Hot water supply system, control device, control method, program, and recording medium

Abstract

To inhibit great decrease in temperature of hot water caused by switching hot water supply means when, for example, hot water is being supplied at stable temperature.SOLUTION: A hot water supply system (2) includes a hot water storage unit (6), a water heater (10), and a control part (12-1 and 12-2). The hot water storage unit includes a hot water storage tank (24) and a first water control valve (32-1), and supplies heated water (HW) when the first water control valve is open as demanded. The water heater includes a heat source machine (46-1 and 46-2) and a second water control valve (52-1 and 53-1), and supplies heated water when the second water control valve is open as demanded. The control part changes the second water control valve from a closed state to an open state when the water heater satisfies a first condition while the hot water supply system is in a stand-by mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a hot water supply system including a hot water storage unit and a hot water heater, and a control device, control method, program, or recording medium for controlling the hot water supply system. [Background technology]

[0002] Hot water is supplied by various hot water supply means. Hot water supply means using a heat pump heats water by the heat pump. Although hot water supply means using a heat pump have high energy efficiency for heating, they are inferior in the amount of heat provided to water per unit time. Therefore, in hot water supply means using a heat pump, water heated by the heat pump is temporarily stored in a hot water storage tank and supplied as hot water via the hot water storage tank. Regarding hot water supply means using such a heat pump, there is a hot water supply system that prevents hot water shortage by adding an auxiliary hot water supply means using gas or oil (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-349202 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the supply of water to the auxiliary hot water supply means by gas or oil heating is started due to a lack of hot water remaining in the hot water storage tank, cold water supplied from the auxiliary hot water supply means is mixed with the hot water until the auxiliary hot water supply means warms up, causing a temporary large drop in the temperature of the hot water. When hot water at a stable temperature is being supplied, even if the amount of hot water used by the user is constant, if the temperature of the hot water temporarily drops, this causes the user to feel uncomfortable. Patent Document 1 does not disclose or suggest such a problem, and the configuration disclosed in Patent Document 1 cannot solve such a problem.

[0005] Therefore, a first object of the present disclosure is to prevent a large drop in hot water temperature caused by switching of hot water supply means when hot water at a stable temperature is being supplied.

[0006] A second object of the present disclosure is to improve the comfort of hot water supplied from a hot water supply system. [Means for solving the problem]

[0007] In order to achieve the above object, according to a first aspect of the present disclosure, a hot water supply system includes a hot water storage unit, a hot water heater, and a control unit. The hot water storage unit includes a hot water storage tank and a first water control valve, and supplies heated water according to demand when the first water control valve is open. The hot water heater includes a heat source unit and a second water control valve, and supplies heated water according to demand when the second water control valve is open. The control unit changes the second water control valve from closed to open when the hot water heater satisfies a first condition during a standby mode of the hot water supply system.

[0008] In the hot water supply system, when the water heater satisfies the first condition while the hot water supply system is in a standby mode, the control unit may change the first water control valve from open to closed.

[0009] In the hot water supply system, the first condition may be a condition that directly or indirectly represents a temperature state of the hot water heater.

[0010] In the above-mentioned hot water supply system, the first condition may be that the time during which the continuous provision of heated water by the water heater has stopped exceeds a set time, or the first condition may be that the temperature detected by a temperature sensor installed in the outlet pipe of the water heater is below a set temperature.

[0011] In the above hot water supply system, when the water heater satisfies a second condition during operation of the hot water supply system, the control unit may change the second water control valve from closed to open.

[0012] In the above hot water supply system, the hot water heater may be a multi-hot water heater further including another heat source unit and another second water control valve.

[0013] In order to achieve the above-mentioned objective, according to a second aspect of the present disclosure, a control device for controlling a hot water supply system having a hot water storage unit and a hot water heater includes a control unit that changes a water control valve of the hot water heater from closed to open when the hot water supply system is in standby mode and the hot water heater satisfies a first condition.

[0014] In order to achieve the above-mentioned object, according to a third aspect of the present disclosure, a control method for a hot water supply system including a hot water storage unit and a water heater includes a process of opening a first water control valve of the hot water storage unit and closing a second water control valve of the water heater, and a process of changing the second water control valve of the water heater from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system.

[0015] In order to achieve the above-mentioned object, according to a fourth aspect of the present disclosure, a program for controlling a hot water supply system having a hot water storage unit and a water heater causes a computer to realize a function of opening a first water control valve of the hot water storage unit and closing a second water control valve of the water heater, and a function of changing the second water control valve of the water heater from closed to open when the water heater satisfies a first condition during standby mode of the hot water supply system.

[0016] To achieve the above object, according to a fifth aspect of the present disclosure, a recording medium stores a program for controlling a hot water supply system including a hot water storage unit and a hot water heater, the program causing a computer to realize a function of opening a first water control valve of the hot water storage unit and closing a second water control valve of the hot water heater, and a function of changing the second water control valve of the hot water heater from closed to open when the hot water heater satisfies a first condition during a standby mode of the hot water supply system. Effect of the Invention

[0017] According to the present disclosure, the following effects can be obtained.

[0018] (1) During the standby mode of the hot water supply system, the second water control valve of the hot water supply unit is changed from closed to open. Therefore, when water supply or hot water supply is started, the hot water supply unit is preheated. In other words, the hot water supply unit is warmed at the initial stage of water supply or hot water supply. During water supply or hot water supply, the supply source of heated water is switched from the hot water storage unit to the warmed hot water supply unit, so that the drop in the temperature of the heated water is suppressed.

[0019] (2) When the water heater satisfies the first condition, the second water control valve of the water heater is changed from closed to open, thereby avoiding unnecessary preheating of the water heater.

[0020] (3) When the supply source of heated water is switched from the hot water storage unit to the hot water heater, the drop in the temperature of the heated water is suppressed, thereby suppressing discomfort felt by users of hot water. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram showing an example of a hot water supply system according to an embodiment; [Diagram 2] FIG. 2 is a diagram showing an example of a control system of the hot water supply system. [Diagram 3] 13 is a flowchart showing an example of a mode selection process during standby. [Figure 4] 13 is a flowchart illustrating an example of an operation process from a second standby mode. [Diagram 5] FIG. 11 is a sequence diagram showing an example of an operation process from a second standby mode. [Figure 6] FIG. 4 is a diagram showing an example of changes in temperature and flow rate of heated water over time. [Figure 7] FIG. 11 is a diagram showing a comparative example of changes in temperature and flow rate of heated water over time. [Figure 8] FIG. 11 is a diagram showing an example of changes in temperature and flow rate of heated water over time when preheating of a water heater is repeated. [Figure 9] FIG. 2 is a diagram for explaining a form of providing heated water. [Figure 10]13 is a flowchart showing another example of the operation process from the second standby mode. [Figure 11] FIG. 4 is a diagram showing an example of a change in raw heating water temperature over time. [Figure 12] 13 is a flowchart showing another example of the operation process from the second standby mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIG. 1 shows an example of a hot water supply system according to an embodiment.

[0023] The hot water supply system 2 includes a water supply path 4, a hot water storage unit 6, a heat source device 8, a water heater 10, control units 12-1 and 12-2, a remote control device 14, and a hot water supply path 16. The hot water supply system 2 heats the water supply W supplied to the hot water storage unit 6 and the water heater 10 through the water supply path 4 to generate heated water HW, and supplies the heated water HW to the hot water supply path 16. The water supply W is, for example, tap water. The heated water HW may be hot water or water obtained after the hot water is cooled. The hot water storage unit 6, the heat source device 8, and the control unit 12-1 form a first hot water supply device such as a heat pump water heater, and the water heater 10 and the control unit 12-2 form a second hot water supply device such as a gas water heater.

[0024] The water supply path 4 is connected to a hot water storage unit 6, a water heater 10, and, for example, a water pipe.

[0025] The hot water storage unit 6 includes a hot water storage tank 24, a circulation path 26, a water supply pipe 28, a hot water outlet pipe 30, a water control mechanism 32, a flow rate sensor 34, and temperature sensors 36-1, 36-2, ... 36-10. The hot water storage unit 6 supplies hot water stored in the hot water storage tank 24 to the hot water supply path 16 as heated water HW.

[0026] The hot water storage tank 24 stores water, hot water, or water and hot water, and supplies the stored hot water to the hot water outlet pipe 30 as heated water HW. The hot water storage tank 24 has a heat retention function and suppresses a drop in the temperature of the stored hot water. When the hot water storage tank 24 stores water and hot water, the hot water is placed above the water, suppressing convection of the water and hot water. Therefore, a drop in the temperature of the hot water is suppressed.

[0027] Circulation path 26 includes pipes 26-1, 26-2, 26-3, a pump 42, and a switching valve 44. Pipe 26-1 is connected to a lower part of hot water storage tank 24 and heat source unit 8. Pipe 26-2 is connected to heat source unit 8 and an upper part of hot water storage tank 24. Pipe 26-3 is a bypass pipe, and is connected to pipes 26-1 and 26-2. Pump 42 is installed in pipe 26-1, for example.

[0028] The switching valve 44 is installed, for example, at the connection portion between the pipe 26-2 and the pipe 26-3. The switching valve 44 may be installed at the connection portion between the pipe 26-1 and the pipe 26-3. The switching valve 44 switches the flow of water in the circulation path 26. When the pump 42 operates in the first switching state of the switching valve 44, the water in the lower part of the hot water storage tank 24 flows into the upper part of the hot water storage tank 24 through the pipe 26-1, the heat source unit 8, and the pipe 26-2. When the pump 42 operates in the second switching state of the switching valve 44, the water circulates through the pipe 26-1, the heat source unit 8, the pipe 26-2, and the pipe 26-3. Therefore, the water in the lower part of the hot water storage tank 24 is heated to a heating setting temperature such as 80°C by the heat source unit 8, and then returned to the upper part of the hot water storage tank 24.

[0029] The water supply pipe 28 is connected to the water supply path 4 and the lower part of the hot water storage tank 24, and supplies the water W to the lower part of the hot water storage tank 24. The hot water outlet pipe 30 is connected to the hot water supply path 16 and the upper part of the hot water storage tank 24, and supplies the hot water in the upper part of the hot water storage tank 24 as heated water HW to the hot water supply path 16. The hot water outlet pipe 30 may temporarily supply water obtained after the hot water is cooled to the hot water supply path 16 as heated water HW.

[0030] The water control mechanism 32 is installed across the water supply pipe 28 and the hot water outlet pipe 30, and includes a water control valve 32-1, a bypass pipe 32-2, and a bypass valve 32-3. The water control valve 32-1 is a first water control valve, and is installed, for example, on the hot water outlet pipe 30. When the water control valve 32-1 is opened, the water supply W and the heated water HW flow according to demand. When the water control valve 32-1 is closed, the flow of the water supply W and the heated water HW stops. The bypass pipe 32-2 is connected to the water supply pipe 28 and the hot water outlet pipe 30, and supplies the water supply W from the water supply pipe 28 to the hot water outlet pipe 30. The bypass pipe 32-2 is connected to the hot water outlet pipe 30 between the water control valve 32-1 and the hot water storage tank 24. Therefore, when the water control valve 32-1 is closed, the flow of the water supply W in the bypass pipe 32-2 stops. The bypass valve 32-3 is installed, for example, at the connection portion of the bypass pipe 32-2 and the water supply pipe 28, and provides the supply water W to the hot water outlet pipe 30 according to the opening degree of the bypass valve 32-3. The supply water W provided to the hot water outlet pipe 30 mixes with the heated water HW, lowering the temperature of the heated water HW. The opening degree of the bypass valve 32-3 is adjusted so that the temperature of the heated water HW flowing through the hot water outlet pipe 30 becomes, for example, a hot water supply setting temperature. The hot water supply setting temperature is, for example, a temperature set by a user of the hot water supply system 2, and is, for example, 60°C. The water control valve 32-1 may be installed in the water supply pipe 28, and the bypass valve 32-3 may be installed at the connection portion of the bypass pipe 32-2 and the hot water outlet pipe 30 or in the bypass pipe 32-2.

[0031] The flow rate sensor 34 is installed, for example, in the water supply pipe 28 and measures the flow rate of the supply water W flowing through the water supply pipe 28. The flow rate sensor 34 may be installed in the hot water outlet pipe 30 and may measure the flow rate of the heated water HW flowing through the hot water outlet pipe 30.

[0032] The temperature sensor 36-1 is installed, for example, in the hot water outlet pipe 30 between the hot water storage tank 24 and the water control mechanism 32, and measures the temperature of the heated water HW supplied from the hot water storage tank 24. The temperature sensor 36-1 measures the temperature (hereinafter referred to as the "raw heated water temperature") of the heated water HW before the feed water W is mixed (hereinafter referred to as the "raw heated water HW"). The temperature sensor 36-2 is installed, for example, in the hot water outlet pipe 30 between the water control mechanism 32 and the hot water supply path 16, and measures the temperature (hereinafter referred to as the "adjusted heated water temperature") of the heated water HW after the feed water W is mixed (hereinafter referred to as the "adjusted heated water HW"). The temperature sensor 36-2 is installed, for example, near the hot water outlet of the hot water storage unit 6, and measures the adjusted heated water temperature of the adjusted heated water HW near the outlet. The adjusted heated water HW may be heated water HW with which the feed water W is not mixed because the raw heated water temperature is equal to or lower than the hot water supply setting temperature. The temperature sensors 36-3, 36-4, ..., 36-10 are installed in the hot water storage tank 24, the circulation path 26, or the water supply pipe 28, and measure the temperature of the water or hot water at the installation location. The temperature sensors 36-1, 36-2, ..., 36-10 include, for example, thermistors.

[0033] The heat source machine 8 is connected to the circulation path 26 of the hot water storage unit 6. The heat source machine 8 includes a heat source unit such as a heat pump unit, and heats water supplied from the hot water storage unit 6, for example, by a heat pump, and returns the hot water to the hot water storage unit 6. The water supplied from the hot water storage unit 6 is, for example, cold water or hot water, and the hot water is, for example, hot water or high-temperature water. The hot water is stored in a hot water storage tank 24.

[0034] The water heater 10 is connected to the water supply path 4 and the hot water supply path 16. The water heater 10 is, for example, a multi-water heater having a multi-system with heat source units 46-1 and 46-2, and is, for example, a gas water heater that heats water by burning gas. The water heater 10 heats the water supply W from the water supply path 4 to generate heated water HW, and supplies the heated water HW to the hot water supply path 16. The heated water HW may be hot water or water obtained after the hot water is cooled. The water heater 10 has a setting regarding a priority unit (hereinafter referred to as a "priority unit setting"), and either the heat source unit 46-1 or the heat source unit 46-2 is set as the priority unit based on this priority unit setting. The water heater 10 supplies the heated water HW by the priority unit or by multiple heat source units 46-1 and 46-2 according to demand. Water heater 10 includes heat source units 46-1, 46-2, a water supply pipe 48, a hot water outlet pipe 50, water control mechanisms 52, 53, flow rate sensors 54-1, 54-2, and temperature sensors 56-1, 56-2, 58-1, 58-2, 60-1, 60-2.

[0035] The heat source units 46-1, 46-2 are connected to a water supply pipe 48 and a hot water outlet pipe 50, and are connected in parallel to the water supply pipe 48 and the hot water outlet pipe 50. The heat source units 46-1, 46-2 each include a burner 62, a primary heat exchanger 64, and a secondary heat exchanger 66, and generate heated water HW by heating feed water W by combustion of a fuel such as gas G. The heated water HW generated by the heat source units 46-1, 46-2 has a temperature equal to or higher than the hot water supply set temperature.

[0036] The water supply pipe 48 is connected to the water supply path 4 and the heat source units 46-1, 46-2, and supplies water W to the heat source units 46-1, 46-2. The hot water outlet pipe 50 is connected to the hot water supply path 16 and the heat source units 46-1, 46-2, and supplies heated water HW generated by the heat source units 46-1, 46-2 to the hot water supply path 16. The hot water outlet pipe 50 may temporarily supply water obtained after the hot water is cooled to the hot water supply path 16 as heated water HW.

[0037] The water control mechanism 52 is installed across the water supply pipe 48 and hot water outlet pipe 50 on the heat source unit 46-1 side, and the water control mechanism 53 is installed across the water supply pipe 48 and hot water outlet pipe 50 on the heat source unit 46-2 side. The water control mechanism 52 includes a water control valve 52-1, a bypass pipe 52-2, and a bypass valve 52-3. The water control valve 52-1 is a second water control valve, and is installed, for example, on the hot water outlet pipe 50. When the water control valve 52-1 is opened, the water supply W and the heated water HW flow according to demand. When the water control valve 52-1 is closed, the flow of the water supply W and the heated water HW stops. The bypass pipe 52-2 is connected to the water supply pipe 48 and the hot water outlet pipe 50, and supplies the water supply W from the water supply pipe 48 to the hot water outlet pipe 50. The bypass pipe 52-2 is connected to the hot water outlet pipe 50 between the water control valve 52-1 and the heat source unit 46-1. Therefore, when the water control valve 52-1 is closed, the flow of the water supply W in the bypass pipe 52-2 is stopped. The bypass valve 52-3 is installed, for example, at the connection portion of the bypass pipe 52-2 and the water supply pipe 48, and provides the water supply W to the hot water outlet pipe 50 according to the opening degree of the bypass valve 52-3. The water supply W provided to the hot water outlet pipe 50 mixes with the heated water HW, lowering the temperature of the heated water HW. The opening degree of the bypass valve 52-3 is adjusted so that the temperature of the heated water HW flowing in the hot water outlet pipe 50 becomes, for example, a hot water supply set temperature. The water control valve 52-1 may be installed in the water supply pipe 48, and the bypass valve 52-3 may be installed in the connection portion of the bypass pipe 52-2 and the hot water outlet pipe 50 or in the bypass pipe 52-2. The water control mechanism 53 includes a water control valve 53-1, a bypass pipe 53-2, and a bypass valve 53-3. The water control valve 53-1, the bypass pipe 53-2, and the bypass valve 53-3 are installed in the same manner as the water control valve 52-1, the bypass pipe 52-2, and the bypass valve 52-3, and have the same functions as the water control valve 52-1, the bypass pipe 52-2, and the bypass valve 52-3. Both the water control valves 52-1 and 53-1 may be closed or open. Either one of the water control valves 52-1 and 53-1 may be open.

[0038] The flow rate sensors 54-1 and 54-2 are installed, for example, in the water supply pipe 48 and measure the flow rate of the supply water W flowing through the water supply pipe 48. The flow rate sensor 54-1 measures the flow rate of the supply water W flowing toward the heat source unit 46-1, and the flow rate sensor 54-2 measures the flow rate of the supply water W flowing toward the heat source unit 46-2.

[0039] The temperature sensors 56-1 and 56-2 are installed in the water supply pipe 48 and measure the temperature of the supply water W at the installation location. The temperature sensor 58-1 is installed in the hot water outlet pipe 50 between the heat source unit 46-1 and the water control mechanism 52 and measures the temperature of the heated water HW supplied from the heat source unit 46-1. The temperature sensor 58-2 is installed in the hot water outlet pipe 50 between the heat source unit 46-2 and the water control mechanism 53 and measures the temperature of the heated water HW supplied from the heat source unit 46-2. The temperature sensors 58-1 and 58-2 measure the raw heated water temperature of the raw heated water HW before the supply water W is mixed. The temperature sensor 60-1 is installed in the hot water outlet pipe 50 between the water control mechanism 52 and the hot water supply path 16, and the temperature sensor 60-2 is installed in the hot water outlet pipe 50 between the water control mechanism 53 and the hot water supply path 16. Temperature sensors 60-1, 60-2 measure, for example, the temperature of conditioned heated water HW after being mixed with feed water W. Temperature sensors 56-1, 56-2, 58-1, 58-2, 60-1, 60-2 include, for example, thermistors.

[0040] The control units 12-1 and 12-2 are an example of the control device of the present disclosure, and include a computer, forming, for example, a multi-controller. The computer is formed, for example, by electronic circuits arranged on a board. The control units 12-1 and 12-2 are connected to each other by wire or wirelessly, and communicate various information with each other. The control unit 12-1 is, for example, a master control unit, and the control unit 12-2 is, for example, a slave control unit.

[0041] The control unit 12-1 is installed, for example, in the housing of the hot water storage unit 6. The control unit 12-1 controls the hot water storage unit 6 and the heat source unit 8, and transmits, for example, an instruction signal to the control unit 12-2 to instruct the hot water heater 10 to operate or stop. The control unit 12-2 is installed, for example, in the housing of the hot water heater 10. The control unit 12-2 controls the hot water heater 10, and transitions the state of the hot water heater 10 to an operating state or a stop state based on, for example, an instruction signal received from the control unit 12-1. The operating state of the hot water heater 10 is defined as a state in which at least one of the water control valves 52-1, 53-1 is open, and the stop state of the hot water heater 10 is defined as a state in which all of the water control valves 52-1, 53-1 of the hot water heater 10 are closed. Note that the control unit 12-1 may be a slave control unit, and the control unit 12-2 may be a master control unit. That is, control unit 12-2 may transmit an instruction signal to control unit 12-1 to instruct operation or suspension of hot water storage unit 6, and control unit 12-1 may transition the state of hot water storage unit 6 to an operation state or suspension state based on the instruction signal received from control unit 12-2. The operation state of hot water storage unit 6 is defined as a state in which water control valve 32-1 is open, and the suspension state of hot water storage unit 6 is defined as a state in which water control valve 32-1 is closed. Control units 12-1 and 12-2 have a timer function and a memory function, and can measure operation duration, stop duration, etc., and can store a set temperature, etc.

[0042] The remote control device 14 is installed, for example, in a building and is connected, for example, to the control units 12-1 and 12-2 by wire or wirelessly. The remote control device 14 is used, for example, to input or change set values ​​such as temperature setting and time setting. The remote control device 14 may also be used, for example, to display set values.

[0043] FIG. 2 shows an example of a control system for a hot water supply system.

[0044] The control unit 12-1 includes a processor 72-1, a memory unit 74-1, a communication unit 76-1, and an input / output unit 78-1. The processor 72-1 executes a program stored in the memory unit 74-1 to realize the above-mentioned control.

[0045] The memory unit 74-1 stores programs, as well as settings such as the hot water supply temperature setting, other temperature settings, and time settings, and information obtained by information processing. The memory unit 74-1 is a recording medium such as a semiconductor memory, and is, for example, a non-volatile memory. The memory unit 74-1 includes a read-only memory (ROM) and a random-access memory (RAM).

[0046] The communication unit 76-1 is connected to the control unit 12-2 via a communication cable 80 and to the remote control device 14 via a communication cable 81, and transmits and receives control information between the respective units under the control of the processor 72-1.

[0047] The input / output unit 78-1 is connected to the flow sensor 34, the temperature sensors 36-1, 36-2, ... 36-10, the pump 42, the switching valve 44, the water control valve 32-1, and the bypass valve 32-3. The input / output unit 78-1 acquires detection signals from the flow sensor 34 and the temperature sensors 36-1, 36-2, ... 36-10, and outputs control signals to the pump 42, the switching valve 44, the water control valve 32-1, and the bypass valve 32-3.

[0048] The control unit 12-2 includes a processor 72-2, a memory unit 74-2, a communication unit 76-2, and an input / output unit 78-2. The processor 72-2 executes a program stored in the memory unit 74-2 to realize the above-mentioned control.

[0049] The memory unit 74-2 has, for example, the same configuration as the memory unit 74-1. The memory unit 74-2 further stores priority unit settings for the heat source units 46-1 and 46-2.

[0050] The communication unit 76-2 is connected to the control unit 12-1 by a communication cable 80, and transmits and receives control information between the various units under the control of the processor 72-2.

[0051] The input / output unit 78-2 is connected to the flow rate sensors 54-1, 54-2, the temperature sensors 56-1, 56-2, 58-1, 58-2, 60-1, 60-2, the heat source units 46-1, 46-2, the water control valves 52-1, 53-1, and the bypass valves 52-3, 53-3, etc. The input / output unit 78-2 acquires detection signals from the flow rate sensors 54-1, 54-2, the temperature sensors 56-1, 56-2, 58-1, 58-2, 60-1, 60-2, etc., and outputs control signals to the heat source units 46-1, 46-2, the water control valves 52-1, 53-1, and the bypass valves 52-3, 53-3.

[0052] FIG. 3 is a flowchart showing an example of a mode selection process during standby. The mode selection process during standby (hereinafter referred to as "mode selection process") is an example of a control method of the present disclosure. The mode selection process is realized, for example, by control unit 12-1 executing a program. The mode selection process may also be realized by control unit 12-2 executing a program. The mode selection process shown in FIG. 3 is an example, and the control method of the present disclosure is not limited to such a process. In FIG. 3, S indicates a step.

[0053] When hot water supply (i.e., supply of heated water HW) is stopped, the hot water supply system 2 stands by to prepare to start operation. While the hot water supply system 2 is on standby, the control unit 12-1 determines whether heat is stored in the hot water storage tank 24 of the hot water storage unit 6 (S101). The control unit 12-1 determines whether heat is stored, for example, based on the temperature of water or hot water detected by the temperature sensor 36-3. The control unit 12-1 may determine whether heat is stored using any of the other temperature sensors 36-3, 36-4, ... 36-7 installed in the hot water storage tank 24.

[0054] If heat is stored in hot water storage tank 24 (YES in S101), control unit 12-1 determines whether water heater 10 satisfies a first condition. The first condition is, for example, that the time that has elapsed since water heater 10 stopped discharging hot water has exceeded a first set time (for example, six minutes) (S102). The time that has elapsed since water heater 10 stopped discharging hot water is an example of the time that water heater 10 stops continuously providing heated water HW. Control unit 12-1, for example, uses a timer function to measure the time that has elapsed since an instruction signal (hereinafter referred to as a "pause instruction signal") instructing water heater 10 to be paused is sent to control unit 12-2, and determines whether the first set time has elapsed based on whether the measured time has exceeded the first set time.

[0055] If the elapsed time has not exceeded the first set time (NO in S102), control unit 12-1 transitions the mode of hot water supply system 2 to a first standby mode (S103). The first standby mode is a mode for supplying heated water HW from hot water storage unit 6 when hot water supply system 2 starts operating. In other words, the first standby mode is a mode for performing a hot start by hot water storage unit 6 when hot water supply system 2 starts operating. In the first standby mode, control unit 12-1 opens water control valve 32-1 of hot water storage unit 6 and sends a pause instruction signal to control unit 12-2 to close both water control valves 52-1 and 53-1 of water heater 10.

[0056] When the elapsed time exceeds the first set time (YES in S102), the control unit 12-1 transitions the mode of the hot water supply system 2 to a second standby mode (S104). The second standby mode is a mode for supplying heated water HW from the hot water supply system 2 at the start of operation in order to preheat the hot water supply system 2. In other words, the second standby mode is a mode for preheating the hot water supply system 2 at the start of operation. In the second standby mode, the control unit 12-1 closes the water control valve 32-1 of the hot water storage unit 6 and transmits an instruction signal (hereinafter referred to as an "operation instruction signal") to the control unit 12-2 to instruct the operation of the hot water supply system 2. In response to the operation instruction signal, the control unit 12-2 opens, for example, the water control valve 52-1 or the water control valve 53-1 on the priority unit side.

[0057] If heat is not stored in the hot water storage tank 24 (NO in S101), the control unit 12-1 transitions the mode of the hot water supply system 2 to a third standby mode (S105). The third standby mode is a mode for supplying heated water HW from the water heater 10 when the hot water supply system 2 starts operating due to a shortage of hot water in the hot water storage tank 24. In other words, the third standby mode is a mode for operating the water heater 10 independently when the operation starts. In the third standby mode, the control unit 12-1 closes the water control valve 32-1 of the hot water storage unit 6 and transmits an operation instruction signal for the water heater 10 to the control unit 12-2. In response to the operation instruction signal, the control unit 12-2 opens, for example, the water control valve 52-1 or the water control valve 53-1 on the priority unit side.

[0058] After transitioning to the first standby mode, the second standby mode, or the third standby mode (S103, S104, S105), the process returns to S101 and the mode selection process is repeated. When hot water supply is started during the first standby mode, the supply of heated water HW from the hot water storage unit 6 including the open water control valve 32-1 is started, and the hot water supply system 2 transitions to an operating state. When hot water supply is started during the second standby mode or the third standby mode, the supply of heated water HW from the water heater 10 including at least one open water control valve 52-1, 53-1 is started, and the hot water supply system 2 transitions to an operating state.

[0059] FIG. 4 is a flowchart showing an example of the operation process from the second standby mode. FIG. 5 is a sequence diagram showing an example of the operation process from the second standby mode. The operation process of the hot water supply system 2 (hereinafter referred to as "operation process") is an example of the control method of the present disclosure. The operation process is a process that is realized when hot water supply is started during the second standby mode. The operation process is realized, for example, by control units 12-1 and 12-2 executing a program. The operation process shown in FIG. 4 and FIG. 5 is an example, and the control method of the present disclosure is not limited to such a process. In FIG. 4 and FIG. 5, S indicates a step.

[0060] When water supply starts due to the start of hot water supply (YES in S121), the flow rate detected by the flow rate sensor 54-1 or 54-2 on the priority unit side increases. Based on the flow rate information acquired from the flow rate sensors 54-1 and 54-2, the control unit 12-2 starts the combustion of gas G in the priority unit and starts the supply of heated water HW from the water heater 10 (S122).

[0061] After the supply of heated water HW from water heater 10 starts, it is determined whether the temperature of heated water HW in water heater 10 has increased (S123). S123 includes, for example, S123-1 to S123-3 shown in FIG. 5. Control unit 12-2 transmits status information of water heater 10 to control unit 12-1 (S123-1), and control unit 12-1 receives the status information (S123-2). The status information of water heater 10 includes at least information on the adjusted heated water temperature detected by temperature sensor 60-1 or temperature sensor 60-2 on the priority unit side. For example, when the adjusted heated water temperature detected by temperature sensor 60-1 or temperature sensor 60-2 on the priority unit side is a temperature equal to or higher than the hot water supply setting temperature, and the temperature equal to or higher than the hot water supply setting temperature continues for a second setting time (for example, 1 second) or more, control unit 12-1 determines that the temperature of heated water HW has increased. When the control unit 12-1 determines that the temperature of the heated water HW is not increasing (NO in S123, NO in S123-3), S123 or S123-1 to S123-3 are repeated.

[0062] When the control unit 12-1 determines that the temperature of the heated water HW is increasing (YES in S123, YES in S123-3), the control unit 12-1 opens the water control valve 32-1 of the hot water storage unit 6, and the hot water storage unit 6 and the water heater 10 start to simultaneously provide the heated water HW (S124). Simultaneous provision is defined as a state in which both the hot water storage unit 6 and the water heater 10 provide the heated water HW.

[0063] Control unit 12-1 determines whether the time elapsed from the start of simultaneous provision has exceeded a third set time (e.g., 10 seconds) (S125). For example, control unit 12-1 measures the time elapsed from opening water control valve 32-1 using a timer function, and determines whether the third set time has elapsed based on whether the measured time has exceeded the third set time.

[0064] If the elapsed time has not reached the third set time (NO in S125), S125 is repeated. If the elapsed time has reached the third set time (YES in S125), water control valves 52-1 and 53-1 of water heater 10 are closed, and the supply of heated water from water heater 10 is stopped (S126). S126 includes, for example, S126-1 to S126-3 shown in FIG. 5. Control unit 12-1 transmits a pause instruction signal for water heater 10 to control unit 12-2 (S126-1). Control unit 12-2 receives the pause instruction signal (S126-2), closes water control valves 52-1 and 53-1, and stops the supply of heated water HW from water heater 10 (S126-3).

[0065] Control unit 12-1 determines whether water heater 10 satisfies a second condition. The second condition is, for example, that the time that has elapsed since water heater 10 stopped providing heated water HW has elapsed a fourth set time (for example, six minutes) (S127). Control unit 12-1 measures, for example, the time that has elapsed since sending a pause instruction signal (S126-1) using a timer function, and determines whether the fourth set time has elapsed based on whether the measured time has exceeded the fourth set time (S127).

[0066] If the elapsed time has not passed the fourth set time (NO in S127), control unit 12-1 repeats S127. If the elapsed time has passed the fourth set time (YES in S127), water control valve 52-1 or water control valve 53-1 on the priority unit side of water heater 10 is opened to start simultaneous provision (S128). S128 includes, for example, S128-1 to S128-3 shown in FIG. 5. Control unit 12-1 transmits an operation instruction signal for water heater 10 to control unit 12-2 (S128-1). Control unit 12-2 receives the operation instruction signal (S128-2), opens water control valve 52-1 or water control valve 53-1 on the priority unit side, and starts simultaneous provision (S128-3).

[0067] After the simultaneous provision starts, control units 12-1 and 12-2 return to S125 and between S123-1 and S126-2, respectively, and the operation process is repeated. Therefore, preheating of water heater 10 is repeated. Note that, in the operation process of hot water supply system 2, when the flow of water ends, control unit 12-1 transitions hot water supply system 2 to a standby state and executes the mode selection process described above. Also, in the operation process, when control unit 12-1 determines that heat is not stored in hot water storage tank 24 of hot water storage unit 6, control unit 12-1 transitions the process to a process of solely providing heated water HW by water heater 10.

[0068] In the first standby mode, the first set time has not elapsed after hot water supply from water heater 10 stopped (NO in S102), and so the temperature of heated water HW in water heater 10 is high. Therefore, in the operation process from the first standby mode, the preheating process of water heater 10 at the start of operation of hot water supply system 2 is omitted. When water supply begins and water flow begins, provision of heated water HW from hot water storage unit 6 begins. After water flow begins, control units 12-1, 12-2 may proceed to, for example, S127 in the flowchart shown in FIG. 4, and perform operation process in accordance with the flowchart shown in FIG. 4.

[0069] In the operation process from the third standby mode, when water supply starts due to the start of hot water supply, heated water HW is supplied from water heater 10. When control unit 12-1 determines that heat is stored in hot water storage tank 24 of hot water storage unit 6, control units 12-1 and 12-2 may proceed to, for example, S123 of the flowchart shown in FIG. 4 and perform the operation process according to the flowchart shown in FIG.

[0070] FIG. 6 shows an example of the change in temperature and flow rate of the heated water over time when the water heater is preheated, and FIG. 7 shows a comparative example of the change in temperature and flow rate of the heated water over time (when the water heater is not preheated). FIG. 8 shows an example of the change in temperature and flow rate of the heated water over time when the water heater is repeatedly preheated. In the diagrams shown in FIG. 6, FIG. 7, and FIG. 8, the horizontal axis represents time, and the vertical axis represents the flow rate and temperature of the heated water HW. In FIG. 6, FIG. 7, and FIG. 8, the flow rate Fh of the heated water HW in the hot water storage unit 6 is the flow rate detected by the flow rate sensor 34, and the flow rate Fg of the heated water HW in the water heater 10 is the total flow rate of the flow rates detected by the flow rate sensors 54-1 and 54-2. The flow rates Fh and Fg of the heated water HW correspond to the flow rates of the water supply W to the hot water storage unit 6 and the water heater 10, respectively. 6, 7, and 8, the temperature Th of the heated water HW in the hot water storage unit 6 is the adjusted heated water temperature detected by the temperature sensor 36-2, and the temperature Tg of the heated water HW in the water heater 10 is the adjusted heated water temperature detected by the temperature sensor 60-1 or temperature sensor 60-2 on the priority unit side. The temperature Ts of the heated water HW in the hot water supply system 2 is the temperature of the heated water HW near the outlet of the hot water supply path 16. The temperature Ts is generally expressed by the following formula (1). Ts≒(Tg×Fg+Th×Fh) / (Fg+Fh) ···(1) Temperatures Th, Tg, and Ts respectively represent the temperature (outlet temperature) of the heated water HW provided from the hot water storage unit 6, the temperature (outlet temperature) of the heated water HW provided from the water heater 10, and the temperature (outlet temperature) of the heated water HW provided from the hot water supply system 2.

[0071] Before time t1, hot water supply system 2 is on standby in the second standby mode. When water flow starts at time t1 (S121), the flow rate Fg of heated water HW in water heater 10 increases, and water heater 10 starts burning gas G. The temperature Tg of heated water HW in water heater 10 increases over time from the initial temperature T0 and reaches the hot water supply setting temperature T1. The temperature Ts of heated water HW in hot water supply system 2 increases with a delay from the temperature Tg.

[0072] At time t2, it is determined that the temperature Tg has risen (S123), and the hot water supply system 2 shifts the mode of providing heated water HW from the sole provision of heated water HW by the water heater 10 shown in A of Fig. 9 (hereinafter referred to as "sole provision by the water heater 10") to the simultaneous provision of heated water HW by the hot water storage unit 6 and the water heater 10 shown in B of Fig. 9. At time t2, the adjusted heated water HW in the hot water storage unit 6 has a temperature Th that is lower than, for example, the hot water supply setting temperature T1. Therefore, in the period from time t2 to time t3, the temperature Ts temporarily drops. However, the temperature Th rises over time, and the temperature Ts stabilizes at the hot water supply setting temperature T1 at time t3.

[0073] At time t4, it is determined that the time elapsed since the start of simultaneous provision has exceeded the third set time (YES in S125), and hot water supply system 2 shifts the provision mode from simultaneous provision to the sole provision of heated water HW by hot water storage unit 6 shown in C of Fig. 9 (hereinafter referred to as "sole provision by hot water storage unit 6"). During the period from time t4 to time t5, water heater 10 is inactive. The temperature Tg of heated water HW in water heater 10 gradually decreases.

[0074] At time t5, when it is determined that there is no heat stored in the hot water storage unit 6, the hot water supply system 2 shifts the provision mode to simultaneous provision, and at time t6, the provision mode shifts to sole provision by the hot water heater 10. After time t5, the temperature Ts fluctuates slightly due to fluctuations in the flow rates Fg and Fh. However, in the period from time t4 to time t5, the temperature Tg is maintained without a large drop, so fluctuations in the temperature Ts are suppressed.

[0075] As shown in FIG. 7, when the hot water storage unit 6 starts supplying water alone at time t1, the temperature Ts rises after the temperature Th, and is stabilized at the hot water supply setting temperature T1 at time t7.

[0076] At time t5, when it is determined that there is no heat stored in the hot water storage unit 6, the hot water supply system 2 shifts the provision mode to simultaneous provision, and at time t6, the provision mode shifts to sole provision by the water heater 10. However, since there is no temperature increase due to preheating of the water heater 10 and the temperature Tg is low at time t5, there is a large fluctuation in temperature Ts in the period from time t5 to time t6.

[0077] The period t13 required for the temperature Ts shown in Fig. 6 to stabilize is longer than the period t17 required for the temperature Ts shown in Fig. 7 to stabilize. However, the temperature Ts shown in Fig. 6 is more stable than the temperature Ts shown in Fig. 7 in the period from time t5 to time t6 when the supply source is switched from the hot water storage unit 6 to the water heater 10. Preheating the water heater 10 can suppress a drop in the temperature Ts in the period from time t5 to time t6.

[0078] The drop in temperature Ts in the period from time t5 to time t6 shown in Fig. 7 is a temperature drop after the temperature Ts has stabilized, and causes discomfort to users of the heated water HW. However, the drop in temperature Ts in period t13 shown in Fig. 6 is a temperature drop immediately after hot water supply begins, before the temperature Ts has stabilized, and can reduce the discomfort caused to users of the heated water HW.

[0079] Before it is determined that there is no heat stored in the hot water storage unit 6, the hot water supply system 2 may repeat preheating of the hot water heater 10. The changes in flow rate and temperature shown in Fig. 8 are the same as the changes in flow rate and temperature shown in Fig. 6 during the period from time t0 to time t4, and a description thereof will be omitted.

[0080] If it is determined at time t8 that the time elapsed since the supply of heated water HW from the water heater 10 stopped has exceeded the fourth set time (YES in S127) before it is determined that there is no heat stored in the hot water storage unit 6, the hot water supply system 2 shifts the supply mode from sole supply by the hot water storage unit 6 to simultaneous supply, and starts preheating the water heater 10. After time t8, the temperature Ts fluctuates slightly due to fluctuations in the flow rates Fg and Fh. However, the temperature Tg does not drop significantly and is maintained, so fluctuations in the temperature Ts are suppressed.

[0081] The process performed at time t9 is the same as the process performed at time t4. Changes in flow rate and temperature are repeated from time t9 to time t9, and the temperature Tg is maintained. Therefore, when the supply mode is shifted from single supply by the hot water storage unit 6 to single supply by the hot water heater 10 via simultaneous supply, a drop in temperature Ts can be suppressed.

[0082] According to the embodiment, for example, the following actions and effects can be obtained.

[0083] (1) Control units 12-1, 12-2 of hot water supply system 2 select the first standby mode or the second standby mode during standby, so that water heater 10 is not left in a cold state when water flow begins. Therefore, when the mode of providing heated water HW shifts from sole provision by hot water storage unit 6 to sole provision by water heater 10, temperature fluctuations of heated water HW can be suppressed.

[0084] (2) Since temperature fluctuations are suppressed after the temperature of the heated water HW has stabilized, users of the hot water supply system 2 can comfortably use the heated water HW without having to worry about temperature fluctuations.

[0085] (3) It is possible to improve the stability of the temperature of the heated water HW in the multi-hot water supply system including the hot water storage unit 6 and the heat source unit 8. When hot water at a stable temperature is being supplied by the hot water supply system 2 including the hot water storage unit 6 and the hot water heater 10, the preheated hot water heater 10 suppresses a drop in the hot water temperature caused by switching the hot water supply means. This improves the comfort of the supplied hot water.

[0086] (4) In the hot water supply system 2, except for the preheating process of the water heater 10, the operation of the hot water storage unit 6, which stores hot water heated by the energy-efficient heat pump, takes priority over the operation of the water heater 10. This reduces energy consumption and carbon dioxide emissions.

[0087] Regarding the embodiment described above, characteristics and modifications thereof will be listed below.

[0088] (1) In the above embodiment, the hot water supply system 2 includes a first hot water supply device such as a heat pump hot water supply device. This first hot water supply device is not limited to a heat pump hot water supply device as long as it includes a unit that generates hot water and a hot water storage tank 24 that stores the hot water. For example, the first hot water supply device may be a fuel cell cogeneration system that includes a fuel cell unit and a hot water storage unit 6.

[0089] (2) Water heater 10 may be a water heater having one heat source unit 46-1. In addition, water heating system 2 may include a plurality of hot water storage units 6, may include a plurality of water heaters 10, or may include a plurality of hot water storage units 6 and a plurality of water heaters 10. When water heating system 2 includes a plurality of hot water storage units 6, a master hot water storage unit 6 and a slave hot water storage unit 6 may be set by a setting function possessed by hot water heating system 2. When water heating system 2 includes a plurality of water heaters 10, a master water heater 10 and a slave water heater 10 may be set by a setting function possessed by hot water heating system 2.

[0090] (3) The settings of the set time, set temperature, etc. are not limited to the times or temperatures described in the embodiment. The settings of the set time, set temperature, etc. may be adjusted according to, for example, the installation location of the hot water supply system 2, may be adjusted according to the season, or may be appropriately selected from within the range of allowable settings.

[0091] (4) In the above embodiment, the first condition is that the time elapsed after the water heater 10 stops discharging hot water exceeds a first set time. Also, the second condition is that the time elapsed after the water heater 10 stops providing heated water HW exceeds a fourth set time. However, the first condition and the second condition may be any condition that directly or indirectly represents the temperature state of the water heater 10, and are not limited to the first condition and the second condition already described in the above embodiment. For example, the first condition and the second condition may be that the time elapsed after the water heater 10 stops burning exceeds a set time.

[0092] In the operation process of the hot water supply system 2 from the second standby mode, as shown in FIG. 10, S1127 may be processed instead of S127. In S1127, the control unit 12-1 judges whether the hot water supply system 10 satisfies the second condition. The second condition in S1127 is, for example, that the raw heated water temperature Tg0 (FIG. 11) on the priority unit side of the hot water supply system 10 is a temperature equal to or lower than the set temperature T2. The set temperature T2 may be the hot water supply set temperature T1, or may be, for example, a temperature higher than the hot water supply set temperature T1. The control unit 12-1 acquires information on the raw heated water temperature Tg0 detected by the temperature sensor 58-1 or temperature sensor 58-2 on the priority unit side from the control unit 12-2, and judges whether the raw heated water temperature Tg0 is a temperature equal to or lower than the set temperature T2.

[0093] FIG. 11 shows the time change in the temperature and flow rate of the heated water shown in FIG. 8, as well as the time change in the original heated water temperature Tg0 on the priority unit side of the water heater 10.

[0094] In the period from time t1 to time t4, the raw heated water temperature Tg0 on the water heater 10 side rises, and then stabilizes at a temperature T3 equal to or higher than the hot water supply setting temperature T1. At time t4, when the hot water supply system 2 shifts the supply mode to the sole supply by the hot water storage unit 6, the raw heated water temperature Tg0 drops. At time t8, when it is determined that the raw heated water temperature Tg0 is equal to or lower than the setting temperature T2 (YES in S1127), the hot water supply system 2 shifts the supply mode from the sole supply by the hot water storage unit 6 to the simultaneous supply, and starts preheating the water heater 10. When the raw heated water temperature Tg0 is a temperature higher than the setting temperature T2 (NO in S1127), the control unit 12-1 repeats S1127. The hot water supply system 2 according to the modified example determines the temperature state of the water heater 10 by the raw heated water temperature instead of the elapsed time, and can preheat the water heater 10 before the water heater 10 cools down.

[0095] The second condition may include a plurality of different conditions. In the operation process of the hot water supply system 2 from the second standby mode, as shown in FIG. 12, if the elapsed time does not exceed the fourth set time (NO in S127), the control unit 12-1 judges whether the raw heated water temperature Tg0 on the priority unit side is equal to or lower than the set temperature T2 (S1127). If the control unit 12-1 judges that the raw heated water temperature Tg0 is equal to or lower than the set temperature T2 (YES in S1127), the supply form is shifted from the single supply by the hot water storage unit 6, and simultaneous supply is started (S128), and if the control unit 12-1 judges that the raw heated water temperature Tg0 is not equal to or lower than the set temperature T2 (NO in S1127), the control unit 12-1 returns to S127. In the hot water supply system 2 according to the modified example, even if one of the plurality of conditions is not satisfied, the hot water supply device 10 can be preheated if the other of the plurality of conditions is satisfied. In other words, the hot water supply device 10 can be preheated more reliably.

[0096] The second condition may be that the adjusted heated water temperature on the priority unit side of water heater 10 is equal to or lower than another set temperature, or that the temperature detected by another temperature sensor installed on the priority unit side of water heater 10 or the ambient temperature on the priority unit side is equal to or lower than another set temperature. The first condition may be the same as the second condition according to the modified example.

[0097] (5) In the above embodiment, in S123, it is determined whether the temperature of the heated water HW has increased based on the adjusted heated water temperature and the duration. However, in S123, the temperature state of the water heater 10 may be confirmed directly or indirectly, and the preheating state of the water heater 10 may be determined. For example, in S123, the temperature state of the water heater 10 may be confirmed directly or indirectly based on the duration from the start of gas combustion, the temperature of the water heater 10 or the ambient temperature detected by another temperature sensor installed in the water heater 10, etc.

[0098] As described above, the most preferred embodiment of the present disclosure has been described. The technology of the present disclosure is not limited to the above description. Based on the gist of the invention described in the claims or disclosed in the specification, those skilled in the art can make various modifications and changes. It goes without saying that such modifications and changes are included in the scope of the present disclosure. [Industrial Applicability]

[0099] INDUSTRIAL APPLICABILITY The present disclosure is useful in that it can provide heated water such as hot water to a person who desires hot water. [Explanation of symbols]

[0100] 2. Hot water system 4 Water supply route 6 Hot water storage unit 8 Heat source machine 10. Water heater 12-1, 12-2 Control section 14 Remote control device 16 Hot water supply route 24 Hot water tank 26 Circulation path 26-1, 26-2, 26-3 pipes 28, 48 Water supply pipe 30, 50 outlet pipe 32, 52, 53 Water control mechanism 32-1, 52-1, 53-1 Water control valve 32-2, 52-2, 53-2 Bypass pipe 32-3, 52-3, 53-3 Bypass valve 34, 54-1, 54-2 Flow sensor 36-1, 36-2, 36-10, 56-1, 56-2, 58-1, 58-2, 60-1, 60-2 Temperature Sensors 42 Pump 44 Switching valve 46-1, 46-2 Heat source machine 62 Burner 64 Primary heat exchanger 66 Secondary heat exchanger 72-1, 72-2 processor 74-1, 74-2 Memory section 76-1, 76-2 Communications Department 78-1, 78-2 Input / output section 80, 81 Communication cable

Claims

1. 1. A hot water supply system, comprising: a hot water storage unit including a hot water storage tank and a first water control valve, the hot water storage unit supplying heated water according to demand when the first water control valve is open; a water heater including a heat source unit and a second water control valve, and supplying heated water according to demand when the second water control valve is open; a control unit that changes the second water control valve from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system; A hot water supply system comprising:

2. The hot water supply system of claim 1 , wherein when the hot water supply system is in a standby mode and the hot water supply unit satisfies the first condition, the control unit changes the first water control valve from open to closed.

3. 2. The hot water supply system according to claim 1, wherein the first condition is a condition that directly or indirectly represents a temperature state of the hot water heater.

4. The first condition is that the time during which the continuous supply of heated water by the water heater is stopped exceeds a set time, or The first condition is that the temperature detected by a temperature sensor installed in a hot water outlet pipe of the water heater is equal to or lower than a set temperature. The hot water supply system according to claim 3 .

5. The hot water supply system according to claim 1 or claim 2, characterized in that when the hot water heater satisfies a second condition during operation of the hot water supply system, the control unit changes the second water control valve from closed to open.

6. The hot water supply system according to claim 1 , wherein the hot water supply system is a multi-hot water supply system further including another heat source unit and another second water control valve.

7. A control device for controlling a hot water supply system including a hot water storage unit and a hot water heater, A control device comprising: a control unit that changes a water control valve of the water heater from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system.

8. A control method for a hot water supply system including a hot water storage unit and a hot water heater, A process of opening a first water control valve of the hot water storage unit and closing a second water control valve of the hot water heater; a process of changing the second water control valve of the water heater from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system; A control method comprising:

9. A program for controlling a hot water supply system including a hot water storage unit and a hot water heater, A function of opening a first water control valve of the hot water storage unit and closing a second water control valve of the hot water heater; a function of changing the second water control valve of the water heater from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system; A program to make the above happen on a computer.

10. A recording medium storing a program for controlling a hot water supply system including a hot water storage unit and a hot water heater, The program is A function of opening a first water control valve of the hot water storage unit and closing a second water control valve of the hot water heater; a function of changing the second water control valve of the water heater from closed to open when the water heater satisfies a first condition during a standby mode of the hot water supply system; A recording medium for causing a computer to realize the above.

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