Hvac cascade heat pump

Abstract

An assembly includes a fluid conditioning system including a cascade module and an active charge compensator integrated into the fluid conditioning system. The fluid conditioning system is transformable between a first mode and a second mode. In the first mode, the fluid conditioning system includes a first vapor compression loop and a second vapor compression loop. The first vapor compression loop and the second vapor compression loop are thermally coupled at the cascade module and the second vapor compression loop is fluidly separate from the first vapor compression loop. In the second mode, the fluid conditioning system includes a single vapor compression loop. The active charge compensator is operable to control a working fluid charge within the fluid conditioning system based on the mode of operation selected from the plurality of modes.

What is claimed is: 
     
         1 . An assembly comprising:
 a fluid conditioning system including a cascade module;   an active charge compensator integrated into the fluid conditioning system;   wherein the fluid conditioning system is transformable between a plurality of modes including a first mode and a second mode, in the first mode, the fluid conditioning system includes a first vapor compression loop and a second vapor compression loop, the first vapor compression loop and the second vapor compression loop being fluidly coupled at the cascade module and the second vapor compression loop being fluidly separate from the first vapor compression loop, and in the second mode, the fluid conditioning system includes a single vapor compression loop; and   wherein the active charge compensator is operable to control a working fluid charge within the fluid conditioning system based on the mode of operation selected from the plurality of modes.   
     
     
         2 . The assembly of  claim 1 , wherein the cascade module is fluidly connected to the fluid conditioning system during the first mode and the cascade module is not fluidly connected to the fluid conditioning system during the second mode. 
     
     
         3 . The assembly of  claim 1  wherein the active charge compensator further includes at least one flow path that fluidly couples the first vapor compression loop and the second vapor compression loop and at least one charge compensation valve associated with the at least one flow path. 
     
     
         4 . The assembly of  claim 3 , wherein the active charge compensator is operable to balance the working fluid charge between the first vapor compression loop and the second vapor compression loop. 
     
     
         5 . The assembly of  claim 3 , wherein the at least one flow path includes a first flow path for moving a working fluid from the first vapor compression loop to the second vapor compression loop, and a second flow path for moving the working fluid from the second vapor compression loop to the first vapor compression loop. 
     
     
         6 . The assembly of  claim 5 , wherein the first flow path is fluidly connected to the first vapor compression loop at a first connection and is fluidly connected to the second vapor compression loop at a second connection, and a pressure differential exists between the first connection and the second connection. 
     
     
         7 . The assembly of  claim 6 , wherein the second flow path is fluidly connected to the first vapor compression loop at the first connection and is fluidly connected to the second vapor compression loop at a third connection, and another pressure differential exists between the first connection and the third connection. 
     
     
         8 . The assembly of  claim 1 , wherein the fluid conditioning system further comprises a compressor, a first heat exchanger, at least one expansion device, and a second heat exchanger and the cascade module further comprises a cascade compressor and a cascade heat exchanger. 
     
     
         9 . The assembly of  claim 1 , wherein the active charge compensator further includes an expansion valve and the cascade module further includes an accumulator, the expansion valve being operable to direct a flow of working fluid to the accumulator. 
     
     
         10 . The assembly of any  claim 9 , wherein the expansion valve is operable when the fluid conditioning system is in the second mode. 
     
     
         11 . The assembly of  claim 1 , further comprising:
 at least one sensor for monitoring the working fluid charge within the fluid conditioning system;   a controller operably coupled to the active charge compensator and to the at least one sensor, the controller being configured to:   identify a mode of operation of the fluid conditioning system, associated with a demand on the fluid conditioning system;   receive a signal indicating at least one sensed parameter of the fluid conditioning system;   evaluate the working fluid charge of the first vapor compression loop and the second vapor compression loop; and   operate the active charge compensator to adjust the working fluid charge based on the mode of operation and the at least one sensed parameter of the fluid conditioning system.   
     
     
         12 . The assembly of  claim 11 , wherein the fluid conditioning system further includes an indoor unit and an outdoor unit, and the cascade module is selectively fluidly coupled to the indoor unit and the outdoor unit by a plurality of cascade connection valves. 
     
     
         13 . The assembly of  claim 12 , wherein the controller is configured to:
 identify a mode of operation selected from the plurality of modes of the fluid conditioning system associated with the demand on the fluid conditioning system; and   operate at least one of the plurality of cascade connection valves to initiate operation in the identified mode.   
     
     
         14 . A method of operating a fluid conditioning system, the method comprising:
 receiving a demand on the fluid conditioning system;   determining a mode of operation in response to the demand by comparing the demand with a heating capacity of the fluid conditioning system; and   adjusting a working fluid charge within at least one vapor compression loop of the fluid conditioning system.   
     
     
         15 . The method of  claim 14 , further comprising operating the fluid conditioning system in a first mode in response to the demand being greater than the heating capacity of the fluid conditioning system, wherein operating the fluid conditioning system in the first mode further comprises fluidly connecting a cascade module to the fluid conditioning system. 
     
     
         16 . The method of  claim 15 , wherein during operation in the first mode, the at least one vapor compression loop includes a first vapor compression loop and a second vapor compression loop and adjusting the working fluid charge includes at least one of supplying working fluid from the first vapor compression loop to the second vapor compression loop and supplying working fluid from the second vapor compression loop to the first vapor compression loop. 
     
     
         17 . The method of  claim 16 , wherein working fluid is moved between the first vapor compression loop and the second vapor compression loop in response to a pressure differential. 
     
     
         18 . The method of  claim 14 , further comprising operating the fluid conditioning system in a second mode in response to the demand being less than the heating capacity of the fluid conditioning system, wherein operating the fluid conditioning system in the second mode further comprises fluidly isolating a cascade module from the fluid conditioning system. 
     
     
         19 . The method of  claim 18 , wherein during operation in the second mode, adjusting the working fluid charge includes supplying working fluid from the at least one vapor compression loop to an accumulator. 
     
     
         20 . The method of  claim 14 , wherein adjusting the working fluid charge within the at least one vapor compression loop of the fluid conditioning system further comprises operating at least one charge compensation valve of an active charge compensator integrated into the fluid conditioning system.