dampers
to more greatly restrict the exhaust from the individual appliances
and/or from all appliances. The routine then returns to block 600
for continuous intermittent monitoring.
[0104] FIG. 7 is a flow chart illustrating an embodiment of a
procedure for running a priority sub-routine in the situation when
the differential pressure is determined to be outside of an
acceptable range and the exhaust fan cannot provide adequate draft.
Insufficient draft may be caused by the exhaust fan not operating
properly or when the speed of the exhaust fan has reached its
maximum speed and a request for a greater speed is called for. In
such situations, the appliances are shut down, and a priority list,
which is established during system set-up as described above, may
then be used to establish which appliance is turned on first,
provided that the chimney is capable of naturally exhausting air
with an inadequate exhaust fan. If adequate draft can be maintain
after restarting the first appliance on the priority list, then the
second appliance on the list is turned on. This procedure is
repeated until the greatest number of appliances has been turned on
while a natural draft can be maintained in the chimney. Reference
is now made to the flow chart of FIG. 7.
[0105] In block 700, when sufficient draft cannot be maintained and
the differential pressure is outside acceptable levels, the
appliances are shut down. In block 702, only the first appliance on
the priority list is allowed to run. In block 704, after the
appliance has run for a short amount of time, the differential
pressure is checked again to determine if the chimney provides an
adequate natural draft. In decision block 706, it is determined
whether or not the differential pressure is within an acceptable
range. If it is, the next appliance on the priority list is allowed
to operate, as indicated in block 708, and flow returns to block
704 to recheck the differential pressure. Blocks 704, 706, and 708
are repeated until it is determined that the differential pressure
is determined to be unacceptable in decision block 706. In this
case, the appliance on the priority list that was added last is
shut down, as indicated in block 710.
[0106] In decision block 712, the priority procedure determines if
the exhaust fan is working. If not, then the differential pressure
is checked again in decision block 714. As long as the pressure is
determined to be fine, the appliances turned on in the exhaust
system are allowed to run and the exhaust fan is checked until it
is working again. If the pressure is determined to be unacceptable
in block 714, the latest-added appliance on the priority list is
turned off in block 710. Once it is determined that the exhaust fan
is working in decision block 712, all of the appliances may be
turned on, as indicated in block 716, and the priority sub-routine
ends.
[0107] FIG. 8 is a flow chart illustrating an embodiment of a
bearing cycle routine. A bearing cycle is a cycle of turning the
fans on during periods of appliance inactivity. For instance, when
heating appliances are not used for long periods of time, such as
during warm summer months, the bearing cycle operates the fans for
a predetermined amount of time, preferably at a low speed, such as
25% capacity, after a certain period of inactivity. The bearing
cycle thus works the bearings of the fans in order to keep the fans
from becoming rusty or locking up.
[0108] The bearing cycle procedure contains block 800, which
includes resetting a timer that is used to determine a continuous
length of time that the appliances are not running. In block 802,
the appliances are checked to determine whether or not they are
running. In decision block 804, if the appliances are running, they
are intermittently checked again in block 802 until they are shut
down. When the appliances are shut down, the timer is started, as
indicated in block 806, to time the length of inactivity. If it is
determined in decision block 808 that a predetermined time period
has elapsed, indicating an extended period of inactivity, then the
fans are turned on for a certain amount of time, as indicated in
block 810, to adequately work the bearings of the fans. If the
predetermined time period has not elapsed in block 808, then flow
proceeds to decision block 812 in which it is determined whether or
not the appliances have been called back into service. If they are,
then flow returns to block 800 to restart the timer and repeat the
process. If the appliances remain off, then the timer continues to
run until the predetermined time period has elapsed in block
808.
[0109] FIG. 9 depicts a flow chart of an embodiment of a sequencing
subroutine 900 that may be used in conjunction with the described
mechanical draft system. Such sequencing blocks may, for example,
be executed by processor 200 of pressure and combustion controller
124. At block 902, a signal is received from a remote device which
can be used for determining a change in an operating characteristic
of the system. For example, such operating characteristics may be a
change in total system demand, a change in emissions output, or a
change in efficiency. For example, such a signal may be transmitted
from a building management system, an appliance, a fan, or one or
more sensors. The signal could, for example, be a pressure reading,
a call for heat, an emissions reading, an equipment alarm, an
equipment failure, a measurement of efficiency, or any other signal
to the controller that indicates (or could be used to indicate) a
change in the active number or identity of appliances is needed.
Such a change could include an increase or decrease in the number
of appliances, or a change in the identity of the operating
appliances to meet one or more desired system objectives. In one
embodiment, the desired system objective is meeting a total system
demand. However, system objectives may vary and could be also be,
for example, meeting a desired efficiency or emissions output, for
example.
[0110] At step 904, it is determined whether the system operating
characteristics have changed such that a different quantity or
identity of appliances are needed to meet the objective based on
the received signals. If the characteristics have not changed
enough to warrant a change in the activated appliances (the NO
condition), the signals are continuously monitored at block 902
until such a change occurs.
[0111] However, if the operating characteristics have changed (the
YES condition), it is determined whether all available appliances
are needed to satisfy the desired system objective at block 906.
For example, the system may determine that all appliances should be
activated to operate at the desired system efficiency or to meet a
desired demand. If all available appliances in the system are
required to meet the system objective (the YES condition), all of
the appliances are activated through their communications interface
with appliance controller 210 and/or relay board 212 of pressure
and combustion controller 124. In this case, no further sequencing
decisions are required.
[0112] However, if less than all of the available appliances are
needed to meet the system objective (the NO condition), the
sequencing algorithm may perform a number of sequencing decisions.
For example, at block 910, the number of appliances needed to meet
the indicated exhaust system objective is determined. In addition
to determining the total appliances needed to meet the demand, this
step may also include calculating how many appliances need to be
activated or deactivated to reach the total. The step of
determining the number of appliances needed to meet the objective
may be programmable, and may, for example, be determined using
collected data (e.g. from the received signal) and a look up table,
a calculation, or one or more thresholds.
[0113] At block 912, the identity of the appliances to be activated
or deactivated may also be determined based on programmable
settings, appliance specifications, and/or historical appliance
operational data. For example, the appliance identities may be
advantageously selected to equalize their use over a period of
time, increase efficiency, and/or increase performance.
Accordingly, at block 914, the identified appliances are activated
or deactivated are through their respective communications
interface with appliance controller 210 and/or relay board 212 of
pressure and combustion controller 124.
[0114] The flow charts of FIGS. 4-9 show the architecture,
functionality, and operation of possible implementations of the
mechanical draft system control software. In this regard, each
block represents a module, segment, or portion of code, which
comprises one or more executable instructions for implementing the
specified logical functions. It should also be noted that in some
alternative implementations, the functions noted in the blocks may
occur out of the order noted in the figures. For example, in the
set-up routine of FIG. 4, two blocks shown in succession may in
fact be executed substantially concurrently or the blocks may be
executed in the reverse order, depending upon the specific
functional programming involved.
[0115] The mechanical draft system control programs, which comprise
an ordered listing of executable instructions for implementing
logical functions, can be embodied in any computer-readable medium
for use by an instruction execution system, apparatus, or device,
such as the processor 200 or other suitable computer-based system,
processor-controlled system, or other system that can fetch the
instructions from the instruction execution system, apparatus, or
device and execute the instructions. In the context of this
document, a "computer-readable medium" can be any medium that can
contain, store, communicate, propagate, or transport the program
for use by the instruction execution system, apparatus, or device.
The computer-readable medium can be, for example, an electronic,
magnetic, optical, electromagnetic, infrared, or semiconductor
system, apparatus, device, or propagation medium. More specific
examples of the computer-readable medium include the following: an
electrical connection having one or more wires, a portable magnetic
computer diskette, a random access memory (RAM), a read-only memory
(ROM), an erasable programmable read-only memory (EPROM or Flash
memory), an optical fiber, and a portable compact disc read-only
memory (CDROM). In addition, the scope of the present disclosure
includes the functionality of the herein-disclosed embodiments
configured with logic in hardware and/or software mediums.
[0116] It should be emphasized that the above-described embodiments
are merely examples of possible implementations. Many variations
and modifications may be made to the above-described embodiments
without departing from the principles of the present disclosure.
All such modifications and variations are intended to be included
herein within the scope of this disclosure and protected by the
following claims.
* * * * *