Heat pump protection against high pressure trips in defrost cycle

Abstract

A HVAC&R system includes a heat pump configured to selectively circulate a working fluid. The heat pump includes an outdoor heat exchanger, an indoor heat exchanger, a compressor, a reversing valve configured to direct the working fluid from the compressor to the outdoor heat exchanger or to the indoor heat exchanger, and a controller. The controller is configured to determine whether a pressure of the working fluid exiting the compressor exceeds a pressure threshold, and, in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, control the reversing valve to block the working fluid from flowing from the compressor through the reversing valve to the outdoor heat exchanger.

1 . A heat pump configured to selectively circulate a working fluid, the heat pump comprising:
 an outdoor heat exchanger;   an indoor heat exchanger;   a compressor;   a reversing valve configured to direct the working fluid from the compressor to the outdoor heat exchanger or to the indoor heat exchanger; and   a controller configured to:
 determine whether a pressure of the working fluid exiting the compressor exceeds a pressure threshold; and 
 in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, control the reversing valve to block the working fluid from flowing from the compressor through the reversing valve to the outdoor heat exchanger. 
   
     
     
         2 . The heat pump of  claim 1 , wherein the pressure threshold is lower than a trip pressure value of the compressor. 
     
     
         3 . The heat pump of  claim 1 , wherein the controller is configured to, in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, control the reversing valve to disconnect a first flow path from the compressor to the outdoor heat exchanger and establish a second flow path from the compressor to the indoor heat exchanger. 
     
     
         4 . The heat pump of  claim 1 , comprising a pressure sensor disposed at a discharge side of the compressor, wherein the pressure of the working fluid exiting the compressor is determined based on a pressure measurement of the pressure sensor. 
     
     
         5 . The heat pump of  claim 4 , wherein the pressure sensor is disposed along a working fluid flow path between the compressor and the reversing valve. 
     
     
         6 . The heat pump of  claim 1 , comprising a temperature sensor configured to measure a temperature of the working fluid, wherein the pressure of the working fluid exiting the compressor is determined based on a temperature measurement of the temperature sensor. 
     
     
         7 . The heat pump of  claim 1 , wherein the controller is configured to:
 control the reversing valve to enable the working fluid to flow from the compressor to the indoor heat exchanger;   determine whether to defrost the outdoor heat exchanger based on measured parameters of the heat pump;   in response to determining to defrost the outdoor heat exchanger:
 control the reversing valve to enable the working fluid to flow from the compressor to the outdoor heat exchanger via the reversing valve; 
 determine whether a pressure measurement of a pressure sensor exceeds the pressure threshold; and 
 in response to determining that the pressure measurement of the pressure sensor exceeds the pressure threshold, control the reversing valve to block the working fluid from flowing from the compressor to the outdoor heat exchanger via the reversing valve. 
   
     
     
         8 . The heat pump of  claim 1 , wherein the controller is configured to determine whether to defrost the outdoor heat exchanger based on an outdoor temperature measure. 
     
     
         9 . The heat pump of  claim 1 , comprising a temperature sensor configured to measure a temperature of the working fluid within the outdoor heat exchanger, wherein the controller is configured to:
 determine whether the pressure of the working fluid exiting the compressor exceeds the pressure threshold or the temperature of the working fluid within the outdoor heat exchanger exceeds a temperature threshold; and   in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold or the temperature of the working fluid within the outdoor heat exchanger exceeds the temperature threshold, control the reversing valve to block the working fluid from flowing from the compressor to the outdoor heat exchanger.   
     
     
         10 . The heat pump of  claim 9 , wherein the controller is configured to:
 determine whether the pressure of the working fluid exiting the compressor exceeds the pressure threshold and the temperature of the working fluid within the outdoor heat exchanger exceeds the temperature threshold; and   in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold and the temperature of the working fluid within the outdoor heat exchanger exceeds the temperature threshold, control the reversing valve to block the working fluid from flowing from the compressor to the outdoor heat exchanger.   
     
     
         11 . The heat pump of  claim 9 , wherein the temperature sensor is disposed at a discharge end of the outdoor heat exchanger. 
     
     
         12 . The heat pump of  claim 9 , wherein:
 the temperature threshold corresponds to a temperature value of the working fluid within the outdoor heat exchanger during cooling mode operation in absence of frosting, and   the controller is configured to direct the working fluid, via control of the reversing valve, from the compressor to the outdoor heat exchanger during the cooling mode operation.   
     
     
         13 . The heat pump of  claim 1 , wherein the heat pump comprises an expansion device configured to create a pressure drop in the working fluid as the working fluid passes through the expansion device. 
     
     
         14 . The heat pump of  claim 1 , wherein the compressor, the reversing valve, and the outdoor heat exchanger are housed in an outdoor unit. 
     
     
         15 . A method of operating a heat pump, comprising:
 determining that a pressure of a working fluid exiting a compressor of the heat pump exceeds a pressure threshold; and   in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, controlling a reversing valve to block the working fluid from flowing from the compressor through the reversing valve to an outdoor heat exchanger.   
     
     
         16 . The method of  claim 15 , comprising, in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, controlling the reversing valve to enable the working fluid to flow from the compressor through the reversing valve to an indoor heat exchanger. 
     
     
         17 . The method of  claim 16 , comprising:
 controlling the reversing valve to enable the working fluid to flow from the compressor to the outdoor heat exchanger;   determining a total time elapsed since the working fluid is enabled to flow from the compressor to the outdoor heat exchanger;   determining whether the pressure of the working fluid exiting the compressor of the heat pump exceeds the pressure threshold; and   in response to determining that the total time elapsed since the working fluid is enabled to flow from the compressor to the outdoor heat exchanger exceeds a time threshold or the pressure of a working fluid exiting the compressor of the heat pump exceeds the pressure threshold, controlling the reversing valve to block the working fluid from flowing from the compressor to the outdoor heat exchanger via the reversing valve.   
     
     
         18 . The method of  claim 17 , comprising, in response to determining that the total time elapsed since the working fluid is enabled to flow from the compressor to the outdoor heat exchanger exceeds a time threshold and the pressure of the working fluid exiting the compressor of the heat pump exceeds the pressure threshold, controlling the reversing valve to block the working fluid from flowing from the compressor to the outdoor heat exchanger. 
     
     
         19 . A heating, ventilation, and air conditioning (HVAC) system, comprising:
 a heat pump configured to circulate a working fluid through two or more circuits, comprising:
 a first outdoor heat exchanger in a first circuit; 
 a second outdoor heat exchanger in a second circuit; 
 an indoor heat exchanger; 
 a compressor; 
 a pressure sensor disposed downstream of the compressor to measure a pressure of the working fluid exiting the compressor; 
 a first temperature sensor configured to measure a first temperature of the working fluid within the first outdoor heat exchanger; 
 a reversing valve configured to direct the working fluid from the compressor to the first outdoor heat exchanger, the second outdoor heat exchanger, or the indoor heat exchanger; and 
 a controller configured to:
 determine whether the pressure exceeds a pressure threshold; 
 determine whether the first temperature exceeds a temperature threshold; and 
 in response to determining that the pressure exceeds the pressure threshold or the first temperature exceeds the temperature threshold, control the reversing valve to direct the working fluid to flow from the compressor through the reversing valve to the indoor heat exchanger. 
 
   
     
     
         20 . The heating, ventilation, and air conditioning (HVAC) system of  claim 19 , comprising a second temperature sensor configured to measure a second temperature of the working fluid within the second outdoor heat exchanger, wherein the controller is configured to:
 determine whether the second temperature exceeds a temperature threshold; and   in response to determining that the pressure exceeds the pressure threshold or one of the first temperature and the second temperature exceeds the temperature threshold, control the reversing valve to direct the working fluid to flow from the compressor through the reversing valve to the indoor heat exchanger.