Variable refrigerant charge control

Abstract

An apparatus and method for adjusting refrigerant charge level are provided. The apparatus has a reservoir, a reservoir line, a reservoir valve, and one or more side valves. The reservoir line connects the reservoir and a liquid line, and has a connection to the liquid line. The liquid line connects an indoor heat exchanger and an outdoor heat exchanger. The reservoir valve is on the reservoir line. The one or more side valves are on the liquid line. In the method, an indicator of effectiveness of a refrigerant-using system is calculated. The indicator is compared to a target indicator of effectiveness. A refrigerant charge level is adjusted to reduce the difference between the indicator and the target indicator.

We claim: 
     
         1 . An apparatus for adjusting refrigerant charge level, the apparatus comprising:
 a reservoir;   a reservoir line connecting the reservoir and a liquid line, the liquid line connecting an indoor heat exchanger and an outdoor heat exchanger, the reservoir line comprising a connection to the liquid line;   a reservoir valve on the reservoir line; and   one or more side valves on the liquid line.   
     
     
         2 . The apparatus of  claim 1 , wherein the one or more side valves comprises an indoor side valve on the liquid line between the indoor heat exchanger and the connection to the reservoir line. 
     
     
         3 . The apparatus of  claim 1 , wherein the one or more side valves comprises an outdoor side valve on the liquid line between the outdoor heat exchanger and the connection to the reservoir line. 
     
     
         4 . The apparatus of  claim 1 , wherein the one or more side valves comprises:
 an indoor side valve on the liquid line between the indoor heat exchanger and the connection to the reservoir line; and   an outdoor side valve on the liquid line between the outdoor heat exchanger and the connection to the reservoir line.   
     
     
         5 . The apparatus of  claim 1 , wherein the reservoir valve and the one or more side valves each comprise a solenoid valve. 
     
     
         6 . The apparatus of  claim 1 , wherein the reservoir is above the liquid line. 
     
     
         7 . The apparatus of  claim 1 , wherein:
 a suction line passes through the reservoir; and   the suction line is connected to a compressor.   
     
     
         8 . A method for adjusting refrigerant charge level, the method comprising:
 calculating an indicator of effectiveness of a refrigerant-using system;   comparing the indicator to a target indicator of effectiveness; and   adjusting a refrigerant charge level to reduce the difference between the indicator and the target indicator.   
     
     
         9 . The method of  claim 8 , wherein adjusting the refrigerant charge level comprises opening or closing a solenoid valve. 
     
     
         10 . The method of  claim 8 , wherein:
 the indicator comprises a subcooling value;   the target indicator comprises a subcooling value; and   calculating the indicator comprises measuring a liquid temperature and liquid pressure.   
     
     
         11 . The method of  claim 8 , wherein:
 the indicator comprises an energy efficiency ratio;   the target indicator comprises an energy efficiency ratio; and   calculating the indicator comprises:
 measuring an energy usage of a compressor; and 
 measuring a heat transferring capacity of the system. 
   
     
     
         12 . The method of  claim 11 , wherein the heat transferring capacity comprises a sensible capacity of the system. 
     
     
         13 . The method of  claim 12 , wherein measuring the sensible capacity comprises measuring an indoor airflow, a return air temperature, and a supply air temperature. 
     
     
         14 . The method of  claim 11 , wherein the heat transferring capacity comprises a latent capacity of the system. 
     
     
         15 . The method of  claim 11 , wherein the heat transferring capacity comprises a total of:
 a sensible capacity of the system; and   a latent capacity of the system.