System and method for controlling operation of a heat pump

Abstract

Described herein is a system and a method for controlling operation of a heat pump. The system comprises an electronic expansion valve (EXV) configured to fluidically connect an indoor unit of the heat pump with an outdoor unit of the heat pump, and a controller operatively connected to the EXV, where the controller is configured to issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.

1 . A system for controlling operation of a heat pump, the system comprising:
 an electronic expansion valve (EXV) configured to fluidically connect an indoor unit of the heat pump with an outdoor unit of the heat pump; and   a controller operatively connected to the EXV, the controller configured to:
 issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil. 
   
     
     
         2 . The system of  claim 1 , wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil. 
     
     
         3 . The system of  claim 1 , wherein during the first defrost mode, responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure, the controller is configured to issue a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure. 
     
     
         4 . The system of  claim 1 , wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the controller is configured to issue a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure. 
     
     
         5 . The system of  claim 1 , wherein the controller is further configured to issue a second control signal, during a second defrost mode, to enable and control flow of hot or warm refrigerant from a compressor associated with the heat pump to the outdoor coil, to facilitate defrosting of the outdoor coil. 
     
     
         6 . The system of  claim 5 , wherein responsive to the second control signal during the second defrost mode, the controller is configured to completely close the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil. 
     
     
         7 . A method for controlling operation of a heat pump, the heat pump comprising an electronic expansion valve (EXV) fluidically connecting an indoor unit of the heat pump with an outdoor unit of the heat pump and a controller operatively connected to the EXV, the method comprising the steps of:
 issuing, by the controller, a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.   
     
     
         8 . The method of  claim 7 , wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil. 
     
     
         9 . The method of  claim 7 , wherein responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure during the first defrost mode, the method comprises the step of issuing, by the controller, a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure. 
     
     
         10 . The method of  claim 7 , wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the method comprises the step of issuing, by the controller, a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure. 
     
     
         11 . The method of  claim 7 , wherein during a second defrost mode, the method comprises the step of issuing, by the controller, a second control signal to enable and control flow of hot or warm refrigerant from a compressor associated with the heat pump to the outdoor coil, to facilitate defrosting of the outdoor coil. 
     
     
         12 . The method of  claim 11 , wherein responsive to the second control signal during the second defrost mode, the method comprises the step of completely closing the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil. 
     
     
         13 . A heat pump comprising:
 an indoor unit fluidically connected to an outdoor unit via a compressor and an electronic expansion valve (EXV);   a controller connected to the compressor and the EXV, wherein the controller is configured to:
 issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil. 
   
     
     
         14 . The heat pump of  claim 13 , wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil. 
     
     
         15 . The heat pump of  claim 13 , wherein responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure during the first defrost mode, the controller is configured to issue a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure. 
     
     
         16 . The heat pump of  claim 13 , wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the controller is configured to issue a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure. 
     
     
         17 . The heat pump of  claim 13 , wherein the controller is further configured to issue a second control signal, during a second defrost mode, to enable and control flow of hot or warm refrigerant from the compressor to the outdoor coil, to facilitate defrosting of the outdoor coil. 
     
     
         18 . The heat pump of  claim 17 , wherein responsive to the second control signal during the second defrost mode, the controller is configured to completely close the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil.