Hybrid heat pump system

Abstract

The heat pump system can include a compressor, an outdoor heat exchanger, an indoor heat exchanger, an expansion device, and a supplemental heater. The outdoor heat exchanger can be in fluid communication with the compressor. The indoor heat exchanger can be in fluid communication with the compressor. The expansion device can be in fluid communication with the indoor heat exchanger and the outdoor heat exchanger. The supplemental heater can include a burner and a working fluid conduit. The burner can be configured to combust a fuel and heat the working fluid conduit. When the heat pump system is operating in a heating mode, the indoor heat exchanger can receive working fluid from the working fluid conduit such that the working fluid flows from an outlet of the working fluid conduit to an inlet of the indoor heat exchanger.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Patent Application No. 17 / 210,160, filed March 23, 2021. The entire disclosure of the above application is incorporated herein by reference. Technical Field

[0003] This disclosure relates to hybrid heat pump systems. Background Technology

[0004] This section provides background information relating to this disclosure and is not necessarily prior art.

[0005] Heat pump systems can operate in heating mode to heat a space and in cooling mode to cool a space. Conventional heat pump systems are relatively effective for cooling and are generally effective for heating in climates where temperatures do not frequently fall below freezing. Furthermore, operating conventional heat pump systems in cold weather, especially when electricity costs are relatively high, can be expensive. This disclosure provides a heat pump system that can more effectively heat a residence or building in cold climates and can reduce the energy costs associated with the operating system. Summary of the Invention

[0006] This section provides a general overview of the disclosure, rather than a full disclosure of the entire scope or all features of the disclosure.

[0007] This disclosure provides a heat pump system including a compressor, an outdoor heat exchanger, an indoor heat exchanger, an expansion device, and a supplemental heater. The outdoor heat exchanger may be in fluid communication with the compressor. The indoor heat exchanger may be in fluid communication with the compressor. The expansion device may be in fluid communication with both the indoor and outdoor heat exchangers. The supplemental heater may include a burner and a working fluid conduit. The burner may be configured to burn fuel and heat the working fluid conduit. When the heat pump system operates in heating mode, the indoor heat exchanger may receive working fluid from the working fluid conduit, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through any or more of the compressor, the outdoor heat exchanger, and the expansion device.

[0008] In some configurations, the heat pump system described above includes a first reversing valve in fluid communication with the compressor, expansion unit, and indoor and outdoor heat exchangers. The first reversing valve is movable between a first position and a second position. The first reversing valve is in the first position when the heat pump system is in heating mode. The first reversing valve is in the second position when the heat pump system is in cooling mode.

[0009] In some configurations of the heat pump system in any of the paragraphs above, when the heat pump system is operating in cooling mode, the indoor heat exchanger receives working fluid from the working fluid conduit of the supplemental heater, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through any or more of the compressor, the outdoor heat exchanger, and the expansion device.

[0010] In some configurations of the heat pump system in any one or more of the above paragraphs, the working fluid flows in the same direction through the indoor heat exchanger in both heating and cooling modes, the working fluid flows in the same direction through the outdoor heat exchanger in both heating and cooling modes, the working fluid flows in the same direction through the expansion device in both heating and cooling modes, and the working fluid flows in the same direction through the working fluid conduit in both heating and cooling modes.

[0011] In some configurations, the heat pump system of any one or more of the above paragraphs includes a second reversing valve in fluid communication with the compressor, the expansion device, and the indoor and outdoor heat exchangers. The second reversing valve is movable between a first position and a second position. The second reversing valve is in the first position when the heat pump system is in heating mode. The second reversing valve is in the second position when the heat pump system is in cooling mode.

[0012] In some configurations, the heat pump system of any one or more of the above paragraphs includes: a first bypass flow path selectively fluidly connected to a first reversing valve and a second reversing valve; a first bypass valve fluidly connected to the first bypass flow path and movable between a first position restricting fluid flow through the first bypass flow path and allowing fluid flow to the compressor's suction inlet, and a second position allowing fluid flow through the first bypass flow path and restricting fluid flow to the compressor's suction inlet; a second bypass flow path selectively fluidly connected to the first reversing valve and the second reversing valve; and a second bypass valve fluidly connected to the second bypass flow path and movable between a first position restricting fluid flow through the second bypass flow path and allowing fluid flow through an expansion device, and a second position allowing fluid flow through the second bypass flow path and restricting fluid flow through the expansion device.

[0013] In some configurations of the heat pump system in any one or more of the above paragraphs, the second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

[0014] In some configurations, the heat pump system of any one or more of the above paragraphs includes another indoor heat exchanger, wherein the working fluid conduit of the supplemental heater is fluidly disposed between the indoor heat exchangers.

[0015] In some configurations of the heat pump system in any one or more of the paragraphs above, the indoor heat exchanger and supplemental heater are located inside the building when the heat pump system is fully installed and operating.

[0016] In some configurations of the heat pump system in any one or more of the paragraphs above, the indoor heat exchanger is located inside the building when the heat pump system is fully installed and operating, while the supplemental heater is located outside the building when the heat pump system is fully installed and operating.

[0017] In some configurations of the heat pump system in any one or more of the preceding paragraphs, the fuel burned by the burner is a substance different from the working fluid. In some configurations, the fuel is selected from the group consisting of natural gas, propane, butane, and kerosene.

[0018] In some configurations, the heat pump system of any one or more of the paragraphs above includes: a fuel valve fluidly connected to a burner and configured to control the flow of fuel to the burner; and a control module configured to control the operation of the burner and the fuel valve.

[0019] In some configurations of the heat pump system in any one or more of the paragraphs above, the control module controls the operation of the burner and fuel valves based on the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

[0020] In some configurations of the heat pump system in any one or more of the above paragraphs, the control module controls the operation of the burner and fuel valves based on the outdoor ambient air temperature.

[0021] In some configurations of the heat pump system in any one or more of the paragraphs above, the control module controls the operation of the burner and fuel valves based on fluctuations in electricity costs.

[0022] In some configurations of the heat pump system in any one or more of the preceding paragraphs, the control module controls the operation of the burner and fuel valve based on any one or more of the following: outdoor ambient air temperature, fluctuations in electricity costs, fluctuations in fuel costs, and the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

[0023] This disclosure also provides a heat pump system that may include a compressor, an outdoor heat exchanger, an indoor heat exchanger, an expansion device, a first reversing valve, a second reversing valve, and a supplementary heater. The outdoor heat exchanger may be in fluid communication with the compressor. The indoor heat exchanger may be in fluid communication with the compressor. The expansion device may be in fluid communication with both the indoor and outdoor heat exchangers. The first reversing valve may have a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the first reversing valve may be in fluid connection to the discharge outlet of the compressor. The second inlet of the first reversing valve may be in fluid connection to the outlet of the expansion device. The first outlet of the first reversing valve may be in fluid connection to the inlet of the outdoor heat exchanger. The second outlet may provide working fluid to the indoor heat exchanger. The second reversing valve may have a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the second reversing valve may be in fluid connection to the outlet of the outdoor heat exchanger. The second inlet of the second reversing valve may be in fluid connection to the outlet of the indoor heat exchanger. The first outlet of the second reversing valve may be in fluid connection to the inlet of the expansion device. The second outlet may provide working fluid to the suction inlet of the compressor. The supplementary heater may include a burner and a working fluid conduit. The burner can be configured to burn fuel and heat the working fluid conduit. The indoor heat exchanger can receive working fluid from the working fluid conduit, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through any or more of the compressor, outdoor heat exchanger, and expansion device.

[0024] In some configurations, the heat pump system described above includes a first bypass flow path, a first bypass valve, a second bypass flow path, and a second bypass valve. The first bypass flow path may be selectively fluid in communication with a first reversing valve and a second reversing valve. The first bypass valve may be fluidly connected to the first bypass flow path and is movable between a first position restricting fluid flow through the first bypass flow path and allowing fluid flow to the compressor's suction inlet, and a second position allowing fluid flow through the first bypass flow path and restricting fluid flow to the compressor's suction inlet. The second bypass flow path may be selectively fluid in communication with the first reversing valve and the second reversing valve. The second bypass valve may be fluidly connected to the second bypass flow path and is movable between a first position restricting fluid flow through the second bypass flow path and allowing fluid flow through an expansion device, and a second position allowing fluid flow through the second bypass flow path and restricting fluid flow through the expansion device.

[0025] In some configurations of the heat pump system in any one or more of the above paragraphs, the second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

[0026] In some configurations of the heat pump system in any one or more of the preceding paragraphs, a first directional valve is movable between a first position and a second position, and a second directional valve is movable between the first position and the second position. When the first directional valve is in its first position: (a) the first inlet of the first directional valve is fluidly connected to the second outlet of the first directional valve, and (b) the second inlet of the first directional valve is fluidly connected to the first outlet of the first directional valve. When the second directional valve is in its first position: (a) the first inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve. When the first directional valve is in its second position: (a) the first inlet of the first directional valve is fluidly connected to the first outlet of the first directional valve, and (b) the second inlet of the first directional valve is fluidly connected to the second outlet of the first directional valve. When the second directional valve is in its second position: (a) the first inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve.

[0027] In some configurations of the heat pump system in any one or more of the preceding paragraphs, the heat pump system can operate in a first heating mode, a cooling mode, a defrosting mode, and a second heating mode. In the first heating mode: (a) the first and second directional valves are in their first positions, (b) the first and second bypass valves are in their first positions, (c) the pump is turned off, and (d) the compressor operates. In the cooling mode: (a) the first and second directional valves are in their second positions, (b) the first and second bypass valves are in their first positions, (c) the pump is turned off, and (d) the compressor operates. In the defrosting mode: (a) the first and second directional valves are in their first positions, (b) the first and second bypass valves are in their second positions, (c) the pump operates, and (d) the compressor is turned off. In the second heating mode: (a) the first directional valve is in its second position, (b) the second directional valve is in its first position, (c) the second bypass valve is in its second position, (d) the pump is operated, and (e) the compressor is shut down.

[0028] In some configurations, the heat pump system of any one or more of the above paragraphs includes: a fuel valve fluidly connected to a burner and configured to control the flow of fuel to the burner; and a control module configured to control the operation of the burner and the fuel valve. The control module selectively operates the burner and opens the fuel valve when the heat pump system is operating in a first heating mode, a defrost mode, and a second heating mode.

[0029] In some configurations of the heat pump system in any one or more of the above paragraphs, the working fluid flows through the indoor heat exchanger in the same direction in the first heating mode, cooling mode, defrosting mode, and second heating mode.

[0030] In some configurations of the heat pump system in any one or more of the above paragraphs, the working fluid flows through the outdoor heat exchanger in the same direction in the first heating mode, cooling mode, defrosting mode, and second heating mode.

[0031] In some configurations of the heat pump system in any one or more of the above paragraphs, the working fluid flows through the expansion device in the same direction in the first heating mode, cooling mode, defrosting mode, and second heating mode.

[0032] In some configurations of the heat pump system in any one or more of the above paragraphs, the working fluid flows in the same direction through the working fluid conduit in the first heating mode, cooling mode, defrosting mode, and second heating mode.

[0033] In some configurations of the heat pump system in any one or more of the paragraphs above, the control module controls the operation of the burner and fuel valves based on the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

[0034] In some configurations of the heat pump system in any one or more of the above paragraphs, the control module controls the operation of the burner and fuel valves based on the outdoor ambient air temperature.

[0035] In some configurations of the heat pump system in any one or more of the paragraphs above, the control module controls the operation of the burner and fuel valves based on fluctuations in electricity costs.

[0036] In some configurations of the heat pump system in any one or more of the preceding paragraphs, the control module controls the operation of the burner and fuel valve based on any one or more of the following: outdoor ambient air temperature, fluctuations in electricity costs, fluctuations in fuel costs, and the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

[0037] In some configurations, the heat pump system of any one or more of the above paragraphs includes another indoor heat exchanger. A working fluid conduit for the supplemental heater may be fluidly disposed between the indoor heat exchangers.

[0038] This disclosure also provides a heat pump system including a compressor, an outdoor heat exchanger, an indoor heat exchanger, an expansion device, and a supplementary heater. The outdoor heat exchanger may be in fluid communication with the compressor. The indoor heat exchanger may be in fluid communication with the compressor. The expansion device may be in fluid communication with both the indoor and outdoor heat exchangers. The supplementary heater may include a heat source and a working fluid conduit. The heat source and the working fluid conduit are in a heat transfer relationship, such that the heat source is configured to heat the working fluid conduit. The working fluid conduit may be fluidly disposed between the expansion device and the indoor heat exchanger.

[0039] In some configurations of the heat pump system described above, the heat source may include any one or more of the following: a burner (configured to burn fuel), an electric heating element, and a heat exchanger for a waste heat recovery system.

[0040] Other application areas will become apparent from the descriptions provided herein. The descriptions and specific examples in this overview are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0041] The accompanying drawings described herein are for illustrative purposes only, and not for all possible implementations, and are not intended to limit the scope of this disclosure.

[0042] Figure 1 This is a schematic diagram of a heat pump system operating in heating mode;

[0043] Figure 2 It operates in cooling mode. Figure 1 A schematic diagram of a heat pump system;

[0044] Figure 3 This is a schematic diagram of another heat pump system;

[0045] Figure 4 This is a schematic diagram of yet another heat pump system;

[0046] Figure 5 This is a schematic diagram of yet another heat pump system;

[0047] Figure 6 This is a schematic diagram of yet another heat pump system;

[0048] Figure 7 This is a schematic diagram of another heat pump system operating in the first heating mode;

[0049] Figure 8 It operates in cooling mode. Figure 7 A schematic diagram of a heat pump system;

[0050] Figure 9 It is operating in defrost mode. Figure 7 A schematic diagram of a heat pump system; and

[0051] Figure 10 It operates in the second heating mode. Figure 7 A schematic diagram of a heat pump system.

[0052] Throughout the various views of the accompanying drawings, corresponding reference numerals indicate the corresponding components. Detailed Implementation

[0053] The exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0054] These exemplary embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous specific details, such as examples of particular components, apparatuses, and methods, are set forth to provide a thorough understanding of embodiments of this disclosure. It will be apparent to those skilled in the art that specific details are not required, that exemplary embodiments may be implemented in many different forms, and none of them should be construed as limiting the scope of this disclosure. In some exemplary embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

[0055] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may also be intended to include the plural forms unless the context clearly indicates otherwise. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the particular order discussed or illustrated, unless specifically indicated as such. It should also be understood that additional or alternative steps may be employed.

[0056] When an element or layer is referred to as “on another element or layer,” “joined to,” “connected to,” or “attached to” another element or layer, the element or layer may be directly on, joined to, connected to, or attached to the other element or layer, or there may be intermediate elements or layers present. Conversely, when an element is referred to as “directly on another element or layer,” “directly joined to,” “directly connected to,” or “directly attached to” another element or layer, there may be no intermediate elements or layers present. Other terms used to describe relationships between elements (e.g., “between” vs. “directly between,” “adjacent” vs. “directly adjacent,” etc.) should be interpreted in a similar manner. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0057] Although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or segment from another region, layer, or segment. Unless the context clearly indicates otherwise, terms such as “first,” “second,” and other numerical terms used herein do not imply any order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as a second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0058] For ease of description, spatial relative terms such as “inside,” “outside,” “below,” “below,” “lower,” “above,” “upper,” etc., are used herein to describe the relationship between one element or feature as illustrated in the accompanying drawings and another element or feature (or other elements or features). Spatial relative terms may be intended to cover different orientations of the device in use or operation other than those depicted in the accompanying drawings. For example, if the device in the accompanying drawings is flipped, an element described as “below other elements or features” or “below other elements or features” will be oriented “above other elements or features.” Thus, the example term “below” can encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

[0059] Reference Figures 1 to 2 A heat pump system 10 is provided. System 10 is capable of operating in heating mode (…). Figure 1 ) and cooling mode ( Figure 2 As will be described in more detail below, system 10 is a hybrid heat pump system—that is, system 10 includes an electrically operated vapor compression loop 12 and a supplemental heater (e.g., a fuel-fired boiler) 14, which selectively heats the working fluid in the vapor compression loop 12 to provide supplemental heating capacity to system 10 in heating mode. This supplemental heating capacity can be particularly beneficial in cold weather climates, where conventional heat pump systems typically cannot adequately heat homes or buildings.

[0060] The vapor compression circuit 12 may include a compressor 16, a first indoor heat exchanger 18, a second indoor heat exchanger 20, an expansion device 22 (expansion valve or capillary tube), an outdoor heat exchanger 24, an accumulator 26, a first multi-way valve (reversing valve) 28, and a second multi-way valve (reversing valve) 30.

[0061] Compressor 16 can pump working fluid (refrigerant) through vapor compression circuit 12 in both heating and cooling modes. Compressor 16 can be, for example, a scroll compressor (including a first and second scroll with meshing helical scrolls), or any other type of compressor, such as a reciprocating compressor (including a piston reciprocally received in a cylindrical section) or a rotary vane compressor (including a rotor rotating within a cylindrical section). Compressor 16 can be a variable-capacity compressor capable of operating in full-capacity and reduced-capacity modes. In some configurations, compressor 16 may include additional or alternative capacity regulation capabilities (e.g., variable-speed motor, vapor injection, obstructed suction, etc.). Compressor 16 may include suction inlet 63 and discharge outlet 65. Inlet 63 can receive working fluid from accumulator 26. The working fluid received through inlet 63 can be compressed in compressor 16 (by a compression mechanism) and discharged through outlet 65.

[0062] The first indoor heat exchanger 18 may include a coil (or duct) 32 having an inlet 34 and an outlet 36. Similarly, the second indoor heat exchanger 20 may include a coil (or duct) 38 having an inlet 40 and an outlet 42. The first indoor heat exchanger 18 and the second indoor heat exchanger 20 are disposed inside a building (or house) 43. A fan 44 may force air through the first heat exchanger 18 and the second heat exchanger 120 to facilitate heat transfer between the working fluid in the coils 32, 38 and the air in the building 43, to heat the space inside the building 43 in a heating mode or to cool the space inside the building 43 in a cooling mode. In some configurations, each indoor heat exchanger 18, 20 may have its own fan. The outdoor heat exchanger 24 may include a coil (or duct) 46 having an inlet 48 and an outlet 50. A fan 52 may force air through the outdoor heat exchanger 24 to facilitate heat transfer between outdoor ambient air and the working fluid flowing through the coil 46.

[0063] The first valve 28 and the second valve 30 can be in the first position corresponding to the heating mode of system 10 ( Figure 1 ) and the second position corresponding to the cooling mode of system 10 ( Figure 2The movement of the first valve 28 and the second valve 30 between a first position and a second position causes the system 10 to switch between a heating mode and a cooling mode. Each of the first valve 28 and the second valve 30 may include a movable valve member (e.g., a sliding or rotatable body) capable of moving between the first and second positions and may be actuated by a solenoid, a stepper motor, or fluid pressure. The control module 53 controls the operation of the first valve 28 and the second valve 30 and controls the movement between the first and second positions. The control module 53 may also control the operation of the expansion device 22 (e.g., based on data from the temperature sensor 54 and / or other operating parameters), the compressor 16, and the fans 44 of the indoor heat exchangers 18, 20 and the fan 52 of the outdoor heat exchanger 24.

[0064] The first valve 28 may include a first inlet 58, a second inlet 60, a first outlet 62, and a second outlet 64. The valve components of the first valve 28 are movable relative to the inlets 58 and 60 and the outlets 62 and 64 between a first position and a second position. The first inlet 58 of the first valve 28 is fluidly connected to the discharge outlet 65 of the compressor 16. The second inlet 60 of the first valve 28 is fluidly connected to the outlet 67 of the expansion device 22. The first outlet 62 of the first valve 28 is fluidly connected to the inlet 48 of the outdoor heat exchanger 24. The second outlet 64 of the first valve 28 is fluidly connected to the inlet 34 of the first indoor heat exchanger 18.

[0065] The second valve 30 may include a first inlet 66, a second inlet 68, a first outlet 70, and a second outlet 72. The valve member of the second valve 30 is movable relative to the inlets 66, 68 and the outlets 70, 72 between a first position and a second position. The first inlet 66 of the second valve 30 is fluidly connected to the outlet 50 of the outdoor heat exchanger 24. The second inlet 68 of the second valve 30 is fluidly connected to the outlet 42 of the second indoor heat exchanger 20. The first outlet 70 of the second valve 30 is fluidly connected to the inlet 69 of the expansion device 22. The second outlet 72 of the second valve 30 is fluidly connected to the inlet of the accumulator 26 (or to the suction inlet 63 of the compressor 16).

[0066] The supplementary heater 14 may include a housing 75, a burner 76 disposed within the housing 75, and a working fluid coil (or conduit or container) 79 disposed within the housing 75. The working fluid conduit 79 includes a working fluid inlet 78 and a working fluid outlet 80. The burner 76 includes a fuel inlet 74 fluidly connected to a fuel conduit 82. A fuel valve 84 (actuated by a solenoid, stepper motor, or other actuator) may be disposed along the fuel conduit 82 or at the fuel inlet 74. The fuel valve 84 is movable between an open position and a closed position to control the fuel flow from a fuel source (not shown) and the burner 76. The control module 53 may control the operation of the fuel valve 84 based on data from a temperature sensor 86 (and / or other operating parameters of the system 10). The temperature sensor 86 may be disposed along a conduit 88 that fluidly connects the working fluid outlet 80 of the heater 14 to the inlet 40 of the second indoor heat exchanger 20. The temperature sensor 86 measures the temperature of the working fluid flowing through the conduit 88. In some configurations, a pressure sensor may also be positioned along conduit 88, and data from the pressure sensor may be used to calculate superheat.

[0067] Burner 76 may include an igniter configured to ignite fuel received from a fuel source. The fuel may be a flammable gas or liquid, such as natural gas, propane, butane, kerosene (paraffin), or heating oil. The fuel source may be, for example, a gas utility supplier or a fuel storage tank. In some configurations, burner 76 may be or include a wood-burning stove or a coal-burning stove. In some configurations, heater 14 may include an electric heating element in place of burner 76 (or include an electric heating element in addition to burner 76). In some configurations, heater 14 may include a heat exchanger of a wastewater heat recovery system in place of burner 76 (or include a heat exchanger of a wastewater heat recovery system in addition to burner 76). Figure 1 and Figure 2 In the specific example shown, the supplementary heater 14 may be located inside building 43. The fuel valve 84 may be located inside or outside building 43.

[0068] A working fluid conduit 79 is fluidly connected to a working fluid inlet 78 and a working fluid outlet 80, and extends between the working fluid inlet 78 and the working fluid outlet 80. When the burner 76 is operating, the working fluid flowing through the working fluid conduit 79 can be heated by the burner 76. The working fluid conduit 79 can be disposed between a first indoor heat exchanger 18 and a second indoor heat exchanger 20. That is, the working fluid conduit 79 can receive working fluid from the outlet 36 of the first indoor heat exchanger 18, and the inlet 40 of the second indoor heat exchanger 20 can receive working fluid from the working fluid conduit 79.

[0069] Continue to refer to Figures 1 to 2 The operation of system 10 will be described in detail below. When heat pump system 10 is in heating mode ( Figure 1 When: (a) the first valve 28 allows fluid connection between the first inlet 58 of the first valve 28 and the second outlet 64 of the first valve 28; (b) the first valve 28 allows fluid connection between the second inlet 60 of the first valve 28 and the first outlet 62 of the first valve 28; (c) the second valve 30 allows fluid connection between the first inlet 66 of the second valve 30 and the second outlet 72 of the second valve 30; and (d) the second valve 30 allows fluid connection between the second inlet 68 of the second valve 30 and the first outlet 70 of the second valve 30.

[0070] Accordingly, when the heat pump system 10 is in heating mode, the compressed working fluid is discharged from the compressor 16, flows into the first inlet 58 of the first valve 28, and exits the first valve 28 through the second outlet 64. The working fluid flows from the second outlet 64 into the inlet 34 of the first indoor heat exchanger 18, flows through the indoor heat exchanger 18 (in which heat is transferred from the working fluid to the space within the building 43), and exits the first indoor heat exchanger 18 through the outlet 36. The working fluid flows from the first indoor heat exchanger 18 into the working fluid inlet 78 of the supplementary heater 14, flows through the working fluid conduit 79, and exits the heater 14 through the working fluid outlet 80.

[0071] The working fluid flowing through the working fluid conduit 79 of heater 14 can be heated by burner 76. Control module 53 can operate burner 76, for example, based on outdoor ambient temperature, data from sensor 86, the difference between the thermostat setpoint temperature and the actual temperature inside building 43, and / or utility rates (e.g., the cost of electricity and / or natural gas). That is, when system 10 is in heating mode, control module 53 can control the operation of burner 76 and fuel valve 84 to heat the working fluid in working fluid conduit 79: for example, (a) when the outdoor ambient temperature is below a predetermined temperature, (b) when the temperature measured by sensor 86 is below a predetermined temperature, (c) when the difference between the setpoint temperature and the actual indoor temperature is greater than a predetermined threshold, (d) during times of day when electricity costs are relatively high, (e) during times of day when natural gas (or other fuel) costs are relatively low, and / or (f) when control module 53 determines that system 10 should operate in a defrost cycle. In some configurations, the control module 53 may include or communicate with a user interface that allows the user to manually turn the burner 76 on or off.

[0072] The working fluid flows from the working fluid outlet 80 of heater 14 to the inlet 40 of the second indoor heat exchanger 20, flows through the second indoor heat exchanger 20 (in which heat is transferred from the working fluid to the space within building 43), and exits the second indoor heat exchanger 20 through outlet 42. The working fluid flows from the outlet 42 of the second indoor heat exchanger 20 to the second inlet 68 of the second valve 30, and exits the second valve 30 through the first outlet 70. The working fluid flows from the first outlet 70 to the inlet 69 of expansion device 22. As the working fluid flows through expansion device 22, its temperature and pressure decrease. The working fluid flows from the outlet 67 of expansion device 22 to the second inlet 60 of the first valve 28, and exits the first valve 28 through the first outlet 62. The working fluid flows from the first outlet 62 to the inlet 48 of the outdoor heat exchanger 24, flows through the outdoor heat exchanger 24 (in which the working fluid has a heat transfer relationship with the outdoor ambient air), and exits the outdoor heat exchanger 24 through the outlet 50. The working fluid flows from the outdoor heat exchanger 24 to the first inlet 66 of the second valve 30 and exits the second valve 30 through the second outlet 72. The working fluid flows from the second outlet 72 to the suction inlet 63 of the compressor 16 (or flows through the accumulator 26 and then to the suction inlet 63 of the compressor 16). The working fluid is then compressed in the compressor 16, and the above cycle can be repeated.

[0073] When the heat pump system 10 is in cooling mode ( Figure 2 (a) First valve 28 allows first inlet 58 of first valve 28 to be fluidly connected to first outlet 62 of first valve 28, (b) First valve 28 allows second inlet 60 of first valve 28 to be fluidly connected to second outlet 64 of first valve 28, (c) Second valve 30 allows first inlet 66 of second valve 30 to be fluidly connected to first outlet 70 of second valve 30, and (d) Second valve 30 allows second inlet 68 of second valve 30 to be fluidly connected to second outlet 72 of second valve 30.

[0074] Accordingly, when the heat pump system 10 is in cooling mode, the compressed working fluid is discharged from the compressor 16, flows into the first inlet 58 of the first valve 28, and exits the first valve 28 through the first outlet 62. The working fluid flows from the first outlet 62 into the inlet 48 of the outdoor heat exchanger 24, flows through the outdoor heat exchanger 24 (in which heat is transferred from the working fluid to the outdoor ambient air), and exits the outdoor heat exchanger 24 through the outlet 50. The working fluid flows from the outdoor heat exchanger 24 into the first inlet 66 of the second valve 30 and exits the second valve 30 through the first outlet 70. The working fluid flows from the first outlet 70 into the inlet 69 of the expansion device 22. As the working fluid flows through the expansion device 22, the temperature and pressure of the working fluid decrease. The working fluid flows from the outlet 67 of the expansion device 22 into the second inlet 60 of the first valve 28 and exits the first valve 28 through the second outlet 64. The working fluid flows from the second outlet 64 to the inlet 34 of the first indoor heat exchanger 18, flows through the indoor heat exchanger 18 (in which heat is transferred from the space within the building 43 to the working fluid), and exits the first indoor heat exchanger 18 through the outlet 36. The working fluid flows from the first indoor heat exchanger 18 through the working fluid conduit 79 of the supplementary heater 14 (when the system 10 is in cooling mode, the burner 76 of the heater 14 is off, and the fuel valve 84 is closed). The working fluid flows from the heater 14 to the second inlet 68 of the second valve 30 and exits the second valve 30 through the second outlet 72. The working fluid flows from the second outlet 72 to the suction inlet 63 of the compressor 16 (or flows through the accumulator 26 and then to the suction inlet 63 of the compressor 16). The working fluid is then compressed in the compressor 16, and the above cycle can be repeated.

[0075] As described above, the direction of fluid flow through the outdoor heat exchanger 24 is the same in both cooling and heating modes. That is, as... Figure 1 and Figure 2As shown, fluid flows into the outdoor heat exchanger 24 through inlet 48 and exits through outlet 50. To state it another way, the opening designated as the "inlet" of the outdoor heat exchanger 24 is the same in both heating and cooling modes, and the opening designated as the "outlet" of the outdoor heat exchanger 24 is the same in both heating and cooling modes. The same applies to the first indoor heat exchanger 18 and the second indoor heat exchanger 20—that is, the direction of fluid flow through the first indoor heat exchanger 18 and the second indoor heat exchanger 20 is the same in both cooling and heating modes. In other words, the openings designated as the "inlets" of the first indoor heat exchanger 18 and the second indoor heat exchanger 20 are the same in both heating and cooling modes, and the openings designated as the "outlets" of the first indoor heat exchanger 18 and the second indoor heat exchanger 20 are the same in both heating and cooling modes. Furthermore, as... Figure 1 and Figure 2 As shown, in both cooling and heating modes, the direction of fluid flow through the expansion device 22 and the heater 14 is the same.

[0076] Enabling the fluid flow to pass through heat exchangers 24, 18, and 20 in the same direction in both heating and cooling modes allows for optimized heat transfer in both modes. Reversing (or opposite to) the direction of the working fluid flow compared to the airflow forced through heat exchangers 24, 18, and 20 by their respective fans improves heat transfer. By ensuring the working fluid flows in the same direction through heat exchangers 24, 18, and 20 in both heating and cooling modes, the direction of the working fluid flow can be reversed compared to the airflow direction in both modes. This improved heat transfer between the air and the working fluid increases the efficiency of the heat pump system 10. Furthermore, because the working fluid flows in the same direction through heat exchangers 18, 20, and 24 and expansion device 22 in both heating and cooling modes, system 10 can operate using only a single expansion device 16 (unlike prior art heat pump systems with two expansion devices).

[0077] Now refer to Figure 3Another heat pump system 110 is provided. System 110 may include a supplementary heater 114, a compressor 116, a first indoor heat exchanger 118, a second indoor heat exchanger 120, a first expansion device 121, a second expansion device 122, an outdoor heat exchanger 124, an energy storage device 126, a multi-way valve (reversing valve) 128, and a control module 153. The structure and function of the supplementary heater 114, compressor 116, first indoor heat exchanger 118, second indoor heat exchanger 120, expansion devices 121 and 122, outdoor heat exchanger 124, energy storage device 126, and control module 153 may be similar to or the same as the structure and function of the supplementary heater 14, compressor 16, first indoor heat exchanger 18, second indoor heat exchanger 120, expansion device 22, outdoor heat exchanger 24, energy storage device 26, and control module 153 described above.

[0078] The difference between system 10 and system 110 is that, unlike the two valves 28 and 30 of system 10, system 110 has a single directional valve 128. Valve 128 of system 110 includes a first opening 158, a second opening 160, a third opening 162, and a fourth opening 164. The first opening 158 is an inlet for receiving working fluid from compressor 116 in both cooling and heating modes. The second opening 160 is fluidly connected to outdoor heat exchanger 124, such that it supplies working fluid to outdoor heat exchanger 124 in cooling mode and receives working fluid from outdoor heat exchanger 124 in heating mode. The third opening 162 is fluidly connected to second indoor heat exchanger 120, such that it supplies working fluid to second indoor heat exchanger 120 in heating mode and receives working fluid from second indoor heat exchanger 120 in cooling mode. The fourth opening 164 is an outlet for supplying working fluid to compressor 116 (or accumulator 126) in both cooling and heating modes. In cooling mode, the first opening 158 and the second opening 160 are fluidly connected to each other, and the third opening 162 and the fourth opening 164 are fluidly connected to each other. In heating mode, the first opening 158 and the third opening 162 are fluidly connected to each other, and the second opening 160 and the fourth opening 164 are fluidly connected to each other.

[0079] In cooling mode, the working fluid flows from compressor 116 to the first opening 158 of valve 128, flows through the second opening 160, and flows to the outdoor heat exchanger 124. From the outdoor heat exchanger 124, the working fluid flows from the outdoor heat exchanger 124 through a first bypass conduit 123 surrounding a second expansion device 122 (which can be closed during cooling mode) (i.e., through a first check valve 125 disposed along the first bypass conduit 123). The working fluid flows from the first bypass conduit 123 through the first expansion device 121. A second check valve 127 prevents fluid from flowing through the second bypass conduit 129 in cooling mode. The working fluid flows from the first expansion device 121 through the first indoor heat exchanger 118, through the working fluid conduit 179 of heater 114, and through the second indoor heat exchanger 120. From the second indoor heat exchanger 120, the working fluid flows from the second indoor heat exchanger 120 to the third opening 162, flows through the fourth opening 164, and flows back to compressor 116 (or back to accumulator 126).

[0080] In heating mode, the working fluid flows from compressor 116 to the first opening 158 of valve 128, flows through the third opening 162, and flows into the second indoor heat exchanger 120. The working fluid flows through the second indoor heat exchanger 120, then through the working fluid conduit 179 of heater 114, and then through the first indoor heat exchanger 118. The working fluid flows from the first indoor heat exchanger 118 through a second bypass conduit 129 surrounding a first expansion device 121 (which can be closed during cooling mode) (i.e., through a second check valve 127 disposed along the second bypass conduit 129). The working fluid flows from the second bypass conduit 129 through the second expansion device 122. A first check valve 125 prevents fluid from flowing through the first bypass conduit 123 in heating mode. The working fluid flows from the second expansion device 122 through the outdoor heat exchanger 124 and into the second opening 160. The working fluid flows from the second opening 160 through the fourth opening 164 and returns to the compressor 116 (or returns to the accumulator 126).

[0081] Unlike system 10, the direction of fluid flow through heat exchangers 118, 120, 124, working fluid conduit 179 and expansion device 122 is different in heating mode and cooling mode.

[0082] Now refer to Figure 4Another heat pump system 210 is provided. System 210 may include a supplementary heater 214, a compressor 216, a first indoor heat exchanger 218, a second indoor heat exchanger 220, an expansion device 222, an outdoor heat exchanger 224, an accumulator 226, a first multi-way valve (reversing valve) 228, a second multi-way valve 230 (reversing valve), and a control module 253. The structure and function of the supplementary heater 214, compressor 216, first indoor heat exchanger 218, second indoor heat exchanger 220, expansion device 222, outdoor heat exchanger 224, accumulator 226, valves 228, 230, and control module 253 may be similar to or the same as the structure and function of the supplementary heater 14, compressor 16, first indoor heat exchanger 18, second indoor heat exchanger 20, expansion device 22, outdoor heat exchanger 24, accumulator 26, valves 28, 30, and control module 253 described above. The difference between system 210 and system 10 is that the supplementary heater 214 and fuel valve 284 of system 210 are located outside the building 43.

[0083] Now refer to Figure 5 Another heat pump system 310 is provided. System 310 may include a supplementary heater 314, a compressor 316, an indoor heat exchanger 320, an expansion device 322, an outdoor heat exchanger 324, an accumulator 326, a first multi-way valve (reversing valve) 328, a second multi-way valve (reversing valve) 330, and a control module 353. The structure and function of the supplementary heater 314, compressor 316, indoor heat exchanger 320, expansion device 322, outdoor heat exchanger 324, accumulator 326, valves 328, 330, and control module 353 may be similar to or the same as the structure and function of the supplementary heater 14, compressor 16, second indoor heat exchanger 20, expansion device 22, outdoor heat exchanger 24, accumulator 26, valves 28, 30, and control module 53 described above.

[0084] The difference between system 310 and system 10 is that system 310 includes a single indoor heat exchanger 320, instead of including a first indoor heat exchanger and a second indoor heat exchanger. Therefore, in system 310, the working fluid flows from the second outlet 364 of the first valve 328 to the supplementary heater 314, instead of flowing through the first indoor heat exchanger before flowing through the supplementary heater 314.

[0085] Now refer to Figure 6 Another heat pump system 410 is provided, which may be identical in structure and function to system 310, except that a supplementary heater 414 of system 410 is located outside the building 43.

[0086] Now refer to Figures 7 to 10Another heat pump system 510 is provided. System 510 may include a supplementary heater 514, a compressor 516, a first indoor heat exchanger 518, a second indoor heat exchanger 520, an expansion device 522, an outdoor heat exchanger 524, an accumulator 526, a first multi-way valve (reversing valve) 528, a second multi-way valve (reversing valve) 530, and a control module 553. The structure and function of the supplementary heater 514, compressor 516, first indoor heat exchanger 518, second indoor heat exchanger 520, expansion device 522, outdoor heat exchanger 524, accumulator 526, valves 528, 530, and control module 553 may be similar to or the same as the structure and function of the supplementary heater 14, compressor 16, first indoor heat exchanger 18, second indoor heat exchanger 20, expansion device 22, outdoor heat exchanger 24, accumulator 26, valves 28, 30, and control module 53 described above.

[0087] Similar to the first valve 28, the first valve 528 includes a first inlet 558, a second inlet 560, a first outlet 562, and a second outlet 564. Similarly, the second valve 530 includes a first inlet 566, a second inlet 568, a first outlet 570, and a second outlet 572. Like valves 28 and 30, valves 528 and 530 are movable between a first position and a second position. When the first valve 528 is in the first position (… Figure 7 and Figure 9 When the first valve 528 is in the second position, the first inlet 558 is fluidly connected to the second outlet 564, and the second inlet 560 is fluidly connected to the first outlet 562. Figure 8 and Figure 10 When the second valve 530 is in the first position, the first inlet 558 is fluidly connected to the first outlet 562, and the second inlet 560 is fluidly connected to the second outlet 564. Figure 7 , Figure 9 and Figure 10 When the second valve 530 is in the second position, the first inlet 566 is fluidly connected to the second outlet 572, and the second inlet 568 is fluidly connected to the first outlet 570. Figure 8 When the first inlet 566 is fluidly connected to the first outlet 570, the second inlet 568 is fluidly connected to the second outlet 572.

[0088] System 510 may include a first bypass flow path 588 and a second bypass flow path 590. The first bypass flow path 588 extends from a first conduit 589 to a second conduit 591. The first conduit 589 is fluidly connected to a second outlet 572 of a second valve 530 and receives working fluid from the second outlet 572. A first bypass valve 592 (having an inlet and two outlets) is fluidly connected to the first conduit 589, the first bypass flow path 588, and the suction line 593 of the compressor 516 (or connected to an accumulator 526 disposed along the suction line 593). The first bypass valve 592 is a three-way valve (e.g., a solenoid-actuated three-way valve) movable between a first position that allows fluid to flow from the first conduit 589 to the suction line 593 and restricts fluid flow through the first bypass flow path 588, and a second position that allows fluid to flow from the first conduit 589 to the first bypass flow path 588 and restricts fluid flow through the suction line 593.

[0089] The second conduit 591 is fluidly connected to the first inlet 558 of the first valve 528 and the discharge outlet 565 of the compressor 516, such that the working fluid discharged from the compressor 516 flows through the second conduit 591 to the first inlet 558 of the first valve 528.

[0090] When the first bypass valve 592 is in the first position ( Figure 7 and Figure 8 When the second valve 530 is in the second outlet 572, the working fluid flows from the second outlet 572 through the first bypass valve 592 and into the accumulator 526 or the suction line 593, and the fluid flow through the first bypass flow path 588 is restricted or blocked. When the first bypass valve 592 is in the second position ( Figure 9 When the first bypass valve 592 is in the second position, the fluid flowing to the accumulator 526, the suction line 593, and the compressor 516 is restricted or blocked. Conversely, when the first bypass valve 592 is in the second position, the working fluid flows from the second outlet 572 of the second valve 530 through the first bypass valve 592, through the first bypass flow path 588, through the second conduit 591, and into the first inlet 558 of the first valve 528. In other words, when the first bypass valve 592 is in the second position, the working fluid bypasses the compressor 516.

[0091] The second bypass flow path 590 extends from the third conduit 594 to the fourth conduit 595. The third conduit 594 is fluidly connected to the first outlet 570 of the second valve 530 and receives working fluid from the first outlet 570. The second bypass valve 596 (having an inlet and two outlets) is fluidly connected to the third conduit 594, the second bypass flow path 590, and the inlet 569 of the expansion device 522. The second bypass valve 596 is a three-way valve (e.g., a solenoid-actuated three-way valve) movable between a first position that allows fluid to flow from the third conduit 594 to the inlet 569 of the expansion device 522 and restricts fluid flow through the second bypass flow path 590, and a second position that allows fluid to flow from the third conduit 594 to the second bypass flow path 590 and restricts fluid flow through the expansion device 522.

[0092] The fourth conduit 595 is fluidly connected to the second inlet 560 of the first valve 528 and the outlet 567 of the expansion device 522, such that the working fluid leaving the expansion device 522 flows through the fourth conduit 595 to the second inlet 560 of the first valve 528.

[0093] When the second bypass valve 596 is in the first position ( Figure 7 and Figure 8 When the second valve 530 is in the first outlet 570, the working fluid flows from the second valve 530 through the second bypass valve 596 and through the expansion device 522, and the fluid flow through the second bypass flow path 590 is restricted or blocked. When the second bypass valve 596 is in the second position ( Figure 9 and Figure 10 When the expansion device 522 is in the second position, the fluid flow is restricted or blocked. Conversely, when the second bypass valve 596 is in the second position, the working fluid flows from the first outlet 570 of the second valve 530 through the second bypass valve 596, through the second bypass flow path 590, through the fourth conduit 595, and into the second inlet 560 of the first valve 528. In other words, when the second bypass valve 596 is in the second position, the working fluid bypasses the expansion device 522.

[0094] The second bypass flow path 590 may include a pump 598 disposed downstream of the second bypass valve 596 and upstream of the fourth conduit 595. The pump 598 operates when the second bypass valve 596 is in a second position to pump working fluid through the second bypass flow path 590 (i.e., from the first outlet 570 of the second valve 530 to the second inlet 560 of the first valve 528). When the second bypass valve 596 is in a first position, the pump 598 may be shut off.

[0095] The control module 553 communicates with and controls the operation of the compressor 516, the fans 544 and 552 of the heat exchangers 520 and 524, the burner 576 of the supplementary heater 514, the fuel valve 584, the first valve 528 and the second valve 530, the expansion device 522, the bypass valves 592 and 596, and the pump 598.

[0096] System 510 is capable of the first heating mode ( Figure 7 ), Cooling mode ( Figure 8 ), defrost mode or free cooling mode ( Figure 9 And the second heating mode (non-compressor heating mode) Figure 10 Operate in the first heating mode. Figure 7 In this mode, control module 553 can operate compressor 516 to move bypass valves 592 and 596 to their first positions (to restrict or prevent fluid flow through the first bypass flow path 588 and the second bypass flow path 590), and to move first valve 528 and second valve 530 to their first positions. Accordingly, in the first heating mode, system 510 operates in the same manner as system 10 operates in heating mode as described above.

[0097] In cooling mode ( Figure 8 In this mode, control module 553 can operate compressor 516 to move bypass valves 592 and 596 to their first positions (to restrict or prevent fluid flow through the first bypass flow path 588 and the second bypass flow path 590), and to move first valve 528 and second valve 530 to their second positions. Accordingly, in cooling mode, system 510 operates in the same manner as system 10 operates in cooling mode as described above.

[0098] In defrost mode ( Figure 9 Under these conditions, the control module 553 can shut down the compressor 516, move the bypass valves 592 and 596 to their second positions (to allow fluid to flow through the first bypass flow path 588 and the second bypass flow path 590 to bypass the compressor 516 and the expansion device 522), operate the pump 598, and move the first valve 528 and the second valve 530 to their first positions.

[0099] Since compressor 516 is off in defrost mode, pump 598 circulates the working fluid throughout system 510. Specifically, the working fluid discharged from pump 598 flows through a second bypass flow path 590 (bypassing expansion device 522), through the second inlet 560 of first valve 528, through the first outlet 562 of first valve 528, and into outdoor heat exchanger 524. From outdoor heat exchanger 524, the working fluid flows through the first inlet 566 of second valve 530, through the second outlet 572 of second valve 530, and into first conduit 589. From first conduit 589, the working fluid flows through first bypass valve 592, through first bypass flow path 588 (bypassing compressor 516), and into second conduit 591. From second conduit 591, the working fluid flows through the first inlet 558 of first valve 528, through the second outlet 564 of first valve 528, and into first indoor heat exchanger 518. The working fluid flows from the first indoor heat exchanger 518 through the working fluid conduit 579 of the supplementary heater 514, and flows through the second indoor heat exchanger 520. The working fluid flows from the second indoor heat exchanger 520 through the second inlet 568 of the second valve 530, through the first outlet 570 of the second valve 530, through the second bypass valve 596, and back into the second bypass flow path 590.

[0100] When system 510 operates in defrost mode for the purpose of defrosting outdoor heat exchanger 524 (e.g., when control module 533 determines that frost exists or may exist on outdoor heat exchanger 524), control module 533 may continuously or intermittently operate burner 576 of supplemental heater 514 and open fuel valve 584 to heat working fluid flowing through working fluid conduit 579 of heater 514. The working fluid heated by heater 514 will still be relatively warm as it flows through outdoor heat exchanger 524, which accelerates defrosting of outdoor heat exchanger 524. Since compressor 516 is off during defrost mode, the power consumption of system 510 is relatively low.

[0101] System 510 can also be based on the above and Figure 8The cooling mode shown operates in defrost mode for the purpose of cooling the interior of building 43 in a way that consumes less electrical energy (i.e., when the air inside building 43 is warmer than the outdoor ambient air). When system 510 operates in defrost mode for low-energy cooling purposes, the system can operate as described above for defrosting the outdoor heat exchanger 524, except that control module 533 will not operate the burner 576 of heater 514 and will close fuel valve 584. In this way, the relatively cool outdoor air will cool the working fluid in outdoor heat exchanger 524, so that the working fluid in indoor heat exchangers 518, 520 can absorb heat from the air inside building 43.

[0102] Second heating mode ( Figure 10 Under these conditions, the control module 553 can shut down the compressor 516, move the second bypass valve 596 to its second position (to allow fluid to flow through the second bypass flow path 590 to bypass the expansion device 522), operate the pump 598, move the first valve 528 to its second position, and move the second valve 530 to its first position.

[0103] Positioning the first valve 528 in its second position and the second valve 530 in its first position (e.g.) Figure 10 (As shown) System 510 is divided into two fluid-separated working fluid loops. One loop includes an outdoor heat exchanger 524 and a compressor 516, and the other loop includes a second bypass flow path 590, indoor heat exchangers 518 and 520, and a supplementary heater 514. Since compressor 516 is off in the second heating mode, the working fluid in the loop with compressor 516 and outdoor heat exchanger 524 can remain stagnant.

[0104] Operation of pump 598 in the second heating mode circulates the working fluid through indoor heat exchangers 518 and 520 and heater 514. Specifically, in the second heating mode, the working fluid discharged from pump 598 flows through a second bypass flow path 590 (bypassing expansion device 522), through a fourth conduit 595, through the second inlet 560 of the first valve 528, and through the second outlet 564 of the first valve 528. The working fluid flows from the second outlet 564 through the first indoor heat exchanger 518 and through the working fluid conduit 579 of heater 514. When system 510 operates in the second heating mode, control module 533 can continuously or intermittently operate the burner 576 of heater 514 and open fuel valve 584 to allow heater 514 to heat the working fluid in working fluid conduit 579. The heated working fluid flows from working fluid conduit 579 through the second indoor heat exchanger 520, where heat from the working fluid is transferred to the air inside building 43. The working fluid flows from the second indoor heat exchanger 520 through the second inlet 568 of the second valve 530, through the first outlet 570 of the second valve 530, through the second bypass valve 596, and back into the second bypass flow path 590.

[0105] Because compressor 516 is shut off during the second heating mode, system 510 consumes significantly less electrical energy than it does during operation in the first heating mode. Therefore, it can be particularly advantageous to operate system 510 in the second heating mode during periods when electrical costs are relatively high.

[0106] It will be understood that when system 510 operates in the second heating mode, the position of the first bypass valve 592 is irrelevant because the first bypass valve 592 and the first bypass flow path 588 (along with compressor 516 and outdoor heat exchanger 524) are isolated from the loop in which the working fluid circulates (i.e., the loop including indoor heat exchangers 518, 520, heater 514, and the second bypass flow path 590). It should also be noted that when system 510 operates in defrost mode or the second heating mode, the working fluid does not flow through any compressor or any expansion device.

[0107] In this application, the term "module" is replaced by the term "circuit" as defined below. The term "module" may refer to, be part of, or include the following: Application-Specific Integrated Circuit (ASIC); Digital, Analog, or Mixed-Signal / Digital Discrete Circuit; Digital, Analog, or Mixed-Signal / Digital Integrated Circuit; Combinational Logic Circuit; Field-Programmable Gate Array (FPGA); Processor Circuit (shared, dedicated, or grouped) that executes code; Memory Circuit (shared, dedicated, or grouped) that stores code executed by the processor circuit; Other suitable hardware components that provide the aforementioned functionality; or combinations of some or all of the foregoing, such as combinations in a system-on-a-chip.

[0108] This module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functionality of any given module of this disclosure may be distributed across multiple modules connected via the interface circuits. For example, multiple modules may allow for load balancing. In another example, a server (also referred to as a remote or cloud) module may perform some functions on behalf of a client module.

[0109] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuitry" covers a single processor circuitry that executes some or all of the code from multiple modules. The term "grouped processor circuitry" covers processor circuitry that executes some or all of the code from one or more modules in combination with additional processor circuitry. The reference to multiple processor circuitry covers multiple processor circuitry on a discrete die, multiprocessor circuitry on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term "shared memory circuitry" covers a single memory circuitry that stores some or all of the code from multiple modules. The term "grouped memory circuitry" includes memory circuitry that stores some or all of the code from one or more modules in combination with additional memory.

[0110] The term memory circuit is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not encompass transient electrical or electromagnetic signals propagating through a medium (e.g., on a carrier wave); therefore, the term computer-readable medium can be considered tangible and non-transient. Non-limiting examples of non-transient, tangible computer-readable media are non-volatile memory circuits (e.g., flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (e.g., static random access memory circuits or dynamic random access memory circuits), magnetic storage media (e.g., analog magnetic tape or digital magnetic tape or hard disk drives), and optical storage media (e.g., CDs, DVDs, or Blu-ray discs).

[0111] The apparatus and methods described in this application can be implemented, in part or in whole, by a special-purpose computer, which is created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The aforementioned function blocks, flowchart components, and other elements serve as software specifications, which can be routinely compiled into a computer program by a skilled technician or programmer.

[0112] A computer program includes processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. A computer program may also include or depend on stored data. A computer program may encompass a basic input / output system (BIOS) that interacts with the hardware of a special-purpose computer, device drivers that interact with specific devices of a special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0113] Computer programs may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code executed by an interpreter; and (v) source code compiled and executed by a just-in-time (JIT) compiler, etc. As an example only, source code may be written using syntax from languages ​​including: C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, etc. Fortran, Perl, Pascal, Curl, OCaml, HTML5 (Hypertext Markup Language, Fifth Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Lua, MATLAB, SIMULINK and

[0114] The foregoing description of various embodiments has been provided for purposes of illustration and description. These descriptions are not intended to be exhaustive or limiting of this disclosure. Elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable and can be used in selected embodiments, even if not specifically shown or described. Elements or features of a particular embodiment may also be varied in many ways. Such variations are not considered to depart from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

Claims

1. A heat pump system, comprising: compressor; An outdoor heat exchanger, which is in fluid communication with the compressor; An indoor heat exchanger, which is in fluid communication with the compressor; An expansion device, which is in fluid communication with the indoor heat exchanger and the outdoor heat exchanger; and A supplementary heater, comprising a burner and a working fluid conduit, wherein the burner is configured to burn fuel and heat the working fluid conduit, and The working fluid conduit is fluidly disposed between the expansion device and the indoor heat exchanger, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through the compressor, the outdoor heat exchanger, or the expansion device.

2. The heat pump system according to claim 1, further comprising a first reversing valve in fluid communication with the compressor, the expansion device, the indoor heat exchanger, and the outdoor heat exchanger. in, The first directional valve is movable between a first position and a second position. Wherein, the first reversing valve is in the first position when the heat pump system is in heating mode, and The first reversing valve is in the second position when the heat pump system is in cooling mode.

3. The heat pump system according to claim 2, wherein, The working fluid flows in the same direction through the indoor heat exchanger in both the heating and cooling modes, the working fluid flows in the same direction through the outdoor heat exchanger in both the heating and cooling modes, the working fluid flows in the same direction through the expansion device in both the heating and cooling modes, and the working fluid flows in the same direction through the working fluid conduit in both the heating and cooling modes.

4. The heat pump system according to claim 3 further includes a second reversing valve in fluid communication with the compressor, the expansion device, the indoor heat exchanger, and the outdoor heat exchanger. in, The second directional valve is movable between a first position and a second position. Wherein, the second reversing valve is in the first position when the heat pump system is in the heating mode, and The second reversing valve is in the second position when the heat pump system is in the cooling mode.

5. The heat pump system according to claim 4, further comprising: A first bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. A first bypass valve is fluidly connected to a first bypass flow path and is movable between a first position that restricts fluid flow through the first bypass flow path and allows fluid flow to the suction inlet of the compressor, and a second position that allows fluid flow through the first bypass flow path and restricts fluid flow to the suction inlet of the compressor. A second bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. as well as A second bypass valve is fluidly connected to the second bypass flow path and is movable between a first position that restricts fluid flow through the second bypass flow path and allows fluid flow through the expansion device, and a second position that allows fluid flow through the second bypass flow path and restricts fluid flow through the expansion device.

6. The heat pump system according to claim 5, wherein, The second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

7. The heat pump system according to claim 1 further includes another indoor heat exchanger, wherein, The working fluid conduit of the supplementary heater is fluidly disposed between the indoor heat exchangers.

8. The heat pump system according to claim 1, wherein, The indoor heat exchanger and the supplemental heater are located inside the building when the heat pump system is fully installed and in operation.

9. The heat pump system according to claim 1, wherein, The indoor heat exchanger is located inside the building when the heat pump system is fully installed and operating, and the supplementary heater is located outside the building when the heat pump system is fully installed and operating.

10. The heat pump system according to claim 1, wherein, The fuel burned by the burner is a substance different from the working fluid, and wherein the fuel is selected from the group consisting of natural gas, propane, butane, kerosene and heating oil.

11. The heat pump system according to claim 1, further comprising: A fuel valve, which is fluidly connected to the burner and configured to control the flow of fuel to the burner; as well as A control module configured to control the operation of the burner and the fuel valve.

12. The heat pump system according to claim 11, wherein, The control module controls the operation of the burner and the fuel valve based on the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

13. The heat pump system according to any one of claim 11 or 12, wherein, The control module controls the operation of the burner and the fuel valve based on the outdoor ambient air temperature.

14. The heat pump system according to any one of claim 11 or 12, wherein, The control module controls the operation of the burner and the fuel valve based on fluctuations in electricity costs.

15. A heat pump system, comprising: compressor; An outdoor heat exchanger, which is in fluid communication with the compressor; An indoor heat exchanger, which is in fluid communication with the compressor; An expansion device, which is in fluid communication with the indoor heat exchanger and the outdoor heat exchanger; A first reversing valve has a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the first reversing valve is fluidly connected to the discharge outlet of the compressor, the second inlet of the first reversing valve is fluidly connected to the outlet of the expansion device, the first outlet of the first reversing valve is fluidly connected to the inlet of the outdoor heat exchanger, and the second outlet provides working fluid to the indoor heat exchanger. A second reversing valve has a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the second reversing valve is fluidly connected to the outlet of the outdoor heat exchanger, the second inlet of the second reversing valve is fluidly connected to the outlet of the indoor heat exchanger, the first outlet of the second reversing valve is fluidly connected to the inlet of the expansion device, and the second outlet provides working fluid to the suction inlet of the compressor. A supplementary heater, comprising a burner and a working fluid conduit, wherein the burner is configured to burn fuel and heat the working fluid conduit, and The working fluid conduit is fluidly disposed between the expansion device and the indoor heat exchanger, and the indoor heat exchanger receives working fluid from the working fluid conduit such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through the compressor, without flowing through the outdoor heat exchanger, and without flowing through the expansion device.

16. The heat pump system according to claim 15, further comprising: A first bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. A first bypass valve is fluidly connected to a first bypass flow path and is movable between a first position that restricts fluid flow through the first bypass flow path and allows fluid flow to the suction inlet of the compressor, and a second position that allows fluid flow through the first bypass flow path and restricts fluid flow to the suction inlet of the compressor. A second bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. as well as A second bypass valve is fluidly connected to the second bypass flow path and is movable between a first position that restricts fluid flow through the second bypass flow path and allows fluid flow through the expansion device, and a second position that allows fluid flow through the second bypass flow path and restricts fluid flow through the expansion device.

17. The heat pump system according to claim 16, wherein, The second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

18. The heat pump system according to claim 17, wherein: The first directional valve is movable between a first position and a second position, and the second directional valve is also movable between a first position and a second position. When the first directional control valve is in the first position: (a) the first inlet of the first directional control valve is fluidly connected to the second outlet of the first directional control valve, and (b) the second inlet of the first directional control valve is fluidly connected to the first outlet of the first directional control valve. When the second directional valve is in the first position: (a) the first inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve. When the first directional control valve is in its second position: (a) the first inlet of the first directional control valve is fluidly connected to the first outlet of the first directional control valve, and (b) the second inlet of the first directional control valve is fluidly connected to the second outlet of the first directional control valve. When the second directional valve is in the second position of the second directional valve: (a) the first inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve.

19. The heat pump system according to claim 18, wherein: The heat pump system can operate in a first heating mode, a cooling mode, a defrosting mode, and a second heating mode. In the first heating mode: (a) the first reversing valve and the second reversing valve are in the first position of the first reversing valve and the second reversing valve, (b) the first bypass valve and the second bypass valve are in the first position of the first bypass valve and the second bypass valve, (c) the pump is turned off, and (d) the compressor is operated. In the cooling mode: (a) the first reversing valve and the second reversing valve are in their second positions; (b) the first bypass valve and the second bypass valve are in their first positions; (c) the pump is shut off; and (d) the compressor is operated. In the defrosting mode: (a) the first reversing valve and the second reversing valve are in their first positions, (b) the first bypass valve and the second bypass valve are in their second positions, (c) the pump operates, and (d) the compressor is shut down. In the second heating mode: (a) the first reversing valve is in the second position of the first reversing valve, (b) the second reversing valve is in the first position of the second reversing valve, (c) the second bypass valve is in the second position of the second bypass valve, (d) the pump is operated, and (e) the compressor is turned off.

20. The heat pump system according to claim 19, further comprising: A fuel valve, which is fluidly connected to the burner and configured to control the flow of fuel to the burner; as well as A control module configured to control the operation of the burner and the fuel valve. The control module selectively operates the burner and opens the fuel valve when the heat pump system is operating in the first heating mode, the defrosting mode, and the second heating mode.

21. The heat pump system according to claim 20, wherein: The working fluid flows through the indoor heat exchanger in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode. The working fluid flows through the outdoor heat exchanger in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode. The working fluid flows through the expansion device in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode, and The working fluid flows through the working fluid conduit in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode.

22. The heat pump system according to claim 20, wherein, The control module controls the operation of the burner and the fuel valve based on the temperature of the working fluid flowing between the burner and the indoor heat exchanger.

23. The heat pump system according to any one of claim 20 or 22, wherein, The control module controls the operation of the burner and the fuel valve based on the outdoor ambient air temperature.

24. The heat pump system according to any one of claim 20 or 22, wherein, The control module controls the operation of the burner and the fuel valve based on fluctuations in electricity costs.

25. The heat pump system of claim 15 further includes another indoor heat exchanger, wherein, The working fluid conduit of the supplementary heater is fluidly disposed between the indoor heat exchangers.

26. A heat pump system, comprising: compressor; An outdoor heat exchanger, which is in fluid communication with the compressor; An indoor heat exchanger, which is in fluid communication with the compressor; An expansion device, which is in fluid communication with the indoor heat exchanger and the outdoor heat exchanger; as well as A supplementary heater, comprising a heat source and a working fluid conduit, wherein the heat source and the working fluid conduit are in a heat transfer relationship, such that the heat source is configured to heat the working fluid conduit, and The working fluid conduit is fluidly disposed between the expansion device and the indoor heat exchanger, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through the compressor, the outdoor heat exchanger, or the expansion device.

27. The heat pump system of claim 26, further comprising a first reversing valve in fluid communication with the compressor, the expansion device, and the indoor and outdoor heat exchangers. in, The first directional valve is movable between a first position and a second position. Wherein, the first reversing valve is in the first position when the heat pump system is in heating mode, and The first reversing valve is in the second position when the heat pump system is in cooling mode.

28. The heat pump system according to claim 27, wherein, The working fluid flows in the same direction through the indoor heat exchanger in both the heating and cooling modes, the working fluid flows in the same direction through the outdoor heat exchanger in both the heating and cooling modes, the working fluid flows in the same direction through the expansion device in both the heating and cooling modes, and the working fluid flows in the same direction through the working fluid conduit in both the heating and cooling modes.

29. The heat pump system of claim 28, further comprising a second reversing valve in fluid communication with the compressor, the expansion device, and the indoor and outdoor heat exchangers. in, The second directional valve is movable between a first position and a second position. Wherein, the second reversing valve is in the first position when the heat pump system is in the heating mode, and The second reversing valve is in the second position when the heat pump system is in the cooling mode.

30. The heat pump system according to claim 29, further comprising: A first bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. A first bypass valve is fluidly connected to a first bypass flow path and is movable between a first position that restricts fluid flow through the first bypass flow path and allows fluid flow to the suction inlet of the compressor, and a second position that allows fluid flow through the first bypass flow path and restricts fluid flow to the suction inlet of the compressor. A second bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. as well as A second bypass valve is fluidly connected to the second bypass flow path and is movable between a first position that restricts fluid flow through the second bypass flow path and allows fluid flow through the expansion device, and a second position that allows fluid flow through the second bypass flow path and restricts fluid flow through the expansion device.

31. The heat pump system according to claim 30, wherein, The second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

32. The heat pump system of claim 26 further includes another indoor heat exchanger, wherein, The working fluid conduit of the supplementary heater is fluidly disposed between the indoor heat exchangers.

33. The heat pump system of claim 26 further includes a control module configured to control the operation of the supplementary heater based on the temperature of the working fluid flowing between the supplementary heater and the indoor heat exchanger.

34. The heat pump system according to claim 33, wherein, The control module controls the operation of the supplementary heater based on the outdoor ambient air temperature.

35. The heat pump system according to claim 34, wherein, The control module controls the operation of the supplementary heater based on fluctuations in electricity costs.

36. A heat pump system, comprising: compressor; An outdoor heat exchanger, which is in fluid communication with the compressor; An indoor heat exchanger, which is in fluid communication with the compressor; An expansion device, which is in fluid communication with the indoor heat exchanger and the outdoor heat exchanger; A first reversing valve has a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the first reversing valve is fluidly connected to the discharge outlet of the compressor, the second inlet of the first reversing valve is fluidly connected to the outlet of the expansion device, the first outlet of the first reversing valve is fluidly connected to the inlet of the outdoor heat exchanger, and the second outlet provides working fluid to the indoor heat exchanger. A second reversing valve has a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet of the second reversing valve is fluidly connected to the outlet of the outdoor heat exchanger, the second inlet of the second reversing valve is fluidly connected to the outlet of the indoor heat exchanger, the first outlet of the second reversing valve is fluidly connected to the inlet of the expansion device, and the second outlet provides working fluid to the suction inlet of the compressor. A supplementary heater, comprising a heat source and a working fluid conduit, wherein the heat source and the working fluid conduit are in a heat transfer relationship, such that the heat source is configured to heat the working fluid conduit, and The working fluid conduit is fluidly disposed between the expansion device and the indoor heat exchanger, such that the working fluid flows from the outlet of the working fluid conduit to the inlet of the indoor heat exchanger without flowing through the compressor, the outdoor heat exchanger, or the expansion device.

37. The heat pump system according to claim 36, further comprising: A first bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. A first bypass valve is fluidly connected to a first bypass flow path and is movable between a first position that restricts fluid flow through the first bypass flow path and allows fluid flow to the suction inlet of the compressor, and a second position that allows fluid flow through the first bypass flow path and restricts fluid flow to the suction inlet of the compressor. A second bypass flow path is selectively in fluid communication with the first reversing valve and the second reversing valve. as well as A second bypass valve is fluidly connected to the second bypass flow path and is movable between a first position that restricts fluid flow through the second bypass flow path and allows fluid flow through the expansion device, and a second position that allows fluid flow through the second bypass flow path and restricts fluid flow through the expansion device.

38. The heat pump system according to claim 37, wherein, The second bypass flow path includes a pump that operates when the second bypass valve is in the second position.

39. The heat pump system according to claim 38, wherein: The first directional valve is movable between a first position and a second position, and the second directional valve is also movable between a first position and a second position. When the first directional control valve is in the first position: (a) the first inlet of the first directional control valve is fluidly connected to the second outlet of the first directional control valve, and (b) the second inlet of the first directional control valve is fluidly connected to the first outlet of the first directional control valve. When the second directional valve is in the first position: (a) the first inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve. When the first directional control valve is in its second position: (a) the first inlet of the first directional control valve is fluidly connected to the first outlet of the first directional control valve, and (b) the second inlet of the first directional control valve is fluidly connected to the second outlet of the first directional control valve. When the second directional valve is in the second position of the second directional valve: (a) the first inlet of the second directional valve is fluidly connected to the first outlet of the second directional valve, and (b) the second inlet of the second directional valve is fluidly connected to the second outlet of the second directional valve.

40. The heat pump system according to claim 39, wherein: The heat pump system can operate in a first heating mode, a cooling mode, a defrosting mode, and a second heating mode. In the first heating mode: (a) the first reversing valve and the second reversing valve are in the first position of the first reversing valve and the second reversing valve, (b) the first bypass valve and the second bypass valve are in the first position of the first bypass valve and the second bypass valve, (c) the pump is turned off, and (d) the compressor is operated. In the cooling mode: (a) the first reversing valve and the second reversing valve are in their second positions; (b) the first bypass valve and the second bypass valve are in their first positions; (c) the pump is shut off; and (d) the compressor is operated. In the defrosting mode: (a) the first reversing valve and the second reversing valve are in their first positions, (b) the first bypass valve and the second bypass valve are in their second positions, (c) the pump operates, and (d) the compressor is shut down. In the second heating mode: (a) the first reversing valve is in the second position of the first reversing valve, (b) the second reversing valve is in the first position of the second reversing valve, (c) the second bypass valve is in the second position of the second bypass valve, (d) the pump is operated, and (e) the compressor is turned off.

41. The heat pump system of claim 40, further comprising a control module configured to control the operation of the supplementary heater. in, The control module selectively operates the supplementary heater when the heat pump system operates in the first heating mode, the defrosting mode, and the second heating mode.

42. The heat pump system according to claim 41, wherein: The working fluid flows through the indoor heat exchanger in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode. The working fluid flows through the outdoor heat exchanger in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode. The working fluid flows through the expansion device in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode, and The working fluid flows through the working fluid conduit in the same direction in the first heating mode, the cooling mode, the defrosting mode, and the second heating mode.

43. The heat pump system according to claim 41, wherein, The control module controls the operation of the supplementary heater based on the temperature of the working fluid flowing between the supplementary heater and the indoor heat exchanger.

44. The heat pump system according to claim 43, wherein, The control module controls the operation of the supplementary heater based on the outdoor ambient air temperature.

45. The heat pump system according to claim 44, wherein, The control module controls the operation of the supplementary heater based on fluctuations in electricity costs.

46. ​​The heat pump system of claim 36 further includes another indoor heat exchanger, wherein, The working fluid conduit of the supplementary heater is fluidly disposed between the indoor heat exchangers.

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