JP2012093062A - Water heating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heating system capable of achieving hot water supply in consideration of the user's intention of energy saving without causing a user to have a sense of incongruity or distrust while starting combustion heating in response to a heat source supply request even if the heat source supply request is simultaneously output for heating during the execution of a non-combustion hot water supply mode.SOLUTION: When a combustion stop switch is turned on (YES in S2), combustion by an auxiliary heat source machine is inhibited, and hot water in a hot water storage tank is discharged and supplied as it is even if its temperature is lower than a set hot water supply temperature (S4). When a heating request (heat source supply request) is simultaneously generated in the midst (YES in S5), a combustion operation of the auxiliary heat source machine is executed to supply the hot water heated to a required temperature as a heat source, and on a hot water supply side, the temperature is controlled to a temperature of hot water supply conducted until that time, namely the lower one of a hot water storage temperature and the set hot water supply temperature by mixing water from a water supply path, and then, the temperature-controlled hot water is supplied.

Description

  The present invention stores natural hot water as heat storage by recovering heat from an external heat source such as solar heat from natural energy, cooling water exhaust heat from a gas engine or fuel cell, or heat from a heat pump refrigerant, and the stored hot water is used as hot water. With regard to the hot water system that is used as a heat source for external heat load, especially when the user is intentionally prohibiting combustion operation and performing hot water supply that is conscious of energy saving, The present invention relates to a technique for avoiding the occurrence of a situation in which the user feels uncomfortable or energy saving is hindered due to the forced combustion operation.

  Conventionally, as a hot water system, a solar priority switch that can be set by the user's selection to use hot water from a solar water heater preferentially for hot water supply is provided, and this solar priority switch is turned on by the user during hot water supply. In some cases, it has been proposed to supply hot water as it is without performing combustion heating by the auxiliary heat source device even if the hot water from the solar water heater is slightly lower than the set hot water supply temperature (see, for example, Patent Document 1). Then, if the hot water from the solar water heater is considerably lower than the set hot water temperature, the auxiliary heat source machine is operated for combustion for the first time, heated to the set hot water temperature, and then hot water is supplied. Thereby, even if the actual hot water supply temperature is slightly lower than the set hot water supply temperature, the user's intention for energy saving is prioritized.

JP 2003-14295 A

  By the way, in a hot water system configured to store heat as hot water storage in a hot water storage tank using an external heat source such as solar heat, in addition to using the hot water for hot water supply, for example, a heat source for heating, a heat source for bathing, etc. It may be used as a heat source for external heat loads. When using it as a heat source for such an external heat load, it is necessary to use a hot water temperature of about 80 ° C., for example. Usually, the hot water in the hot water storage tank is taken out and heated with an auxiliary heat source machine. It comes to supply with.

  However, when using the hot water in the hot water storage tank as a heat source for such an external heat load, even if the user supplies hot water with the intention of energy saving as described above, the heating request is simultaneously made on the way. If it occurs, the result may be contrary to the intention of energy saving, or may cause the user to feel uncomfortable or distrust of the hot water system because the hot water supply temperature fluctuates.

  That is, in the example of FIG. 5, the auxiliary heat source unit 304 is interposed in the hot water supply passages 301, 302, 303 for supplying hot water from the hot water storage tank 300 to a hot water tap (not shown), and hot water supply at a position downstream of the auxiliary heat source unit 304. If the circulation path 305 for circulating and supplying the hot water for heat source is branched from the path 303 to the heat exchanger of the heating circuit, it is considered that a particular inconvenience occurs. That is, it is considered that inconvenience occurs when the hot water discharged from the hot water storage tank for supplying hot water is supplied after passing through the auxiliary heat source unit 304.

  For example, prioritizing the user's intention to save energy, even if the hot water in the hot water storage tank is lower than the set hot water temperature, the hot water taken out from the hot water storage tank remains as it is while the auxiliary heat source device is kept non-combusting. If a heating request is output while the non-combustion hot water supply mode is being executed, the auxiliary heat source machine is burned and even hot water supplied for hot water supply is heated. Become. As a result, the hot water temperature discharged from the hot water tap fluctuates clearly and makes the user feel uncomfortable, etc., or consumes combustion energy up to the amount of hot water, which is contrary to the user's intention of energy saving. Will be invited.

  The present invention has been made in view of such circumstances, and the object thereof is to simultaneously output a heat source supply request to an external heat load such as a heating request during execution of the non-combustion hot water supply mode. However, while starting combustion heating in response to the heat source supply request, a hot water system that can realize hot water supply that does not make the user feel uncomfortable or distrustful and respects the user's intention to save energy Is to provide.

  In order to achieve the above object, in the present invention, a hot water storage tank for storing heat as hot water storage by recovering heat from an external heat source, and a hot water for taking out hot water stored in the hot water storage tank from the hot water storage tank and using it as hot water supply A circuit, an auxiliary heat source unit interposed in the hot water supply circuit, a heat source supply circuit that circulates and supplies a heat source for an external heat load by being branched in the hot water source circuit downstream of the auxiliary heat source unit, a non-combustion hot water supply mode, and Control means having an external heat load control mode as a control mode, and in the external heat load control mode, the auxiliary heat source machine is operated for combustion, and hot water after combustion heating is circulated and supplied to the heat source supply circuit by the operation of the circulation means On the other hand, in the non-combustion hot water supply mode, a temperature configured to discharge hot water in the hot water storage tank to the hot water circuit while maintaining the auxiliary heat source device in non-combustion. And the system to the target, it was decided to include the following specific matters.

  That is, as the control means, when the user selects the execution of the non-combustion hot water supply mode, when the hot water supply request and the heat source supply request for the external heat load are output at the same time, the auxiliary heat source machine is operated for combustion. The hot water heated up to the set temperature in the external heat load control mode is discharged into the hot water circuit, and the hot water temperature in the hot water storage tank or the set hot water temperature is set by mixing clean water at the downstream end of the hot water circuit. The hot water is supplied after adjusting the temperature to the lower one (Claim 1).

  In the case of the present invention, while the execution of the non-combustion hot water supply mode is selected by the user and the non-combustion hot water supply mode is being executed, the external heat load control mode is simultaneously executed to start the combustion operation of the auxiliary heat source machine. Therefore, even if hot water heated to the set temperature in the external heat load control mode is discharged into the hot water supply circuit, for hot water supply, the hot water is mixed by the mixing means and the stored hot water temperature or the set hot water temperature is set. Hot water whose temperature is adjusted (temperature-controlled) to the lower temperature is supplied. For this reason, even if the hot water in the hot water storage tank is heated as it is even if the hot water in the hot water storage tank is lower than the set hot water temperature by the execution of the non-combustion hot water supply mode, The hot water supply temperature remains unchanged and remains the same. This makes the user feel uncomfortable, or causes the user to feel distrust with the hot water system due to a sudden rise in hot water temperature even though the non-combustion hot water supply mode is selected for energy saving. It is possible to reliably avoid the occurrence of. In addition, the hot water temperature is lowered to the lower of either the hot water storage temperature or the set hot water temperature by mixing water with the water mixing means, so the required supply amount for hot water supply is controlled by the external heat load. As a result, the amount of combustion energy consumed for hot water supply is reduced as a result of the amount being smaller than before the modes are executed simultaneously, and energy saving can be achieved accordingly.

  As described above, according to the hot water system of the present invention, the external heat load control mode is simultaneously executed while the execution of the non-combustion hot water supply mode is selected by the user and the non-combustion hot water supply mode is executed. Even if the combustion operation of the auxiliary heat source machine is started, the hot water supply temperature can be maintained the same as before without changing the hot water supply temperature by the non-combustion hot water supply mode. become. This makes the user feel uncomfortable, or causes the user to feel distrust with the hot water system due to a sudden rise in hot water temperature even though the non-combustion hot water supply mode is selected for energy saving. Can be reliably avoided. In addition, the hot water temperature is lowered to the lower one of the stored hot water temperature or the set hot water temperature by mixing with the water mixing means, reducing the combustion energy consumed for hot water supply. As a result, energy can be saved.

It is a mimetic diagram of a hot water system concerning an embodiment of the present invention. It is a flowchart which shows the control content when a heating request | requirement is output during execution of non-combustion hot-water supply mode. FIG. 2 is a diagram corresponding to FIG. 1 for explaining a hot water supply operation in a non-combustion hot water supply mode. FIG. 4 is a diagram corresponding to FIG. 3 for explaining the operation when the heating control mode is added during the non-combustion hot water supply mode. It is a partial explanatory view showing typically an example of a system for explaining a subject of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of a hot water system according to an embodiment of the present invention. In the figure, reference numeral 1 is a collector for collecting solar heat as an external heat source, 2 is a hot water supply circuit for taking out hot water in the hot water storage tank 3 from the top or bottom and supplying it for hot water supply, etc., 4 is tap water from the outside A hot water supply circuit for supplying hot water to the hot water tap 50 using hot water stored in the hot water supply circuit 2 or hot water after auxiliary heating from the auxiliary heat source 6, and 7 for heating hot water from the hot water circuit 2. A heating circuit as an external heat load as a heat source, 9 similarly a bath reheating circuit as another external heat load using hot water from the tapping circuit 2 as a heat source, and 10 a controller for controlling the operation of this hot water system , 11 is a heat collection circuit that utilizes heat collection in the heat collector 1.

  The hot water storage tank 3 is configured in a sealed manner, and is provided with hot water storage temperature sensors (for example, hot water storage temperature sensors 30, 31 at the bottom position and the top position) for detecting the temperature of the hot water at an appropriate place. And the hot water circuit 2 draws hot water from the bottom part 32 of the hot water storage tank 3 by the operation of the top part taking-out circuit part 21 for taking out hot water from the top part 33 of the hot water storage tank 3 and the circulation pump (for example, variable discharge flow rate type) 22 as circulation means. A mixing valve that serves as a three-way switching valve that connects the bottom extraction circuit section 23 to be extracted and the downstream ends of both the top extraction circuit section 21 and the bottom extraction circuit section 23 and the upstream end of the tapping circuit section 24 extending to the auxiliary heat source unit 6. 25. After passing through the auxiliary heat source unit 6, the tapping circuit unit 24 is communicated with the hot water supply processing circuit 5 via a flow rate adjusting valve 28 via a branch point 26 and a branch point 27 described later.

  Reference numeral 61 in FIG. 1 denotes an inlet temperature sensor that detects a hot water temperature (inlet temperature) that enters the auxiliary heat source unit 6, and 62 denotes a heated hot water temperature (outlet temperature) immediately after exiting the outlet of the auxiliary heat source unit 6. ) Is an outlet temperature sensor.

  In the water supply circuit 4, the upstream end of the main water supply channel 41 is connected to an external water pipe or the like, and the downstream end is connected to the bottom extraction circuit unit 23 in the vicinity of the bottom 32 of the hot water storage tank 3 via a check valve 42. Water can be supplied to the bottom 32 of the hot water storage tank 3 or can be supplied to the downstream side of the hot water circuit 2. A mixed water supply passage 44 branched from the upstream side of the main water supply passage 41 via a check valve 43 is connected to a later-described mixed water valve 54 of the hot water supply processing circuit 5 so that water can be supplied. In addition, the code | symbol 46 of FIG. 1 is a water supply temperature sensor which detects the temperature of the water supplied by the water supply circuit 4. FIG.

  The hot water supply processing circuit 5 constitutes the downstream end portion of the hot water supply circuit 2 on the hot water supply side, and is connected so that the upstream end communicates with the downstream end of the hot water supply circuit portion 24 and the downstream end side extends to the hot water tap 50. A hot water supply circuit unit 53, a mixed water valve 54 interposed in the hot water supply circuit unit 53, and a hot water supply flow rate sensor 57 and a hot water supply temperature sensor 55 disposed downstream of the mixed water valve 54. Yes. The mixed water valve 54 mixes (mixed water) the hot water from the upstream side of the hot water supply circuit unit 53 and the water supplied from the mixed water supply channel 44 at a predetermined mixing ratio (mixed water). The temperature is adjusted to a preset hot water supply temperature or a hot water storage temperature described later, and then hot water is supplied to the hot water tap 50. The hot water supply temperature sensor 55 detects the temperature of the hot water to be finally supplied after temperature control and outputs the detected temperature to the controller 10. Based on the output from the hot water supply temperature sensor 55, the water mixing valve The controller 10 performs mixed water control for temperature control by the controller 54.

  The auxiliary heat source unit 6 is constituted by, for example, an instantaneous water heater, and is interposed in the middle of the hot water circuit 2. When the combustion operation is performed according to a command from the controller 10, the hot water flowing in from one side of the hot water circuit 2 is subjected to heat exchange heating by the combustion heat, and the heated hot water is discharged to the other side of the hot water circuit 2, thereby causing the hot water circuit 2. Auxiliary heating of hot water flowing through The auxiliary heat source unit 6 performs predetermined combustion operation control (for example, combustion operation control so that the outlet temperature becomes 80 degrees) by the controller 10 based on the output from the outlet temperature sensor 62 provided on the outlet side. It has become.

  The heating circuit 7 heats the low-temperature heat medium taken out from the expansion tank 71 by the operation of the circulation heating pump 70 by liquid-liquid heat exchange in the heat exchanger 73 located on one side from the branch point 72 to generate high-temperature heat. And a high-temperature heating medium circuit 75 that circulates and supplies this to a high-temperature heating terminal (for example, a bathroom dryer) 74 and a low-temperature heating terminal (for example, floor heating) from the branch point 72 to the other side via a bypass heat valve 76. A low-temperature heat medium circuit 78 that circulates and supplies a low-temperature heat medium to 77, 77,. In addition, a high-temperature bypass circuit 80 that branches from the middle of the high-temperature heat medium circuit 75 and joins to the low-temperature heat medium circuit 78 downstream of the bypass heat valve 76 via the check valve 79 is provided. The high-temperature heat medium heated at 73 can be combined with the low-temperature heat medium supplied via the bypass heat valve 76 to raise the temperature. The heat medium that has been radiated from the low temperature heating terminals 77 and the high temperature heating terminals 74 to a low temperature is returned to the expansion tank 71.

  And as the heating source (heat source for heating) of the liquid-liquid heat exchange in the heat exchanger 73, the hot water heated to the predetermined temperature by the auxiliary heat source unit 6 from the hot water circuit section 24 of the hot water circuit 2 is heat exchanged. Circulatingly supplied to the heat source side of the vessel 73. That is, hot water of a predetermined temperature is supplied to the heat exchanger 73 as a heating heat source through the heat source supply circuit 81 branched from the branch point 26 of the hot water circuit section 24 by opening the on-off valve 81a, and liquid-liquid heat exchange is performed. Accordingly, the hot water whose temperature has been reduced is led out to the bottom take-out circuit portion 23 of the hot water circuit 2 through the on-off valve 81a, and is circulated through the hot water circuit 2 and the auxiliary heat source unit 6.

  The bath reheating circuit 9 operates the reheating pump 91 to circulate the bath water in the bathtub 92 through the recirculation circuit 93 and the heat exchanger 94, and the liquid-liquid in the heat exchanger 94 is circulated. Reheating is performed by heat exchange. To the heat source side of the heat exchanger 94, hot water heated by the auxiliary heat source unit 6 to a predetermined temperature through a heat source supply circuit 95 branched from the branch point 28 of the tap water circuit unit 24 is supplied as a heat source for reheating the bath. It has become so. Then, the hot water whose temperature has decreased due to the liquid-liquid heat exchange passes through the on-off valve 95a and is led out to the bottom take-out circuit section 23 of the hot water circuit 2 in the same manner as the heating circuit 7, and the hot water circuit 2 and the auxiliary heat source machine 6 are It will be circulated after that.

  The heat collection and circulation circuit 11 circulates the heat collection in the heat collector 1 with the heat exchange coil 14 installed in the hot water storage tank 3 to heat and heat the hot water in the hot water storage tank 3 to store the heat. A heat storage circulation circuit 15 and a direct circulation circuit 17 for heat exchange heating of the return hot water of the heating circuit 7 by a liquid-liquid heat exchange type heat exchanger 16 by collecting heat in the heat collector 1, and 15 and 17 are switched by a switching valve 18 so that one of them is operated by the operation of the circulation pump 12. And the heat medium which became low temperature after heat exchange is supplied to the heat collector 1 through the expansion tank 13. The controller 10 includes a heat storage control unit for storing heat as hot water storage using the heat collected by the heat collector 1.

  The operation of each of the circuits 2, 5, 7, 9, 11 is performed by outputting input setting signals and operation signals from the remote controller 101, and detection signals from various temperature sensors 31, 46, 55, 61, 62, etc. Is controlled by the controller 10. For such operation control, the controller 10 includes various control units such as a heating control unit and a reheating control unit as an external heat load control unit in addition to the heat storage control unit and the hot water supply control unit. Here, the remote controller 101 is provided with a combustion stop switch. When the user turns on this combustion stop switch, the hot water in the hot water storage tank 3 is partially extracted while the auxiliary heat source unit 6 is not combusted. From the hot water supply at the set hot water temperature, the hot water is supplied as it is even if the temperature is lower than the set hot water temperature, while the hot water temperature is higher than the set hot water temperature. However, the non-combustion hot water supply mode in which hot water storage is given priority is executed.

  Next, a hot water supply control by the hot water supply control unit, a heating request (a heat source supply request for an external heat load) or a bath renewal request (a heat source supply request for an external heat load) is output during the hot water control and the heating control ( The case where external heat load control mode) and bath reheating control (external heat load control mode) are added will be described. As the hot water supply control, in addition to the normal hot water supply mode, the above-described non-combustion hot water supply mode is provided. Hereinafter, a description will be given with reference to the flowchart of FIG.

  Whether or not there is a hot water supply request, that is, whether or not the hot water tap 50 has been opened is determined by detection by the hot water flow rate sensor 57 (step S1), and when the hot water tap 50 has been opened (YES in step S1), After confirming whether or not the combustion stop switch is ON, the normal hot water supply mode or the non-combustion hot water supply mode is selected based on the result. If the combustion stop switch remains OFF, control is performed so that hot water at the set hot water temperature set by the user in the remote controller 101 is supplied (NO in step S2, step S3).

  In the normal hot water supply mode, if the amount of heat stored in the hot water storage tank 3 is sufficient, specifically, the hot water storage temperature is higher than a predetermined value by comparison with the set hot water temperature set by the user on the remote controller 101 (for example, the set hot water temperature +6 The hot water from the top of the hot water storage tank 3 is taken out from the top take-out circuit part 21 and mixed with the mixed water valve 54 via the hot water circuit part 24 based on the feed water pressure from the water supply circuit 4. Hot water is supplied after adjusting the set hot water temperature. On the other hand, if the amount of heat stored in the hot water storage tank 3 is insufficient, specifically, if the hot water storage temperature is not higher than a predetermined value in comparison with the set hot water supply temperature, the hot water is supplied after being auxiliary heated by the auxiliary heat source unit 6. Will be.

  On the other hand, if the combustion stop switch is turned on in step S2 (YES in step S2), the non-combustion hot water supply mode is executed (step S4). That is, while the combustion of the auxiliary heat source unit 6 is stopped or the auxiliary heat source unit 6 is maintained in the non-combustion state, the mixing valve 25 is switched so that the top extraction circuit unit 21 and the tapping circuit unit 24 communicate with each other. As a result, hot water is supplied from the top of the hot water storage tank 3 through the top take-out circuit unit 21 and the hot water circuit unit 24 based on the supply water pressure from the water supply circuit 4 (the portion where the flow occurs in FIG. 3 is indicated by a thick solid line). Also see the dashed arrow). At this time, if the hot water storage temperature in the hot water storage tank 3 is higher than the set hot water supply temperature, the water from the mixed water supply passage 44 is mixed in the mixed water valve 54 so that the temperature is adjusted to the set hot water supply temperature. It will be.

  In short, in the non-combustion hot water supply mode, hot water having a temperature lower than the hot water storage temperature at that time or the set hot water supply temperature is supplied. Therefore, even if the hot-water storage temperature at that time is lower than the set hot-water supply temperature, this is based on the ON operation of the combustion stop switch by the user and is allowed, and the auxiliary heat source unit 6 is made non-combustible. The user's intention to save energy is given priority. Here, the hot water storage temperature is displayed on the remote controller 101, and the combustion stop switch is turned on based on the user's intention by looking at the hot water storage temperature. For example, if the user has set 40 ° C. as the set hot water supply temperature, even if the current hot water storage temperature is 38 ° C., the combustion stop switch is turned ON by the user to allow it and save energy. A case is assumed.

  When a heating request is output during the execution of the non-combustion hot water supply mode, for example, when the heating switch of the remote control 101 is turned on (YES in step S5), the heating control mode is executed, but the non-combustion described above is performed. Control for maintaining the hot water supply temperature in the hot water supply mode is also executed (step S6). That is, the auxiliary heat source unit 6 is combusted and the open / close valve 81a is opened and hot water heated to a set temperature (for example, 80 ° C.) required as a heating heat source flows from the branch point 26 to the heat source supply circuit 81. Then, the heat exchanger 73 is circulated and supplied to the heat exchanger 73 (the portion where the flow occurs in FIG. On the other hand, since hot water having the same temperature as the temperature to be circulated and supplied to the heat exchanger 73 is supplied to the hot water supply processing circuit 5 through the hot water supply circuit section 24, water from the mixed water supply passage 44 is supplied to the water mixing valve. The temperature is adjusted by mixing with water at 54 so as to maintain the same hot water temperature as the temperature of the hot water supplied so far (in FIG. 4, the portion where the flow occurs is indicated by a thick solid line; see also the broken arrow) ). That is, hot water supply at the lower temperature of the hot water storage temperature or the set hot water supply temperature is continued. In this case, the mixing valve 52 is switched so as to supply hot water from the bottom take-out circuit unit 23 to the tapping circuit unit 24 in place of or together with the top take-out circuit unit 21. Also good.

  By performing such control, even if the heating control mode is additionally executed during execution of the non-combustion hot water supply mode and the auxiliary heat source unit 6 starts combustion, the hot water supply temperature remains the same without changing. This makes the user feel uncomfortable, or makes the user feel distrust of the hot water system due to a sudden rise in hot water temperature even though the combustion stop switch is turned on to save energy It is possible to reliably avoid the occurrence of inconvenience. In addition, since the hot water supply temperature is lowered to the lower one of the stored hot water temperature and the set hot water temperature by mixing the water with the mixed water valve 54, the necessary supply amount for hot water supply is set to the heating control mode. As a result, the amount of combustion energy consumed for hot water supply can be reduced, and energy saving can be achieved.

<Other embodiments>
The present invention is not limited to the above-described embodiments, but includes other various embodiments. That is, although the embodiment has shown the case where solar heat (solar heat collection) is used as an external heat source that is a target of heat recovery that stores hot water in the hot water storage tank 3, a gas engine (engine cooling water exhaust heat), or A heat pump (exhaust heat of the refrigerant) may be used to store heat as hot water storage, and the present invention can be applied even in such a case.

  Furthermore, in the said embodiment, although the heat storage heat exchanger 14 was installed in the hot water storage tank 3, the heat exchanger was installed in the exterior of the hot water storage tank 3, and this heat exchanger is not limited to this. On the other hand, the heat medium in the heat collecting circulation circuit is circulated and supplied to the heat source side, while the hot water in the hot water storage tank 3 is circulated and supplied to the heated side by another circulation pump, so that the hot water in the hot water storage tank is heated by the heat medium. A hot water system configured to be heated by exchange is also included in the present invention.

  In the above embodiment, the case where the heating request is output and the heating control mode is simultaneously executed while the non-combustion hot water supply mode is being executed has been described. The same control is also performed when a bathing request (for example, an ON operation of a chasing switch or an automatic bath switch of the remote controller 101) is output and the bath chasing control mode is executed simultaneously. That is, the auxiliary heat source unit 6 heats up to a set temperature necessary as a heat source temperature for bathing, flows to the hot water circuit unit 24, branches to the heat source supply circuit 95, and circulates it, while the mixed water valve 54 Mix water to adjust the temperature so that the same hot water temperature is maintained. Therefore, the heating circuit 7 and the bath reheating circuit 9 constitute an external heat load, and the heating control mode and the bath reheating control mode constitute an external heat load control mode.

1 Heat collector (external heat source)
2 Hot water circuit 3 Hot water storage tank 6 Auxiliary heat source machine 7 Heating circuit (external heat load)
9 Reheating circuit (external heat load)
10 Controller (control means)
22 Circulation pump (circulation means)
54 Water mixing means 81, 95 Heat source supply circuit

Claims (1)

A hot water storage tank for storing hot water as heat storage by recovering heat from an external heat source, a hot water storage circuit for removing the hot water stored in the hot water storage tank from the hot water storage tank and using it for hot water use, and an auxiliary device provided in the hot water supply circuit A heat source device, a heat source supply circuit that circulates and supplies a heat source for an external heat load that is branched in a hot water supply circuit downstream of the auxiliary heat source device, and a control means that has a non-combustion hot water supply mode and an external heat load control mode as control modes In the external heat load control mode, the auxiliary heat source machine is operated to burn and circulates and supplies hot water after combustion heating to the heat source supply circuit by the operation of a circulation means, while in the non-combustion hot water supply mode, the auxiliary heat source A hot water system configured to discharge hot water in a hot water storage tank to the hot water circuit while maintaining the machine in non-combustion,
When the user selects the execution of the non-combustion hot water supply mode and the control means outputs a hot water supply request and a heat source supply request for an external heat load at the same time, the control means performs the combustion operation of the auxiliary heat source machine. Hot water heated to a set temperature in the external heat load control mode is discharged into the hot water circuit, and hot water is mixed in the water mixing means provided at the downstream end of the hot water circuit to mix hot water in the hot water storage tank. Or it is configured to supply hot water after adjusting the temperature to the lower of the set hot water temperature,
A hot water system characterized by that.