WO2006128264A1

WO2006128264A1 - Refrigerant system with water heating

Info

Publication number: WO2006128264A1
Application number: PCT/BR2005/000099
Authority: WO
Inventors: Toshio Murakami; Carlos Afonso Tesche; Roberto Gustavo Fernandez
Original assignee: Springer Carrier Ltda; Carrier Corporation
Priority date: 2005-06-03
Filing date: 2005-06-03
Publication date: 2006-12-07
Also published as: CN100549561C; EP1886081A1; MX2007001455A; US20080197206A1; CN101084404A; EP1886081A4; JP2008520945A; CA2574876A1; BRPI0520239A2

Abstract

A heat pump system (10) includes a compressor (20), a reversing valve (30), an outdoor heat exchanger (40) and an indoor heat exchanger (50) coupled via refrigerant lines (35, 45) in a conventional refrigeration circuit, and a refrigerant-to-water heat exchanger (60). In the air cooling with water heating mode, the air heating with water heating mode and the water heating only mode, water from a water reservoir (64), such as a storage tank or swimming pool, is passed through heat exchanger (60) in heat exchange relationship with refrigerant passing through an additional refrigerant line (27) that establishes a fluid flow path through the heat exchanger (60) into the refrigerant circuit intermediate the outdoor heat exchanger (40) and indoor heat exchanger (50). A refrigerant reservoir (70) may be provided for use in refrigerant charge control.

Description

REFRIGERANT SYSTEM WITH WATER HEATING

TECHNICAL FIELD

This invention relates generally to refrigerant systems for cooling or cooling/heating indoor air and, more particularly, to such refrigerant systems including auxiliary liquid heating, including for example heating water for swimming pools, household water systems and the like.

BACKGROUND ART Refrigerant systems, such as air conditioners and reversible heat pumps are well known in the art and commonly used for cooling and cooling/heating, respectively, a climate controlled comfort zone within a residence or a building. A conventional air conditioner or heat pump refrigerant system includes a compressor, a suction accumulator, an outdoor heat exchanger with an associated fan, an indoor heat exchanger 50 with an associated fan, and an expansion valve operatively associated with the indoor heat exchanger. A heat pump system further includes a reversing valve and an additional expansion valve operatively associated with the outdoor heat exchanger. The aforementioned components are typically arranged in a closed refrigerant circuit employing the well known Carnot vapor compression cycle. When operating in the cooling mode, excess heat absorbed by the refrigerant in passing through the indoor heat exchanger is rejected to the environment as the refrigerant passes through the outdoor heat exchanger.

It is well known in the art that an additional refrigerant-to-water heat exchanger may be added to a heat pump system to absorb this excess heat for the purpose of heating water, rather than simply rejecting the excess heat to the environment. Further, heat pumps often have non-utilized heating capacity when operating in the heating mode for heating the climate controlled zone. For example, each of U.S. Patent Nos. 3,188,829; 4,098,092; 4,492,092 and 5,184,472 discloses a heat pump system including an auxiliary hot water heat exchanger. U.S. Patent No. 5,802,864 discloses an air conditioning system for use in cooling and dehumidifying air for an interior space while rejecting heat to several alternative heat sinks, such as the atmosphere, domestic hot water heating and pool water heating. However, these systems do not include any device for controlling the refrigerant charge within the refrigerant circuit. Therefore, while functional, these systems would not be optimally efficient in all modes of operation.

In heat pump systems, the outdoor heat exchanger and the indoor heat exchanger each operate as evaporator, condenser or subcooler, depending on the mode and point of operation. As such, condensing may occur in either heat exchangers, and the suction line may be filled with refrigerant in a gaseous or liquid state. As a consequence, the amount of system refrigerant charge required in each mode of operation in order to ensure operation within an acceptable efficiency envelope will be different for each mode.

U.S. Patent 4,528,822 discloses a heat pump system including an additional refrigerant-to-liquid heat exchanger for heating liquid utilizing the heat that would otherwise be rejected to the environment. The system is operable in four independent modes of operation: space heating, space cooling, liquid heating and simultaneous space cooling with liquid heating. In the liquid heating only mode, the indoor heat exchanger fan is turned off, while in the space cooling and liquid heating mode, the outdoor heat exchanger fan is turned off. A refrigerant charge reservoir is provided into which liquid refrigerant drains by gravity from the refrigerant to liquid heat exchanger during the liquid heating only mode and the simultaneous space cooling and liquid heating mode. However, no control procedure is disclosed for actively controlling refrigerant charge in the refrigerant circuit in all modes of operation. Further, no simultaneous space heating and liquid heating mode is disclosed.

Accordingly, it is desirable that the system be provide that includes active refrigerant charge control in all modes of operation whereby the heat pump system may operate effectively in an air cooling only mode, an air cooling and liquid heating mode, an air heating only mode, an air heating and liquid heating mode, and a liquid heating only mode.

SUMMARY OF THE INVENTION

In one aspect, it is an object of the invention to provide an air conditioner/heat pump system having liquid heating capability and improved refrigerant charge control.

In one aspect, it is a object of the invention to provide an air conditioner/heat pump refrigerant system having liquid heating capability with refrigerant charge control in all operating modes.

In one embodiment of the invention, the system includes a refrigerant compressor having a suction port and a discharge port; a selectively positionable four-port reversing valve having a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication, and a second position for coupling the first port and the fourth port in fluid flow communication and the second port and the third port in fluid flow communication; and a refrigerant circuit providing a closed loop refrigerant circulation flow path. The refrigerant circuit has a first refrigerant line establishing a flow path between the discharge port of the compressor and the first port of the reversing valve, a second refrigerant line establishing a flow path between the second port of the reversing valve and the suction port of the compressor. An outdoor heat exchanger is disposed in operative association with the second refrigerant line and is adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with ambient air. An indoor heat exchanger is disposed inoperative association with the second refrigerant line and is adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with the air from the comfort zone. The indoor heat exchanger is disposed downstream of the outdoor exchanger with respect to refrigerant flow in the air cooling mode. A third refrigerant line establishes a flow path between the fourth port of the reversing valve and the second refrigerant line at a location intermediate the outdoor heat exchanger and the indoor heat exchanger. A refrigerant to liquid heat exchanger is disposed in operative association with the third refrigerant line and is adapted for passing refrigerant passing through the third refrigerant line in heat exchange relationship with a liquid. A refrigerant reservoir may be provided having an inlet coupled in fluid flow communication to the second refrigerant line at a location intermediate the outdoor heat exchanger and the indoor heat exchanger and an outlet coupled in fluid flow communication to the suction inlet of the compressor. A first flow control valve is disposed in the second refrigerant line intermediate the outdoor heat exchanger and the location of the intersection of the third refrigerant line with the second refrigerant line, and a second flow control valve is disposed in the second refrigerant line intermediate the indoor heat exchanger and the location of the intersection of the third refrigerant line with the second refrigerant line. A controller is provided to selectively control the respective positioning of the first and second flow control valves between their respective open and closed positions so as to selectively control refrigerant flow through the second refrigerant line. A flow check valve may be disposed in the third refrigerant line so as to permit refrigerant flow therethrough in a direction from the reversing valve into the second refrigerant line and to block flow from the second refrigerant line to the reversing valve.

In another embodiment of the invention, a heat pump system includes a refrigerant compressor having a suction port and a discharge port; a first selectively positionable four-port valve having a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication, and a second position for coupling the first port and the fourth port in fluid flow communication and the second port and the third port in fluid flow communication; and a refrigerant circuit providing a closed loop refrigerant circulation flow path. The refrigerant circuit has a first refrigerant line establishing a flow path between the discharge port of the compressor and the first port of the reversing valve, a second refrigerant line establishing a flow path between the second port of the reversing valve and the suction port of the compressor. An outdoor heat exchanger is disposed in operative association with the second refrigerant line and is adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with ambient air. An indoor heat exchanger is disposed inoperative association with the second refrigerant line and is adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with the air from the comfort zone. The indoor heat exchanger is disposed downstream of the outdoor exchanger with respect to refrigerant flow in the air cooling mode and upstream of the outdoor heat exchanger with respect to refrigerant flow through the second refrigerant line in the air heating mode.

In this embodiment, a second selectively positionable four-port valve is provided having a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication and a second position for coupling the first port and the third port in fluid flow communication and the second port and the fourth port in fluid flow communication. A third refrigerant line establishes a flow path between the fourth port of the first reversing valve and the first port of the second reversing valve. A fourth refrigerant line establishes a flow path between the third port of the second reversing valve and the second refrigerant line at a location intermediate the outdoor heat exchanger and the indoor heat exchanger. A fifth refrigerant line establishes a flow path between the second port of the reversing valve and the second refrigerant line at a location intermediate the indoor heat exchanger and the suction inlet to the compressor. A refrigerant to liquid heat exchanger is disposed in operative association with the fourth refrigerant line and is adapted for passing refrigerant passing through the fourth refrigerant line in heat exchange relationship with a liquid.

A first flow control valve is disposed in the second refrigerant line intermediate the outdoor heat exchanger and the location of the intersection of the third refrigerant line with the second refrigerant line. A second flow control valve is disposed in the second refrigerant line intermediate the indoor heat exchanger and the location of the intersection of the third refrigerant line with the second refrigerant line. A third flow control valve is disposed in the second refrigerant line intermediate the location of the intersection of the fifth refrigerant line with the second refrigerant line and the suction inlet to the compressor. A controller is provided to selectively control the respective positioning of the first, second and third flow control valves between their respective open and closed positions so as to selectively control refrigerant flow through the second refrigerant line. A flow check valve may be disposed in the third refrigerant line so as to permit refrigerant flow therethrough in a direction from the reversing valve into the second refrigerant line and to block flow from the second refrigerant line to the reversing valve.

In the heat pump embodiment, as in the air conditioning embodiment of the system, a refrigerant reservoir may be provided having an inlet coupled in fluid flow communication to the second refrigerant line at a location intermediate the outdoor heat exchanger and the indoor heat exchanger and an outlet coupled in fluid flow communication to the suction inlet of the compressor. Advantageously, a first flow control valve may be provided in operative association with the refrigerant reservoir for controlling the flow of refrigerant from the second refrigerant line to the inlet of the refrigerant reservoir; and a second flow control valve may be provided in operative association with the refrigerant reservoir for controlling the flow refrigerant between the outlet of refrigerant reservoir and the suction inlet of the compressor. The controller selectively controls the respective positioning of these flow control valves between their respective open and closed positions so as to selectively control the refrigerant charge within the refrigerant circuit. These flow control valves may also have at least one partially open position and may comprise pulse width modulated solenoid valves. The controller may be further operative to selectively modulate the respective positioning of these flow control valves between their open, partially open and closed positions.

In a further embodiment, a liquid level sensor may be provided for sensing the level of liquid refrigerant in the refrigerant reservoir and for providing a signal to the controller indicative of the liquid level within the refrigerant reservoir. In response to the liquid level signal, the controller will selectively control the respective positioning of the first and second flow control valves operatively associated with the refrigerant reservoir so as to selectively control the refrigerant charge within the refrigerant circuit.

In a further aspect of the invention, in the heat pump embodiment, the system may be used to heat both indoor air and water by cycling between the indoor air heating mode and the water heating mode. To do so, the system controller will switch between the air heating only mode and the water heating only mode every few minutes until the water temperature set point or the air indoor temperature set point has been reached.

BRIEF DESCRIPTION OF THE DRAWINGS For a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, where:

Figure 1 is a schematic diagram illustrating a first embodiment of the system of the invention illustrating operation in the indoor air cooling only mode;

Figure 2 is a schematic diagram illustrating a first embodiment of the system of the invention illustrating operation in the indoor air cooling with water heating mode;

Figure 3 is a schematic diagram illustrating a first embodiment of the system of the invention illustrating operation in the water heating only mode;

Figure 4 is a schematic diagram illustrating a second embodiment of the heat pump system of the invention illustrating operation in an air cooling only mode;

Figure 5 is a schematic diagram illustrating a second embodiment of the system of the invention illustrating operation in the indoor air cooling with water heating mode; Figure 6 is a schematic diagram illustrating a second embodiment of the heat pump system of the invention illustrating operation in an air heating mode;

Figure 7 is a schematic diagram illustrating a second embodiment of the heat pump system of the invention illustrating operation in a water heating mode;

Figure 8 is a schematic diagram illustrating an embodiment of a control system arrangement for the system of the invention;

Figure 9 is block diagram illustrating a first embodiment of a refrigerant charge adjustment procedure at start-up in a new mode of operation;

Figure 10 is a block diagram illustrating a second embodiment of a refrigerant charge adjustment procedure at start-up in a new mode of operation;

Figure 11 is a block diagram illustrating a third embodiment of a refrigerant charge adjustment procedure at start-up in a new mode of operation;

Figure 12 is a block diagram illustrating a discharge temperature limit control procedure for adjusting refrigerant charge post start-up; and

Figure 13 is a block diagram illustrating a charge control procedure for adjusting refrigerant charge post start-up. DETAILED DESCRIPTION OF THE INVENTION

The refrigerant heat pump system 10, depicted in a first embodiment in Figures 1-3 and a second embodiment in Figures 4-7, provides in the first embodiment cooling of air to a comfort region and in the second embodiment cooling and heating of air to a comfort region, for example an indoor zone located on the inside of a building (not shown), and also auxiliary water heating in each embodiment when desired. The system includes a compressor 20, a suction accumulator 22, a reversing valve 30, an outdoor heat exchanger 40 and associated fan 42 located on the outside of the building in heat transfer relation with the surrounding ambient, an indoor heat exchanger 50 and associated fan 52 situated in the comfort zone, a first expansion valve 44 operatively associated with the outdoor heat exchanger 40 and a second expansion valve 54 operatively associated with the indoor heat exchanger 50. A refrigerant circuit including refrigerant lines 35, 45 and 55 provide a closed loop refrigerant flow path coupling these components in a conventional manner for a heat pump system employing the well known Carnot vapor compression cycle. Additionally, the system 10 includes a refrigerant-to-water heat exchanger 60 wherein refrigerant is passed in heat exchange relationship with water to be heated. The water to be heated is pumped by a circulating pump 62 via water circulation line 65 from a water reservoir 64, for example a hot water storage tank or a swimming pool, through the heat exchanger 60 and back to the reservoir 64.

The compressor 20, which may comprise a rotary compressor, a scroll compressor, a reciprocating compressor, a screw compressor or any other type of compressor, has a suction inlet for receiving refrigerant from the suction accumulator 22 and an outlet for discharging compressed refrigerant. The reversing valve 30 may comprise a selectively positionable, two-position, four-port valve having a first port 30-1, a second port 30-2, a third port 30-3 and a fourth port 30-4. The reversing valve 30 is positionable in a first position for coupling the first port and the second port in fluid flow communication and for simultaneously coupling the third port and the fourth port in fluid flow communication. The reversing valve 30 is positionable in a second position for coupling the first port and the fourth port in fluid flow communication and for simultaneously coupling the second port and the third port in fluid flow communication. Advantageously, the respective port-to-port couplings established in the first and second positions are accomplished internally within the reversing valve 30. The outlet 28 of the compressor 20 is connected in fluid flow communication via refrigerant line 35 to the first port 30-1 of the reversing valve 30. The second port 30-2 of the reversing valve 30 is connected in fluid flow communication to refrigerant line 45 A. The third port 30-3 of the reversing valve 30 is connected in fluid flow with refrigerant line 47. The refrigerant-to-water heat exchanger 60 is operatively associated with the refrigerant line 25 whereby refrigerant flowing through the refrigerant line 25 passes in heat exchange relationship with water passing through water circulation line 65.

The outdoor heat exchanger 40 and the indoor heat exchanger 50 are operatively disposed in the refrigerant line 45. The outdoor heat exchanger 50 is connected in fluid flow communication via section 45 A of the refrigerant line 45 with the second port 30-2 of the reversing valve 30. The indoor heat exchanger 50 is connected in fluid flow communication to the third port 30-3 of the reversing valve 30 via section 45C of the refrigerant line 45. Section 45B of the refrigerant line 45 couples the outdoor heat exchanger 40 and the indoor heat exchanger 50 in refrigerant flow communication. A suction accumulator 22 may be disposed in refrigerant line 55 on the suction side of the compressor 20, having its inlet connected in refrigerant flow communication to refrigerant line 45C via section 45C of refrigerant line 55 and having its outlet connected in refrigerant flow communication to the suction inlet of the compressor 20 via refrigerant line 55. Therefore, refrigerant lines 35, 45 and 55 together couple the compressor 20, the outdoor heat exchanger 40 and the indoor heat exchanger 50 in refrigerant flow communication, thereby creating a closed loop for refrigerant flow circulation through the heat pump system 10.

A first flow control valve 48 and a second flow control valve 58 are disposed in section 45B of refrigerant line 45 between the outdoor heat exchanger 40 and the indoor heat exchanger 50. After traversing the refrigerant-to-water heat exchanger 60, refrigerant line 25 connects in fluid flow communication into refrigerant line 45 at a point intermediate the two flow control valves 48 and 58. A check valve 26 disposed in refrigerant line 25 permits flow through line 25 into refrigerant line 45, but closes line 25 to flow in the reverse direction. Advantageously, both of the flow control valves 48 and 58 are solenoid valves selectively positionable by controller 100 in either the open position or the closed position.

In the both embodiments, an expansion valve 54 is disposed in section 45B of the refrigerant line 45 in operative association with the indoor heat exchanger. In the heat pump embodiment, illustrated in Figures 4-7, an expansion valve 44 is also provided in operative association eith the outdoor heat exchanger. Each of the expansion valves 44 and 54 is provided with a bypass line equipped with a check valve permitting flow in only one direction. Check valve 46 in bypass line 43 associated with the outdoor heat exchanger expansion valve 44 passes refrigerant flowing from the outdoor heat exchanger 40 to the indoor heat exchanger 50, thereby bypassing the outdoor heat exchanger expansion valve 44 and passing the refrigerant to the indoor heat exchanger expansion valve 54. Conversely, check valve 56 in bypass line 53 associated with the indoor heat exchanger expansion valve 54 passes refrigerant flowing from the indoor heat exchanger 50 to the outdoor heat exchanger 40, thereby bypassing the indoor heat exchanger expansion valve 54 and passing the refrigerant to the outdoor heat exchanger expansion valve 44.

In the embodiment of the system depicted in Figures 4-7, the system includes, in addition to the previously mentioned components, a second reversing valve 130 and an additional flow control valve 68. The second reversing valve 130 may comprise a selectively positionable, two-position, four-port valve having a first port 130-1, a second port 130-2, a third port 130-3 and a fourth port 130-4. The second reversing valve 130 is positionable in a first position for coupling the first port and the second port in fluid flow communication and for simultaneously coupling the third port and the fourth port in fluid flow communication. The reversing valve 130 is positionable in a second position for coupling the first port and the third port in fluid flow communication and for simultaneously coupling the second port and the fourth port in fluid flow communication. Advantageously, the respective port-to-port couplings established in the first and second positions are accomplished internally within the reversing valve 30. The first port 130-1 of the reversing valve 130 is connected in refrigerant flow communication via refrigerant line 23 to the fourth port 30- 1 of the reversing valve 30. The second port 130-2 of the reversing valve 130 is connected in refrigerant flow communication via refrigerant line 27 into refrigerant line 45 C. The third port 130-3 of the reversing valve 130 is connected in refrigerant flow communication via refrigerant line 25 into refrigerant line 45B. The fourth port 130-4 of the reversing valve 130 is connected in refrigeration flow communication via refrigerant line 29 into refrigerant line 47.

Like the first and second flow control valves 48 and 58, the third flow control valve 68 may advantageously be a solenoid valve selectively positionable by controller 100 in either the open position or the closed position. When flow control valve 68 is in its open position, refrigerant can flow through refrigerant line 45 C to the suction accumulator through line 45C. When flow control valve 68 is in its closed position, however, refrigerant can not flow through refrigerant line 45 C back to the suction accumulator through line 45C.

In the embodiment of the system of the invention depicted in Figures 1-3, the system functions to cool air to a comfort region, and also to heat water on demand. Therefore, in this embodiment, the system must operate effectively in an air cooling only mode, an air cooling and water heating mode, and a water heating only mode. In the embodiment of the system depicted in Figures 4-7, the system functions to cool and to heat air to a comfort region, and to also heat water on demand except when in the air heating mode. Therefore, in this embodiment, the system must operate effectively in an air cooling only mode, an air cooling and water heating mode, an air heating only mode, and a water heating only mode. As each of the outdoor heat exchanger 40, the indoor heat exchanger 50 and the refrigerant-to-water heat exchanger 60 will operate one as a condenser, another as an evaporator and another bled of refrigerant depending on the mode, the refrigerant charge required in each mode in order to ensure operation within an acceptable efficiency envelope will be different, the optimal refrigerant charge will also depend on the operation temperatures within each mode and the amount of refrigerant within the working and bleed lines for each mode.

Accordingly, the system 10 further includes a refrigerant storage reservoir 70, termed a charge tank, having an inlet connected in fluid flow communication with the refrigerant line 45 via refrigerant line 71 and an outlet connected in fluid flow communication with the refrigerant line 45 C via refrigerant line 73, a first flow control valve 72 disposed in the refrigerant line 71, and a second flow control valve 74 disposed in the refrigerant line 73. Each of the first and second flow control valves 72 and 74 has an open position and a closed position so that flow therethrough may be selectively controlled whereby the refrigerant charge within the refrigerant circuit may be actively controlled. Advantageously, each of the first and second flow control valves 72 and 74 may also have at least one partially open position and may be a pulse width modulated solenoid valve. Additionally, a liquid level meter 80, such as for example a transducer, may be disposed in the charge tank 70 for monitoring the refrigerant level within the charge tank. Referring now to Figure 8, a system controller 100, advantageously a microprocessor, controls the operation of the water pump 62, the compressor 20, the reversing valve 30 and other heat pump components, such as the outdoor heat exchanger fan 42 and the indoor heat exchanger fan 52, in response to the cooling or heating demand of the comfort region in a conventional manner and/or the demand for water heating. In the embodiment depicted in Figures 4-7, the system controller 100 also controls operation of the second reversing valve 130 and the additional flow control valve 68. In addition, the system controller 100 controls the opening and closing of the flow control valves 72 and 74 to adjust the refrigerant charge to coordinate with system requirements for the various modes of operation. The system controller 100 receives input signals indicative of various system operational parameters from a plurality of sensors, including, without limitation, a suction temperature sensor 81, a suction pressure sensor 83, a discharge temperature sensor 85, a discharge pressure sensor 87, a water temperature sensor 89, an outdoor heat exchanger refrigerant temperature sensor 82, an indoor heat exchanger refrigerant temperature sensor 84, and a refrigerant temperature sensor 86 disposed in operative association with section 45B of refrigerant line 45 at a location between the expansion valves 44 and 54.

The suction temperature sensor 81 and the suction pressure sensor 83 are disposed in operative association with refrigerant line 55 near the suction inlet to the compressor 20 as in conventional practice for sensing the refrigerant temperature and pressure, respectively, at the compressor suction inlet and for passing respective signals indicative thereof to the system controller 100. The discharge temperature sensor 85 and the discharge pressure sensor 87 are disposed in operative association with refrigerant line 35 near the discharge outlet to the compressor 20 as in conventional practice for sensing the refrigerant temperature and pressure, respectively, at the compressor discharge outlet and for passing respective signals indicative thereof to the system controller 100. The water temperature sensor 89 is disposed in operative association with the water reservoir 64 for sensing the temperature of the water therein and for passing a signal indicative of the sensed water temperature to the system controller 100. The temperature sensor 82 is disposed in operative association with the outdoor heat exchanger 40 at a location appropriate for measuring the refrigerant phase change temperature of refrigerant passing therethrough when the indoor heat exchanger is operating and for sending a signal indicative of that sensed temperature to the system controller 100 for controlling operation of the expansion valve 44. Similarly, the temperature sensor 84 is disposed in operative association with the indoor heat exchanger 50 at a location for measuring the refrigerant phase change temperature of refrigerant passing therethrough when the outdoor heat exchanger is operating and for sending a signal indicative of that sensed temperature to the system controller 100 for controlling operation of the expansion valve 54. The system controller 100 determines the degree of superheat from the refrigerant temperature sensed by whichever of sensors 82 and 84 is associated with the heat exchanger that is acting as an evaporator in the current operating mode. The refrigerant temperature sensor 86 operatively associated with refrigerant line 45 senses the temperature of the refrigerant at a location between the expansion valves 44 and 54 and passes a signal indicative of the sensed temperature to the system controller 100. The system controller determines the degree of subcooling present from the sensed temperature received from temperature sensor 86.

Referring now to Figure 1, in the indoor air cooling only mode, in response to a demand for cooling, the system controller 100 activates the compressor 20, the outdoor heat exchanger fan 42 and the indoor heat exchanger fan 52 and opens both of the flow control valves 48 and 58. High pressure, superheated refrigerant from the compressor 20 passes through refrigerant line 35 to the reversing valve 30 wherein the refrigerant is directed to and through section 45 A of refrigerant line 45 to the outdoor heat exchanger 40, which in the air cooling mode functions as a condenser. With the outdoor heat exchanger fan 42 operating, ambient air flows through the outdoor heat exchanger 40 in heat exchange relationship with the refrigerant passing therethrough, whereby the high pressure refrigerant is condensed to a liquid and subcooled. With the flow control valves 48 and 58 open, high pressure liquid refrigerant passes from the outdoor heat exchanger 40 through section 45B of refrigerant line 45 to the indoor heat exchanger 50, which in the air cooling mode functions as an evaporator. In passing through section 45B of refrigerant line 45, the high pressure liquid refrigerant bypass the expansion valve 44 through bypass line 43 and check valve 46 and thence passes through the expansion valve 54 wherein the high pressure liquid refrigerant expands to a lower pressure, thereby further cooling the refrigerant prior to the refrigerant entering the indoor heat exchanger 50. As the refrigerant traverses the indoor heat exchanger, the refrigerant evaporates. With the indoor heat exchanger fan 52 operating, indoor air passes through the indoor heat exchanger 50 in heat exchange relationship with the refrigerant thereby evaporating the refrigerant and cooling the indoor air. The refrigerant passes from the indoor heat exchanger through section 45C of refrigerant line 45 to the suction accumulator 22 before returning to the compressor 20 through refrigerant line 55 connecting to the suction inlet of the compressor 20. In this air cooling only mode, the check 26 in refrigerant line 25 is closed and any refrigerant that may be in line 25, for example refrigerant remaining in the refrigerant-to-water heat exchanger 60 from a prior water heating mode, is bleed back to the suction accumulator 22 through line 57 to line 45C.

Referring now to Figure 2, when there is a demand for water heating while the system is in the indoor air cooling mode, the system controller 100 repositions the reversing valve 30, closes the flow control valve 48, keeps the flow control valve 58 open, deactivates the outdoor heat exchanger fan 42, and activates the water pump 60. With the water pump activated, water is pumped via water line 65 from water reservoir 64 through heat exchanger 60 in heat exchange relationship with the high pressure superheated refrigerant flowing through refrigerant line 25 to heat the water. Having traversed the heat exchanger 60, the heated water returns to the reservoir 64. The high pressure superheated refrigerant from the compressor 20 is directed in the reversing valve 30 from port 30-1 to port 30-4 into the refrigerant line 25. As the refrigerant passes through the heat exchanger 60, the refrigerant is condensed and subcooled as it gives up heat to heat the water flowing through the heat exchanger 60 in heat exchange relationship with the refrigerant. Having already condensed and subcooled, the refrigerant pass directly into the refrigerant line 45B through the check valve 26 in line 25, thereby bypassing the outdoor heat exchanger 40. With valve 48 closed and valve 58 open, the refrigerant continues on through the expansion valve 54 and traverses the indoor heat exchanger 50 wherein the refrigerant is evaporated as it passes in heat exchange relationship with and cools the indoor air being circulated through the indoor heat exchanger 50 via fan 52. The refrigerant vapor leaving the indoor heat exchanger thence passes through line 45 C to line 45C to the suction accumulator 22 and returns to the compressor 20 through line 55B. With the reversing valve 30 in this position, ports 30-2 and 30-3 are connected in flow communication thereby coupling line 45A in refrigerant flow communication with refrigerant line 57, whereby any refrigerant remaining within the outdoor heat exchanger 40 from a prior operating mode will bleed back through lines 45A and 57 back to the line 45C to the suction accumulator 22.

Referring now to Figure 3, when there is a demand for water heating while the system is off, that is not in the indoor air cooling mode, the system controller 100 activates the water pump 60, the compressor 20, and the outdoor heat exchanger fan 42, but not the indoor heat exchanger fan 52, opens flow control valve 48 and closes flow control valve 58. With the pump 60 turned on, water is pumped via water line 65 from storage tank 64 through heat exchanger 60 in heat exchange relationship with the high pressure superheated vapor refrigerant flowing through refrigerant line 25. Having traversed the heat exchanger 60, the heated water returns to the reservoir 64. The high pressure superheated refrigerant from the compressor 20 is directed in the reversing valve 30 from port 30-1 to port 30-4 into the refrigerant line 25. Having already condensed and subcooled, the refrigerant pass directly into the refrigerant 45 through the check valve 26 in line 25. With valve 48 open and valve 58 closed, the refrigerant continues on through the expansion valve 44 and traverses the outdoor heat exchanger 40 wherein the refrigerant is evaporated as it passes in heat exchange relationship with and cools the ambient air being circulated through the outdoor heat exchanger 40 via fan 42. With the reversing valve 30 in this position, ports 30-2 and 30-3 are connected in flow communication thereby coupling line 45A in refrigerant flow communication with refrigerant line 45D. Therefore, the refrigerant vapor leaving the outdoor heat exchanger passes through line 45 A, thence via the reversing valve 30 to line 57, thence to line 45C to the suction accumulator 22 and returns to the compressor 20 through line 55. With valve 58 closed, any refrigerant remaining within the indoor heat exchanger 50 from a prior operating mode will bleed back through line 45 C back to the suction accumulator 22.

As noted previously, the embodiment of the refrigerant system 10 depicted in Figures 4-7 provides for not only cooling air to a comfort region, for example an indoor zone located on the inside of a building (not shown), but also for heating air to the comfort zone and also auxiliary water heating when desired. Referring now to Figure 4, in the indoor air cooling only mode, in response to a demand for cooling, the system controller 100 activates the compressor 20, the outdoor heat exchanger fan 42 and the indoor heat exchanger fan 52 and opens both of the flow control valves 48 and 58. High pressure, superheated refrigerant from the compressor 20 passes through refrigerant line 35 to the reversing valve 30 wherein the refrigerant is directed to and through section 45 A of refrigerant line 45 to the outdoor heat exchanger 40, which in the air cooling mode functions as a condenser. With the outdoor heat exchanger fan 42 operating, ambient air flows through the outdoor heat exchanger 40 in heat exchange relationship with, the refrigerant passing therethrough, whereby the high pressure refrigerant is condensed to a liquid and subcooled. With the flow control valves 48 and 58 open, high pressure liquid refrigerant passes from the outdoor heat exchanger 40 through section 45B of refrigerant line 45 to the indoor heat exchanger 50, which in the air cooling mode functions as an evaporator. In passing through section 45B of refrigerant line 45, the high pressure liquid refrigerant bypass the expansion valve 44 through bypass line 43 and check valve 46 and thence passes through the expansion valve 54 wherein the high pressure liquid refrigerant expands to a lower pressure, thereby further cooling the refrigerant prior to the refrigerant entering the indoor heat exchanger 50. As the refrigerant traverses the indoor heat exchanger, the refrigerant evaporates. With the indoor heat exchanger fan 52 operating, indoor air passes through the indoor heat exchanger 50 in heat exchange relationship with the refrigerant thereby evaporating the refrigerant and cooling the indoor air. With the flow control valve 68 open, the refrigerant passes from the indoor heat exchanger through section 45 C of refrigerant line 45 to the suction accumulator 22 before returning to the compressor 20 through refrigerant line 55 connecting to the suction inlet of the compressor 20. In the air cooling only mode, as the check valve 26 in refrigerant line 25 is closed to flow from line 45B, any refrigerant that may be in line 25, for example refrigerant remaining in the refrigerant-to-water heat exchanger 60 from a prior water heating mode, is bleed back through reversing valve 130 and reversing valve 130 to the suction accumulator 22 through line 57 to line 45C.

Referring now to Figure 5, when there is a demand for water heating while the system is in the indoor air cooling mode, the system controller 100 repositions the reversing valve 30, closes the flow control valve 48, keeps the flow control valve 58 open, deactivates the outdoor heat exchanger fan 42, and activates the water pump 60. With the water pump activated, water is pumped via water line 65 from water reservoir 64 through heat exchanger 60 in heat exchange relationship with the high pressure superheated refrigerant flowing through refrigerant line 25 to heat the water. Having traversed the heat exchanger 60, the heated water returns to the reservoir 64. The high pressure superheated refrigerant from the compressor 20 is directed in the reversing valve 30 from port 30-1 to port 30-4 into the refrigerant line 23 to port 130-1 of the reversing valve 130 and through the reversing valve 130 to line 25 which connects to port 130-3 of the reversing valve 130. As the refrigerant passes through the heat exchanger 60, the refrigerant is condensed and subcooled as it gives up heat to heat the water flowing through the heat exchanger 60 in heat exchange relationship with the refrigerant. Having already condensed and subcooled, the refrigerant pass directly into the refrigerant line 45B through the check valve 26 in line 25, thereby bypassing the outdoor heat exchanger 40. With valve 48 closed and valve 58 open, the refrigerant continues on through the expansion valve 54 and traverses the indoor heat exchanger 50 wherein the refrigerant is evaporated as it passes in heat exchange relationship with and cools the indoor air being circulated through the indoor heat exchanger 50 via fan 52. With flow control valve 68 open, the refrigerant vapor leaving the indoor heat exchanger thence passes through line 45C to the suction accumulator 22 and returns to the compressor 20 through line 55. With the reversing valves 30 and 130 in this position, ports30-2 and 30-3 are connected in flow communication and ports 130-2 and 130-4 are also connected in flow communication thereby coupling line 45A in refrigerant flow communication with refrigerant line 57, whereby any refrigerant remaining within the outdoor heat exchanger 40 from a prior operating mode will bleed back through lines 45A and 57 back to the line 45C to the suction accumulator 22.

Referring now to Figure 6, in the indoor air heating only mode, in response to a demand for cooling, the system controller 100 activates the compressor 20, the outdoor heat exchanger fan 42 and the indoor heat exchanger fan 52, closes flow control valve 68, and opens both of the flow control valves 48 and 58. Further, the system controller 100 positions the reversing valve 30 such that port 30-1 communicates with port 30-4 and port 30-2 communicates with 30-3, and also positions the reversing valve 130 such that port 130 — 1 communicates with port 130-2 and port 130-3 communicates with port 130-4. High pressure, superheated refrigerant from the compressor 20 passes through refrigerant line 35 to port 30-1 of the reversing valve 30 wherein the refrigerant is directed to port 30-4 thereof and through refrigerant line 23 to port 130-1 of the reversing valve 130. From the reversing valve 130, the high pressure, superheated refrigerant passes from port 130-2 through refrigerant line 27 and refrigerant line 45C to the indoor heat exchanger 50, which in the air heating mode functions as a condenser. With the indoor heat exchanger fan 52 operating, indoor air flows through the indoor heat exchanger 50 in heat exchange relationship with the refrigerant passing therethrough, whereby the high pressure refrigerant is condensed to a liquid and subcooled. With the flow control valves 48 and 58 open, high pressure liquid refrigerant passes from the indoor heat exchanger 50 through section 45B of refrigerant line 45 to the outdoor heat exchanger 40, which in the air heating mode functions as an evaporator. In passing through section 45B of refrigerant line 45, the high pressure liquid refrigerant bypass the expansion valve 54 through bypass line 53 and check valve 56 and thence passes through the expansion valve 44 wherein the high pressure liquid refrigerant expands to a lower pressure, thereby further cooling the refrigerant prior to the refrigerant entering the outdoor heat exchanger 40. As the refrigerant traverses the outdoor heat exchanger, the refrigerant evaporates. With the outdoor heat exchanger fan 42 operating, ambient air passes through the outdoor heat exchanger 50 in heat exchange relationship with the refrigerant thereby evaporating the refrigerant and cooling the ambient air. With the flow control valve 68 closed, the refrigerant passes from the outdoor heat exchanger 40 through section 45 A of refrigerant line 45 to port 30-2 of the reversing valve 30, thence from port 30-3 of the reversing valve 30 through line 57 and refrigerant line 45 C to the suction accumulator 22 before returning to the compressor 20 through refrigerant line 55 connecting to the suction inlet of the compressor 20. In the air heating only mode, as the check valve 26 in refrigerant line 25 is closed to flow from line 45B, any refrigerant that may be in line 25, for example refrigerant remaining in the refrigerant-to-water heat exchanger 60 from a prior water heating mode, is bleed back through reversing valve 130 to the suction accumulator 22 through refrigerant line 29, refrigerant line 57 and refrigerant line 45C.

Referring now to Figure 7, when there is a demand for water heating while the system is off, that is not in the indoor air cooling or indoor heating mode, the system controller 100 activates the water pump 60, the compressor 20, and the outdoor heat exchanger fan 42, but not the indoor heat exchanger fan 52, opens flow control valve 48 and flow control valve 68 and closes flow control valve 58. With the pump 60 turned on, water is pumped via water line 65 from storage tank 64 through heat exchanger 60 in heat exchange relationship with the high pressure superheated vapor refrigerant flowing through refrigerant line 25. Having traversed the heat exchanger 60, the heated water returns to the reservoir 64. The high pressure superheated refrigerant from the compressor 20 is directed in the reversing valve 30 from port 30-1 to port 30-4, thence through line 23 to port 130-1 of the reversing valve 130-1 and through port 130-3 into the refrigerant line 25. Having traversed the refrigerant-to-water heat exchanger 60, the already condensed and subcooled refrigerant pass directly into refrigerant line 45 through the check valve 26 in line 25. With valve 48 open and valve 58 closed, the refrigerant continues on through the expansion valve 44 and traverses the outdoor heat exchanger 40 wherein the refrigerant is evaporated as it passes in heat exchange relationship with and cools the ambient air being circulated through the outdoor heat exchanger 40 via fan 42. With the reversing valve 30 in this position, ports 30-2 and 30-3 are connected in flow communication thereby coupling line 45A in refrigerant flow communication with refrigerant line 45D. Therefore, the refrigerant vapor leaving the outdoor heat exchanger passes through line 45A, thence via the reversing valve 30 to line 57, thence to line 45 C to the suction accumulator 22 and returns to the compressor 20 through line 55. With valve 58 closed and valve 68 open, any refrigerant remaining within the indoor heat exchanger 50 from a prior operating mode will bleed back through line 45 C to the suction accumulator 22.

As noted hereinbefore, in the embodiment of the system of the invention 99

28

depicted in Figures 1-3, the system must operate effectively in an air cooling only mode, an air cooling and water heating mode, and a water heating only mode. In the embodiment of the system of the invention depicted in Figures 4-7, the system must additionally operate effectively in an air heating mode. As each of the outdoor heat exchanger 40, the indoor heat exchanger 50 and the refrigerant-to-water heat exchanger 60 will operate one as a condenser, another as an evaporator and another bled of refrigerant depending on the mode, the refrigerant charge required in each mode in order to ensure operation within an acceptable efficiency envelope will be different, the optimal refrigerant charge will also depend on the operation temperatures within each mode and the amount of refrigerant within the working and bleed lines for each mode. Accordingly, the system controller system 100 controls the amount of refrigerant flowing through the refrigerant circuit at any time, i.e. the refrigerant charge, by monitoring and adjusting the level of refrigerant in the charge tank 70 by selectively opening and closing the first flow control valve 72 disposed in the refrigerant line 71 and a second flow control valve 74 disposed in the refrigerant line 73.

In a most advantageous embodiment, the charge tank 70 is provided with a liquid level meter 80 that generates and transmits a signal indicative of the refrigerant level within the charge tank 70 to the system controller 100. The liquid level meter 80 may be configured to transmit a liquid level signal to the system controller 100 continuously, on a periodic basis at specified intervals, or only when prompted by the controller. Referring now to Figure 9, in operation, when the controller switches from one mode of operation to a new mode of operation, the controller 100 turns on the compressor 20 at block 101, and then, at block 102, the controller 100 compares the then current liquid level in the charge tank 70 with the liquid level last experienced the last time the system was operated in a mode equivalent to the new mode of operation, the liquid level last experienced having been stored in the controller's memory. If the current level is the same as the last experienced level for this particular mode of operation, the controller at block 105 activates the normal charge control procedure and/or discharge temperature control procedure.

However, if the current liquid level is not the same as the last experienced level for this particular mode of operation, the controller 100 will selectively modulate the solenoid valves 72 and 74 to open and close as necessary to adjust the current liquid level to equal the last experienced level for this particular mode of operation. If the current level is below the last experienced level, at block 103 the controller 100 will close the solenoid valve 74 and modulate the solenoid valve 72 open to drain refrigerant from the refrigerant circuit into the charge tank 70 until the current reaches the last experience level. Conversely, if the current level is above the last experienced level, the controller 100 at block 104 will close the solenoid valve 72 and modulate the solenoid valve 74 open to drain refrigerant from the charge tank 70 into the refrigerant circuit until the current liquid level reaches the last experienced level. For example, the controller will open the appropriate valve for a short period of time, for example 2 seconds, close the valve, recheck the level and repeat this sequence until the current liquid level equalizes to the last experience level. Once the current level has been equalized to the last experienced level, the controller at block 105 activates the normal charge control procedure and/or discharge temperature control procedure.

The system controller 100 may also employ the control procedure discussed herein in embodiments of the heat pump system of the invention that do not include a liquid level sensor in association with the charge tank 70. However, when the heat pump system switches to a new operation mode, the system controller 100 first fills the charge tank either with refrigerant in the liquid state or with refrigerant in the gas state depending upon the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 vis-a-vis the volume of refrigerant charge required for efficient operation of either the outdoor air-to- refrigerant heat exchanger 40 or the indoor heat air-to-refrigerant exchanger 50 depending upon the particular mode of operation being entered.

If the new mode of operation involves air cooling, whether air cooling only or air cooling with water heating, the system controller will proceed either to fill the refrigerant tank 70 with liquid refrigerant according to the procedure illustrated by the block diagram in Figure 10 if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is significantly greater than the volume of refrigerant charge required for efficient operation of either the outdoor air-to- refrigerant heat exchanger 40, or to fill the refrigerant tank 70 with gaseous refrigerant according to the procedure illustrated by the block diagram in Figure 11 if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is significantly less than the volume of refrigerant charge required for efficient operation of either the outdoor air-to-refrigerant heat exchanger 40. If the new mode of operation involves indoor air heating or water heating only, the system controller will proceed either to fill the refrigerant tank 70 with liquid refrigerant according to the procedure illustrated by the block diagram in Figure 10 if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is significantly greater than the volume of refrigerant charge required for efficient operation of either the indoor air-to-refrigerant heat exchanger 50, or to fill the refrigerant tank 70 with gaseous refrigerant according to the procedure illustrated by the block diagram in Figure 11 if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is significantly less than the volume of refrigerant charge required for efficient operation of either the indoor air-to-refrigerant heat exchanger 50. However, in any air cooling operating mode, if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is relatively equal to the volume of refrigerant charge required for efficient operation of the outdoor air-to-refrigerant heat exchanger 40, then the system controller 100 will enter the new mode of operation without adjusting the refrigerant level in the refrigerant charge tank 70. Similarly, in the air heating or water heating modes of operation, if the volume of refrigerant charge required for efficient operation of the refrigerant to water heat exchanger 60 is relatively equal to the volume of refrigerant charge required for efficient operation of the indoor air-to- refrigerant heat exchanger 50, then the system controller 100 will enter the new mode of operation without adjusting the refrigerant level in the refrigerant charge tank 70. Referring now to Figure 10, to fill the refrigerant charge tank 70 with liquid refrigerant, after turning the compressor 20 on at block 201, the system controller at block 202 closes solenoid valve 74 and opens solenoid valve 72 to allow liquid refrigerant to pass from line 71 into the charge tank 70. After a programmed time delay at block 203 sufficient to allow the charge tank 70 to fill with liquid refrigerant, for example about 3 minutes, the system controller at block 205 proceeds to adjust the refrigerant circuit charge as need by the discharge temperature control procedure and/or the charge control procedure as desired. The solenoid valve 72 may be positioned either open or closed at this point.

Referring now to Figure 11, to fill the refrigerant charge tank 70 with gaseous refrigerant, after turning the compressor 20 on at block 211, the system controller at block 212 closes solenoid valve 72 and modulates solenoid valve 74 on/off for a period of time, for example open 3 seconds, closed 17 seconds repeatedly for two minutes, to allow refrigerant in the gas state to pass from line 73 into the charge tank 70. After a programmed time delay at block 213 sufficient to allow the charge tank 70 to fill with gaseous refrigerant, for example about 3 minutes, the system controller at block 214 proceeds to adjust the refrigerant circuit charge as need by the discharge temperature control procedure and/or the charge control procedure as desired. The solenoid valve 74 may be positioned either open or closed at this point. In any water heating mode, the controller 100 will shut the pump 62 off when temperature sensor 89 detects that the water temperature in water reservoir 64 has reached a desired limit value, for example 60 degrees C. In accord with the discharge temperature limit control procedure, illustrated by the block diagram of Figure 12, after a brief time delay, for example about 30 seconds, following turning on the compressor at block 301, the system controller compares at block 302 the current discharge temperature, TDC, i.e. the temperature of the refrigerant discharging from the compressor 20, received from temperature sensor 150 to a discharge temperature limit, TDL, preprogrammed into the controller 100. A typical compressor discharge limit might be a desired number of degrees, for example about 7 degrees C, below the manufacturer's application guide specification. A typical compressor discharge temperature limit would be about 128 degrees C. If the current discharge temperature, TDC, exceeds the discharge temperature limit, the system controller 100 at block 303 deactivates the charge control procedure if it is currently active, and then at block 304 closes the solenoid valve 72 and modulates the solenoid valve 74 open to drain refrigerant from the charge tank 70 into the refrigerant circuit through the refrigerant line 73. If the current discharge temperature received from temperature sensor 150 is equal to or below the discharge temperature limit, the system controller 100 at block 305 activates the charge control procedure if it is not currently active and proceeds to follow the charge control procedure to adjust the refrigerant charge in the refrigerant circuit as necessary.

In the charge control procedure, illustrated in Figure 13, with the refrigerant charge initially set, the system controller 100 at block 401 closes both solenoid valves 72 and 74. After a brief time delay, for example about one minute, depending upon the particular mode of current operation, the system controller will at block 402 compare either or both of the degree of superheat or the degree of subcooling currently present in the system to a permissible range of superheat preprogrammed into the controller 100. For example, in the air cooling only and the air cooling with water heating modes, the permissible range of superheat may be from 0.5 to 20 degrees C and the permissible range of subcooling may be from 2 to 15 degrees C. In the air heating only, the air heating with water heating and the water heating only modes, the permissible range of superheat may be from 0.5 to 11 degrees C and the permissible range of subcooling may be from 0.5 to 10 degrees C, for example.

If operating in a mode with fixed expansion, the system controller, at block 403, compares the current degree of superheat against the permissible range of superheat preprogrammed into the controller 100. If the current degree of superheat is below the permissible range, at block 404, the system controller 100 will modulate the solenoid valve 72 open to drain refrigerant from the refrigerant circuit into the charge tank 70. If the current degree of superheat is above the permissible range, at block 405, the system controller 100 will modulate the solenoid valve 74 open to drain refrigerant from the charge tank 70 into the refrigerant circuit. If the degree of superheat falls within the permissible range of superheat, the system controller proceeds to block 406.

If operating in a mode without fixed expansion, the system controller, at block 406, compares the current degree of subcooling against a permissible range of subcooling programmed into the controller. If the current degree of subcooling is above the permissible range, at block 404, the system controller 100 will modulate the solenoid valve 72 open to drain refrigerant from the refrigerant circuit into the charge tank 70. If the current degree of subcooling is below the permissible range, at block 405, the system controller 100 will modulate the solenoid valve 74 open to drain refrigerant from the charge tank 70 into the refrigerant circuit. If the degree of subcooling falls within the permissible range of subcooling, the system controller proceeds to control refrigerant charge through the charge control procedure and the discharge temperature limit control procedure as described.

The various control parameters presented as examples hereinbefore, such as compressor discharge temperature limit, the various time delays, the desired superheat ranges, the desired subcooling ranges, are for a typical 5 ton capacity, split-system heat pump system having a brazed plate water to refrigerant heat exchanger 60, a refrigerant reservoir (charge tank) 70 having a liquid refrigerant storage capacity of 4 kilograms, a system refrigerant charge of 8 kilograms, and overall refrigerant lines of 7 meters. These parameters are presented for purposes of illustration and those skilled in the art will understand that these parameters may vary from the examples presented for different heat pump configurations and capacities. Those having ordinary skill in the art will select precise parameters to be used in implementing the invention to best suit operation of any particular heat pump system.

In the embodiment of the heat pump system of the invention depicted in Figures 4-7, the heat pump system may be used to heat both indoor air and water by cycling between the indoor air heating mode and the water heating mode. To do so, the system controller 100 will simply operate the system in the indoor air heating mode for a desired period, such as a few minutes, then switch to water heating mode for a desired period, such as a few minutes, and the switch back to the air heating mode. The system controller will continue switching from one mode to the other every few minutes until the water temperature set point or the air indoor temperature set point has been reached. Importantly, the system controller 100 can effectuate this cycling mode of operation without shutting the compressor 20 down. To switch from the indoor air heating mode to the water heating mode, the system controller 100 will reposition the reversing valve 130 to its second position, activate the water pump 62, close flow control valve 58 and open flow control valve 68. To return to the indoor air heating mode from the water heating mode, the system controller 100 will reposition the reversing valve 130 to its first position, turn off the water pump 62, close flow control valve 68 and open flow control valve 58.

While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. A refrigerant system operable in at least an air cooling mode and having liquid heating capability comprising: a refrigerant compressor having a suction port and a discharge port; a selectively positionable reversing valve having a first port, a second port, a third port and a fourth port, said reversing valve being positionable in a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication, said reversing valve being positionable in a second position for coupling the first port and the fourth port in fluid flow communication and the second port and the third port in fluid flow communication; a refrigerant circuit providing a closed loop refrigerant circulation flow path, said refrigerant circuit having a first refrigerant line establishing a flow path between the discharge port of said compressor and the first port of said reversing valve and a second refrigerant line establishing a flow path between the second port of said reversing valve and the suction port of said compressor; an outdoor heat exchanger operatively associated with the second refrigerant line and adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with ambient air; an indoor heat exchanger operatively associated with the second refrigerant line and adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with the air from the comfort zone, said indoor heat exchanger disposed downstream of said outdoor exchanger with respect to refrigerant flow in the air cooling mode; a third refrigerant line establishing a flow path between the fourth port of said reversing valve and the second refrigerant line at a location intermediate said outdoor heat exchanger and said indoor heat exchanger; a refrigerant to liquid heat exchanger operatively associated with the third refrigerant line and adapted for passing refrigerant passing through the third refrigerant line in heat exchange relationship with a liquid; a first flow control valve disposed in the second refrigerant line intermediate said outdoor heat exchanger and the location of the intersection of the third refrigerant line with the second refrigerant line, said first control valve having an open position and a closed position; a second flow control valve disposed in the second refrigerant line intermediate said indoor heat exchanger and the location the intersection of the third refrigerant line with said second refrigerant line, said second control valve having an open position and a closed position; a controller operatively associated with said first and second flow control valves, said controller operative to selectively control the respective positioning of said first and second flow control valves between their respective open and closed positions so as to selectively control refrigerant flow through the second refrigerant line; and a refrigerant reservoir having an inlet coupled in fluid flow communication to said second refrigerant line at a location intermediate said outdoor heat exchanger and said indoor heat exchanger and an outlet coupled in fluid flow communication to the second refrigerant line at a location intermediate the indoor heat exchanger and the suction port of said compressor.

2. A system as recited in claim 1 further comprising a flow check valve disposed in the third refrigerant line so as to permit refrigerant flow therethrough in a direction from said reversing valve into the second refrigerant line and to block flow from the second refrigerant line to said reversing valve.

3. A system as recited in claim 2 further comprising a fourth refrigerant line establishing a flow path between a refrigerant flow path between the third port of said reversing valve and the suction port of said compressor.

4. A system as recited in claim 1 further comprising: a first flow control valve operatively associated with said refrigerant reservoir for controlling the flow refrigerant from the second refrigerant line to the inlet of said refrigerant reservoir, said first control valve having an open position and a closed position; a second flow control valve operatively associated with said refrigerant reservoir for controlling the flow refrigerant between the outlet of said refrigerant reservoir and the second refrigerant line at a location intermediate the indoor heat exchanger and the suction port of said compressor, said second control valve having an open position and a closed position; and a controller operatively associated with said first and second flow control valves, said controller operative to selectively control the respective positioning of said first and second flow control valves between their respective open and closed positions so as to selectively control the refrigerant charge within the refrigerant circuit.

5. A system as recited in claim 4 wherein said first and second flow control valves operatively associated with said refrigerant reservoir comprise valves having at least one partially open position between their respective open and closed positions; and said controller is further operative to selectively modulate the respective positioning of said first and second flow control valves operatively associated with said refrigerant reservoir between their open, at one partially open and closed positions.

6. A system as recited in claim 5 wherein said first and second flow control valves operatively associated with said refrigerant reservoir comprise pulse width modulated solenoid valves.

7. A system as recited in claim 4 further comprising a liquid level sensor operatively associated with said refrigerant reservoir, said liquid level sensor operative to sense the level of liquid refrigerant in said refrigerant reservoir and provide a signal indicative of the liquid level within said refrigerant reservoir to said controller.

8. A system as recited in claim 7 wherein said controller is operative to selectively control the respective positioning of said first and second flow control valves operatively associated with said refrigerant reservoir between their respective open and closed positions so as to selectively control the refrigerant charge within the refrigerant circuit in response to the liquid level signal received from said liquid level sensor.

9. A refrigerant circuit heat pump system operable in at least an air cooling mode and an air heating air mode and having liquid heating capability comprising: a refrigerant compressor having a suction port and a discharge port; a first selectively positionable reversing valve having a first port, a second port, a third port and a fourth port, said reversing valve being positionable in a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication, said reversing valve being positionable in a second position for coupling the first port and the fourth port in fluid flow communication and the second port and the third port in fluid flow communication; a refrigerant circuit providing a closed loop refrigerant circulation flow path, said refrigerant circuit having a first refrigerant line establishing a flow path between the discharge port of said compressor and the first port of said first reversing valve and a second refrigerant line establishing a flow path between the second port of said first reversing valve and the suction port of said compressor; an outdoor heat exchanger operatively associated with the second refrigerant line and adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with ambient air; an indoor heat exchanger operatively associated with the second refrigerant line and adapted for passing refrigerant passing through the second refrigerant line in heat exchange relationship with the air from the comfort zone, said indoor heat exchanger disposed downstream of said outdoor exchanger with respect to refrigerant flow in the air cooling mode; a second selectively positionable valve having a first port, a second port, a third port and a fourth port, said second selectively positionable valve being positionable in a first position for coupling the first port and the second port in fluid flow communication and the third port and the fourth port in fluid flow communication, said second selectively positionable valve being positionable in a second position for coupling the first port and the third port in fluid flow communication and the second port and the fourth port in fluid flow communication; a third refrigerant line establishing a flow path between the fourth port of said first reversing valve and the first port of said second reversing valve; a fourth refrigerant line establishing a flow path between the third port of said second reversing valve and the second refrigerant line at a location intermediate said outdoor heat exchanger and said indoor heat exchanger; a fifth refrigerant line establishing a flow path between the second port of said reversing valve and the second refrigerant line at a location intermediate said indoor heat exchanger and the suction inlet to said compressor; a refrigerant to liquid heat exchanger operatively associated with the fourth refrigerant line and adapted for passing refrigerant passing through the fourth refrigerant line in heat exchange relationship with a liquid; a first flow control valve disposed in the second refrigerant line intermediate said outdoor heat exchanger and the location the intersection of the third refrigerant line with the second refrigerant line, said first flow control valve having an open position and a closed position; a second flow control valve disposed in the second refrigerant line intermediate said indoor heat exchanger and the location the intersection of the third refrigerant line with said second refrigerant line, said second flow control valve having an open position and a closed position; a third flow control valve disposed in the second refrigerant line intermediate the location of the intersection of the fifth refrigerant line with the second refrigerant line and the suction inlet to said compressor, said third flow control valve having an open position and a closed position; and a controller operatively associated with said first, second and third flow control valves, said controller operative to selectively control the respective positioning of said first, second and third flow control valves between their respective open and closed positions so as to selectively control refrigerant flow through the second refrigerant line.

10. A heat pump system as recited in claim 9 further comprising a flow check valve disposed in the fourth refrigerant line so as to permit refrigerant flow therethrough in a direction from said second reversing valve into the second refrigerant line and to block flow from the second refrigerant line to said second reversing valve.

11. A heat pump system as recited in claim 9 further comprising: a sixth refrigerant line establishing a refrigerant flow path between the third port of said first reversing valve and the suction port of said compressor; and a seventh refrigerant line establishing a refrigerant flow path between the fourth port of said second reversing valve and the suction port of said compressor.

12. A heat pump system as recited in claim 9 further comprising a refrigerant reservoir having an inlet coupled in fluid flow communication to the second refrigerant line at a location intermediate said outdoor heat exchanger and said indoor heat exchanger and an outlet coupled in fluid flow communication to the second refrigerant line at a location intermediate the indoor heat exchanger and the suction port of said compressor.

13. A heat pump system as recited in claim 12 further comprising: a first flow control valve operatively associated with said refrigerant reservoir for controlling the flow refrigerant from the second refrigerant line to the inlet of said refrigerant reservoir, said first control valve having an open position and a closed position; a second flow control valve operatively associated with said refrigerant reservoir for controlling the flow refrigerant between the outlet of said refrigerant reservoir and the second refrigerant line at a location intermediate the third flow control valve associated with the second refrigerant line and the suction port of said compressor, said second flow control valve having an open position and a closed position; and a controller operatively associated with said first and second flow control valves operatively associated with said refrigerant reservoir, said controller operative to selectively control the respective positioning of said first and second flow control valves operatively associated with said refrigerant reservoir between their respective open and closed positions so as to selectively control the refrigerant charge within the refrigerant circuit.

14. A heat pump system as recited in claim 12 further comprising a liquid level sensor operatively associated with said refrigerant reservoir, said liquid level sensor operative to sense the level of liquid refrigerant in said refrigerant reservoir and provide a signal indicative of the liquid level within said refrigerant reservoir to said controller.

15. A heat pump system as recited in claim 14 wherein said controller is operative to selectively control the respective positioning of said first and second flow control valves operatively associated with said refrigerant reservoir between their respective open and closed positions so as to selectively control the refrigerant charge within the refrigerant circuit in response to the liquid level signal received from said liquid level sensor.

16. A heat pump system as recited in claim 9 wherein said controller is operative to cycle between the indoor air heating mode and the water heating mode whereby the system may effectively heat water while also heating air.

17. A heat pump system as recited in claim 9 further comprising: a first expansion valve disposed in the second refrigerant line intermediate said outdoor heat exchanger and the first flow control valve in the first refrigerant line; and a second expansion valve disposed in the second refrigerant line intermediate said indoor heat exchanger and the second flow control valve in the second refrigerant line; said first expansion valve being operative associated with said outdoor heat exchanger and said second expansion valve being operatively associated with said indoor heat exchanger.

18. A heat pump system as recited in claim 17 further comprising: a first expansion valve bypass line operatively associated with the second refrigerant line for bypassing refrigerant passing through the second refrigerant line in a direction from said outdoor heat exchanger to said indoor heat exchanger around said first expansion valve and through said second expansion valve.

19. A heat pump system as recited in claim 17 further comprising: a second expansion valve bypass line operatively associated with the second refrigerant line for bypassing refrigerant passing through the second refrigerant line in a direction from said indoor heat exchanger to said outdoor heat exchanger around said second expansion valve and through said first expansion valve.