Heat pump defrost control

Abstract

A heat pump system is provided having an exterior coil, an exterior fan and fan motor, an interior blower, a reversing valve, and an auxiliary heater element. A method for defrosting the exterior coil includes the steps of initiating a defrost cycle by activating the auxiliary heater element for a period of time, and thereafter deactivating the exterior fan and fan motor and shifting the reversing valve to a cooling mode. After the defrost cycle has ended, the reversing valve is shifted to a heating mode, the exterior fan and fan motor are activated, and the auxiliary heater element is deactivated. The heat pump system results in less “cold blow” during the defrost cycle of a typical heat pump system, by providing additional heat to the interior space and interior duct work before the system is operated in a cooling mode to defrost the exterior coil.

I claim  
     
         1 . For a heat pump system having an exterior coil, an exterior fan and fan motor, an interior blower, a reversing valve, and an auxiliary heater element, a method for defrosting the exterior coil comprising the steps of: 
 a. first activating the auxiliary heater element for a period of time; and    b. after the period of time has passed, deactivating the exterior fan and fan motor and shifting the reversing valve to a cooling mode.    
     
     
         2 . The method of  claim 1  wherein the deactivating of the exterior fan motor and shifting the reversing valves occurs a predetermined period of time after the activating of the auxiliary heater element.  
     
     
         3 . The method of  claim 1  wherein the deactivating of the exterior fan motor and shifting the reversing valve occurs a variable period of time after the activating of the auxiliary heater element.  
     
     
         4 . For a heat pump system having an exterior coil, an exterior fan and fan motor, an interior blower, a reversing valve, and an auxiliary heater element, a method for defrosting the exterior coil comprising the steps: 
 a. initiating a defrost cycle;    b. activating the auxiliary heating element for a period of time during the period of time the auxiliary heater element is activated, operating the interior blow to pass air over the auxiliary heater element;    c. deactivating the exterior fan motor and shifting the reversing valve to end the defrost cycle; and    d. shifting the reversing valve, activating the exterior fan and fan motor, and deactivating the auxiliary heater element:    
     
     
         5 . The method of  claim 4 , wherein the deactivating of the exterior fan and fan motor and shifting the reversing valve occurs a predetermined period of time after the activating of the auxiliary heater element.  
     
     
         6 . The method of  claim 4  wherein the de-activating of the exterior fan and fan motor and shifting the reversing valve occurs a variable period of time time after the activating of the auxiliary heater element.  
     
     
         7 . A heat pump system comprising: 
 at least one exterior coil;    an exterior fan and fan motor;    an interior blower;    a reversing valve;    an auxiliary heater unit; and    a control unit associated with the exterior fan and fan motor, reversing valve, and auxiliary heating unit, the control unit configured to defrost the at least one coil by activating the auxiliary heating unit for a period of time prior to shifting the reversing valve and prior to deactivating the fan and fan motor.    
     
     
         8 . The heat pump system of  claim 7 , wherein the control unit is configured to defrost the coils by activating the auxiliary heating unit for a predetermined period of time prior to shifting the reversing valve or de-activating the fan motor.  
     
     
         9 . The heat pump system of  claim 7 , wherein the control unit is configured to defrost the coils by activating the auxiliary heating unit for a variable period of time prior to shifting the reversing valve or de-activating the fan motor.