Blocked fan detection system for heat pump

• US 5,440,890 A
• Filed: 12/10/1993
• Issued: 08/15/1995
• Est. Priority Date: 12/10/1993
• Status: Expired due to Term

• Current Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Original Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Inventors: Bahel, Vijay, Pham, Hung, Hickey, Mickey, Millet, Hank, Herroon, Gregory P.
• Primary Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US08/165,725
• Time in Patent Office: 613 Days
• Field of Search: 62/156, 62/129, 62/126, 62/125, 62/81, 374/45
• US Class Current: 62/81
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/41 Defrosting; Preventing freezing
• CPC Class Codes: F25B 13/00 Compression machines, plants or systems, with reversible cycle defrosting cycles F25B47/02
• CPC Class Codes: F25B 2313/0293 related to the indoor fan, e.g. controlling speed
• CPC Class Codes: F25B 2313/0294 related to the outdoor fan, e.g. controlling speed
• CPC Class Codes: F25B 2313/0315 Temperature sensors near the outdoor heat exchanger
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/21152 at the discharge side of the compressor
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: F25D 21/006 with electronic control circuits
• CPC Class Codes: F25D 21/02 Detecting the presence of frost or condensate
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A blocked fan or obstructed airflow condition is detected by measuring the difference between outdoor air temperature and outdoor exchanger coil temperature. If a very high difference is detected, or if no decrease in the difference is achieved after termination of the defrost cycle, and if either of these conditions persists over a plurality of defrost cycles, then the blocked condition is declared. The diagnostic system can be integrated in an existing demand defrost cycle and is capable of detecting blocked conditions attributable to foreign matter such as leaves, paper and debris which cannot be cleared by defrosting.

Claims

1. An airflow obstruction detection method for detecting an airflow obstruction condition in an outdoor heat exchanger, comprising the steps of:

at first time, determining a first temperature difference parameter indicative of a temperature difference between the outdoor heat exchanger and the ambient air surrounding said heat exchanger;

performing a defrost cycle when the first temperature difference parameter is equal or exceeds a first predetermined value;

at a second time, determining a second temperature difference parameter indicative of a temperature difference between the outdoor heat exchanger and the ambient air surrounding said heat exchanger after the defrost cycle has been completed;

declaring an obstruction condition due to foreign matter or debris to exist if the second temperature difference parameter is equal or exceeds a second predetermined value.

2. The method of claim 1 wherein said step of determined a first temperature difference parameter comprises the steps of determining a first parameter indicative of the temperature of the outdoor heat exchanger, determining a second parameter indicative of the ambient air temperature in the vicinity of the outdoor heat exchanger, and using said first and second parameters to calculate the first temperature difference parameter.

3. The method of claim 1 wherein said step of determining a second temperature difference parameter comprises the steps of determining a first parameter indicative of the temperature of the outdoor heat exchanger, determining a second parameter indicative of the ambient air temperature in the vicinity of the outdoor heat exchanger, and using said first and second parameters to calculate the second temperature difference parameter.

4. The method of claim 1 wherein said step of performing a defrost cycle comprises the steps of determining an air temperature parameter indicative of the temperature of the ambient air surrounding said heat exchanger and using said ambient air temperature to obtain said first predetermined value.

5. The method of claim 1 further comprising implementing a lockout timer to restrain the performing of said defrost cycle.

6. The method of claim 5 wherein said lockout timer is reset in connection with said defrost cycle performing step and wherein said lockout timer prevents the subsequent defrost cycle performing step for a predetermined time determined at least in part by said reset.

7. The method of claim 1 further comprising performing a predetermined time delay between said defrost cycle performing step and said step of determining a second temperature difference parameter.

8. The method of claim 7 wherein said predetermined time delay is chosen to allow the temperature difference to stabilize following the defrost cycle.

9. The method of claim 7 wherein said predetermined time delay is about fifteen minutes.

10. The method of claim 1 further comprising shutting off the fan in response to the detected obstruction condition.

11. The method of claim 1 wherein said outdoor heat exchanger has associated with it a compressor for pumping refrigerant through said heat exchanger and wherein said method further comprises turning off the compressor in response to the detected obstruction condition.

12. The method of claim 1 wherein said outdoor heat exchanger has associated with it an expansion valve for regulating refrigerant flow through said heat exchanger and wherein said method further comprises closing the expansion valve in response to the detected obstruction condition.