Reverse fan heat pump defrost control system
AssigneeDunham-Bush, Inc.
InventorDavid N. Shaw
Life of this patent
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Abstract
A defrost control system includes in an electrical control circuit, a number of relay coils and contacts responsive thereto for insuring a delay in termination of the defrost mode and reverse refrigerant flow to the outdoor coil of the heat pump system to delay coil operation as an evaporator, and to effect automatically fan motor reversal and energization to blow air downwardly over the outdoor coil fins to assist gravity in removing the condensate during delay in initiation of heat pump heating cycle, thereby preventing refreezing of condensate on the coil fins.
Claims7
In a heat pump including a finned outdoor coil acting selectively as a refrigeration condenser and evaporator and having a fan mounted adjacent the coil for blowing air upwardly and across the coil fins for effecting heat exchange between the moving air and refrigerant within the coil tubing, said heat pump including control means responsive to frost accumulation on the fins of said outdoor coil when said outdoor coil is acting as an evaporator under near-freezing ambient conditions for effecting a change in heat pump operation from heating mode to cooling mode and to thereby initiate defrosting of the coil by supplying hot refrigerant vapor to said coil and for terminating fan operation, the improvement comprising:
- said fan being a reversible direction fan, and said control means further comprising means for first delaying the termination of the heat pump cooling mode for defrost operation and the initiation of the heating mode, and secondly, for reversing the direction of forced air flow over the coil such that the air flow acts in conjunction with gravity to remove the last of the melted condensate from the fins.
Dependencies are inferred from the claim text.