Regrigerant charge control system for heat pump systems

Abstract

An air source or water sourced packaged self-contained heat pump unit comprises indoor and outdoor sections. Heat exchangers present in these sections transfer heat between the indoor building space and the outdoor ambient. The heat exchangers are connected to form a closed loop and a compressor present in the loop pressurizes the refrigerant. A refrigerant charge control system present controls the charge of refrigerant in the main refrigerant system during heating and cooling modes. A hot-gas heat exchanger is added to the indoor section of the unit downstream of the indoor heat exchanger with respect to the airflow. Valves are used to bypass the flow of refrigerant from the compressor to the hot-gas heat exchanger during regular heating and cooling modes. In the hot-gas reheat mode, the compressed refrigerant is first directed to the hot gas heat exchanger which reheats the air to decrease the relative humidity. The charge control system is active during the hot gas reheat cycle to control the charge of refrigerant in the system.

1 . A method of operating an air source heat pump unit comprising:
 during a heating cycle of the heat pump unit, separating a portion of refrigerant in a main refrigerant system of the heat pump away from the main refrigerant system by way of a refrigerant charge control system conductively engaged to the main refrigerant system;   wherein the refrigerant charge control system comprises at least the following conductively engaged components: at least one refrigerant reservoir, at least one inlet conduit with a tip, and at least one outlet conduit with a tip that extends into the reservoir such that the tip of the inlet pipe is located at a higher location relative to the tip of the outlet pipe; and   wherein the system further comprises a hot gas reheat system conductively engaged to the main refrigerant system, wherein the heat pump unit distributes its total charge of refrigerant between said main refrigerant system, said refrigerant charge control system conductively engaged to the main refrigerant system, and said hot gas reheat system; wherein said main refrigerant system is a variable-refrigerant-charge main refrigerant system; and wherein the heat pump unit operates with a first amount of refrigerant in the main refrigerant system during a cooling or heating cycle and a smaller second amount of refrigerant in the main refrigerant system during a heating or cooling cycle, respectively.   
     
     
         2 . The method of  claim 1  further comprising:
 during a cooling cycle of the heat pump unit, adding the separated refrigerant back to the main refrigerant system by way of the refrigerant charge control system. 
 
     
     
         3 . The method of  claim 1  further comprising:
 during a hot gas reheat cycle of the heat pump unit, directing a portion of refrigerant away from the main refrigerant system through a hot gas heat exchanger and back to the main refrigerant system. 
 
     
     
         4 . The method of  claim 1 , wherein the heat pump unit further comprises a charge of refrigerant distributed between the main refrigerant system and the refrigerant charge control system; wherein
 during a heating cycle operation of the heat pump unit no less than 50±5% of the refrigerant charge is in the main refrigerant system and up to 50±5% of the refrigerant charge is in the refrigerant charge control system; and   during a cooling cycle operation of the heat pump unit at least 50±5% of the refrigerant charge is in the main refrigerant system and no more than 50±5% of the refrigerant charge is in the refrigerant charge control system.   
     
     
         5 . The method of  claim 4 , wherein a majority of the refrigerant in the refrigerant charge control system is vertically lower than a majority of the charge of refrigerant in the main refrigerant. 
     
     
         6 . The method of  claim 1 , wherein the main refrigerant system comprises at least the following conductively engaged components: at least one compressor, at least one high pressure heat exchanger, at least one low pressure heat exchanger, at least one expansion valve, and at least one reversing valve. 
     
     
         7 . The heat pump of  claim 1 , wherein the at least one high pressure heat exchanger is an outdoor heat exchanger; and the low pressure heat exchanger is an indoor heat exchanger. 
     
     
         8 . The method of  claim 1 , wherein the heat pump unit further comprises at least one blower fan. 
     
     
         9 . The method of  claim 1 , wherein the refrigerant charge control system further comprises at least the following conductively engaged components: at least one flow control valve, and at least one check valve, wherein the check valve is downstream of the reservoir, and the reservoir is downstream of the flow control valve. 
     
     
         10 . A method of operating a water source heat pump unit comprising:
 during a cooling cycle of the heat pump unit, separating a portion of refrigerant in a main refrigerant system of the heat pump away from the main refrigerant system by way of a refrigerant charge control system conductively engaged to the main refrigerant system;   wherein the refrigerant charge control system comprises at least the following conductively engaged components: at least one refrigerant reservoir, at least one inlet conduit with a tip, and at least one outlet conduit with a tip that extends into the reservoir such that the tip of the inlet pipe is located at a higher location relative to the tip of the outlet pipe; and   wherein the system further comprises a hot gas reheat system conductively engaged to the main refrigerant system, wherein the heat pump unit distributes its total charge of refrigerant between said main refrigerant system, said refrigerant charge control system conductively engaged to the main refrigerant system, and said hot gas reheat system; wherein said main refrigerant system is a variable-refrigerant-charge main refrigerant system; and wherein the heat pump unit operates with a first amount of refrigerant in the main refrigerant system during a cooling or heating cycle and a smaller second amount of refrigerant in the main refrigerant system during a heating or cooling cycle, respectively.   
     
     
         11 . The method of  claim 10  further comprising:
 during a heating cycle of the heat pump unit, adding the separated refrigerant back to the main refrigerant system by way of the refrigerant charge control system. 
 
     
     
         12 . The method of  claim 10 , wherein the heat pump unit further comprises a charge of refrigerant distributed between the main refrigerant system and the refrigerant charge control system; wherein
 during a cooling cycle operation of the heat pump unit no less than 50±5% of the refrigerant charge is in the main refrigerant system and up to 50±5% of the refrigerant charge is in the refrigerant charge control system; and   during the heating cycle operation of the heat pump unit at least 50±5% of the refrigerant charge is in the main refrigerant system and no more than 50±5% of the refrigerant charge is in the refrigerant charge control system.   
     
     
         13 . The method of  claim 12 , wherein a majority of the refrigerant in the refrigerant charge control system is vertically lower than a majority of the charge of refrigerant in the main refrigerant. 
     
     
         14 . The method of  claim 10 , wherein the main refrigerant system comprises at least the following conductively engaged components: at least one compressor, at least one high pressure heat exchanger, at least one low pressure heat exchanger, at least one expansion valve, and at least one reversing valve. 
     
     
         15 . The method of  claim 10 , wherein the at least one high pressure heat exchanger is an indoor heat exchanger; and the low pressure heat exchanger is an outdoor heat exchanger. 
     
     
         16 . The method of  claim 10  further comprising at least one blower fan. 
     
     
         17 . The method of  claim 10 , wherein the refrigerant charge control system further comprises at least the following conductively engaged components: at least one flow control valve, and at least one check valve, wherein the check valve is downstream of the reservoir, and the reservoir is downstream of the flow control valve. 
     
     
         18 . A method of operating a heat pump unit comprising a total charge of refrigerant distributed between a main refrigerant system and a refrigerant charge control system conductively engaged to the main refrigerant system, the method comprising distributing the total charge of refrigerant between a first amount of refrigerant in the main refrigerant system during a cooling or heating cycle and a smaller second amount of refrigerant in the main refrigerant system during a heating or cooling cycle, respectively, wherein the total charge of refrigerant in the heat pump unit is constant;
 wherein the refrigerant charge control system comprises at least the following conductively engaged components: at least one flow control valve, at least one refrigerant reservoir downstream of the flow control valve, at least one check valve downstream of the reservoir, at least one inlet conduit with a tip that extends into the reservoir, and at least one outlet conduit with a tip such that the tip of the inlet pipe is located at a higher location relative to the tip of the outlet pipe; and   wherein said main refrigerant system is a variable-refrigerant-charge main refrigerant system comprising at least one indoor heat exchanger, at least one outdoor heat exchanger, at least one compressor, at least one expansion valve, and at least one reversing valve; and   wherein the reservoir is located at a height that is at or near the lowest point of the heat pump unit.   
     
     
         19 . The method of  claim 18 , wherein the heat pump unit is a packaged air source or water source heat pump unit further comprising an indoor hot gas reheat system conductively engaged to the main refrigerant system, and the heat pump unit distributes its total charge of refrigerant between said main refrigerant system, said refrigerant charge control system conductively engaged to the main refrigerant system, and said hot gas reheat system.