JP5814643B2 - Hot water storage system - Google Patents

Description

  The present invention relates to a hot water storage system in which hot water in a hot water storage tank heated using solar heat or exhaust heat is supplied to an auxiliary heat source device at a subsequent stage, and a shortage is heated by the auxiliary heat source device to generate hot water.

  Water that has been heated using exhaust heat from various devices or solar heat is stored in a hot water storage tank. When the hot water temperature in the hot water storage tank is sufficiently high, water is mixed with hot water from the hot water storage tank using a mixing valve. There is a hot water supply system in which hot water at a set temperature is discharged, and when the set temperature is insufficient, a deficient portion is heated by an auxiliary heat source device at a later stage (see, for example, Patent Document 1).

  In such a hot water supply system, the hot water storage tank side and the auxiliary heat source machine side are assembled as a pair, and the hot water supply to the auxiliary heat source machine is controlled by controlling the mixing valve on the hot water storage tank side after familiarizing the characteristics of the auxiliary heat source machine. Had been supplying. For example, when the auxiliary heat source device is a gas water heater, there are restrictions on the minimum combustion amount and the minimum working water amount for burning the burner, and therefore, the mixing valve on the hot water storage tank side is controlled based on the characteristics.

  By the way, when the above hot water supply system using solar heat or the like is introduced into an existing house, in many cases, there are hot water heaters used so far. However, since the newly installed system cannot fully know the above-mentioned characteristics regarding the existing water heater, the water heater cannot be reused as an auxiliary heat source device and is discarded.

JP 2006-010114 A

  In the above hot water supply system that heats the water in the hot water storage tank using exhaust heat, solar heat, etc., it is possible to save energy by preferentially using the hot water in the hot water storage tank and refraining from heating in the auxiliary heat source machine. Therefore, when hot water is sufficiently stored in the hot water storage tank, the mixing ratio of the mixing valve is set so that the temperature of the hot water supplied to the auxiliary heat source unit becomes the set temperature, and heating in the auxiliary heat source unit is stopped. It was controlled to let it.

  However, even if hot water at the set temperature is supplied from the mixing valve to the auxiliary heat source unit in the heating stop state, if the heat exchanger of the auxiliary heat source unit is cold, the heat of the hot water is taken away through the heat exchanger. Therefore, there was a problem that hot water of a set temperature did not come out easily in the hot water supply pipe on the outlet side of the auxiliary heat source machine. In other words, since the cooled heat exchanger is gradually warmed by the hot water passing through the heat exchanger, it may take several minutes for the hot water at the set temperature to come out. For example, in the case of a shower, there was a consumer behavior that during this time it was not possible to take a shower and hot water was wasted. As a result, not only was hot water wasted, but wasted valuable time for consumers.

  In particular, when an existing water heater is reused as an auxiliary heat source machine, characteristics such as how much the temperature of the hot water drops while passing through the heat exchanger cannot be known, and the temperature sensor inside the water heater It is also difficult to perform cooperative operations such as acquiring information such as Therefore, if the problem of the temperature drop by the cold heat exchanger is considered, it becomes more difficult to reuse the existing water heater as an auxiliary heat source machine.

  The present invention is intended to solve the above problems, and when hot water at a set temperature can be supplied from the hot water storage tank side, the hot water temperature does not fall below the set temperature through the cooled auxiliary heat source machine, An object of the present invention is to provide a hot water storage system capable of securing hot water at a set temperature.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] A hot water storage tank with a water supply channel connected to the entrance;
A heater for heating the water stored in the hot water storage tank;
A connection pipe that connects the water inlet of the auxiliary heat source machine that heats and supplies the water supplied from the water inlet with a heat exchanger and the outlet of the hot water storage tank;
A mixing valve that is inserted in the middle of the connection pipe and mixes water supplied from the hot water storage tank and water supplied from a water supply channel;
A control unit for controlling the mixing ratio of the mixing valve so that the set temperature is discharged without heating by the auxiliary heat source device or by adding heating by the auxiliary heat source device;
With
Serial control unit, at the start of hot water supply, the case of the state stored hot predetermined temperature or higher than the set temperature in the tank higher the previous even when the hot water is stored Symbol auxiliary heat source machine heat exchanger is cold, the entering- The mixing ratio of the mixing valve at the start of hot water supply is controlled so that the temperature of the water supplied to the water inlet becomes the incoming water temperature at which the hot water of the set temperature is discharged by adding heating by the auxiliary heat source device, and at the start of hot water supply In the case where hot water higher than the preset temperature is stored in the hot water storage tank and the heat exchanger of the auxiliary heat source machine is not in a cold state, the set temperature without heating by the auxiliary heat source machine A hot water storage system, wherein the mixing ratio of the mixing valve at the start of hot water supply is controlled so that hot water is discharged.

In the above invention, when the heat exchanger of the auxiliary heat source machine is in a cold state, the temperature of hot water drops while passing through this heat exchanger, so that hot water at a set temperature can be supplied from the hot water storage tank to the auxiliary heat source machine. However, if the heat exchanger of the auxiliary heat source device is cold at the start of hot water supply, the temperature of the hot water supplied to the auxiliary heat source device is intentionally lowered at the start of hot water supply so that the auxiliary heat source device can be heated. To.

In the above invention, hot water having a set temperature can be supplied without heating by the auxiliary heat source unit unless sufficiently hot water can be supplied from the hot water storage tank to the auxiliary heat source unit and the heat exchanger of the auxiliary heat source unit is not cooled at the start of hot water supply. Supply hot water at the temperature at which the hot water is discharged to the auxiliary heat source machine. For example, when a temperature drop of 1 ° C. is expected by the hot water supply port, the mixing ratio is set so that the water temperature supplied to the water inlet of the auxiliary heat source machine becomes the set temperature + 1 ° C.

[ 2 ] The control unit determines that the heat exchanger is in the cold state when a predetermined determination reference time has elapsed since the end of the last hot water discharge, and the determination reference time from the end of the previous hot water supply. If it is before progress, it will be judged that the said heat exchanger is not the said cold state. The hot water storage system as described in [1 ] characterized by the above-mentioned.

  In the above invention, it is determined whether or not the heat exchanger is in a cold state based on the elapsed time from the end of the last hot water discharge.

[ 3 ] The control unit makes the determination reference time longer when the feed water temperature or the outside air temperature is higher than the first temperature than the time set when the feed water temperature or the outside air temperature is lower than the first temperature. The hot water storage system according to [ 2 ], characterized in that

  In the above invention, the temperature drop of the heat exchanger of the auxiliary heat source machine after the end of the hot water is moderately generated in the summer compared to the winter. Therefore, in summer (when the water supply temperature or the outside air temperature is high), the determination reference time that the heat exchanger is in a cold state is set longer than in winter. Thereby, the frequency of additional heating decreases in summer, and the energy saving effect can be enhanced by preferentially using the hot water in the hot water storage tank.

[ 4 ] The auxiliary heat source machine can only perform a heating operation of a predetermined minimum heating amount or more.
The control unit sets a heat amount obtained by adding a predetermined margin to a maximum minimum heating amount among a plurality of auxiliary heat source units that can be used by being connected to the hot water storage system as a minimum heating amount, and performs heating by the auxiliary heat source unit. In the case where the hot water is discharged at the set temperature, the temperature of the water supplied to the water inlet is a temperature obtained by subtracting the temperature rise in the auxiliary heat source unit due to the minimum heating amount from the set temperature. The hot water storage system according to any one of [1] to [ 3 ], wherein the mixing ratio is set to be as follows.

  In the above invention, even when the type of the auxiliary heat source device cannot be specified, such as when the hot water heater used in the existing hot water supply system is diverted to the auxiliary heat source device, it is the largest among the water heaters that may be diverted. The amount of heat obtained by adding a margin due to the variation of the appliance to the minimum amount of heating is set as the minimum amount of heating, so that additional heating with the auxiliary heat source device can be performed reliably.

[ 5 ] having the auxiliary heat source machine,
The auxiliary heat source machine can only perform a heating operation over a predetermined minimum heating amount,
In the case where the control unit sets a heat amount obtained by adding a predetermined margin to a minimum heating amount of the auxiliary heat source unit as a minimum heating amount, and adds heating by the auxiliary heat source unit so that the set temperature is discharged. The mixing ratio is set so that the temperature of the water supplied to the water inlet is equal to or lower than the temperature obtained by subtracting the temperature increase in the auxiliary heat source unit due to the minimum heating amount from the set temperature. The hot water storage system according to any one of [1] to [ 3 ].

  In the above invention, the hot water storage system includes an auxiliary heat source unit, and the minimum heating amount corresponding to the minimum heating amount of the auxiliary heat source unit is set to control the mixing ratio.

  According to the hot water storage system of the present invention, when hot water having a set temperature can be supplied from the hot water storage tank side, the hot water temperature does not fall below the set temperature through the cooled auxiliary heat source machine, and the hot water at the set temperature is Can be secured.

It is explanatory drawing which shows the structure of the hot water supply system containing the hot water storage system of this invention. It is explanatory drawing which shows schematic structure of the water heater as an auxiliary heat source machine. It is explanatory drawing which shows schematic operation | movement of heat collecting operation. It is explanatory drawing which shows schematic operation | movement of a hot water supply driving | operation. It is explanatory drawing which shows schematic operation | movement of a solar reheating operation. It is explanatory drawing which shows schematic operation | movement of a bath heat recovery driving | operation. It is explanatory drawing which shows the driving | running state in hot water storage hot water prohibition. It is a flowchart which shows operation | movement of the hot water storage system at the time of hot water supply driving | operation.

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

  FIG. 1 shows a configuration of a hot water supply system 10 including a hot water storage system of the present invention. The hot water supply system 10 includes a hot water storage system 11 and a hot water heater 12 as an auxiliary heat source machine.

  The hot water storage system 11 includes a hot water storage tank 14 that stores hot water heated using sunlight, and supplies hot water from the hot water storage tank 14 to the water inlet of the water heater 12. The hot water heater 12 serving as an auxiliary heat source device fulfills the function of heating the water supplied from the hot water storage system 11 to a set temperature as needed and discharging the hot water to the hot water supply pipe 13. The hot water storage system 11 preferentially uses hot water heated by sunlight to suppress heating by the hot water heater 12 (hereinafter referred to as “follow-up heating”), and to save hot water with energy saving. Enable.

  A detailed configuration of the hot water storage system 11 will be described. The hot water storage tank 14 is a hollow, substantially cylindrical tank, and has piping connection ports at the bottom and the ceiling. The terminal end of the water supply pipe 15 is connected to the bottom pipe connection port. One end of the connection pipe 16 is connected to the pipe connection port of the ceiling, and the other end of the connection pipe 16 is connected to the water inlet of the water heater 12.

  A mixing valve 17 that mixes hot water and hot water from the hot water storage tank 14 is provided in the middle of the connection pipe 16. Here, the mixing valve 17 includes two valves, a first valve 17a and a second valve 17b. The first valve 17 a is inserted in the connection pipe 16. The second valve 17b is inserted in the middle of the branch water supply pipe 15a which branches from the middle of the water supply pipe 15 and merges with the connection pipe 16 on the water heater 12 side of the first valve 17a. The first valve 17a and the second valve 17b are water amount adjusting valves whose opening degrees (water flow amount) can be adjusted from 0% to 100%, respectively. The mixing ratio of hot water and hot water from the hot water storage tank 14 is adjusted by the opening degree of the first valve 17a and the second valve 17b.

  The hot water storage tank 14 has, for example, a capacity of 100 liters, and a first temperature sensor 41 for detecting the water temperature at a water level of 20 liters from the bottom is located at a water level of 40 liters from the bottom. The second temperature sensor 42 for detecting the water temperature of the water is located at a location where the water level is 60 liters from the bottom, and the third temperature sensor 43 for detecting the water temperature at that location is located at the location where the water level is 80 liters from the bottom. A fourth temperature sensor 44 for detecting the above is provided.

  In addition, the connection piping 16 in the vicinity of the piping connection port on the ceiling of the hot water storage tank 14 is provided with a tank hot water temperature sensor 46 that detects the temperature of the hot water coming out of the hot water storage tank 14. A water supply temperature sensor 47 for detecting the water supply temperature is provided in the middle of the water supply pipe 15. Further, a water amount sensor 48 is detected in the connection pipe 16 on the outlet side (hot water heater 12 side) of the mixing valve 17, and the temperature of hot water after mixing is detected by the mixing valve 17 on the downstream side (hot water heater 12 side). A mixed temperature sensor 49 is provided.

  A heat exchange pipe 18 that forms part of the heat medium circulation path 22 is inserted through the lower part of the hot water storage tank 14. The heat medium circulation path 22 circulates the heat medium (here, water) via the heat exchange pipe 18, the cistern 19, the water-water heat exchanger 20, and the solar heat collecting device 21. It is a route.

  Specifically, the heat medium circulation path 22 includes the first heat medium pipe 22 a extending from the outlet side of the heat exchange pipe 18 to the inlet side of the cistern 19 and the inlet of the water-water heat exchanger 20 from the outlet side of the cistern 19. The second heat medium pipe 22b extending to the side, the third heat medium pipe 22c extending from the outlet side of the water-water heat exchanger 20 to the inlet side of the heat collector 21, and for heat exchange from the outlet side of the heat collector 21. It consists of a fourth heat medium pipe 22d that reaches the entry side of the pipe 18. In the figure, the heat collecting device 21 is a component of the hot water storage system 11, but may be an external device.

  The cistern 19 is a tank for storing a heat medium circulating in the heat medium circulation path 22. The cistern 19 is a tank that is open to atmospheric pressure, and absorbs volume fluctuations due to expansion and contraction of the heat medium. The cistern 19 includes a water level sensor 19a that detects the internal water level. The water level sensor 19a of this example includes a low water level detection electrode, a high water level detection electrode, and a common electrode.

  The water-water heat exchanger 20 has two pipes in close contact with each other over a predetermined length, and plays a role of transferring heat from a high temperature side pipe to a low temperature side pipe. The heat medium circulation path 22 is connected to the entry side and the exit side of one pipe line (in the figure, the inner pipe line 20a) of the water-water heat exchanger 20.

  A circulation pump 24 is provided in the middle of the third heat medium pipe 22c from the outlet side of the water-water heat exchanger 20 (inner pipe line 20a) to the inlet side of the heat collector 21. The circulation pump 24 sends the heat medium in the third heat medium pipe 22c to the heat collector 21 side. A switching valve 25 is inserted in the third heat medium pipe 22 c on the downstream side of the circulation pump 24. A third heat medium pipe 22c from the circulation pump 24 side is connected to the first connection port 25a of the switching valve 25, and a third heat medium reaching the heat collector 21 side is connected to the second connection port 25b of the switching valve 25. A pipe 22c is connected. One end of a connection pipe 26 is connected to the third connection port 25c of the switching valve 25, and the other end of the connection pipe 26 is a fourth heat medium pipe extending from the heat collecting device 21 to the entrance side of the heat exchange pipe 18. 22d is joined and connected in the middle.

  The heat collector 21 is provided with a high temperature sensor 51 that detects the temperature of hot water in the heat collector 21. Further, a heat medium temperature sensor 52 for detecting the temperature of the heat medium passing through the fourth heat medium pipe 22d on the heat exchanging pipe 18 side is provided in the middle of the joint connection place of the connecting pipe 26.

  The water heater 12 heats the hot water supplied from the water inlet to a set temperature and discharges it to the hot water supply pipe 13, and also heats the water supplied from the water inlet to the set temperature of the bath and pours it into the bathtub 3. It has a tensioning function and a chasing function for chasing hot water in the bathtub 3.

  The recirculation path for circulating hot water during reheating is a bath return pipe 32 for taking hot water from the bathtub 3 into the water heater 12, a pipe passing through the heat exchanger in the water heater 12, and the heat exchanger. It comprises a bath outlet pipe 31 for sending warm hot water to the bathtub 3 and the like. The bath outlet pipe 31 reaches the bathtub 3 via the other pipe line (outer pipe line 20b in the figure) of the water-water heat exchanger 20 on the way.

  Between the water heater 12 and the water-water heat exchanger 20, a bath temperature sensor 53 for detecting the temperature of hot water taken from the bathtub 3 is provided.

  In addition, the connecting pipe 16 between the tank hot water temperature sensor 46 and the mixing valve 17 (first valve 17a) is provided with a hot water prohibiting electromagnetic valve 54 for switching between closing and opening of the connecting pipe 16. Further, two branch pipes branched from the connection pipe 16 are provided between the hot water prohibition solenoid valve 54 and the tank hot water temperature sensor 46, and a drain electromagnetic valve 55 is provided at one end of the branch pipe and the other branch pipe is provided. Is provided with a pressure relief valve 56. Further, a water filter, a pressure reducing valve, a check valve and the like are inserted in the water supply pipe 15.

  The hot water storage system 11 includes a control unit 60 that performs overall control of the operation of the hot water storage system 11. The control unit 60 temporarily stores a CPU (Central Processing Unit), a flash ROM (Read Only Memory) in which programs executed by the CPU, fixed data, and the like are stored, and various information when the CPU executes the programs. A RAM (Random Access Memory), an I / F (Interface) unit for inputting / outputting various signals, and the like are configured as circuits. Detection signals from various sensors of the hot water storage system 11 are input to the control unit 60. In addition, a control signal is output from the control unit 60 to the control target such as each valve and the circulation pump 24.

  The control unit 60 of the hot water storage system 11 exchanges necessary information with the control base 70 of the water heater 12. Here, the control unit 60 acquires information on the set temperature set on the water heater 12 side, information indicating whether or not the water heater 12 is in a reheating operation, and the like from the water heater 12. Further, a signal for instructing combustion prohibition / permission and a signal for driving the bath circulation pump 85 (see FIG. 2) without burning the burner 73 (bath pump drive signal) are sent from the control unit 60 to the control board 70 of the water heater 12. Send.

  FIG. 2 shows a schematic configuration of the water heater 12. The water heater 12 includes a hot water supply water pipe 72a in which a water inlet pipe 71 is connected to the inlet side and a hot water supply pipe 13 to the outlet side, and a bath return pipe 31 on the outlet side and a bath return pipe 32 to the inlet side. A one-can two-water channel type heat exchanger 72 provided with a water pipe 72b for watering is provided. The starting end of the water intake pipe 71 is a water inlet to which the connection pipe 16 from the hot water storage system 11 side is connected.

  The heat exchanger 72 includes a large number of fins 72c for receiving heat from the burner 73 disposed below. A gas supply pipe 74 is connected to the burner 73. In the middle of the gas supply pipe 74, a gas valve 75 for switching supply / cutoff of gas, a proportional valve 76 for adjusting the amount of supply gas, and the like are provided.

  The hot water supply pipe 13 and the bath return pipe 32 are connected by a connecting pipe 77, and a pouring electromagnetic valve 78 that switches between closing and opening of the connecting pipe 77 is provided in the middle of the connecting pipe 77. Further, in the middle of the hot water supply pipe 13 upstream from the connection point of the connecting pipe 77, a water amount servo 79 capable of adjusting the opening degree from the closed state to the fully opened state is provided in order to adjust the amount of discharged hot water. A tapping temperature sensor 80 for detecting tapping temperature is provided on the downstream side of the water amount servo 79.

  Furthermore, a bypass pipe 81 branched from the water inlet pipe 71 and joined to and connected to the hot water supply pipe 13 at a predetermined location on the hot water supply water pipe 72a side from the water quantity servo 79 is provided. A bypass adjustment valve 82 capable of adjusting the degree is provided. The inlet pipe 71 upstream of the branching point of the bypass pipe 81 is provided with a flow rate sensor 83 that detects the flow rate of water in the inlet pipe 71 and an incoming temperature sensor 84 that detects the incoming water temperature. In addition, in the instrument which estimated the incoming water temperature by calculation, the incoming water temperature sensor 84 may not be provided.

  In the middle of the bath return pipe 32, there is provided a bath circulation pump 85 for circulating the water in the bathtub 3 through the reheating circulation path (the bath return pipe 32, the reheating water pipe 72b, the bath going-out pipe 31). . A flowing water switch 86 provided in the bath return pipe 32 detects whether water is actually circulating in the recirculation path when the bath circulation pump 85 is operated.

  In addition, a bath-out temperature sensor 87 and a bath-return temperature sensor 88 are provided in the bath-out tube 31 and the bath-return tube 32, respectively.

  The control board 70 includes a CPU, a flash ROM that stores programs executed by the CPU, fixed data, and the like, and a RAM that temporarily stores various types of information when the CPU executes programs. Has been. Various sensors, valves, bath circulation pumps 85 and the like that the water heater 12 has are connected to the control base 70.

  Further, an operation panel (remote control) 89 is connected to the control board 70 via wiring. The operation panel 89 includes a switch for receiving various operations from the user, such as designation of a set temperature for hot water supply and a set temperature for a bath, start / end instructions for hot water filling and reheating, and power on / off, It consists of a display unit that displays the set temperature.

  In the hot water supply operation for discharging hot water from the hot water supply pipe 13, the control base 70 of the water heater 12 opens the combustion amount of the burner 73 and opens the bypass adjustment valve 82 so that hot water at the hot water supply set temperature set by the user on the operation panel 89 is discharged. Control the degree.

  In the hot water filling operation for pouring water into the bathtub 3, the control base 70 is heated through the hot water supply water pipe 72 a of the heat exchanger 72 by opening the hot water solenoid valve 78 and the water amount servo 79 with the burner 73 burned. Hot water is sent from the hot water supply pipe 13 to the connecting pipe 77 and flows into the bathtub 3 through both the bath return pipe 32 and the bath outlet pipe 31. At this time, the control board 70 controls the combustion amount of the burner 73, the opening degree of the bypass adjustment valve 82, and the like so that hot water having a bath set temperature set by the user on the operation panel 89 is poured. Further, when the water level in the bathtub 3 reaches the set water level, the pouring operation is stopped and the reheating operation is performed.

  In the reheating operation, the pouring electromagnetic valve 78 is closed, and the burner 73 is burned with the bath circulation pump 85 activated. As a result, the hot water in the bathtub 3 is taken into the water heater 12 through the bath return pipe 32 and heated, and the hot water after overheating is sent out to the bathtub 3 through the bath outlet pipe 31.

  The burner 73 of the water heater 12 cannot be combusted below a predetermined minimum heating amount (minimum number). Therefore, the control board 70 of the water heater 12 controls the burner 73 to be in a state where the burner 73 is burned off when the heating amount necessary for taking out the hot water at the set temperature is smaller than the minimum heating amount. The necessary amount of heating is calculated based on the temperature difference between the set temperature and the incoming water temperature detected by the incoming water temperature sensor 84, the flow rate detected by the flow sensor 83, the thermal efficiency, and the like.

  Next, various operations of the hot water storage system 11 will be described.

<Heat collection operation>
FIG. 3 shows a schematic operation of the heat collecting operation performed by the hot water storage system 11. The heat collecting operation is an operation of heating the water in the hot water storage tank 14 using heat obtained from sunlight by the heat collecting device 21. The heat collection operation is performed when an operation condition is satisfied such that the temperature detected by the high temperature sensor 51 of the heat collection device 21 is higher than the water temperature in the hot water storage tank 14 by a certain temperature or more.

  The hot water storage tank 14 receives supply of water from a water supply pipe 15 connected to a pipe connection port at the bottom, and is normally in a full state. During the heat collecting operation, the control unit 60 sets the switching valve 25 in a state where the first connection port 25a and the second connection port 25b communicate with each other and closes the third connection port 25c, and then drives the circulation pump 24. .

  In FIG. 3, the path through which the heat medium (water) circulates in the heat collecting operation is indicated by a bold line. The direction in which the heat medium flows in each part is indicated by arrows. Specifically, the heat medium in the cistern 19 flows toward the heat collecting device 21 through the third heat medium pipe 22c or the like by the action of the circulation pump 24, and is heated and heated when passing through the heat collecting device 21. Then, the refrigerant circulates from the fourth heat medium pipe 22d through the heat exchanging pipe 18 in the hot water storage tank 14 to return to the system 19. When the water temperature in the hot water storage tank 14 is lower than the heat medium passing through the heat exchange pipe 18, the heat of the heat medium moves to the water in the hot water storage tank 14 through the heat exchange pipe 18 and the water in the hot water storage tank 14 is heated. Is done.

  The heat exchange pipe 18 is located below the hot water storage tank 14, and water is supplied from the bottom of the hot water storage tank 14, and hot water flows out from the ceiling of the hot water storage tank 14 to the connection pipe 16. Has a lower temperature and a higher temperature gradient at the ceiling.

<Hot water supply operation>
FIG. 4 shows a schematic operation of the hot water supply operation. In FIG. 4, a path through which hot water flows in the hot water supply operation is indicated by a thick line. The direction in which hot water flows in each part is indicated by arrows. In the hot water supply operation, hot water from the hot water storage tank 14 and water supplied from the branch water supply pipe 15a are mixed by the mixing valve 17 and supplied to the water inlet (water inlet pipe 71) of the water heater 12. The hot water heater 12 heats the supplied water as needed and discharges it to the hot water supply pipe 13. Details of the hot water supply operation will be described later.

<Solar chasing operation>
FIG. 5 shows a schematic operation of the solar reheating operation. The solar reheating operation is an operation in which hot water in the bathtub 3 is supplementarily replenished using heat obtained from sunlight by the heat collecting device 21.

  In the solar reheating operation, the control unit 60 sets the switching valve 25 in a state where the first connection port 25a communicates with the second connection port 25b and closes the third connection port 25c, and then drives the circulation pump 24. To do. That is, the heat medium is circulated in the same manner as in the heat collection operation, and the heat medium is heated by the heat collection device 21. Further, in the solar reheating operation, the control unit 60 instructs the water heater 12 to drive the bath circulation pump 85 in a state where combustion (heating operation) is stopped.

  In FIG. 5, the path through which the heat medium (water) circulates in the solar reheating operation is indicated by a thick line. Moreover, the circulation path of bathtub water is shown with the thick broken line. Furthermore, the direction in which the heat medium flows and the direction in which the bath water flows are indicated by arrows in each part. In the solar reheating operation, the operation condition is that the temperature of the heat medium circulating in the heat medium circulation path 22 is higher than the temperature of the bath water, and the water-water heat exchanger 20 passes through the inner pipe line 20a. The bathtub water is heated by heat moving from the heat medium to the bathtub water passing through the outer pipe line 20b.

<Bath heat recovery operation>
FIG. 6 shows a schematic operation of the bath heat recovery operation. The bath heat recovery operation is an operation of heating the hot water in the hot water storage tank 14 using the heat of the remaining hot water in the bath.

  In the bath heat recovery operation, the control unit 60 sets the switching valve 25 in a state where the first connection port 25a and the third connection port 25c communicate with each other and the second connection port 25b is closed, and then drives the circulation pump 24. To do. As a result, the heat medium circulates through the water-water heat exchanger 20 and the hot water storage tank 14 without passing through the heat collector 21. Further, the hot water heater 12 is instructed to drive the bath circulation pump 85 in a state where combustion (heating operation) is stopped. As a result, the bathtub water circulates in the recirculation circulation path including the outer conduit 20 b of the water-water heat exchanger 20.

  In FIG. 6, the path through which the heat medium (water) circulates in the bath heat recovery operation and the circulation path of the bath water are indicated by bold lines. Moreover, the circulation path of bathtub water is shown with the thick broken line. Furthermore, in each part, the direction in which the heat medium flows and the direction in which the bathtub water flows are indicated by arrows. The bath heat recovery operation is operated under the condition that the water temperature in the hot water storage tank 14 (first temperature sensor 41) is lower than the water temperature in the bathtub 3, and the water-water heat exchanger 20 passes through the outer conduit 20b. Heat moves from the bathtub water to the bathtub water passing through the inner pipe line 20a, and this heat moves to the water in the hot water storage tank 14 through the heat exchange pipe 18, whereby the water in the hot water storage tank 14 is heated. Thereby, the burden of heat collection operation is reduced.

  More specifically, in the bath heat recovery operation, first, the bath circulation pump 85 is temporarily activated to check whether there is bathtub water. Then, when there is bathtub water and the temperature of the bathtub water is higher than the temperature detected by the first temperature sensor 41 by a predetermined temperature (for example, 15 ° C.) or more, the bath heat recovery operation is performed, and the difference is 10 ° C. or less or 1 hour. If it exceeds, driving is stopped. The time limit is based on the durability of the bath circulation pump 85.

<No hot water storage or hot water operation>
If the hot water in the hot water storage tank 14 is stopped for 100 hours or more, there is a problem due to reproduction of Legionella bacteria, and sterilization is performed as a countermeasure. In the hot water storage hot water prohibition operation, hot water discharge from the hot water storage tank 14 is prohibited, and sterilization is performed by continuing the state in which the water in the hot water storage tank 14 is 60 degrees or more for 15 minutes or longer.

  FIG. 7 shows an operating state during hot water storage / outflow prohibition. If most of the hot water in the hot water storage tank 14 is not used within 98 hours (here, 93 liters in 100 liters), the hot water storage hot water discharge prohibition operation is started. In the hot water storage hot water prohibition operation, the control unit 60 closes the hot water prohibition electromagnetic valve 54. Thereby, only the water supply from the branch water supply pipe 15 a is supplied to the water inlet of the water heater 12 through the connection pipe 16.

  Within 100 hours after entering the hot water storage / outflow prohibition operation, the entire hot water in the hot water storage tank 14 (first temperature sensor 41, second temperature sensor 42, third temperature sensor 43, fourth temperature sensor) by heat collection operation (solar heat). All the detected temperatures of 44) are monitored for 15 minutes or more in the state of 60 degrees or more (sterilization is completed). When sterilization is completed, the hot water prohibition solenoid valve 54 is opened to end the hot water storage and hot water prohibition operation. .

  If sterilization is not completed within 100 hours, the drainage solenoid valve 55 is opened, all hot water in the hot water storage tank 14 is drained with fresh water supplied from the bottom of the tank, and new water is filled in the hot water storage tank 14. Then, the hot water prohibition solenoid valve 54 is opened to end the hot water storage hot water prohibition operation.

<Details of hot water operation>
Next, the hot water supply operation according to the present invention will be described in more detail. As described above, since the water heater 12 cannot perform a heating operation below the minimum heating amount, the burner 73 is not combusted when the tapping temperature exceeds the set temperature when the minimum heating amount is heated. When the incoming water temperature is low and heating at a minimum heating amount or more is required to discharge hot water at a set temperature, the burner 73 is burned so that hot water at the set temperature is produced, and the amount of combustion is controlled.

  Since the hot water heater 12 operates as described above, when hot water is stored in the hot water storage tank 14 and hot water having a set temperature is supplied from the hot water storage system 11 to the water inlet of the hot water heater 12, the hot water heater 12 is combusted. Stays off. Therefore, when the heat exchanger 72 of the water heater 12 is cold at the start of hot water supply (so-called cold start), the heat of hot water is deprived while passing through the cold heat exchanger 72, so that The tapping temperature will be lower than the set temperature.

  In order to avoid this phenomenon, the hot water storage system 11 of the present invention has cooled the heat exchanger 72 of the water heater 12 even when hot water having a temperature higher than a predetermined temperature is stored in the hot water storage tank 14. In the case of the state, the mixing ratio of the mixing valve 17 is set to the water supplied to the water inlet of the water heater 12 so that heating by the water heater 12 (combustion of the burner 73) is performed and hot water is discharged at the set temperature. The mixing ratio is controlled so that the temperature is lower than the set temperature by a predetermined temperature or more. Since the water heater 12 controls the amount of heating in its own device so that the hot water is discharged at the set temperature, the amount of heat required to raise the temperature of the cooled heat exchanger 72 is also automatically controlled on the water heater 12 side. Therefore, the hot water storage system 11 only has to supply hot water at a temperature at which the water heater 12 ignites and performs the heating operation, and the subsequent temperature adjustment may be left to the water heater 12.

  The hot water storage system 11 determines that the heat exchanger 72 is in a cold state (cold start) when the hot water supply start time has passed a predetermined determination reference time from the end of the previous hot water supply operation. If it is before the lapse of time, it is determined that it is not cold (hot start).

  FIG. 8 shows a flow of operation of the hot water storage system 11 during the hot water supply operation. The control unit 60 of the hot water storage system 11 monitors whether or not the operation switch on the hot water heater 12 side is “ON” by communication with the control base 70 of the hot water heater 12 (step S101; No). When the operation switch on the water heater 12 side is turned “ON” (step S101; Yes), the amount of hot water supply (hot water amount) of the water heater 12 is equal to or greater than the minimum water amount (2.7 liters / minute in this example) that the burner 73 burns. Whether or not (step S102). The control unit 60 detects the amount of hot water supply with a water amount sensor 48 provided in the connection pipe 16.

  If the amount of hot water supply (hot water amount) of the water heater 12 is 2.7 liters / minute or more (step S102; Yes), the control unit 60 determines whether the water supply temperature (detected temperature of the water supply temperature sensor 47) is 25 ° C. or higher. Is determined (step S103). Depending on whether the feed water temperature is 25 ° C. or higher, the time (determination reference time) from the end of the previous hot water supply, which is a criterion for determining whether or not to cold start, is switched. That is, the temperature drop of the heat exchanger 72 of the water heater 12 with the passage of time from the end of the previous hot water supply is less in the summer than in the winter. In addition, refraining from additional heating in the water heater 12 leads to energy saving. Therefore, the reference time for determining whether or not it is a cold start is set longer in the summer than in the winter to reduce the frequency of additional heating. In this example, it is determined that a water supply temperature of 25 ° C. or higher is summer.

  If the feed water temperature is less than 25 ° C. (step S103; No), it is determined that a cold start has occurred if 8 minutes and 30 seconds (winter standard judgment time) have elapsed since the end of the previous hot water supply operation (step S104; No). Then, the hot water supply operation is started with combustion on the water heater 12 side (step S106).

  In step S106, the hot water supplied to the water inlet of the water heater 12 is heated by the combustion of the burner 73 regardless of whether or not the hot water in the hot water storage tank 14 has a set temperature of + 1 ° C. or higher. The mixing ratio of the mixing valve 17 is set so as to reach the temperature. That is, mixing is performed so that the temperature of the hot water after mixing by the mixing valve 17 is lower than the set temperature by a temperature increase equal to or higher than the temperature rise when the hot water heater 12 is heated by the minimum heating amount (minimum number). The mixing ratio of the valve 17 is set.

  Here, the set temperature-(the rising temperature when the minimum heating amount is heated in the water heater 12 + margin (for example, 1 ° C)) is set as the upper limit temperature of the hot water temperature supplied to the water inlet of the water heater 12. . When the temperature of hot water stored in the hot water storage tank 14 is equal to or higher than the upper limit temperature, hot water having an upper limit temperature is supplied, and when the temperature of hot water stored in the hot water storage tank 14 is lower than the upper limit temperature, supply is possible. Supply hot water at the highest temperature. That is, only hot water from the hot water storage tank 14 side is supplied without mixing water supply. In addition, after the hot water supply operation in step S106 is started, the temperature of the hot water supplied to the water inlet of the water heater 12 is controlled to be equal to or lower than the above upper limit temperature so that the heating operation by the water heater 12 is continued until the end of the hot water supply. .

  In addition, when installing the hot water storage system 11 in an existing house, assuming that the existing water heater 12 is diverted as an auxiliary heat source machine, various models are assumed as the water heater 12 to be used. Moreover, even if it is the same model, there is variation in the minimum heating amount for each appliance. Therefore, the above mixing ratio is set with the minimum amount of heat (for example, No. 4) as the minimum amount of heat added to the maximum minimum heating amount among all possible models, taking into account instrument variations and adding a predetermined margin. To do. Thereby, whatever type of hot water heater 12 is used for the auxiliary heat source machine, additional heating can be performed as intended on the hot water storage system 11 side.

  In the case of the existing water heater 12, the control unit 60 of the hot water storage system 11 receives various information such as a set temperature from the communication content between the water heater 12 and the remote controller 89 of the water heater 12, or as an instruction from the remote controller 89. A control signal may be transmitted to the control board 70.

  If the feed water temperature is less than 25 ° C. (step S103; No) and within 8 minutes and 30 seconds from the end of the previous hot water supply operation (step S104; Yes), it is determined that the cold start has not occurred. And it is investigated whether feed water temperature is 20 degreeC or more (step S107). If it is 20 ° C. or higher (step S107; Yes), it is checked whether or not the detected temperature of the fourth temperature sensor 44 for detecting the water temperature at the upper part of the hot water storage tank 14 (80 liters of water level from the bottom) is equal to or higher than the set temperature + 1 ° C. ( Step S108). If the set temperature is + 1 ° C. or higher (step S108; Yes), the hot water supply operation is started so that hot water is supplied without combustion on the hot water heater 12 side (step S109). That is, if the water heater 12 is not cold-started and hot water having a set temperature of + 1 ° C. can be supplied from the hot water storage system 11 side to the water inlet of the hot water heater 12, hot water is supplied without combustion on the hot water heater 12 side. Start hot water supply operation.

  In the hot water supply operation in step S109, the mixing ratio of the mixing valve 17 is set so that the temperature detected by the mixing temperature sensor 49 becomes the set temperature + 1 ° C. It should be noted that “+1” is set to the set temperature in consideration of the temperature decrease until the hot water is discharged from the hot water supply pipe 13 through the hot water heater 12. In addition, what is necessary is just to determine suitably how many times hot water sent out to the water inlet of the water heater 12 is set from setting temperature, and is not limited to +1 degreeC.

  If the temperature detected by the fourth temperature sensor 44 at the upper part of the hot water storage tank 14 is lower than the set temperature + 1 ° C. (step S108; No), it is determined that the hot water at the required temperature is not stored in the hot water storage tank 14 and “hot water has run out”. Then, the hot water supply operation is started with combustion on the water heater 12 side (step S106).

  If it is not a cold start and the feed water temperature is less than 20 ° C. (step S107; No), the temperature detected by the third temperature sensor 43 of the hot water storage tank 14 (the temperature sensor at a water level of 60 liters from the bottom) is higher than the set temperature + 1 ° C. Whether or not (step S111). If the temperature detected by the third temperature sensor 43 is equal to or higher than the set temperature + 1 ° C. (step S111; Yes), the hot water heater 12 is not cold-started and hot water having the set temperature + 1 ° C. is entered from the hot water storage system 11 side. It is determined that the water can be supplied to the water inlet, and the hot water supply operation is started so that the hot water is supplied without combustion on the water heater 12 side (step S109).

  When the detected temperature of the third temperature sensor 43 is lower than the set temperature + 1 ° C. (step S111; No), it is determined that the hot water has run out, and the hot water supply operation is started with combustion on the hot water heater 12 side (step S106).

The fourth temperature sensor 44 and the third temperature sensor 43 are switched depending on whether the feed water temperature is lower than 20 ° C. for the following reason.
When hot water runs out, hot water is in the upper part of the hot water storage tank 14, and the lower layer is water having a temperature close to that of water supplied from the lower part of the hot water storage tank 14. For this reason, the temperature difference between the hot water in the upper part of the hot water storage tank 14 and the hot water in the lower layer becomes larger as the feed water temperature is lower. If this temperature difference is large, the hot water at the upper part of the hot water tank 14 disappears, and when the hot water at the lower layer begins to come out of the hot water tank 14 (runs out), the temperature of the hot water supplied to the water heater 12 suddenly decreases. As a result, the combustion control of the water heater 12 cannot catch up, causing a phenomenon that the temperature of the hot water is temporarily lowered. Therefore, when the feed water temperature is low, the temperature of the hot water supplied to the water heater 12 is gradually increased by increasing the mixing rate of the feed water in the mixing valve 17 that mixes the hot water and the feed water from the hot water storage tank 14 before the hot water runs out. Control is performed to gradually reduce the. In this way, when the hot water runs out, the mixing rate of the feed water in the mixing valve 17 has already increased, so even if the temperature of the hot water supplied from the hot water storage tank 14 suddenly drops due to hot water running out, the mixing valve 17 Therefore, the temperature change of the hot water supplied to the hot water heater 12 is kept small. Thereby, the phenomenon in which the temperature of the hot water from the water heater 12 temporarily decreases when the hot water runs out is prevented. As described above, in order to perform control for gradually increasing the mixing rate of the feed water in the mixing valve 17 before running out of hot water, it is necessary to earn time required for the control before running out of hot water. That is, it is necessary to start this control in a state where a lot of hot water remains in the upper part of the hot water storage tank 14. Therefore, when the feed water temperature is low (less than 20 ° C.), the amount of hot water in the upper part of the hot water storage tank 14 necessary for starting hot water supply with combustion of the hot water heater is determined when the feed water temperature is high (when 20 ° C. or more ) And more. That is, if the feed water temperature is 20 ° C. or higher (step S107; Yes), the hot water temperature at the water level 20 liters below the ceiling of the hot water storage tank 14 is detected as to whether or not the hot water supply is started with the hot water heater combustion. Judgment is made using the fourth temperature sensor 44 (step S108), and if it is less than 20 ° C., judgment is made using the third temperature sensor 43 that detects the hot water temperature of the water level 40 liters below from the top (step S111). .

  If the feed water temperature is 25 ° C. or higher (step S103; Yes), if 17 minutes (summer judgment reference time) has elapsed since the end of the previous hot water supply operation (step S105; No), it is determined that the cold start, The hot water supply operation is started with combustion on the water heater 12 side (step S106).

  If the feed water temperature is 25 ° C. or higher (step S103; Yes) and within 17 minutes from the end of the previous hot water supply operation (step S105; Yes), it is determined that the cold start has not occurred. And it is investigated whether the detection temperature of the 4th temperature sensor 44 which detects the water temperature of the upper part of the hot water storage tank 14 is set temperature + 1 degreeC or more (step S112), and if it is set temperature + 1 degreeC or more (step S112; Yes). Then, a hot water supply operation is started so that hot water is supplied without combustion on the hot water heater 12 side (step S109). When the temperature detected by the fourth temperature sensor 44 at the upper part of the hot water storage tank 14 is lower than the set temperature + 1 ° C. (step S112; No), it is determined that the hot water storage tank 14 is out of hot water, and hot water is supplied with combustion on the hot water heater 12 side. The operation is started (step S106).

  In this way, it is determined whether or not the heat exchanger 72 of the water heater 12 is in a cold state (cold start). If the heat exchanger 72 is in a cold state, even if hot water having a set temperature can be supplied from the hot water storage tank 14. In addition, hot water having a low temperature is intentionally supplied to the water heater 12 so that the water heater 12 is heated. Thereby, as a result of supplying hot water at a set temperature from the hot water storage system 11 to the water heater 12, the occurrence of a phenomenon that the hot water is taken away by the cooled heat exchanger 72 and the hot water temperature falls below the set temperature is avoided, The set temperature can be discharged.

  Further, since it is determined whether or not the heat exchanger 72 is in a cold state based on the elapsed time from the end of the previous hot water supply operation, a lot of information about the hot water heater 12 can be obtained as in the case where the existing hot water heater 12 is diverted. Even if it cannot be transferred, it is possible to easily recognize whether or not the heat exchanger 72 of the water heater 12 is in the cold state on the hot water storage system 11 side. Moreover, since the reference time for determining whether or not the heat exchanger 72 is in the cold state is longer in the summer than in the winter, the number of times that the heat exchanger 72 is determined to be cold in the summer is reduced. Accordingly, the execution of additional heating is suppressed, and energy saving is promoted by preferential use of hot water on the hot water storage system 11 side.

  In the embodiment, the determination reference time serving as a determination reference for determining whether or not the heat exchanger 72 of the water heater 12 is in a cold state is switched according to the feed water temperature. However, the outside air temperature or the feed water temperature You may make it switch based on the combination with outside temperature.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  In the embodiment, the auxiliary heat source machine is the type of water heater 12 that burns the burner 73, but is not limited thereto. The application of the present invention is useful if it is an auxiliary heat source device of a system that heats hot and cold water with a heat exchanger that becomes a radiator in a cold state.

  Further, in the embodiment, the determination reference time is switched between 8 minutes 30 seconds and two stages of 17 minutes. However, the determination reference time may be switched to multiple stages according to the water supply temperature or the outside air temperature, or continuously (stepless). It may be configured to change to

  In the embodiment, the water in the hot water storage tank 14 is heated using the solar heat collecting device 21, but the heating device for heating the water in the hot water storage tank 14 is not limited to this. Any device that uses the exhaust heat of the machine may be used.

  In the embodiment, the hot water storage system 11 is assumed to be used for existing hot water heaters, but the hot water storage system 11 may include a dedicated hot water heater 12. In this case, since characteristics such as the minimum heating amount of the water heater 12 can be well understood, the mixing ratio may be adjusted in accordance with the characteristics of the water heater 12.

  In the embodiment, the hot water heater 12 is a single-can two-water channel type, but it may be a hot water heater in which the reheating of the bath and the hot water supply are performed by separate heat exchangers.

  Since the hot water heater 12 cannot perform a heating operation below the minimum heating amount, the burner 73 is not combusted when the tapping temperature exceeds the set temperature when the minimum heating amount is heated. Although it is made not to burn when filling with hot water, it may be made to burn when using a shower or hot water supply. This is because there are people who enter the tub as “donbon” (it takes time to get hot water), but when you use the shower or hot water, you can avoid the shower, This is because it can be removed. Further, since the temperature at which the shower is taken is considered to be 45 degrees or less, for example, when the hot water is filled in the bathtub, the hot water is not burned when the hot water is used at a predetermined temperature or lower.

DESCRIPTION OF SYMBOLS 3 ... Bathtub 10 ... Hot water supply system 11 ... Hot water storage system 12 ... Hot water supply device 13 ... Hot water supply pipe 14 ... Hot water storage tank 15 ... Water supply pipe 15a ... Branch water supply pipe 16 ... Connection pipe 17 ... Mixing valve 17a ... First valve 17b ... Second valve DESCRIPTION OF SYMBOLS 18 ... Piping for heat exchange 19 ... Systurn 19a ... Water level sensor 20 ... Water-water heat exchanger 20a ... Inner pipe line 20b ... Outer pipe line 21 ... Heat collecting device 22 ... Heat-medium circulation path 22a ... First heat-medium pipe 22b 2nd heat medium pipe 22c ... 3rd heat medium pipe 22d ... 4th heat medium pipe 24 ... Circulation pump 25 ... Switching valve 25a ... 1st connection port 25b ... 2nd connection port 25c ... 3rd connection port 26 ... Connection pipe DESCRIPTION OF SYMBOLS 31 ... Bath going pipe 32 ... Bath return pipe 41 ... 1st temperature sensor 42 ... 2nd temperature sensor 43 ... 3rd temperature sensor 44 ... 4th temperature sensor 46 ... Tank hot water temperature sensor 47 ... Supply water temperature Sensor 48 ... Water volume sensor 49 ... Mixing temperature sensor 51 ... High temperature sensor 52 ... Heat medium temperature sensor 53 ... Bath temperature sensor 54 ... Hot water prohibition solenoid valve 55 ... Drain solenoid valve 56 ... Pressure relief valve 60 ... Control unit 70 ... Control base 71 Inlet pipe 72 ... Heat exchanger 72a ... Hot water supply pipe 72b ... Additional cooking water pipe 72c ... Fin 73 ... Burner 74 ... Gas supply pipe 75 ... Gas valve 76 ... Proportional valve 77 ... Connecting pipe 78 ... Pouring solenoid valve 79 ... Water volume servo 80 ... Hot water temperature sensor 81 ... Bypass pipe 82 ... Bypass adjustment valve 83 ... Flow rate sensor 84 ... Incoming water temperature sensor 85 ... Bath circulation pump 86 ... Flowing water switch 87 ... Bathing temperature sensor 88 ... Bath return temperature sensor 89 ... Operation panel (Remote controller)

Claims (5)

A hot water storage tank with a water supply channel connected to the entrance;
A heater for heating the water stored in the hot water storage tank;
A connection pipe that connects the water inlet of the auxiliary heat source machine that heats and supplies the water supplied from the water inlet with a heat exchanger and the outlet of the hot water storage tank;
A mixing valve that is inserted in the middle of the connection pipe and mixes water supplied from the hot water storage tank and water supplied from a water supply channel;
A control unit for controlling the mixing ratio of the mixing valve so that the set temperature is discharged without heating by the auxiliary heat source device or by adding heating by the auxiliary heat source device;
With
Wherein, at the start of hot water supply, the case of the state stored hot predetermined temperature or higher than the set temperature in the tank higher the previous even when the hot water is stored Symbol auxiliary heat source machine heat exchanger is cold, the entering- The mixing ratio of the mixing valve at the start of hot water supply is controlled so that the temperature of the water supplied to the water inlet becomes the incoming water temperature at which the hot water of the set temperature is discharged by adding heating by the auxiliary heat source device, and at the start of hot water supply In the case where hot water higher than the preset temperature is stored in the hot water storage tank and the heat exchanger of the auxiliary heat source machine is not in a cold state, the set temperature without heating by the auxiliary heat source machine A hot water storage system, wherein the mixing ratio of the mixing valve at the start of hot water supply is controlled so that hot water is discharged. The control unit determines that the heat exchanger is in the cold state when a predetermined determination reference time or more has elapsed since the end of the last pouring, and before the elapse of the determination reference time from the end of the last pouring If it is, it will be judged that the said heat exchanger is not the said cold state. The hot water storage system of Claim 1 characterized by the above-mentioned. The control unit makes the determination reference time longer when the feed water temperature or the outside air temperature is higher than the first temperature than the time set when the feed water temperature or the outside air temperature is lower than the first temperature. The hot water storage system according to claim 2 . The auxiliary heat source machine can only perform a heating operation over a predetermined minimum heating amount,
The control unit sets a heat amount obtained by adding a predetermined margin to a maximum minimum heating amount among a plurality of auxiliary heat source units that can be used by being connected to the hot water storage system as a minimum heating amount, and performs heating by the auxiliary heat source unit. In the case where the hot water is discharged at the set temperature, the temperature of the water supplied to the water inlet is a temperature obtained by subtracting the temperature rise in the auxiliary heat source unit due to the minimum heating amount from the set temperature. The hot water storage system according to any one of claims 1 to 3 , wherein the mixing ratio is set to be as follows. Having the auxiliary heat source machine,
The auxiliary heat source machine can only perform a heating operation over a predetermined minimum heating amount,
In the case where the control unit sets a heat amount obtained by adding a predetermined margin to a minimum heating amount of the auxiliary heat source unit as a minimum heating amount, and adds heating by the auxiliary heat source unit so that the set temperature is discharged. The mixing ratio is set so that the temperature of the water supplied to the water inlet is equal to or lower than the temperature obtained by subtracting the temperature increase in the auxiliary heat source unit due to the minimum heating amount from the set temperature. The hot water storage system according to any one of claims 1 to 3 .

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