Air conditioning system with capacity control and controlled hot water generation

Abstract

An HVAC system is disclosed, comprising: (a) a compressor, (b) a source heat exchanger for exchanging heat with a source fluid, (c) a first load heat exchanger operable for heating/cooling air in a space, (d) a second load heat exchanger for heating water, (e) first and second reversing valves, (f) first and second 3-way valves, (f) a bi-directional electronic expansion valve, (g) a first bi-directional valve, and (h) a second bi-directional valve to modulate exchange of heat in the first load heat exchanger when operating as an evaporator and to control flashing of the refrigerant entering the source heat exchanger when operating as an evaporator, (h) a source pump for circulating the source fluid through the first load heat exchanger, (i) a water pump for circulating water through the second load heat exchanger, and (j) a controller to control operation of the foregoing.

1 . An HVAC system for conditioning air in a space, comprising:
 a compressor to circulate a refrigerant through a refrigerant circuit;   a source heat exchanger configured to operate as either a condenser or an evaporator to exchange heat with a source fluid;   a first load heat exchanger configured to operate as either a condenser or an evaporator to heat or cool, respectively, the air in the space;   a second load heat exchanger configured to heat water;   a first 3-way valve and a second 3-way valve; and   a first reversing valve and a second reversing valve,   wherein the first reversing valve is downstream of the compressor to
 selectively direct the refrigerant from the compressor to the second reversing valve, the first 3-way valve, or the second 3-way valve, and 
 selectively return the refrigerant from the second reversing valve or the second 3-way valve to the compressor, 
   wherein the first 3-way valve is configured to selectively direct the refrigerant to the second load heat exchanger from the first reversing valve or the second reversing valve, and   wherein the second 3-way valve is configured to selectively direct the refrigerant to the first reversing valve and the first load heat exchanger.   
     
     
         2 . The HVAC system of  claim 1 , wherein the compressor is a variable capacity compressor. 
     
     
         3 . The HVAC system of  claim 1 , wherein the first load heat exchanger is a refrigerant-to-air heat exchanger. 
     
     
         4 . The HVAC system of  claim 1 , including a fan driven by a variable speed motor, the fan configured to flow air over a portion of the first load heat exchanger. 
     
     
         5 . The HVAC system of  claim 1 , wherein the second load heat exchanger is a refrigerant-to-liquid heat exchanger configured to exchange heat between the refrigerant in the refrigerant circuit and water in a storage loop. 
     
     
         6 . The HVAC system of  claim 5 , including a water pump configured to circulate heated water in the storage loop. 
     
     
         7 . The HVAC system of  claim 1 , wherein the source heat exchanger is a refrigerant-to-liquid heat exchanger configured to exchange heat between the refrigerant in the refrigerant circuit and the source fluid in a source loop. 
     
     
         8 . The HVAC system of  claim 7 , including a source pump configured to circulate the source fluid in the source loop. 
     
     
         9 . The HVAC system of  claim 1 , including
 a first variable speed pump configured to circulate water through the second load heat exchanger; and   a second variable speed pump configured to circulate the source fluid through the source heat exchanger.   
     
     
         10 . The HVAC system of  claim 1 , including a controller comprising a processor and memory, the controller configured to control operation of the compressor, the first reversing valve, the second reversing valve, the first 3-way valve, and the second 3-way valves. 
     
     
         11 . The HVAC system of  claim 10 , wherein the controller is configured to control operation in a space cooling mode, a second cooling mode with the second load heat exchanger being active, a third cooling mode with the second load heat exchanger being active and tempering of the first load heat exchanger, a space heating mode, a second heating mode with the second load heat exchanger being active, and a third heating mode with the second load heat exchanger being active and an expansion valve boost. 
     
     
         12 . The HVAC system of  claim 1 , including
 a bi-directional expansion valve positioned between the source heat exchanger and the first load heat exchanger; and   a first bi-directional valve and a second bi-directional valve,   wherein the first bi-directional valve is positioned downstream of the second reversing valve to selectively convey the refrigerant to at least one of the first 3-way valve, the second 3-way valve, and the second bi-directional valve,   wherein the second bi-directional valve is configured to modulate exchange of heat in the first load heat exchanger when the first load heat exchanger is operating as an evaporator and control flashing of the refrigerant entering the source heat exchanger when the source heat exchanger is operating as an evaporator.   
     
     
         13 . The HVAC system of  claim 12 , wherein in a space cooling mode,
 the source heat exchanger is configured to operate as a condenser,   the first load heat exchanger is configured to operate as an evaporator,   the first reversing valve is configured to convey the refrigerant from the compressor to the second reversing valve and from the second 3-way valve to the compressor,   the second reversing valve is configured to convey the refrigerant from the first reversing valve to the source heat exchanger,   the first bi-directional valve and the second bi-directional valve are closed,   the bi-directional expansion valve is configured to direct the refrigerant to the first load heat exchanger, and   the second 3-way valve is configured to convey the refrigerant from the first load heat exchanger to the first reversing valve.   
     
     
         14 . The HVAC system of  claim 12 , wherein in a cooling mode with the second load heat exchanger being active,
 the source heat exchanger is configured to operate as a condenser,   the first load heat exchanger is configured to operate as an evaporator,   the first reversing valve is configured to convey the refrigerant from the compressor to the second reversing valve and from the second 3-way valve to the compressor,   the second reversing valve is configured to convey the refrigerant from the first reversing valve to the first bi-directional valve and from the second load heat exchanger to the source heat exchanger,   the first bi-directional valve is open and the second bi-directional valve is closed,   the bi-directional expansion valve is configured to direct the refrigerant to the first load heat exchanger, and   the second 3-way valve is configured to convey the refrigerant from the first load heat exchanger to the first reversing valve.   
     
     
         15 . The HVAC system of  claim 12 , wherein in a cooling mode with the second load heat exchanger being active and with the first load heat exchanger being tempered,
 the source heat exchanger is configured to operate as a condenser,   the first load heat exchanger is configured to operate as an evaporator,   the first reversing valve is configured to convey the refrigerant from the compressor to the second reversing valve and from the second 3-way valve to the compressor,   the second reversing valve is configured to convey the refrigerant from the first reversing valve to the first bi-directional valve and from the second load heat exchanger to the source heat exchanger,   the first bi-directional valve and the second bi-directional valve are open,   the first bi-directional valve is configured to convey a first portion of the refrigerant to the first 3-way valve and a second portion of the refrigerant to the second bi-directional valve,   the first 3-way valve is configured to subsequently convey the first portion of the refrigerant to the second load heat exchanger,   the second load heat exchanger is configured to subsequently convey the first portion of the refrigerant to the bi-directional expansion valve via the second reversing valve and the source heat exchanger,   the first load heat exchanger is configured to receive a mixture of the first portion of the refrigerant conveyed by the bi-directional expansion valve and the second portion of the refrigerant conveyed by the second bi-directional valve, and   the second 3-way valve is configured to convey the refrigerant from the first load heat exchanger to the first reversing valve.   
     
     
         16 . The HVAC system of  claim 12 , wherein in a space heating mode,
 the source heat exchanger is configured to operate as an evaporator,   the first load heat exchanger is configured to operate as a condenser,   the first reversing valve is configured to convey the refrigerant from the compressor to the second 3-way valve and from the second reversing valve to the compressor,   the second reversing valve is configured to convey the refrigerant from the source heat exchanger to the first reversing valve,   the second 3-way valve is configured to convey the refrigerant to the first load heat exchanger,   the first bi-directional valve and the second bi-directional valve are closed,   the bi-directional expansion valve is configured to direct the refrigerant to the source heat exchanger, and   the source heat exchanger is configured to direct the refrigerant to the second reversing valve.   
     
     
         17 . The HVAC system of  claim 12 , wherein in a heating mode with the second load heat exchanger being active,
 the first load heat exchanger is configured to operate as a condenser,   the source heat exchanger is configured to operate as an evaporator,   the first reversing valve is configured to convey the refrigerant from the compressor to the first 3-way valve and from the second reversing valve to the compressor,   the first 3-way valve is configured to convey the refrigerant from the first reversing valve to the second load heat exchanger,   the second load heat exchanger is configured to convey the refrigerant to the second reversing valve,   the second reversing valve is configured to convey the refrigerant from the second load heat exchanger to the first bi-directional valve and from the source heat exchanger to the first reversing valve,   the first bi-directional valve is open and configured to convey the refrigerant to the second 3-way valve,   the second 3-way valve is configured to convey the refrigerant to the first load heat exchanger,   the second bi-directional valve is closed,   the bi-directional expansion valve is configured to direct the refrigerant to the source heat exchanger, and   the source heat exchanger is configured to direct the refrigerant to the second reversing valve.   
     
     
         18 . The HVAC system of  claim 12 , wherein in a space heating mode with the second load heat exchanger being active and the bi-directional expansion valve being boosted,
 the first load heat exchanger is configured to operate as a condenser,   the source heat exchanger is configured to operate as an evaporator,   the first reversing valve is configured to convey the refrigerant from the compressor to the first 3-way valve and from the second reversing valve to the compressor,   the first 3-way valve is configured to convey the refrigerant from the first reversing valve to the second load heat exchanger,   the second load heat exchanger is configured to convey the refrigerant to the second reversing valve,   the second reversing valve is configured to convey the refrigerant from the second load heat exchanger to the first bi-directional valve and from the source heat exchanger to the first reversing valve,   the first bi-directional valve and the second bi-directional valve are open,   the first bi-directional valve is configured to convey a first portion of the refrigerant to the second 3-way valve and a second portion of the refrigerant to the second bi-directional valve,   the second 3-way valve is configured to convey the first portion of the refrigerant to the first load heat exchanger,   the bi-directional expansion valve is configured to receive a mixture of the second portion of the refrigerant conveyed by the second bi-directional valve and the first portion of the refrigerant conveyed by the first load heat exchanger,   the bi-directional expansion valve is configured to direct the refrigerant to the source heat exchanger, and   the source heat exchanger is configured to direct the refrigerant to the second reversing valve.   
     
     
         19 . The HVAC system of  claim 12 , including a third bi-directional valve positioned downstream of the second reversing valve and upstream of the first bi-directional valve to convey the refrigerant that is partially condensed from the second load heat exchanger to the bi-directional expansion valve. 
     
     
         20 . The HVAC system of  claim 12 , including a fourth bi-directional valve positioned upstream of the second reversing valve to temporarily convey the refrigerant away from the second reversing valve when switching the second reversing valve from one operating configuration to another.