Diagnostic system and method for a cooling system

• US 6,679,072 B2
• Filed: 11/27/2002
• Issued: 01/20/2004
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Original Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Inventors: Caillat, Jean-Luc M., Bass, Mark, Pham, Hung M., Singh, Abtar
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US10/306,030
• Publication Number:
  US 20030089119A1
• Time in Patent Office: 419 Days
• Field of Search: 621/25, 621/26, 621/27, 621/28, 621/29, 621/30, 621/31, 622/04, 622/05, 622/06, 622/10, 622/11, 622/12, 622/22, 622/23, 622/24, 622/25, 622/17
• US Class Current: 62/126
• CPC Class Codes: A47F 3/04 air-conditioned, refrigerated refrigerators F25D; heating arrangements specially adapted for transparent or reflecting areas H05B3/84
• CPC Class Codes: F04C 18/0215 where only one member is moving
• CPC Class Codes: F04C 2270/015 Controlled or regulated
• CPC Class Codes: F04C 2270/86 Detection
• CPC Class Codes: F04C 23/008 Hermetic pumps
• CPC Class Codes: F04C 27/005 Axial sealings for working fluid
• CPC Class Codes: F04C 28/00 Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
• CPC Class Codes: F04C 28/02 specially adapted for several pumps connected in series or in parallel
• CPC Class Codes: F04C 28/06 specially adapted for stopping, starting, idling or no-load operation
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 28/22 by changing the eccentricity between cooperating members
• CPC Class Codes: F04C 28/265 being obtained by displacing a lateral sealing face
• CPC Class Codes: F04C 28/28 Safety arrangements; Monitoring
• CPC Class Codes: F25B 1/04 with compressor of rotary type F25B1/005, F25B1/10 take precedence
• CPC Class Codes: F25B 2400/22 Refrigeration systems for supermarkets
• CPC Class Codes: F25B 2600/0261 external to the compressor
• CPC Class Codes: F25B 2700/193 of the compressor
• CPC Class Codes: F25B 2700/1933 Suction pressures
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: F25B 2700/21174 : of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 2700/21175 : of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25B 41/22 : between evaporator and compressor
• CPC Class Codes: F25B 41/35 : by rotary motors, e.g. by stepping motors
• CPC Class Codes: F25B 49/005 : of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 49/022 : Compressor control arrangements
• CPC Class Codes: F25B 5/02 : arranged in parallel
• CPC Class Codes: G05D 23/1909 : whose output amplitude can only take two discrete values
• CPC Class Codes: Y02B 30/70 : Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A diagnostic system and method for a cooling system includes producing a control signal for adjusting a valve position of a regulator valve as a demand for cooling, as well as providing an ambient temperature measurement, coil inlet temperature measurement, and coil exit temperature measurement. The valve position and at least one of the ambient temperature measurement, coil inlet temperature measurement, and coil exit temperature measurement are monitored and compared with at least one predetermined fault value indicative of a fault condition to diagnose the system. An alert module responsive to the diagnostic module issues an alert signal when at least one of the ambient temperature measurement, coil inlet temperature measurement, and coil exit temperature measurement bears a predetermined relationship to the fault value. When monitoring and comparing, an error value percentage indicative of a percentage of sampled error within an accepted offset range for a defined period of time is determined.

Claims

1. A diagnostic system for a cooling system including a compressor, evaporator and condenser in fluid communication, the diagnostic system comprising:

a controller associated with a regulator valve and producing a control signal for adjusting a valve position of said regulator valve as a function of demand for cooling;

an ambient temperature sensor associated with the cooling system and operable to provide an ambient temperature measurement to said controller;

an evaporator coil inlet temperature sensor associated with the cooling system and operable to provide coil inlet temperature measurement to said controller;

an evaporator coil exit temperature sensor associated with the cooling system and operable to provide a coil exit temperature measurement to said controller;

a diagnostic module coupled to said controller for monitoring and comparing a valve position and at least one of said ambient temperature measurement, coil inlet temperature measurement and coil exit temperature measurement with at least one predetermined fault value indicative of a fault condition.

2. The diagnostic system of claim 1, further comprising an alert module responsive to said diagnostic module for issuing an alert signal when said at least one of said ambient temperature measurement, coil inlet temperature measurement and coil exit temperature measurement bears a predetermined relationship to said fault value.

3. The diagnostic system of claim 1, wherein said diagnostic module monitors a percentage of sampled error over a defined period of time.

4. The diagnostic system of claim 3, wherein said predetermined fault value is an accepted offset range.

5. The diagnostic system of claim 4, wherein said diagnostic module determines an error value percentage indicative of said percentage of sampled error within said accepted offset range for said defined period of time.

6. The diagnostic system of claim 5, wherein said diagnostic module indicates said electronic stepper regulator valve is stuck open when said error value percentage is approximately zero percent, said valve position of said regulator valve is approximately zero percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature is less than approximately 32°

F., and a superheat value is approximately greater than 5°

F.

7. The diagnostic system of claim 6, wherein said superheat value is a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate said superheat value.

8. The diagnostic system of claim 5, wherein said diagnostic module indicates said regulator valve is stuck closed when said error value percentage is approximately zero percent, said valve position of said regulator valve is approximately one hundred percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature is approximately greater than 32°

F., and a superheat value is approximately greater than 5°

F.

9. The diagnostic system of claim 8, wherein said superheat value is a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate said superheat value.

10. The diagnostic system of claim 5, wherein said diagnostic system indicates that air flow to the evaporator is blocked or evaporator fans are not operating properly when said valve position of said regulator valve is approximately one hundred percent for approximately one hundred percent of said defined period of time, said error value percentage is approximately zero, a superheat value is approximately less than 5°

F., said evaporator coil inlet temperature is approximately less than 25°

F., and said evaporator coil exit temperature value is less than said evaporator coil inlet temperature for greater than fifty percent of said defined period of time.

11. The diagnostic system of claim 10, wherein said superheat value is a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate said superheat value.

12. The diagnostic system of claim 1, wherein said regulator valve is an electronic stepper regulator valve and said control signal for adjusting a valve position of said electronic stepper regulator valve is a variable duty cycle control signal in which said duty cycle is a function of demand for cooling.

13. The diagnostic system of claim 1, wherein said diagnostic module monitors and compares at least one of the following conditions:

said valve position of said regulator valve;

an error value percentage indicative of the percentage of sampled error within an accepted offset range for a defined period of time;

a moving average of said valve position for a defined period of time;

a steady state loading percentage set equal to said moving average of said valve position for a defined period of time when said error value percentage is less than fifty percent;

a discharge cooling fluid temperature;

said evaporator coil inlet temperature;

said evaporator coil exit temperature;

a moving average of a difference between said discharge cooling fluid temperature and said evaporator coil inlet temperature;

a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate a superheat value; and

a length of time said evaporator coil exit temperature is less than said evaporator coil inlet temperature during a predefined period of time.

14. A method for diagnosing a cooling system, said steps comprising:

producing a control signal for adjusting a valve position of a regulator valve as a function of demand for cooling;

detecting an ambient temperature measurement, a coil inlet temperature measurement, and a coil exit temperature measurement; and

comparing said valve position and at least one of said ambient temperature measurement, coil inlet temperature measurement, and coil exit temperature measurement with at least one predetermined fault value indicative of a fault condition.

15. The method of claim 14 further comprising the step of issuing an alert signal when said at least one of said ambient temperature measurement, coil inlet temperature measurement, and coil exit temperature measurement bears a predetermined relationship to said fault value.

16. The method of claim 14 wherein said step of comparing said valve position includes monitoring a percentage of sampled air over a defined period of time.

17. The method of claim 16 further comprising the step of approximating a superheat value as a moving average of a difference between said evaporator coil exit temperature measurement and said evaporator coil inlet temperature measurement.

18. The method of claim 17 further comprising the step of indicating said regulator valve is stuck open when said error value percentage is approximately zero percent, said valve position of said regulator valve is approximately zero percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature is less than approximately 32°

F., and said superheat value is approximately greater than 5°

F.

19. The method of claim 16 further comprising the step of indicating said regulator valve is stuck open when said error value percentage is approximately zero percent, said valve position of said regulator valve is approximately one hundred percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature is approximately greater than 32°

F., and said superheat value is approximately greater than 5°

F.

20. The method of claim 16 further comprising the step of indicating that air flow to the evaporator is blocked or evaporator fans are not operating properly when said valve position of said regulator valve is approximately one hundred percent for approximately one hundred percent of said defined period of time, said error value percentage is approximately zero, said superheat value is approximately less than 5°

F., said evaporator coil inlet temperature is approximately less than 25°

F., and said evaporator coil exit temperature value is less than said evaporator coil inlet temperature for greater than fifty percent of said defined period of time.

21. The method of claim 14 wherein said step of adjusting a valve position includes providing a variable duty cycle control signal as a function of demand for cooling.

22. The method of claim 14 wherein said step of monitoring and comparing a valve position includes monitoring and comparing at least one of the following conditions:

said valve position of said regulator valve;

an error value percentage indicative of the percentage of sampled error within an accepted offset range for a defined period of time;

a moving average of said valve position for a defined period of time;

a steady state loading percentage set equal to said moving average of said valve position for a defined period of time when said error value percentage is less than fifty percent;

a discharge cooling fluid temperature;

said evaporator coil inlet temperature;

said evaporator coil exit temperature;

a moving average of a difference between said discharge cooling fluid temperature and said evaporator coil inlet temperature;

a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate a superheat value; and

a length of time said evaporator coil exit temperature is less than said evaporator coil inlet temperature during a predefined period of time.