Method for preventing overshoot during heat pump defrost using memorized supplemental heater capacity from previous defrost cycle

• US 5,538,072 A
• Filed: 11/08/1994
• Issued: 07/23/1996
• Est. Priority Date: 11/08/1994
• Status: Expired due to Term

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Burns, Larry D., Burkhart, Larry J.
• Primary Examiner(s): Ford, John K.
• Application Number:
  US08/335,677
• Time in Patent Office: 623 Days
• Field of Search: 165/1, 165/12, 165/29, 62/160, 237/2 B, 219/486
• US Class Current: 165/232
• CPC Class Codes: F24F 11/41 Defrosting; Preventing freezing
• CPC Class Codes: F25D 21/08 by electric heating

Abstract

A method of controlling a current defrost cycle for an outdoor coil of a heat pump system, the heat pump system having a plurality of supplemental heating elements for heating an air stream passing from an indoor coil to an air supply duct during defrost operation, wherein an initial quantity of supplemental heating elements energized is a function of a most recent previous defrost cycle. The method has the steps of: energizing the initial quantity of supplemental heating elements upon initiation of a defrost cycle; determining whether the initial quantity of supplemental heating elements provided is excessive; deactivating at least one of the supplemental heating elements if the initial quantity of supplemental heating elements being provided is excessive; determining whether the initial quantity of supplemental heating elements provided is insufficient; activating, if the initial quantity of supplemental heating elements being provided is insufficient, at least one additional supplemental heating element if the element is available; and retaining information as to an initial quantity of supplemental heating elements to be activated for a following defrost cycle, wherein the initial quantity of supplemental heating elements to be activated for a following defrost cycle is equal to a number of supplemental heating elements activated upon termination of the current defrost cycle.

Claims

1. A method of controlling a current defrost cycle for an outdoor coil of a heat pump system, the heat pump system having a plurality of supplemental heating elements for heating an air stream passing from an indoor coil to an air supply duct during defrost operation, wherein an initial quantity of supplemental heating elements energized is a function of a most recent previous defrost cycle, comprising the steps of:

energizing the initial quantity of supplemental heating elements upon initiation of a defrost cycle;

determining whether the initial quantity of supplemental heating elements provided is excessive;

deactivating at least one of the supplemental heating elements if the initial quantity of supplemental heating elements being provided is excessive;

determining whether the initial quantity of supplemental heating elements provided is insufficient;

activating, if the initial quantity of supplemental heating elements being provided is insufficient, at least one additional supplemental heating element if said element is available; and

retaining information as to an initial quantity of supplemental heating elements to be activated for a following defrost cycle, wherein said initial quantity of supplemental heating elements to be activated for a following defrost cycle is equal to a number of supplemental heating elements activated upon termination of the current defrost cycle.

2. The process according to claim 1 comprising the additional step of determining whether the initial quantity of supplemental heating elements provided is neither excessive nor insufficient.

3. The process according to claim 2 wherein said step of determining whether the initial quantity of supplemental heating elements provided is neither excessive nor insufficient comprises determining if defrost is completed while both supplemental and primary heat are being requested and within a first predetermined time and, if so, then maintaining a same quantity of activated supplemental heating elements as the initial quantity.

4. The process according to claim 3 wherein said first predetermined time is between 120 and 480 seconds.

5. The process according to claim 4 wherein said first predetermined time is 240 seconds.

6. The process according to claim 1 wherein said step of determining whether the initial quantity of supplemental heating elements provided is excessive comprises determining if there is a call for supplemental heat without a call for primary heat.

7. The process according to claim 1 wherein said at least one additional supplemental heating element is a single supplementary heating element.

8. The process according to claim 1 wherein said step of determining whether the initial quantity of supplemental heating elements provided is excessive continues for a second predetermined time after defrost is terminated by an outdoor control.

9. The process according to claim 8 wherein said second predetermined time is between 30 and 240 seconds.

10. The process according to claim 9 wherein said second predetermined time is 90 seconds.

11. The process according to claim 1 where the step of determining whether the initial quantity of supplemental heating elements provided is insufficient comprises the steps of:

determining if a call for supplemental heat is issued within a predetermined time range,

determining if a call for primary heat is maintained, and

determining if the call for supplemental heat is maintained.

12. The process according to claim 11 wherein said predetermined time range is between 30 and 900 seconds.

13. The process according to claim 11 wherein said predetermined time range is between 90 and 660 seconds.

14. The process according to claim 1 wherein said at least one supplemental heating element being deactivated is a single supplemental heating element.