Air conditioning device

Abstract

An air conditioning device (100) comprises at least one branch unit (10), a plurality of indoor units (50a, 50b), an outdoor unit (60), at least one boiler (80), a plurality of outward branch pipes (51a, 51b, 51c), a plurality of return branch pipes (52a, 52b, 52c), a forward main pipe (61), and a return main pipe (62). In a first heat exchanger (12), refrigerant flowing through a first refrigerant piping path (R1) and a heat medium flowing through a first piping path (P1) exchange heat with each other. In a second heat exchanger (22), refrigerant flowing through the first refrigerant piping path (R1) and a heat medium flowing through a second piping path (P2) exchange heat with each other.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioning apparatus.

[0002] BACKGROUND ART Conventionally, air conditioners have been known that include an outdoor unit, a plurality of indoor units, and a branch unit, with the outdoor unit and the plurality of indoor units connected via the branch unit.

[0003] International Publication No. 2009 / 133640 discloses an air conditioner in which an outdoor unit (outdoor unit) and a branch unit (relay unit) are connected via first and second extension pipes, and the branch unit and an indoor unit (indoor unit) are connected via third and fourth extension pipes. The air conditioner includes an intermediate heat exchanger disposed in the branch unit.

[0004] In the air conditioner described in the above publication, heat is transferred between the outdoor unit and the branch unit by circulating refrigerant through first and second extension pipes, and heat is transferred between the branch unit and the indoor unit by circulating water through third and fourth extension pipes. Heat is exchanged between the refrigerant and water in an intermediate heat exchanger provided in the branch unit, so that heat is transferred from the indoor unit to the outdoor unit via the intermediate heat exchanger in the branch unit during cooling operation, and from the outdoor unit to the indoor unit via the intermediate heat exchanger in the branch unit during heating operation.

[0005] WO 2009 / 133640

[0006] However, the air conditioning device described in the above publication has a problem in that when the first extension pipe and the second extension pipe between the outdoor unit and the branch unit are installed over a long distance (e.g., 110 meters), the amount of refrigerant charged in the air conditioning device increases.

[0007] Furthermore, there is a problem that the heating capacity may be insufficient when using only the outdoor unit. The present disclosure has been made in consideration of the above problem, and its purpose is to provide an air conditioner that can reduce the amount of refrigerant charged and can compensate for the heating capacity.

[0008] The air conditioning apparatus of the present disclosure includes at least one branch unit, a plurality of indoor units, an outdoor unit, at least one boiler, a plurality of outward branch pipes and a plurality of inward branch pipes connecting the at least one branch unit to each of the plurality of indoor units and the at least one boiler, and a main outward pipe and a main inward pipe connecting the at least one branch unit to the outdoor unit. The at least one branch unit includes a first branch header, a second branch header, a first junction header, a second junction header, a plurality of first outward branch pipe on-off valves, a plurality of second outward branch pipe on-off valves, a plurality of first inward branch pipe on-off valves, a plurality of second inward branch pipe on-off valves, a first bypass valve, a second bypass valve, a first pump, a second pump, a first heat exchanger, a second heat exchanger, a first compressor, a first expansion valve, and a first four-way valve, all of which are arranged within the at least one branch unit. The indoor units each have a plurality of indoor heat exchangers arranged therein. One end of each of the plurality of outward branch pipes is connected to the first branch header via a respective one of a plurality of first outward branch pipe on-off valves and to the second branch header via a respective one of a plurality of second outward branch pipe on-off valves. The other end of each of the plurality of outward branch pipes is connected to one end of each of the plurality of indoor heat exchangers and at least one boiler. One end of each of the plurality of return branch pipes is connected to the first merging header via a respective one of a plurality of first return branch pipe on-off valves and to the second merging header via a respective one of a plurality of second return branch pipe on-off valves. The other end of each of the plurality of return branch pipes is connected to the other end of each of the plurality of indoor heat exchangers and at least one boiler. The first branch header and the first merging header are connected via a first bypass valve. The second branch header and the second merging header are connected via a second bypass valve. The first merging header, the first pump, the first heat exchanger, and the first branch header constitute a first piping path connected in this order so that the heat medium flows through them. The second junction header, the second pump, the second heat exchanger, and the second branch header are connected in this order to form a second piping path through which the heat medium flows, while the first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, and the second heat exchanger are connected to form a first refrigerant piping path through which the refrigerant flows.The first four-way valve is configured to switch between flowing the refrigerant through the first compressor, first four-way valve, first heat exchanger, first expansion valve, second heat exchanger, and first four-way valve in this order, or flowing the refrigerant through the first compressor, first four-way valve, second heat exchanger, first expansion valve, first heat exchanger, and first four-way valve in this order. One end of the outward main pipe is connected to one end of the outdoor unit. The other end of the outward main pipe is connected to the second piping path. One end of the return main pipe is connected to the other end of the outdoor unit. The other end of the return main pipe is connected to the second piping path. In the first heat exchanger, heat exchange occurs between the refrigerant flowing through the first refrigerant piping path and the heat medium flowing through the first piping path. In the second heat exchanger, heat exchange occurs between the refrigerant flowing through the first refrigerant piping path and the heat medium flowing through the second piping path.

[0009] According to the air conditioning apparatus of the present disclosure, it is possible to reduce the amount of refrigerant charged and to supplement heating capacity.

[0010] Fig. 1 is a refrigerant circuit diagram of an air conditioner according to embodiment 1. Fig. 2 is a refrigerant circuit diagram for all heating operation of an air conditioner according to embodiment 1. Fig. 3 is a refrigerant circuit diagram for heating-dominated operation of an air conditioner according to embodiment 1. Fig. 4 is a refrigerant circuit diagram for cooling-dominated operation of an air conditioner according to embodiment 1. Fig. 5 is a refrigerant circuit diagram of an air conditioner according to embodiment 2. Fig. 6 is a refrigerant circuit diagram for all heating operation of an air conditioner according to embodiment 2. Fig. 7 is a refrigerant circuit diagram for heating-dominated operation of an air conditioner according to embodiment 2. Fig. 8 is a refrigerant circuit diagram for cooling-dominated operation of an air conditioner according to embodiment 2. Fig. 9 is a refrigerant circuit diagram of an air conditioner according to embodiment 3. Fig. 10 is a refrigerant circuit diagram of an air conditioner according to embodiment 4.

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and their description will not be repeated in principle.

[0012] Embodiment 1. The configuration of an air conditioning apparatus 100 according to Embodiment 1 will be described with reference to FIG. 1. As shown in FIG. 1, the air conditioning apparatus 100 according to Embodiment 1 includes at least one branch unit 10, multiple indoor units 50a, 50b, an outdoor unit 60, at least one boiler 80, multiple outward branch pipes 51a, 51b, 51c, multiple return branch pipes 52a, 52b, 52c, an outward main pipe 61, and a return main pipe 62. In this embodiment, there is one branch unit 10. In this embodiment, there is one boiler 80. The multiple outward branch pipes 51a, 51b, 51c and the multiple return branch pipes 52a, 52b, 52c connect the at least one branch unit 10 to each of the multiple indoor units 50a, 50b and the at least one boiler 80. In this embodiment, the air conditioning apparatus 100 includes two indoor units 50a, 50b. The main outgoing pipe 61 and the main inbound pipe 62 connect at least one branch unit 10 and the outdoor unit 60.

[0013] At least one branching unit 10 has a first branch header 13, a second branch header 23, a first confluence header 16, a second confluence header 26, a plurality of first outbound branch pipe on / off valves 14a, 14b, 14c, a plurality of second outbound branch pipe on / off valves 24a, 24b, 24c, a plurality of first return branch pipe on / off valves 15a, 15b, 15c, a plurality of second return branch pipe on / off valves 25a, 25b, 25c, a first bypass valve 17, a second bypass valve 27, a first pump 11, a second pump 21, a first heat exchanger 12, a second heat exchanger 22, a first compressor 31, a first expansion valve 32, and a first four-way valve 18 arranged therein.

[0014] The indoor units 50a, 50b have indoor heat exchangers 53a, 53b respectively disposed therein. The indoor units 50a, 50b have indoor fans 54a, 54b respectively disposed therein.

[0015] One end of each of the multiple outward branch pipes 51a, 51b, 51c is connected to the first branch header 13 via each of the multiple first outward branch pipe opening / closing valves 14a, 14b, 14c, and is connected to the second branch header 23 via each of the multiple second outward branch pipe opening / closing valves 24a, 24b, 24c.

[0016] Each of the plurality of first outward branch pipe on-off valves 14a, 14b, 14c opens and closes a piping path connecting each of the plurality of outward branch pipes 51a, 51b, 51c to the first branch header 13. Each of the plurality of second outward branch pipe on-off valves 24a, 24b, 24c opens and closes a piping path connecting each of the plurality of outward branch pipes 51a, 51b, 51c to the second branch header 23. The piping path connecting each of the plurality of outward branch pipes 51a, 51b, 51c to the second branch header 23 branches off from the piping path connecting each of the plurality of outward branch pipes 51a, 51b, 51c to the first branch header 13.

[0017] The other ends of the plurality of outward branch pipes 51 a , 51 b , 51 c are connected to one ends of the plurality of indoor heat exchangers 53 a , 53 b and at least one boiler 80 , respectively.

[0018] One end of each of the multiple return branch pipes 52a, 52b, and 52c is connected to the first merging header 16 via each of the multiple first return branch pipe opening / closing valves 15a, 15b, and 15c, and is connected to the second merging header 26 via each of the multiple second return branch pipe opening / closing valves 25a, 25b, and 25c.

[0019] Each of the first return branch pipe on-off valves 15a, 15b, 15c opens and closes a piping path connecting each of the return branch pipes 52a, 52b, 52c to the first junction header 16. Each of the second return branch pipe on-off valves 25a, 25b, 25c opens and closes a piping path connecting each of the return branch pipes 52a, 52b, 52c to the second junction header 26. The piping path connecting each of the return branch pipes 52a, 52b, 52c to the second junction header 26 branches off from the piping path connecting each of the return branch pipes 52a, 52b, 52c to the first junction header 16.

[0020] The other end of each of the plurality of return branch pipes 52 a , 52 b , 52 c is connected to the other end of each of the plurality of indoor heat exchangers 53 a , 53 b and at least one boiler 80 .

[0021] The first branch header 13 and the first merging header 16 are connected via a first bypass valve 17. The first bypass valve 17 opens and closes a bypass path connecting the first branch header 13 and the first merging header 16.

[0022] The second branch header 23 and the second merging header 26 are connected via a second bypass valve 27. The second bypass valve 27 opens and closes a bypass path connecting the second branch header 23 and the second merging header 26.

[0023] The first junction header 16, the first pump 11, the first heat exchanger 12, and the first branch header 13 are connected to each other in this order to form a first piping path P1 in which the heat medium flows. The first junction header 16, the first pump 11, the first heat exchanger 12, and the first branch header 13 are connected by piping to form the first piping path P1.

[0024] The second junction header 26, the second pump 21, the second heat exchanger 22, and the second branch header 23 are connected to each other so that the heat medium flows in this order, constituting a second piping path P2. The second junction header 26, the second pump 21, the second heat exchanger 22, and the second branch header 23 are connected by piping to constitute the second piping path P2.

[0025] The first compressor 31, the first four-way valve 18, the first heat exchanger 12, the first expansion valve 32, and the second heat exchanger 22 constitute a first refrigerant piping path R1 in which the refrigerant flows. The first compressor 31, the first four-way valve 18, the first heat exchanger 12, the first expansion valve 32, and the second heat exchanger 22 are connected by piping to constitute the first refrigerant piping path R1. The first refrigerant piping path R1 has a refrigeration cycle.

[0026] The first four-way valve 18 is configured to switch between flowing the refrigerant through the first compressor 31, first four-way valve 18, first heat exchanger 12, first expansion valve 32, second heat exchanger 22, and first four-way valve 18 in that order, or flowing the refrigerant through the first compressor 31, first four-way valve 18, second heat exchanger 22, first expansion valve 32, first heat exchanger 12, and first four-way valve 18 in that order.

[0027] One end of the outgoing main pipe 61 is connected to one end of the outdoor unit 60. The other end of the outgoing main pipe 61 is connected to the second piping path P2.

[0028] One end of the return main pipe 62 is connected to the other end of the outdoor unit 60. The other end of the return main pipe 62 is connected to the second piping path P2.

[0029] The branching unit 10 has an outgoing main pipe opening / closing valve 34 and an inbound main pipe opening / closing valve 35 .

[0030] The outward main pipe on-off valve 34 is disposed in the branching unit 10 at a connection point between the second piping path P2 and the outward main pipe 61. The outward main pipe on-off valve 34 is configured to be able to open and close the second piping path P2 and the outward main pipe 61. The return main pipe on-off valve 35 is disposed in the branching unit 10 at a connection point between the second piping path P2 and the return main pipe 62. The return main pipe on-off valve 35 is configured to be able to open and close the second piping path P2 and the return main pipe 62.

[0031] The outward main pipe opening / closing valve 34 closes the second pipe path P2, and the return main pipe opening / closing valve 35 closes the second pipe path P2, so that the second pipe path P2 becomes a closed circuit.

[0032] In the first heat exchanger 12, heat is exchanged between the refrigerant flowing through the first refrigerant piping path R1 and the heat medium flowing through the first piping path P1.

[0033] In the second heat exchanger 22, heat is exchanged between the refrigerant flowing through the first refrigerant piping path R1 and the heat medium flowing through the second piping path P2.

[0034] At least one boiler 80 is configured to heat the heat medium flowing through the first piping path P1 and the second piping path P2. The boiler 80 is, for example, a combustion boiler. The boiler 80 is disposed outside the air-conditioned space. The boiler 80 is disposed, for example, in a machine room of a building or on an outer wall of a house.

[0035] At least one branching unit 10 has a flow rate adjustment valve 33 disposed therein and in the second piping path P2. The flow rate adjustment valve 33 opens and closes the second piping path P2. The flow rate adjustment valve 33 is connected between the branch point of the second piping path P2 with the outgoing main piping 61 and the junction point with the return main piping 62.

[0036] The outdoor unit 60 has a geothermal heat exchanger 70 disposed therein. The geothermal heat exchanger 70 and at least one branch unit 10 are connected via an outgoing main pipe 61 and a return main pipe 62.

[0037] One end of the outgoing main pipe 61 is connected to one end of the underground heat exchanger 70. The other end of the outgoing main pipe 61 is connected to the second piping path P2. In this embodiment, the other end of the outgoing main pipe 61 is connected between the second heat exchanger 22 and the second branch header 23 of the second piping path P2. In other words, the other end of the outgoing main pipe 61 is connected to a pipe that connects the second heat exchanger 22 and the second branch header 23 of the second piping path P2.

[0038] One end of the return main piping 62 is connected to the other end of the underground heat exchanger 70. The other end of the return main piping 62 is connected to the second piping path P2. In this embodiment, the other end of the return main piping 62 is connected between the second heat exchanger 22 and the second branch header 23 of the second piping path P2. In other words, the other end of the return main piping 62 is connected to a pipe that connects the second heat exchanger 22 and the second branch header 23 of the second piping path P2.

[0039] The capacity of the second pump 21 is greater than the capacity of the first pump 11. <Operation of the Air Conditioner> The air conditioner 100 performs full heating operation, heating-dominant operation, or cooling-dominant operation, depending on the operation mode of the multiple indoor units 50a, 50b. When all of the multiple operating indoor units 50a, 50b are in heating operation mode, the air conditioner 100 performs full heating operation. There may be a mixture of heating and cooling operation modes among the multiple operating indoor units 50a, 50b. Then, when the total air conditioning load of the indoor units in heating operation mode is greater than the total air conditioning load of the indoor units in cooling operation mode, the air conditioner 100 performs heating-dominant operation. Furthermore, when the total air conditioning load of the indoor units in cooling operation mode is greater than the total air conditioning load of the indoor units in heating operation mode, the air conditioner 100 performs cooling-dominant operation.

[0040] In heating operation, the temperature of the heat medium flowing through each of the multiple indoor units 50a, 50b when at least one boiler 80 is operating is higher than the temperature of the heat medium flowing through each of the multiple indoor units 50a, 50b when at least one boiler 80 is not operating. For example, the temperature of the heat medium flowing through each of the multiple indoor units 50a, 50b is measured by a temperature sensor provided in each of the multiple indoor units 50a, 50b.

[0041] <Heating only operation> The heating only operation of the air conditioner 100 will be described with reference to Fig. 2. As shown in Fig. 2, when the multiple indoor units 50a, 50b are all operating in the heating operation mode, the air conditioner 100 performs heating only operation. The multiple first outward branch pipe on-off valves 14a, 14b, 14c, the multiple first return branch pipe on-off valves 15a, 15b, 15c, and the second bypass valve 27 are opened, and the multiple second outward branch pipe on-off valves 24a, 24b, 24c, the multiple second return branch pipe on-off valves 25a, 25b, 25c, the first bypass valve 17, and the flow rate adjustment valve 33 are closed. This forms a hot water circuit that passes through the first pump 11, the first heat exchanger 12, the first branch header 13, the first outward branch pipe on / off valves 14a, 14b, and 14c, the outward branch pipes 51a, 51b, and 51c, the indoor heat exchangers 53a and 53b, the boiler 80, the return branch pipes 52a, 52b, and 52c, the first return branch pipe on / off valves 15a, 15b, and 15c, and the first junction header 16, and leads back to the first pump 11. In addition, a cold water circuit that passes through the second pump 21, the second heat exchanger 22, the outward main pipe 61, the underground heat exchanger 70, the return main pipe 62, the second branch header 23, the second bypass valve 27, and the second junction header 26, and leads back to the second pump 21.

[0042] In the refrigeration cycle, a refrigerant circuit is formed in which the refrigerant passes through the first compressor 31, the first four-way valve 18, the first heat exchanger 12, the first expansion valve 32, the second heat exchanger 22, the first four-way valve 18, and returns to the first compressor 31. At this time, the first heat exchanger 12 functions as a condenser, and the second heat exchanger 22 functions as an evaporator.

[0043] First, the operation of the refrigeration cycle will be described. The single-phase gas refrigerant discharged from the first compressor 31 flows into the first heat exchanger 12 via the first four-way valve 18, where it condenses into a single-phase liquid refrigerant by exchanging heat with the heat medium of the hot water circuit flowing through the first heat exchanger 12. The single-phase liquid refrigerant flowing out of the first heat exchanger 12 flows into the first expansion valve 32, where it is decompressed and expanded into a two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant flows into the second heat exchanger 22, where it evaporates into a single-phase gas refrigerant by exchanging heat with the heat medium of the chilled water circuit flowing through the second heat exchanger 22. The single-phase gas refrigerant flowing out of the second heat exchanger 22 is drawn back into the first compressor 31 and circulates through the refrigerant circuit.

[0044] Next, the operation of the hot water circuit will be described. The heat medium circulating through the hot water circuit is water or antifreeze. The heat medium flowing out of the first pump 11 is heated by heat exchange with the refrigerant in the first heat exchanger 12, and flows through the first branch header 13, the first branch pipe on-off valves 14a, 14b, and 14c, and the branch pipes 51a, 51b, and 51c into the indoor heat exchangers 53a, 53b in the indoor units 50a, 50b and the boiler 80. When the indoor units 50a, 50b are operating, the indoor fans 54a, 54b are also operating, and the heat medium heats the indoor air blown by the indoor fans 54a, 54b in the indoor heat exchangers 53a, 53b. The heat medium, whose temperature has been reduced by heat exchange with the indoor air, flows into the first pump 11 via multiple return branch pipes 52a, 52b, multiple first return branch pipe opening / closing valves 15a, 15b, and the first junction header 16, and circulates through the hot water circuit.

[0045] Finally, the operation of the chilled water circuit will be described. The heat medium circulating through the chilled water circuit is water or antifreeze. The heat medium flowing out of the second pump 21 is cooled by exchanging heat with a refrigerant in the second heat exchanger 22, and then passes through the outbound main pipe 61 to the underground heat exchanger 70, where it absorbs heat from the ground. The heat medium, whose temperature has increased by absorbing heat from the ground, flows through the inbound main pipe 62 into the second piping path P2 in the branching unit 10, passes through the second branch header 23, the second bypass valve 27, and the second merging header 26, and flows into the second pump 21, where it circulates through the chilled water circuit.

[0046] The refrigeration cycle in the branch unit 10 generates the heat required by the indoor units 50a, 50b during heating operation. The hot water circuit supplies high-temperature heat medium to the indoor units 50a, 50b via the first heat exchanger 12. The cold exhaust heat generated during refrigeration cycle operation is transferred to a low-temperature heat medium via the second heat exchanger 22, and is then discharged from the underground heat exchanger 70 of the outdoor unit 60 via the cold water circuit.

[0047] <Heating-dominated operation> Heating-dominated operation of the air conditioner 100 will be described with reference to Fig. 3. As shown in Fig. 3, when the indoor unit 50a is operating in the heating operation mode and the indoor unit 50b is operating in the cooling operation mode, the air conditioner 100 performs heating-dominated operation. In heating-dominated operation, the plurality of first outward branch pipe on-off valves 14a, 14c, the plurality of first return branch pipe on-off valves 15a, 15c, the second outward branch pipe on-off valve 24b, the second return branch pipe on-off valve 25b, and the second bypass valve 27 are opened, and the first outward branch pipe on-off valve 14b, the first return branch pipe on-off valve 15b, the first bypass valve 17, the plurality of second outward branch pipe on-off valves 24a, 24c, the plurality of second return branch pipe on-off valves 25a, 25c, and the flow rate adjustment valve 33 are closed. This forms a hot water circuit that passes through the first pump 11, the first heat exchanger 12, the first branch header 13, multiple first outward branch pipe opening / closing valves 14a, 14c, multiple outward branch pipes 51a, 51c, the indoor heat exchanger 53a or the boiler 80, multiple return branch pipes 52a, 52c, multiple first return branch pipe opening / closing valves 15a, 15c, the first merging header 16, and leads back to the first pump 11. In addition, a cold water circuit is formed that passes through the second pump 21, the second heat exchanger 22, the main outbound pipe 61, the underground heat exchanger 70, the main inbound pipe 62, the second branch header 23, the second outbound branch pipe opening / closing valve 24b, the outbound branch pipe 51b, the indoor heat exchanger 53b, the inbound branch pipe 52b, and the second inbound branch pipe opening / closing valve 25b, or from the second branch header 23 via the second bypass valve 27, passes through the second confluence header 26, and returns to the second pump 21.

[0048] The operation of the refrigeration cycle is the same as in heating only operation, and the operation of the hot water circuit is also the same as in heating only operation.

[0049] Next, the operation of the chilled water circuit will be described. The heat medium that flows out of the second pump 21 flows into the second heat exchanger 22 and is cooled by exchanging heat with the refrigerant. The heat medium, whose temperature has been reduced by exchanging heat with the refrigerant, travels through the outward main pipe 61 to the underground heat exchanger 70 and absorbs heat from the ground. The heat medium, whose temperature has increased by absorbing heat from the ground, flows through the return main pipe 62 into the second piping path P2 in the branch unit 10, and then flows through the second branch header 23, the second outward branch pipe on-off valve 24b, and the outward branch pipe 51b into the indoor heat exchanger 53b in the indoor unit 50b. When the indoor unit 50b is operating, the indoor blower 54b is operating, and the heat medium cools the indoor air blown by the indoor blower 54b in the indoor heat exchanger 53b. The heat medium whose temperature has increased by heat exchange with the indoor air passes through the return branch pipe 52b and the second return branch pipe opening / closing valve 25b and reaches the second junction header 26. The remaining heat medium that is not sent to the indoor heat exchanger 53b passes through the second bypass valve 27 and reaches the second junction header 26, where it merges with the heat medium returning from the indoor heat exchanger 53b, flows into the second pump 21, and circulates through the chilled water circuit.

[0050] The refrigeration cycle in the branch unit 10 generates the heat required by the indoor unit 50a in heating operation. The hot water circuit supplies a high-temperature heat medium to the indoor unit 50a via the first heat exchanger 12. The cold heat generated during refrigeration cycle operation is supplied to the indoor unit 50b in cooling operation by the cold water circuit via the second heat exchanger 22, and the remaining cold exhaust heat is discharged from the underground heat exchanger 70 in the outdoor unit 60 by the cold water circuit.

[0051] Note that, when the amount of cold exhaust heat in the outdoor unit 60 is large, the second bypass valve 27 may be closed. When the amount of cold exhaust heat in the outdoor unit 60 is small, the second bypass valve 27 is opened to reduce the flow rate of the heat medium circulating in the indoor heat exchanger 53b, thereby preventing excessive cooling of the indoor space from the indoor heat exchanger 53b.

[0052] Furthermore, when the amount of cold exhaust heat in the outdoor unit 60 is small, the flow rate adjustment valve 33 may be opened. Generally, the branch unit 10 and the outdoor unit 60 are installed apart from each other, so by opening the flow rate adjustment valve 33, the flow rate of the heat medium circulating in the outgoing main pipe 61 and the return main pipe 62 is reduced, and the power consumption of the second pump 21 caused by the friction loss in the outgoing main pipe 61 and the return main pipe 62 can be reduced.

[0053] <Cooling-dominated operation> Cooling-dominated operation of the air conditioning apparatus 100 will be described with reference to Fig. 4. As shown in Fig. 4, when the indoor unit 50a is operating in the cooling operation mode and the indoor unit 50b is operating in the heating operation mode, the air conditioning apparatus 100 performs cooling-dominated operation. In cooling-dominated operation, the first outflow branch pipe on / off valve 14a, the first return branch pipe on / off valve 15a, the plurality of second outflow branch pipe on / off valves 24b, 24c, the plurality of second return branch pipe on / off valves 25b, 25c, and the second bypass valve 27 are opened, and the plurality of first outflow branch pipe on / off valves 14b, 14c, the plurality of first return branch pipe on / off valves 15b, 15c, the first bypass valve 17, the second outflow branch pipe on / off valve 24a, the second return branch pipe on / off valve 25a, and the flow rate adjustment valve 33 are closed. This forms a chilled water circuit that passes through the first pump 11, the first heat exchanger 12, the first branch header 13, the first outbound branch pipe opening / closing valve 14a, the outbound branch pipe 51a, the indoor heat exchanger 53a, the return branch pipe 52a, the first return branch pipe opening / closing valve 15a, the first merging header 16, and then leads back to the first pump 11. In addition, a hot water circuit is formed that passes through the second pump 21, the second heat exchanger 22, the main outbound pipe 61, the underground heat exchanger 70, the main return pipe 62, the second branch header 23, multiple second outbound branch pipe opening / closing valves 24b, 24c, multiple outbound branch pipes 51b, 51c, the indoor heat exchanger 53b or the boiler 80, multiple return branch pipes 52b, 52c, multiple second return branch pipe opening / closing valves 25b, 25c, or from the second branch header 23 via the second bypass valve 27, passes through the second confluence header 26, and returns to the second pump 21.

[0054] In the refrigeration cycle, a refrigerant circuit is formed in which the refrigerant passes through the first compressor 31, the first four-way valve 18, the second heat exchanger 22, the first expansion valve 32, the first heat exchanger 12, the first four-way valve 18, and returns to the first compressor 31. At this time, the second heat exchanger 22 functions as a condenser, and the first heat exchanger 12 functions as an evaporator.

[0055] First, the operation of the refrigeration cycle will be described. The single-phase gas refrigerant discharged from the first compressor 31 flows into the second heat exchanger 22 via the first four-way valve 18, where it condenses into a single-phase liquid refrigerant by exchanging heat with the heat medium of the hot water circuit flowing in the second heat exchanger 22. The single-phase liquid refrigerant flowing out of the second heat exchanger 22 flows into the first expansion valve 32, where it is decompressed and expanded into a two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant flows into the first heat exchanger 12, where it evaporates into a single-phase gas refrigerant by exchanging heat with the heat medium of the chilled water circuit flowing in the first heat exchanger 12. The single-phase gas refrigerant flowing out of the first heat exchanger 12 is drawn back into the first compressor 31 and circulates through the refrigerant circuit.

[0056] Next, the operation of the chilled water circuit will be described. The heat medium circulating through the chilled water circuit is water or antifreeze. The heat medium flowing out of the first pump 11 is cooled by exchanging heat with the refrigerant in the first heat exchanger 12, and then flows into the indoor heat exchanger 53a in the indoor unit 50a via the first branch header 13, the first outward branch pipe on-off valve 14a, and the outward branch pipe 51a. When the indoor unit 50a is operating, the indoor blower 54a operates, and the heat medium cools the indoor air blown by the indoor blower 54a in the indoor heat exchanger 53a. The heat medium, whose temperature has increased by heat exchange with the indoor air, flows into the first pump 11 via the return branch pipe 52a, the first return branch pipe on-off valve 15a, and the first junction header 16, and circulates through the chilled water circuit.

[0057] Next, the operation of the hot water circuit will be described. The heat medium that flows out of the second pump 21 flows into the second heat exchanger 22 and is heated by exchanging heat with the refrigerant. The heat medium, whose temperature has increased by exchanging heat with the refrigerant, travels through the outgoing main pipe 61 to the underground heat exchanger 70 and dissipates heat into the ground. The heat medium, whose temperature has decreased by dissipating heat into the ground, flows through the return main pipe 62 into the second piping path P2 in the branching unit 10, and then flows through the second branch header 23, the second outgoing branch pipe on-off valve 24b, and the outgoing branch pipe 51b into the indoor heat exchanger 53b in the indoor unit 50b. When the indoor unit 50b is operating, the indoor blower 54b is operating, and the heat medium heats the indoor air blown by the indoor blower 54b in the indoor heat exchanger 53b. The heat medium, whose temperature has been reduced by heat exchange with the indoor air, passes through the return branch pipe 52b and the second return branch pipe opening / closing valve 25b and reaches the second junction header 26. The remaining heat medium that is not sent to the indoor heat exchanger 53b passes through the second bypass valve 27 and reaches the second junction header 26, where it merges with the heat medium returning from the indoor heat exchanger 53c, flows into the first pump 11, and circulates through the hot water circuit.

[0058] The refrigeration cycle in the branch unit 10 generates cold heat required by the indoor units 50a in cooling operation. The chilled water circuit supplies low-temperature heat medium to the indoor units 50a via the first heat exchanger 12. The hot water circuit supplies the hot heat generated during refrigeration cycle operation to the indoor units 50b in heating operation via the second heat exchanger 22, and the remaining hot exhaust heat is exhausted from the underground heat exchanger 70 in the outdoor unit 60 by the hot water circuit.

[0059] Note that the second bypass valve 27 may be closed when the amount of hot exhaust heat in the outdoor unit 60 is large. When the amount of hot exhaust heat in the outdoor unit 60 is small, the second bypass valve 27 is opened to reduce the flow rate of the heat medium circulating in the indoor heat exchanger 53b, thereby preventing excessive hot exhaust heat from the indoor heat exchanger 53b to the indoor space.

[0060] Furthermore, when the amount of hot exhaust heat in the outdoor unit 60 is small, the flow rate adjustment valve 33 may be opened. Generally, the branch unit 10 and the outdoor unit 60 are installed apart from each other, so by opening the flow rate adjustment valve 33, the flow rate of the heat medium circulating through the outgoing main pipe 61 and the return main pipe 62 is reduced, and the power consumption of the second pump 21 caused by the friction loss in the outgoing main pipe 61 and the return main pipe 62 can be reduced.

[0061] <Effects> In the air conditioning apparatus 100 according to Embodiment 1, the branching unit 10 and each of the indoor units 50a, 50b are connected by a plurality of outward branch pipes 51a, 51b and a plurality of return branch pipes 52a, 52b, and a first refrigerant piping path R1 is arranged within the branching unit 10. As a result, the refrigerant flows only within the branching unit 10. This allows for a reduction in the amount of refrigerant charged compared to when the refrigerant flows not only to the branching unit 10 but also to the indoor units 50a, 50b and the outdoor unit 60. Reducing the amount of refrigerant charged reduces refrigerant costs. Furthermore, reducing the amount of refrigerant charged reduces the impact of global warming caused by the refrigerant.

[0062] Furthermore, when heating capacity is insufficient, the boiler 80 is started to heat the heat medium, thereby supplementing the heating capacity. For example, when heating capacity is insufficient in cold regions, the heating capacity can be supplemented by supplying heat. Furthermore, when the outdoor unit fails, the heating capacity can be supplemented by supplying heat.

[0063] In the air conditioning apparatus 100 according to Embodiment 1, the flow rate adjustment valve 33 is connected to the second piping path P2 between the branch point with the outbound main piping 61 and the junction point with the return main piping 62. Therefore, by opening the flow rate adjustment valve 33, the flow rate of the heat medium circulating through the outbound main piping 61 and the return main piping 62 can be reduced, and the power consumption of the second pump 21 caused by friction loss within the outbound main piping 61 and the return main piping 62 can be reduced.

[0064] In the air conditioning apparatus 100 according to Embodiment 1, the outdoor unit 60 has a geothermal heat exchanger 70 disposed within the outdoor unit 60. Therefore, the excess heat of the heating capacity and cooling capacity of the refrigeration cycle relative to the heating capacity and cooling capacity of the multiple indoor units 50a, 50b can be adjusted by heat exchange in the geothermal heat exchanger 70, and the heating capacity and cooling capacity of the multiple indoor units 50a, 50b can be adjusted so that they are neither excessive nor insufficient.

[0065] Furthermore, a minimum temperature must be set for the heat medium (water or antifreeze) flowing through the second piping path P2 to prevent freezing and suppress an increase in viscosity. When the outdoor temperature is below freezing, for example, it is difficult to extract heat from the outdoor air during full heating operation or heating-dominated operation. Compared to the outdoor air temperature, underground temperatures are generally stable throughout the year, ranging from 15°C to 25°C. Therefore, the geothermal heat exchanger 70 facilitates the extraction of heat from the ground, enabling stable full heating operation or heating-dominated operation.

[0066] In the air conditioning apparatus 100 according to Embodiment 1, during heating operation, the temperature of the heat medium flowing through each of the indoor units 50a, 50b when at least one boiler 80 is operating is higher than the temperature of the heat medium flowing through each of the indoor units 50a, 50b when at least one boiler 80 is not operating. Therefore, when the boiler 80 is operating, the hot water flow rate can be reduced by increasing the temperature of the hot water delivered to the indoor units 50a, 50b, thereby reducing the power consumption of the first pump 11 and the second pump 21. Hot water at 70°C to 90°C can easily be obtained from the combustion boiler 80, so the amount of water circulated can be reduced by delivering high-temperature water.

[0067] The air conditioning apparatus 100 according to the first embodiment can switch between all heating operation, heating-dominated operation, and cooling-dominated operation according to the settings of the cooling operation mode and heating operation mode of each of the multiple indoor units 50a, 50b, using the hot and cold energy generated by the refrigeration cycle provided in the branch unit 10. For example, in an air conditioning system for a large building, while indoor units located in general living rooms are set to heating, indoor units located in rooms that generate a large amount of heat, such as a computer room or a kitchen, may be set to cooling. The air conditioning apparatus 100 according to the first embodiment is suitable for such air conditioning systems.

[0068] In the air conditioning apparatus 100 according to the first embodiment, the capacity of the second pump 21 is larger than the capacity of the first pump 11. By increasing the capacity of the second pump 21 of the second piping path P2 connected to the outdoor unit 60, it becomes easier to supply the heat medium to the outdoor unit 60 by the second pump 21.

[0069] In the air conditioning apparatus 100 according to Embodiment 1, the outward main pipe on / off valve 34 is disposed within the branching unit 10 at a connection point between the second piping path P2 and the outward main pipe 61. The return main pipe on / off valve 35 is disposed within the branching unit 10 at a connection point between the second piping path P2 and the return main pipe 62. Therefore, by closing the outward main pipe on / off valve 34 and the return main pipe on / off valve 35, the second piping path P2 circulated by the second pump 21 can be formed by the branching unit 10 and the multiple indoor units 50a, 50b.

[0070] If the branch unit 10 and the outdoor unit 60 cannot be installed at the same time, or if there is a concern about water leakage in the outbound main piping 61 and the inbound main piping 62 connecting the branch unit 10 and the outdoor unit 60, a trial run for water leakage and water circulation can be carried out using only the branch unit 10 and multiple indoor units 50a, 50b.

[0071] Second Embodiment Unless otherwise specified, the air conditioning apparatus 100 according to the second embodiment has the same configuration, operation, and effects as the air conditioning apparatus 100 according to the first embodiment.

[0072] The configuration of the air conditioning apparatus 100 according to Embodiment 2 will be described with reference to Fig. 5. As shown in Fig. 5, in the air conditioning apparatus 100 according to Embodiment 2, the outdoor unit 60 has an outdoor unit 40.

[0073] In the air conditioning apparatus 100 according to the second embodiment, the outdoor unit 60 has an outdoor unit 40 arranged therein.

[0074] The outdoor unit 40 has a second compressor 41, a second four-way valve 48, a second expansion valve 42, a third heat exchanger 43, and a fourth heat exchanger 44 arranged therein. The outdoor unit 40 also has an outdoor blower 45 arranged therein.

[0075] The second compressor 41, the second four-way valve 48, the third heat exchanger 43, the second expansion valve 42, and the fourth heat exchanger 44 constitute a second refrigerant piping path R2 that is connected so that the refrigerant flows through them.

[0076] The outdoor unit 40 and at least one branch unit 10 are connected via an outgoing main pipe 61 and an incoming main pipe 62 .

[0077] The second four-way valve 48 is configured to switch between flowing the refrigerant through the second compressor 41, the second four-way valve 48, the third heat exchanger 43, the second expansion valve 42, the fourth heat exchanger 44, and the second four-way valve 48 in that order, or through the second compressor 41, the second four-way valve 48, the fourth heat exchanger 44, the second expansion valve 42, the third heat exchanger 43, and the second four-way valve 48 in that order.

[0078] One end of the outgoing main pipe 61 is connected to one end of the third heat exchanger 43. The other end of the outgoing main pipe 61 is connected to a portion of the second piping path P2 between the second heat exchanger 22 and the second branch header 23. One end of the return main pipe 62 is connected to the other end of the third heat exchanger 43. The other end of the return main pipe 62 is connected to a portion of the second piping path P2 between the second heat exchanger 22 and the second branch header 23.

[0079] The suction volume of the second compressor 41 in the outdoor unit 40 is larger than the suction volume of the first compressor 31 in the branching unit 10 .

[0080] <Operation of Air Conditioner> The air conditioner 100 performs full heating operation, heating-dominated operation, or cooling-dominated operation depending on the operation modes of the multiple indoor units 50a, 50b.

[0081] 6 to 8, in the air conditioning apparatus 100 according to the second embodiment, the outdoor unit 40 is the main heat generator, and the branch unit 10 generates air conditioning capacity corresponding to the cooling capacity during heating-dominated operation and the heating capacity during cooling-dominated operation.

[0082] As shown in FIG. 6, when the indoor units 50a, 50b in operation are all in the heating operation mode, the air conditioner 100 performs full heating operation.

[0083] As shown in Figure 7, when the indoor units 50a, 50b in operation are operating in a mixture of heating and cooling operation modes, and the total air conditioning load of the indoor units in heating operation mode is greater than the total air conditioning load of the indoor units in cooling operation mode, the air conditioning apparatus 100 performs heating-dominant operation.

[0084] As shown in Figure 8, when the indoor units 50a, 50b in operation are operating in a mixture of heating and cooling operation modes, and the total air conditioning load of the indoor units in cooling operation mode is greater than the total air conditioning load of the indoor units in heating operation mode, the air conditioning apparatus 100 will perform cooling-dominated operation.

[0085] Next, we will explain the effects of the air conditioning apparatus 100 pertaining to Embodiment 2. In the air conditioning apparatus 100 pertaining to Embodiment 2, the outdoor unit 60 has an outdoor unit 40 arranged within the outdoor unit 60. By installing a refrigeration cycle in the outdoor unit 40, it is possible to adjust the heating capacity and cooling capacity of the multiple indoor units 50a, 50b just enough, without having to perform underground construction work as with a geothermal heat exchanger.

[0086] Furthermore, during heating operation at low outdoor temperatures (for example, outdoor temperatures below 7°C), if the outdoor unit 40 cannot continue heating operation due to defrosting of the outdoor heat exchanger, the heating and cooling operation of the multiple indoor units 50a, 50b can be continued using the refrigeration cycle in the boiler 80 and branch unit 10.

[0087] In the air conditioning apparatus 100 according to embodiment 1, when the air conditioning apparatus 100 is in full heating operation, heating-dominated operation, or cooling-dominated operation, all of the heating and cooling capacities of the multiple indoor units 50a, 50b must be generated in the refrigeration cycle within the branch unit 10.

[0088] In the air conditioning apparatus 100 according to the second embodiment, the outdoor unit 60 has an outdoor unit 40. Therefore, the heating capacity during full heating operation of the air conditioning apparatus 100 can be generated in the refrigeration cycle within the outdoor unit 40. Therefore, the refrigeration cycle within the branch unit 10 can be made smaller.

[0089] By miniaturizing the refrigeration cycle within the branching unit 10, the installation space, mounting frame, and cost required for the refrigeration cycle of the branching unit 10 can be reduced, the vibration and noise caused mainly by the first compressor 31 can be reduced, and the amount of refrigerant charged within the branching unit 10 can also be reduced.

[0090] In the air conditioning apparatus 100 according to the second embodiment, the suction volume of the second compressor 41 in the outdoor unit 40 is larger than the suction volume of the first compressor 31 in the branching unit 10. This makes it possible to reduce the installation space, frame, and cost for the refrigeration cycle in the branching unit 10, as well as reduce vibration and noise caused by the first compressor 31 and the amount of refrigerant charged in the branching unit 10.

[0091] Third Embodiment Unless otherwise specified, the air conditioning apparatus 100 according to the third embodiment has the same configuration, operation, and effects as the air conditioning apparatus 100 according to the second embodiment.

[0092] The configuration of an air conditioning apparatus 100 according to embodiment 3 will be described with reference to Fig. 9 . As shown in Fig. 9 , in the air conditioning apparatus 100 according to embodiment 3, at least one branch unit 10 includes a plurality of branch units 10a, 10b, and 10c. The air conditioning apparatus 100 includes a plurality of branch units 10 (10a, 10b, and 10c), outward main pipes 61 (61a, 61b, and 61c), and return main pipes 62 (62a, 62b, and 62c). In this embodiment, the air conditioning apparatus 100 includes three branch units 10a, 10b, and 10c. Each of the plurality of branch units 10a, 10b, and 10c is connected to the outdoor unit 40 of the outdoor unit 60.

[0093] At least one boiler 80 is connected to at least one branch unit 10a among the plurality of branch units 10. The branch unit 10a is connected to a plurality of indoor units 50a, 50b and one boiler 80. The plurality of branch units 10b, 10c are each connected to a plurality of indoor units 50a, 50b, 50c. In other words, the plurality of branch units 10b, 10c are not directly connected to the boiler 80.

[0094] The indoor units 50c connected to each of the branch units 10b, 10c have an indoor heat exchanger 53c arranged therein. The indoor units 50c connected to each of the branch units 10b, 10c have an indoor blower 54c arranged therein.

[0095] The other end of the outward branch pipe 51c is connected to one end of the indoor heat exchanger 53c. The other end of the return branch pipe 52c is connected to the other end of the indoor heat exchanger 53c.

[0096] The operation of the air conditioning apparatus 100 according to the third embodiment is similar to the operation of the air conditioning apparatus 100 according to the second embodiment.

[0097] Next, a description will be given of the operation and effect of the air conditioning apparatus 100 according to embodiment 3. In the air conditioning apparatus 100 according to embodiment 3, at least one boiler 80 is connected to at least one branch unit 10a out of the plurality of branch units 10. Therefore, even in the event of a failure of the outdoor unit 40, heat can be supplied from the boiler 80 via the outgoing main pipe 61 and the return main pipe 62 to the branch units 10b and 10c to which the boiler 80 is not connected.

[0098] The air conditioning apparatus 100 according to the third embodiment includes a plurality of branch units 10a, 10b, and 10c. Therefore, each of the plurality of branch units 10a, 10b, and 10c can be placed on each floor of a building or in different locations on a single floor. This allows for greater flexibility in piping.

[0099] Embodiment 4 Unless otherwise specified, the air conditioning apparatus 100 according to embodiment 4 has the same configuration, operation, and effects as the air conditioning apparatus 100 according to embodiment 3.

[0100] The configuration of an air conditioning apparatus 100 according to embodiment 4 will be described with reference to Fig. 10. As shown in Fig. 10, at least one branch unit 10 includes a plurality of branch units 10a, 10b, and 10c. At least one boiler 80 includes a plurality of boilers 80a, 80b, and 80c.

[0101] A plurality of boilers 80 (80a, 80b, 80c) are connected to each of the plurality of branch units 10 (10a, 10b, 10c). Each of the plurality of branch units 10a, 10b, 10c is connected to a plurality of indoor units 50a, 50b and one boiler 80.

[0102] The operation of the air conditioning apparatus 100 according to the fourth embodiment is similar to the operation of the air conditioning apparatus 100 according to the third embodiment.

[0103] Next, the effects of the air conditioning apparatus 100 according to embodiment 4 will be described. In the air conditioning apparatus 100 according to embodiment 4, a plurality of boilers 80 are connected to each of the plurality of branch units 10a, 10b, and 10c. Therefore, heat can be provided from each of the plurality of boilers 80 to each of the plurality of branch units 10a, 10b, and 10c. Therefore, heat can be provided more efficiently than when a boiler 80 is connected to only one of the plurality of branch units. Furthermore, if one of the plurality of boilers 80 fails, heat can be provided by the other boilers 80.

[0104] Furthermore, the size of the boiler 80 selected can be optimized depending on the number and capacity of the indoor units 50a, 50b connected to each of the multiple branch units 10a, 10b, 10c. Furthermore, when heating operation is performed using the boiler 80 as a heat source without operating the outdoor unit 40 due to a malfunction, power outage, or the like, heat is not transported between the multiple branch units 10a, 10b, 10c, so the power consumption of the second pump 21 and the heat radiation loss in the outbound main piping 61 and the return main piping 62 can be reduced. When the water temperature is high, the difference with the outside air temperature increases, so the effect of reducing heat radiation loss is greater when high-temperature water is supplied.

[0105] The above-described embodiments can be combined as appropriate. The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0106] 10 Branch unit, 11 First pump, 12 First heat exchanger, 13 First branch header, 14a, 14b, 14c First forward branch pipe on / off valve, 15a, 15b, 15c First return branch pipe on / off valve, 16 First merging header, 17 First bypass valve, 18 First four-way valve, 21 Second pump, 22 Second heat exchanger, 23 Second branch header, 24a, 24b, 24c Second forward branch pipe on / off valve, 25a, 25b, 25c Second return branch pipe on / off valve, 26 Second merging header, 27 Second bypass valve, 31 First compressor, 32 First expansion valve, 33 Flow control valve, 34 Forward main pipe on / off valve, 35 Return main pipe on / off valve, 40 Outdoor unit, 41 Second compressor, 42 Second expansion valve, 43 Third heat exchanger, 44 Fourth heat exchanger, 45 Outdoor blower, 48 Second four-way valve, 50a, 50b, 50c Indoor unit, 51a, 51b, 51c Outward branch piping, 52a, 52b, 52c Return branch piping, 53a, 53b, 53c Indoor heat exchanger, 54a, 54b, 54c Indoor blower, 60 Outdoor unit, 61 Outward main piping, 62 Return main piping, 70 Underground heat exchanger, 80 Boiler, 100 Air conditioning device, P1 First piping path, P2 Second piping path, R1 First refrigerant piping path, R2 Second refrigerant piping path.

Claims

1. At least one branch unit, a plurality of indoor units, an outdoor unit, at least one boiler, a plurality of supply branch pipes and a plurality of return branch pipes connecting each of the at least one branch unit, the plurality of indoor units, and the at least one boiler, and a supply main pipe and a return main pipe connecting the at least one branch unit and the outdoor unit, wherein the at least one branch unit has a first branch header, a second branch header, a first confluence header, a second confluence header, a plurality of first supply branch pipe on-off valves, a plurality of second supply branch pipe on-off valves, a plurality of first return branch pipe on-off valves, a plurality of second return branch pipe on-off valves, a first bypass valve, a second bypass valve, a first pump, a second pump, a first heat exchanger, a second heat exchanger, a first compressor, a first expansion valve, and a first four-way valve disposed therein; the plurality of indoor units each have a plurality of indoor heat exchangers respectively disposed therein; one end of each of the plurality of supply branch pipes is connected to the first branch header via each of the plurality of first supply branch pipe on-off valves and is connected to the second branch header via each of the plurality of second supply branch pipe on-off valves; the other end of each of the plurality of supply branch pipes is connected to each of the plurality of indoor heat exchangers and one end of the at least one boiler; one end of each of the plurality of return branch pipes is connected to the first confluence header via each of the plurality of first return branch pipe on-off valves and is connected to the second confluence header via each of the plurality of second return branch pipe on-off valves; the other end of each of the plurality of return branch pipes is connected to each of the plurality of indoor heat exchangers and the other end of the at least one boiler; the first branch header and the first confluence header are connected via the first bypass valve; the second branch header and the second confluence header are connected via the second bypass valve; the first confluence header, the first pump, the first heat exchanger, and the first branch header constitute a first piping path connected such that the heat medium flows in this order; the second confluence header, the second pump, the second heat exchanger, and the second branch header constitute a second piping path connected such that the heat medium flows in this order.The first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, and the second heat exchanger constitute a first refrigerant piping path connected so that refrigerant flows therethrough. The first four-way valve is configured to switch the flow of the refrigerant in the order of the first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, the second heat exchanger, and the first four-way valve, or in the order of the first compressor, the first four-way valve, the second heat exchanger, the first expansion valve, the first heat exchanger, and the first four-way valve. One end of the forward main pipe is connected to one end of the outdoor unit. The other end of the forward main pipe is connected to the second piping path. One end of the return main pipe is connected to the other end of the outdoor unit. The other end of the return main pipe is connected to the second piping path. Heat exchange is performed between the refrigerant flowing through the first refrigerant piping path and the heat medium flowing through the first piping path in the first heat exchanger. Heat exchange is performed between the refrigerant flowing through the first refrigerant piping path and the heat medium flowing through the second piping path in the second heat exchanger. An air conditioner.

2. The at least one branch unit has a flow rate adjustment valve disposed within the at least one branch unit and disposed in the second piping path, and the flow rate adjustment valve is connected between a branch point of the second piping path with the forward main pipe and a confluence point with the return main pipe. The air conditioner according to claim 1.

3. The outdoor unit has a ground heat exchanger disposed within the outdoor unit, the ground heat exchanger and the at least one branch unit are connected via the forward main pipe and the return main pipe, one end of the forward main pipe is connected to one end of the ground heat exchanger, the other end of the forward main pipe is connected to the second piping path, one end of the return main pipe is connected to the other end of the ground heat exchanger, and the other end of the return main pipe is connected to the second piping path. The air conditioner according to claim 1 or 2.

4. The outdoor unit has an outdoor machine disposed within the outdoor unit, the outdoor machine has a second compressor, a second four-way valve, a second expansion valve, a third heat exchanger, and a fourth heat exchanger disposed within the outdoor machine, the second compressor, the second four-way valve, the third heat exchanger, the second expansion valve, and the fourth heat exchanger constitute a second refrigerant piping path connected so that refrigerant flows, the outdoor machine and the at least one branch unit are connected via the forward main pipe and the return main pipe, the second four-way valve is configured to switch to flow the refrigerant in the order of the second compressor, the second four-way valve, the third heat exchanger, the second expansion valve, the fourth heat exchanger, the second four-way valve, or in the order of the second compressor, the second four-way valve, the fourth heat exchanger, the second expansion valve, the third heat exchanger, the second four-way valve, one end of the forward main pipe is connected to one end of the third heat exchanger, the other end of the forward main pipe is connected between the second heat exchanger and the second branch header of the second piping path, one end of the return main pipe is connected to the other end of the third heat exchanger, and the other end of the return main pipe is connected between the second heat exchanger and the second branch header of the second piping path. The air conditioner according to claim 1 or 2.

5. The air conditioner according to claim 1 or 2, wherein, in the heating operation, the temperature of the heat medium flowing through each of the plurality of indoor units when the at least one boiler is operating is higher than the temperature of the heat medium flowing through each of the plurality of indoor units when the at least one boiler is not operating.

6. The air conditioner according to claim 1 or 2, wherein the at least one branch unit includes a plurality of branch units, and the at least one boiler is connected to at least one of the plurality of branch units.

7. The air conditioner according to claim 1 or 2, wherein the at least one branch unit includes a plurality of branch units, the at least one boiler includes a plurality of boilers, and each of the plurality of boilers is connected to each of the plurality of branch units.

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