U.S. patent application number 10/964091 was filed with the patent office on 2006-04-13 for refrigeration mechanical diagnostic protection and control device.
Invention is credited to George L. Holstein, Shawn P. Sullivan, George R. JR. Tracey.
Application Number | 20060075771 10/964091 |
Document ID | / |
Family ID | 36143904 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060075771 |
Kind Code |
A1 |
Tracey; George R. JR. ; et
al. |
April 13, 2006 |
Refrigeration mechanical diagnostic protection and control
device
Abstract
In vapor compression refrigeration systems a mechanism and
method are provided for protecting a compressor from failures
related to lack of superheat, loss of lubricating oil and other
system malfunctions. Also provided is a mean of monitoring system
conditions and providing service personnel with a quick manner of
diagnosing problems.
Inventors: |
Tracey; George R. JR.;
(Runnemede, NJ) ; Sullivan; Shawn P.; (Bear,
DE) ; Holstein; George L.; (Bear, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
P O BOX 2207
WILMINGTON
DE
19899
US
|
Family ID: |
36143904 |
Appl. No.: |
10/964091 |
Filed: |
October 13, 2004 |
Current U.S.
Class: |
62/506 ; 62/181;
62/228.3 |
Current CPC
Class: |
Y02B 30/70 20130101;
F25B 2600/111 20130101; F25D 2400/36 20130101; F25B 2700/21152
20130101; F25B 2700/2106 20130101; F25B 2600/19 20130101; F25B
2700/1933 20130101; F25B 49/005 20130101; F25B 49/027 20130101;
F25B 2700/21151 20130101; Y02B 30/743 20130101; F25B 2500/19
20130101; F25B 2700/1931 20130101; F25B 2600/21 20130101; F25B
2339/041 20130101; F25B 2700/2108 20130101 |
Class at
Publication: |
062/506 ;
062/181; 062/228.3 |
International
Class: |
F25D 17/00 20060101
F25D017/00; F25B 41/04 20060101 F25B041/04; F25B 1/00 20060101
F25B001/00; F25B 49/00 20060101 F25B049/00; F25B 39/04 20060101
F25B039/04 |
Claims
1. A cooling system including a compressor, a condenser having a
fan motor and a heat exchange coil, and an evaporator with
refrigerant flowing through the system, an outside ambient
temperature sensor for determining outside ambient temperature, and
a device for constantly calculating sub-cooling of the refrigerant
and determining when the sub-cooling is below a predetermined level
at a given ambient temperature, and generating a signal
representative of the determined sub-cooling.
2. A cooling system as in claim 1 including cooling means for
lowering the temperature of the refrigerant when the determined
sub-cooling is below the predetermined level.
3. A cooling system as in claim 2 wherein the cooling means is
water spray onto the heat exchange coil of the condenser.
4. A cooling system as in claim 2 wherein the cooling means is an
air flow onto the heat exchange coil of the condenser.
5. A cooling system as in claim 1 including a fan limiting device
constructed and arranged to cycle the condenser fan motor at
ambient temperatures below a predetermined level to thereby
maintain a substantially constant pressure on the refrigerant
flowing through the cooling system.
6. A cooling system as in claim 5 wherein the predetermined
temperature level is within the range of 60.degree. to 70.degree.
F.
7. A cooling system as in claim 5 including a device for
determining pressure of the refrigerant flowing through the cooling
system and for deenergizing the compressor when the refrigerant
pressure drops below a predetermined level.
8. A cooling system as in claim 7 wherein the device for
deenergizing the compressor when the refrigerant drops below a
predetermined level also deenergizes the compressor when the
refrigerant pressure is above a predetermined level.
9. A cooling system as in claim 8 including a display of
refrigerant temperature and pressure.
10. A cooling system as in claim 7 including a device for
determining superheat of the refrigerant and for deenergizing the
compressor when the superheat drops below a predetermined
level.
11. A cooling system as in claim 10 including display means for
indicating a low superheat warning within a range slightly above
the predetermined level below which the compressor is
deenergized.
12. A cooling system as in claim 11 including a display for
indicating satisfactory superheat, superheat warning and superheat
failure.
13. A cooling system including a compressor, a condenser having a
fan motor and an exvaporator with refrigerant flowing through the
system, an outside ambient temperature sensor for determining
outside ambient temperature, and a fan limiting device constructed
and arranged to cycle the condenser fan motor at ambient
temperatures below a predetermined temperature level to thereby
maintain a substantially constant pressure on the refrigerant
flowing through the cooling system.
14. A cooling system as in claim 13 wherein the predetermined
temperature level is within the range of 60.degree. to 70.degree.
F.
15. A cooling system as in claim 13 including a device to determine
pressure of the refrigerant flowing through the cooling system and
to deenergize the compressor when the refrigerant pressure drops
below a predetermined level.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to refrigeration, air
conditioning and heat pumps and more particularly to a method and
apparatus for monitoring and controlling system pressures,
temperatures, and superheat and subcooling.
[0002] In the operation of refrigeration and air conditioning
systems, the cooling effect is provided by the change in state of
the refrigerant from a liquid to a gas in the evaporator of the
system. The gaseous refrigerant is compressed by a compressor and
is condensed to a liquid state in a condenser before passing
through an expansion valve upon being returned to the
evaporator.
[0003] The failure of a compressor is usually very costly. Most
compressor failures can be traced back to one of the following
system conditions: "refrigerant floodback", "flooded starts",
"slugging", excessively high discharge temperature or loss of
lubricating oil.
[0004] "Refrigerant floodback" results when liquid refrigerant
returns to the compressor during the running cycle. The lubricant
oil becomes mixed with refrigerant to the point that it cannot
properly lubricate the load bearing surfaces. This situation can
usually be prevented by 1) maintaining proper evaporator and
compressor superheat, 2) correcting abnormally low load conditions,
and/or 3) installing accumulators to stop uncontrolled liquid
return.
[0005] "Flooded starts" are the result of liquid refrigerant vapor
migrating to the crankcase oil during the off cycle. When the
compressor starts, the diluted oil cannot properly lubricate the
load bearing surfaces causing erratic wear. This situation can be
prevented by 1) locating the compressor in a warm ambient location
or installing a continuous pump down system, and/or 2) installing a
crankcase heater.
[0006] "Slugging" is the result of trying to compress liquid
refrigerant and/or oil in the compressor cylinders. Slugging is an
extreme floodback condition. This situation can be prevented by 1)
maintaining proper evaporator and compressor superheat, 2)
correcting abnormally low load conditions, 3) installing
accumulators to stop uncontrolled liquid return, and/or 4) locating
the compressor in warm ambient location or installing a continuous
pump down system.
[0007] In the case of excessively high discharge temperature the
compressor head and cylinders become so hot that the oil loses its
ability to lubricate properly. This causes rings, pistons and
cylinders to wear resulting in "blow by", leaking valves and metal
debris in the oil. Excessively high discharge temperature can be
corrected by 1) correcting abnormally high load conditions, 2)
correcting high discharge pressure conditions, 3) providing proper
compressor cooling, and/or 4) providing proper compressor
cooling.
[0008] Loss of oil is the result of insufficient oil in the
crankcase to properly lubricate the load bearing surfaces. When
there is not enough refrigerant mass flow in the system to return
oil to the compressor as fast as it is pumped out, there will be a
uniform wearing or scoring of all load bearing surfaces. To protect
against loss of oil 1) check oil failure control operation, 2)
check system refrigerant charge, and/or 3) correct abnormally low
load conditions or short cycling.
[0009] Superheat is defined as the temperature of vapor above the
boiling point temperature of its liquid at that pressure. It is
calculated in vapor compression refrigeration systems by 1)
converting the suction side line pressure to a saturated vapor
temperature, using a temperature/pressure chart for the specified
refrigerant, 2) measuring the suction side line temperature six
inches from the inlet to the compressor, and 3) subtracting the
pressure to temperature conversion from the suction line
temperature. The result is the system superheat.
[0010] Subcooling is a measure of the heat being dissipated to the
atmosphere at the exterior heat exchange coils. It is calculated in
vapor compression refrigeration systems by 1) converting the
discharge line pressure to temperature, using a
temperature/pressure chart for the specified refrigerant, 2)
measuring the line temperature at the liquid line service port, and
3) subtracting the pressure to temperature conversion from the line
temperature. The result is the system subcooling temperature.
[0011] In the prior art U.S. Pat. No. 4,563,878 describes a method
for compressor protection from low superheat conditions by system
shutdown, but does not indicate what caused the failure conditions.
Investigation would have to begin, usually involving the connection
of refrigerant pressure gauges. Each time that such industry
standard gauges are connected to service ports on the refrigerant
lines refrigerant is allowed to escape to the atmosphere. Repeated
connections and disconnections allow a significant enough volume of
refrigerant to escape and make up refrigerant must be supplied to
maintain a proper system charge. Another cause for concern is
introduction of foreign materials from the gauge set into the
system.
[0012] Other prior art addresses the monitoring of superheat and
initiate compressor shutdown. U.S. Pat. No. 5,209,076 details a
microprocessor based control device which will shut a compressor
down if a low superheat state is entered. This device does not
monitor or display other system parameters such as temperature and
pressure. Further it does not provide simple system status
indicators for the actual condition of superheat.
[0013] U.S. Pat. No. 5,209,076 does not include in its
functionality the options for energizing external subcooling or fan
cycling relays. This device also relies on analog to digital
converters for refrigerant pressure sensing, a method with inherent
inaccuracies that would not provide the level of accurate control
required with a refrigeration system under heavy load
conditions.
[0014] Other examples of prior art have been found, such as U.S.
Pat. No. 4,038,061 and U.S. Pat. No. 4,545,212 that monitor system
conditions and initiate some action towards compressor protection.
These devices, however, only address one or two dangerous systems
conditions and fail to provide and adequate level of compressor
protection.
SUMMARY OF THE INVENTION
[0015] Accordingly it is the object of the present invention to
protect a refrigeration system or air conditioner compressor
against adverse operating conditions such as floodback, slugging,
excessively high discharge temperature and loss of oil. The present
invention will also protect the system against high refrigerant
line pressure and low refrigerant line pressure.
[0016] This and other objects of the present invention are attained
by monitoring and controlling the system pressures (high and low),
temperatures (both system and ambient), superheat and subcooling.
The present invention uses a microprocessor to sense pressure
inputs using pressure transducers (example: 4-20 mili-amp, 0-10
Volt DC, or resistance) for high side and low side pressures.
Temperature sensors are connected to the liquid line, the suction
line and positioned to sense outdoor ambient temperature. This
information is conveyed to the microprocessor. With this
information the firmware installed in the microprocessor can
calculate the superheat, subcooling, discharge temperature, high
side pressure, low side pressure and outdoor temperature. Through
the use of control relays the microprocessor can protect the
compressor from mechanical failure from the previously mentioned
conditions.
[0017] The present invention will also prove useful on initial
start up of a refrigeration system or air conditioner by checking
the system's refrigerant charge and superheat with the
manufacturer's specifications for both.
[0018] It is also the purpose of this invention to assist a service
technician in determining the present state of the refrigeration
system and in rapidly determining what fault condition(s) may have
occurred. This is done through the use of a bank of LED indicators
showing the present superheat temperature status ("OK", "WARNING"
or "FAILURE"), the low pressure condition, high pressure condition,
discharge temp condition, and sensor status. This bank of LEDs
represents the first line of diagnosis, allowing even moderately
skilled individuals to quickly determine the system's condition
and/or reasons for failure. In the past this would have entailed
the connection of a set of test gauges to service ports on the
refrigeration system, allowing some refrigerant to escape to the
environment as well as possibly allowing non-condensables to enter
the system.
[0019] Further detailed values can be displayed on an LCD digital
display which can show all data collected and calculated by the
microprocessor.
[0020] The present invention is designed to work in conjunction
with most sensing and metering devices presently used on
refrigeration systems. Examples of these devices include capillary
tube, thermostatic expansion valves, fixed orifice and electronic
expansion valves.
[0021] The invention also allows for condenser fan cycling (either
vari-speed or simply ON/OFF) to maintain a head pressure range in
low ambient conditions. Under high ambient conditions when proper
subcooling is difficult to maintain, the invention can energize an
auxiliary subcooling device.
[0022] In its preferred embodiment the apparatus of the present
invention is installed as a stand alone unitary controller but can
easily be connected to building automation controls through the
built in communication port. Further, this communication port can
be configured to energize a telephone access module to alert
service personnel of fault conditions.
[0023] Also, the present invention can be configured for different
refrigerants (example: R-22 or R410-A) through the use of
preprogrammed pressure to temperature charts in the firmware.
[0024] In addition to system protection from low superheat, the
present invention uses the collected data to further increase
system efficiency by providing a method of increasing subcooling
under heavy load conditions or decreasing subcooling when
needed.
[0025] An electrical device monitors the mechanical aspects of
standard refrigeration and air conditioning systems. The device
protects these systems by calculating temperature, pressure,
superheat, sub-cooling, ambient temperature and controlling system
components. The device provides an easy, graphic representation of
system conditions and faults for rapid verification of satisfactory
operating parameters. Further detailed system conditions are
provided for more extensive examination through use of digital
read-outs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Novel features and advantages of the present invention in
addition to those noted above will become apparent to persons of
ordinary skill in the art from reading the following detailed
description in conjunction with the accompanying drawings wherein
similar reference characters refer to similar parts and in
which:
[0027] FIG. 1 is a diagrammatic view of a refrigeration system and
a protection system, according to the present invention;
[0028] FIG. 2 is a functional block diagram of the protection
system of the present invention;
[0029] FIG. 3 is the main logic flow chart of the software in the
microprocessor controller according to the present invention;
[0030] FIG. 4 is a logic flow chart of the software in the sensor
polling subroutine, according to the present invention;
[0031] FIG. 5 is a logic flow chart of the software in the sensor
validity check subroutine, according to the present invention;
[0032] FIG. 6 is a logic flow chart of the software in the fault
logging subroutine, according to the present invention;
[0033] FIG. 7 is an illustration of the device display panel with
detachable diagnostic tool, according to the present invention;
and
[0034] FIG. 8 is an illustration of an alternative device display
panel with LED and LCD displays, according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] Referring in more particularity to the drawings, FIG. 1
illustrates a diagram of a standard refrigeration system which
includes a compressor 26 driven by an electric motor in a
conventional manner. The discharge side of the compressor 26
connects with a discharge line 42 which delivers the compressed
refrigerant in a gaseous state to a condenser 10 or in some systems
multiple condensers. Near the outlet of the compressor 26 a
discharge temperature sensor 36 is connected with the discharge
line 42. The gaseous refrigerant condenses into a liquid state in
the condenser 10. Located at the inlet air side of the condenser 10
is an outdoor temperature sensor 28.
[0036] Exiting the condenser 10, the liquid refrigerant travels in
the liquid line 44 to a receiver 12 which stores excess refrigerant
during low load conditions.
[0037] Exiting the receiver 12 the refrigerant travels through the
liquid line 46. Located on the supply line 46 near the exit of the
receiver 12 are a high pressure transducer 30 and a subcooling
temperature sensor 32. The liquid supply line 46 typically travels
through a filter-dryer 14, then through a sight glass 16 and a
solenoid valve 18 before entering an expansion valve 20 where the
liquid refrigerant changes state back to a gas.
[0038] Gaseous refrigerant enters an evaporator 22 where heat is
exchanged with the building or refrigerated enclosure. Refrigerant
vapor leaves the evaporator 22 and travels through a suction line
48 into a suction accumulator 24 and finally back to the compressor
26. Situated on the suction line 48 after the suction accumulator
24 is a low pressure transducer 40. Situated on the suction line 48
after the suction accumulator 24 but before the compressor 26 is a
suction temperature sensor 34. Both the low pressure transducer 40
and the suction temperature sensor 34 are located from 6'' to 18''
from the compressor.
[0039] FIG. 2 is a functional block diagram of the present
invention in which a device 102 includes a conventional
microprocessor 104 which receives power from a power supply and
isolation circuits 152 connected to the power interface 128 which
receives power from external AC supply 154. The device 102 is
factory programmed but can be modified in the field with dip
switches 134 on a circuit board. A liquid crystal display (LCD)
module 162 may be attached to the device 102.
[0040] A detachable module 162 includes an LCD 168 for monitoring
of system conditions and a key pad 170 for scrolling through the
various system readings. The detachable module 162 has a suitable
interface 164 with the microprocessor 104, and the keypad 170 has
an interface 166 with the microprocessor 104. The detachable module
162 communicates with the microprocessor 104 through the keypad and
display control interface 136.
[0041] A real time clock 150 connects to the microprocessor 104
through a suitable interface 126. A reset key 172 is provided on
the device 102 and permits the device to be reset by a service
technician after a system lockout.
[0042] A light emitting diode (LED) display bank 160 has a number
of LEDs to show system status at all times. These individual LEDs
include, but are not limited to, "System OK", "Low Pressure
Failure", "High Pressure Failure", "Discharge Temperature Failure",
"Sensor Failure", "Superheat OK", "Superheat Warning", "Superheat
Failure". The self diagnosis LED interface 132 on the
microprocessor 104 sends a voltage output to the display bank 160
based on inputs from external sensors and calculations performed in
the microprocessor 104.
[0043] There are six external sensor inputs: outdoor temperature
sensor 106, suction temperature sensor 108, discharge temperature
sensor 110, liquid line temperature sensor 112, low pressure sensor
114 and high pressure sensor 116. All the external sensors
communicate with the microprocessor 104 through a sensor signal
interface 118.
[0044] The device 102 is provided with memory circuits that connect
with the microprocessor 104 through a memory interface 124. The
memory circuits includes random access memory (RAM) 146 having a
battery backup 148, programmable read only memory (PROM) 144 and an
electrically erasable read only memory (EEPROM) 142.
[0045] An equipment cut off and alarm relay control 130 on the
microprocessor 104 communicates with a normally open relay 158
which controls power to the compressor 26.
[0046] A subcooling relay interface 120 on the microprocessor 104
is a normally open contact that would be closed based on
calculations performed in the microprocessor 104. Voltage output
would energize a subcooling relay 138 which would operate an
external device to maintain proper subcooling.
[0047] A fan cycling relay interface 122 on the microprocessor 104
is also a normally open contact that would be closed based on
calculations performed in the microprocessor 104. Voltage output
would de-energize a fan motor relay 140, shutting off the condenser
fan. This will help to maintain a constant refrigerant head
pressure during low ambient temperature conditions. The condenser
fan would be allowed to resume operation when system conditions
demand.
[0048] A communications port interface 174 sends information to the
communications port 156 so the information from the microprocessor
104 can be shared with existing building control systems.
[0049] FIG. 3 is a logic flow chart of the software in the
microprocessor controller 104. From a start block 202, block 204 is
entered to get readings from all sensors, including refrigerant
pressure before the compressor, refrigerant pressure after the
compressor, refrigerant discharge temperature, refrigerant suction
line temperature, refrigerant temperature at the receiver and
ambient temperature. These values are stored for future use.
[0050] In block 206 the values returned from block 204 are
evaluated for plausibility. If they are zero or outside the
possible high limit it is determined that there is a sensor
failure. Block 208 evaluates the result of the sensor check
performed in block 206. If it is determined that a sensor failure
has occurred we proceed to block 234, a fault and logging
subroutine, from there to block 242 for a system shut down, and
then to block 244 to terminate the logic loop.
[0051] If all sensors respond and pass plausibility test in block
208, block 210 is entered and a two minute start up delay is
initiated. This delay is to prevent an operator from initiating
repeated system starts in rapid succession. If a system shutdown
were to occur, a two minute delay may be enough time for minor
system difficulties to stabilize enough for a successful startup
and to provide protection against compressor short cycling.
[0052] After the two minute startup delay, block 212 is entered
wherein the compressor start relay is energized causing the
compressor to start.
[0053] Block 214 polls all sensors as in block 204.
[0054] Block 216 tests for sensor validity as in block 206.
[0055] Block 218 evaluates the response from block 216. If there is
a sensor failure then block 236, a fault and logging subroutine, is
entered.
[0056] If all sensors respond and pass plausibility in block 218
then block 220 is entered, wherein the discharge side refrigerant
temperature is evaluated. If the refrigerant temperature is found
to be within acceptable limits, block 222 is entered. Block 222
evaluates the liquid refrigerant pressure, and if the pressure is
found to be within acceptable limits then block 224 is entered.
Block 224 checks for refrigerant low pressure. If the refrigerant
pressure is found to be above the low limit then block 226 is
entered. Block 226 evaluates the calculated value for superheat to
determine if it is within preset limits. If superheat is acceptable
then block 228 is entered to determine if external system
subcooling is required. If external subcooling is required block
230 is entered and an external subcooling relay is energized. After
block 230 or if subcooling was not required, block 232 is entered
where "system OK" LED is energized and all other system warning
LEDs are turned off.
[0057] Block 234 is then entered where a 0.5 second logic delay is
entered. This delay is built in to reduce the number of sensor
polling events to a reasonable number. Polling 20 or 30 times a
second is not required. After the logic delay in block 234, block
214 is reentered, all sensors are polled and the logic loop
continues.
[0058] In the first logical pass through blocks 220, 222, 224 and
226, the dectections are as follows.
[0059] If block 220 detects a value higher than the compressor
manufacturer specified maximum for discharge temperature then a
system fault has occurred.
[0060] If block 222 detects a value higher than the compressor
manufacturer specified maximum for refrigerant pressure then a
system fault has occurred.
[0061] If block 224 detects a value lower than the compressor
manufacturer specified minimum for refrigerant pressure then a
system fault has occurred.
[0062] If block 226 detects a value lower than the compressor
manufacturer specified minimum for superheat (typically 3 degrees)
then a system fault has occurred.
[0063] If a system fault is determined in blocks 220, 222, 224 or
226 then a fault and logging subroutine 236 is entered.
[0064] After returning from block 236, block 238 determines if the
system has faulted more than three times for the same reason. If
three sequential faults have occurred then a system shut down 242
is initialed. If less than three sequential faults have occurred
then block 240 is entered initiating a 90 second system delay
before attempting a compressor re-start.
[0065] FIG. 4 is a logic flow chart of the software in the sensor
polling subroutine 204. Entering in block 302, block 304
communicates with the discharge temperature sensor 36. This value
is stored in memory.
[0066] Block 306 communicates with the high pressure transducer 30.
This value is stored in memory.
[0067] Block 308 communicates with the low pressure transducer 40.
This value is stored in memory.
[0068] Block 310 communicates with the suction line temperature
sensor 34. This value is stored in memory.
[0069] Block 312 communicates with the subcooling temperature
sensor 32. This value is stored in memory.
[0070] Block 314 communicates with the outdoor temperature sensor
28. This value is stored in memory.
[0071] Block 316 consults the temperature/pressure table for the
selected refrigerant (example: R-22) stored in the programmable
read only memory (PROM) 160 and converts the value returned by the
low pressure transducer to the low side saturated temperature
value.
[0072] Block 318 calculates system superheat. Superheat is the low
side saturated temperature minus the actual suction line
temperature. The result is expressed in degrees Fahrenheit and
stored in memory.
[0073] Block 320 evaluates the calculated superheat value. If
superheat is greater than twenty degrees it is determined to be
acceptable and block 328 is entered wherein the "Superheat OK" LED
is energized. If block 320 determines that superheat is less than
twenty degrees then block 322 is entered.
[0074] Block 322 evaluates the calculated superheat value. If
superheat is greater than three degrees then block 326 is entered
wherein the "Superheat Warning" LED is energized. If block 322
determines that superheat is less than three degrees then block 324
is entered.
[0075] Block 324 energizes the "Superheat Failure" LED. After one
of the three superheat indicator LEDs are energized block 330 is
entered.
[0076] Block 330 consults the temperature/pressure table for the
selected refrigerant (example: R-22) stored in the programmable
read only memory (PROM) 160 and converts the value returned by the
high pressure transducer to the high side saturated temperature
value.
[0077] Block 332 calculates system subcooling. Subcooling is the
high side saturated temperature minus the actual liquid line
temperature. The result is expressed in degrees Fahrenheit and
stored in memory.
[0078] Block 334 returns logic flow to the parent program.
[0079] FIG. 5 is a logic flow chart of the software in the sensor
validity check subroutine 206. Entering in block 402, block 404
checks the value returned by the discharge temperature sensor 144
to see if it is greater than zero.
[0080] Block 406 checks the value returned by the high pressure
transducer 30 to see if it is greater than zero.
[0081] Block 408 checks the value returned by the low pressure
transducer 40 to see if it is greater than zero.
[0082] Block 410 checks the value returned by the suction line
temperature sensor 34 to see if it is greater than zero.
[0083] Block 412 checks the value returned by the subcooling
temperature sensor 32 to see if it is greater than zero.
[0084] Block 414 checks the value returned by the outdoor
temperature sensor 28 to see if it is greater than zero.
[0085] If any of the above values are determined to be zero then
the variable SENSORS_RESPOND_OK=NO is determined in block 418.
Otherwise if all the values are determined to be greater than zero
then the variable SENSORS_RESPOND_OK=YES is determined in block
416.
[0086] Block 420 returns logic flow to the parent program.
[0087] FIG. 6 is a logic flow chart of the software in the fault
logging subroutine 234.
[0088] Entering in block 502, block 504 enters the senor check
subroutine 206 (see FIG. 5).
[0089] In block 506 the result of the sensor check performed in
block 504 is evaluated. If it is determined that a sensor failure
has occurred we proceed to block 534 and set the variable
SYSTEM_SHUTDOWN=YES. Block 536 then performs any event logging
specified by the system configuration (example: output to printer,
output to message display). Block 538 energizes a remote dial
module if the system is equipped with one.
[0090] Block 540 energizes the appropriated LEDs to indicate which
system fault has occurred while de-energizing the LEDs that
indicate positive system status.
[0091] Block 542 returns logic flow to the parent program.
[0092] If in block 506 it is determined that the sensors have
responded properly, then block 508 evaluates the discharge side
refrigerant temperature. If the refrigerant temperature is found to
be within acceptable limits, block 510 is entered. Block 510
evaluates the liquid refrigerant pressure, and if the pressure is
found to be within acceptable limits then block 512 is entered.
Block 512 checks for refrigerant low pressure. If the refrigerant
pressure is found to be above the low limit then block 514 is
entered. Block 514 evaluates the calculated value for superheat to
determine if it is within preset limits.
[0093] If the four system conditions evaluated in blocks 508, 510,
512 and 514 are all found to be within acceptable limits then the
variable SYSTEM_SHUTDOWN=NO in block 532 is determined.
[0094] If in any of the four block 508, 510, 512 or 514 it is
determined that the value is outside the acceptable range then a
counter for that value is incremented by one (blocks 516, 518, 520
and 522). In blocks 524, 526, 528 and 530 each of the four fault
counters are evaluated to see if any one of the four system values
has faulted more than three times. If any one of the four system
values has faulted more than three times the variable
SYSTEM_SHUTDOWN=YES in block 534 is determined, otherwise the
variable SYSTEM_SHUTDOWN=NO in block 532 is determined.
[0095] Logic then flows through blocks 536, 538, 540 and 542 as
described previously.
[0096] FIG. 7 illustrates a display panel of the present
invention.
[0097] This configuration consists of a main display and control
module 602 and a separate diagnostic tool 624. The main display and
control module 602 consists of a case 604 which houses the
microprocessor 104 and other component parts. This case would
typically be attached to the exterior of the refrigeration unit
that it is protecting and controlling.
[0098] The LED display bank 160 can be seen on the face of the case
604. These LEDs indicate system conditions: "System OK" 606, "High
Pressure Failure" 608, "Low Pressure Failure" 610, "Discharge
Temperature Failure" 612, "Sensor Failure" 614, "Superheat OK" 616,
"Superheat Warning" 618, "Superheat Failure" 620.
[0099] The hand held diagnostic tool 624 is connected to the main
display and control module 602 through the use of a female modular
connection 622 mounted on the case 604 and a male modular
connection 628 connected to the hand held diagnostic tool 624 with
an appropriate cable connection 630.
[0100] The hand held diagnostic tool 624 consists of a case 626 on
which is mounted an LCD display 632 for quantitative viewing of
system conditions monitored by the microprocessor 104. This
diagnostic tool 626 is equipped with buttons 634 and 636 for
selecting the system readings to be displayed on the LCD screen
632.
[0101] A manual reset button 638 is used by service personnel to
reset the system after a lockout has occurred.
[0102] FIG. 8 is an illustration of an alternative device display
panel with LED and LCD displays.
[0103] This configuration of the present invention consists of a
main display and control module 702 without a separate diagnostic
tool as in FIG. 7. The main display and control module 702 consists
of a case 704 which houses the microprocessor 104 and other
component parts. This case would typically be attached to the
exterior of the refrigeration unit that it is protecting and
controlling.
[0104] The LED display bank 160 can be seen on the face of the case
704. These LEDs indicate system conditions: "System OK" 706, "High
Pressure Failure" 708, "Low Pressure Failure" 710, "Discharge
Temperature Failure" 712, "Sensor Failure" 714, "Superheat OK" 716,
"Superheat Warning" 718, "Superheat Failure" 720.
[0105] An LCD display 722 is mounted on the case 704 for
quantitative viewing of system conditions monitored by the
microprocessor 104. Buttons 724 and 726 are used to for select the
system readings to be displayed on the LCD screen 722.
[0106] A manual reset button 728 is used by service personnel to
reset the system after a lockout has occurred.
[0107] U.S. Pat. No. 6,318,108, granted Nov. 20, 2001, is
incorporated herein by reference in its entirety for all useful
purposes. As explained therein a water spray onto the heat exchange
coil of a condenser is utilized to wash and clean the condenser
coil for more efficient operation.
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