Heat pump defrost control

Abstract

An electronic defrost system consisting of a circuit board designed to implement defrost cycle of an air source heat pump outdoor coil during the off-cycle period. off-cycle is when the house thermostat is satisfied, heat pump is timed off for two minutes and then reactivated in regular defrost cycle if defrost sensor is calling for defrost. (Temp / off cycle). When sensor opens, heat pump will shut off for two minutes to allow pressure equalization.The automatic emergency heat is an option that can be selected. The automatic setting will activate the same circuit as the manual switch at the indoor house thermostat.Defrost control board designed to activate all heat strips during defrost cycle if desired.

Description

INCORPORATION BY REFERENCE[0001]Title: Defrost system and method for heat pumps[0002]Inventor: Shaw, David N.[0003]Date: Mar. 10, 2009[0004]Application Ser. No. 12 / 401,136[0005]Specific reference: Paragraph [0002]-[0005][0006]The description goes into great detail how a heat pump defrost system operates.SCHEMATIC AND CONNECTION LEGEND[0007]12—Heat pump defrost control circuit board drawing[0008]13—Split unit connection drawing[0009]14—K-1 Defrost relay coil—24 volts[0010]16—K1-1 Energizes main contactor on heat pump[0011]18—K1-2 Energizes auxiliary heat during defrost cycle[0012]20—K1-3 Activates blower motor relay[0013]22—k1-4 Shifts reversing valve to cool mode for defrosting outdoor coil[0014]24—K1-5 Interlocks K-2 during defrost cycle[0015]26—K1-6 Interlocks Y-2[0016]28—K1-7 Energizes TD-4[0017]30—K1-8 Prevents voltage feedback in running mode[0018]31—K1-9 Activates all heat strips[0019]32—K-2 Normal running mode coil—24 volts[0020]34—K2-1 Interlocks defrost coil K-1[0021]36—K2-...

AI Technical Summary

Benefits of technology

[0055]The present invention has timers incorporated so as to alleviate system shock by idling heat pump for a period of time and then initiate defrost cycle. At completion of defrost, it holds reversing valve in cool mode for a short time to allow pressure equalization.

[0056]The higher SEER rated heat pumps that has been mandated uses a higher pressure refrigerant which could wear more on the reversing valve on systems where the compressor continues to run during defrost cycle. Even a small blow-by leak can reduce the efficiency of a heat pump considerably.

[0057]Some heat pump manufacturers have designed their units with just the basic parts necessary. This gives the heat pump an increased reliability and less service call-outs. Switching to a defrost board that adds additional functions could be viewed as counter to what they have accomplished, but by utilizing the Off-Cycle Defrost System presented in the claims section, I believe it would increase reliability for the reversing valve and the entire system. A reversing valve is one of the more expensive repairs to make when leaks occur.

[0058]The biggest advantage to using the off-cycle system is it will have a clean coil on start-up, in addition, it is heating the entire time. It does the defrost after the thermostat has satisfied.

[0059]The automatic emergency heat circuit will save the homeowner from manually switching to emergency heat when temperature is too low to be efficient.

[0065]The system that is presented is a basic modification from the prior art systems that is used in most heat pumps, but after reducing it to practice in a limited way, the present invention is much quieter during change-over, and it eliminates the sudden pressure / temperature change.

Problems solved by technology

Even a small blow-by leak can reduce the efficiency of a heat pump considerably.

A reversing valve is one of the more expensive repairs to make when leaks occur.

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