JP2013133995A - Hot water storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot water storage system that need not use a gas water heater having a heating function as a backup heat source machine.SOLUTION: A hot water storage system includes a hot water storage tank 13 which stores supplied water and an exhaust heat recovery device 50 which recovers heat exhausted from a fuel cell 4 to heat water in the hot water storage tank, wherein a gas water heater 70 performs additional heating to cover shortfall in case heat stored in the hot water storage tank is not sufficient for supplying hot water at a set temperature. The hot water storage system further includes a drainage pipe 46 branched from a hot water supply pipe 63 connected to a hot water supply port of the gas water heater and a drainage control valve 45 which opens or closes the drainage pipe, wherein the drainage control valve 45 is opened to drain the hot water obtained by combusting a gas by the gas water heater 70 via the drainage pipe 46 as an avoidable operation against gas supply stop by a gas meter owing to a long continuous use of a minute amount of gas by the fuel cell 4. In addition, when there remains water in the hot water storage tank for a long time, all water in the hot water storage tank is replaced by new water by turning a three-way valve 43 in the F direction to open the drainage control valve 46.

Description

  The present invention relates to a hot water storage system that recovers exhaust heat from a heat source such as a fuel cell (gas engine generator, fuel processing device (reformer), etc.) and heats hot water in a hot water storage tank to supply hot water. The present invention relates to a hot water storage system that supplies hot water by supplementing the shortage with a gas water heater when the heat storage in the tank is insufficient.

  FIG. 16 shows a configuration example of a hot water storage system 100 that recovers exhaust heat of the fuel cell. The hot water storage system 100 includes a hot water storage tank unit 101, an exhaust heat recovery device 110 that recovers exhaust heat of the fuel cell 130, and a gas water heater 120 as a backup heat source unit. The exhaust heat recovery device 110 includes an exhaust heat recovery heat exchanger 111 and an exhaust heat recovery pump 112. When the exhaust heat recovery pump 112 is operated, the hot water in the hot water storage tank 102 is stored from the lower part of the hot water storage tank via the heat recovery pipe (low temperature) 114, the exhaust heat recovery heat exchanger 111, and the heat recovery pipe (high temperature) 115. It circulates through the path returning to the upper part of the tank 102 and is heated when passing through the exhaust heat recovery heat exchanger 111.

  A water supply pipe 104 is connected to the lower water supply port 103 of the hot water storage tank 102, and a hot water discharge pipe 106 is connected to the upper hot water outlet 105. A mixer 107 that mixes hot water from the hot water storage tank 102 and water from the water supply pipe 104 at a set mixing ratio is provided in the middle of the hot water discharge pipe 106, and the outlet side of the mixer 107 is connected piping. A pipe 121 is connected to a water supply connection port 122 of the gas water heater 120.

  In the hot water storage system 100, when hot water is supplied in a state where the hot water storage tank 102 has sufficiently stored heat, the hot water in the hot water storage tank 102 and the hot water are mixed by the mixer 107 to form hot water having a set temperature and sent to the gas water heater 120. The gas water heater 120 supplies hot water as it is without performing additional heating. When there is no heat storage in the hot water storage tank 102, hot water or water having a temperature lower than the set temperature in the hot water storage tank 102 is sent to the gas water heater 120 and heated to the set temperature by the gas water heater 120 to supply hot water. If the hot water in the hot water storage tank 102 is slightly lower than the set temperature and is sent to the gas water heater 120 as it is, the hot water temperature will exceed the set temperature even if the gas water heater 120 is operated with the minimum capacity. For example, the hot water from the hot water storage tank 102 mixed with the hot water and deliberately lowered in temperature is sent to the gas water heater 120 and heated to the set temperature by the gas water heater 120 to supply hot water.

  By the way, the fuel cell, which is a heat source for raising the temperature of the water in the hot water storage tank, extracts hydrogen from the gas supplied from the gas supply company and generates electricity from this hydrogen and oxygen in the air. The amount of gas used for power generation is very small compared to gas water heaters. In addition, power generation by the fuel cell is often continued for a long time.

  On the other hand, recent gas meters equipped with a microcomputer incorporate a control for shutting off gas when a constant flow rate of gas continues for a long time for safety. This control is generally referred to as microcomputer meter shut-off after long use.

  A fuel cell having a power generation output of 1 Kw or less used for home use consumes a small amount of gas, and even if the power generation output is changed, the gas meter side determines that the flow rate is constant. Therefore, if power generation by the fuel cell continues for a long time in a state where no gas is used by another instrument, even if the power generation amount is changed, the microcomputer meter shutoff is activated. When the microcomputer meter shut-off operates, other gas appliances such as a gas stove as well as a fuel cell and a gas water heater as a backup heat source machine cannot be operated, which is inconvenient for the user. In addition, it is possible to recover from shut-down of the microcomputer meter by performing a predetermined operation on the gas meter, but general users often do not know this countermeasure. Further, in a fuel cell, if the fuel gas suddenly stops during power generation, the durability is not good.

  Therefore, in a conventional hot water storage system using a fuel cell as a heat source, a gas water heater equipped with a heating circuit is used as a backup heat source machine, and the gas flow rate is greatly changed by burning a burner for the heating circuit. The microcomputer meter was cut off. Specifically, as shown in FIG. 16, a reheating heat exchanger 141 for exchanging heat between the heating circuit (heating pipe) 127 and the heat recovery pipe (high temperature) 115 is provided in the hot water storage tank unit 101. In the gas water heater 120, the heating pump 126 is operated while the heating heat exchanger 124 is heated by the burner 125, and the exhaust heat recovery pump 112 of the exhaust heat recovery device 110 is operated. Thereby, gas is consumed in the operation | movement which heats the water of the hot water storage tank 102 with the reheating heat exchanger 141, and microcomputer meter interruption | blocking is avoided.

  In addition, the heating by the heating circuit 127 is also used for sterilizing hot water in the hot water storage tank 102. That is, if the water (or hot water) in the hot water storage tank stays for a long time without being used, the water (or hot water) may become unsanitary due to reproduction of Legionella bacteria. Legionella bacteria die when heated to a high temperature (about 60 ° C). Conventionally, water (or hot water) in a hot water tank is used for a long time to keep the water (or hot water) in the hot water tank hygienic. It incorporates a reheating control to boil all the water (or hot water) in the hot water storage tank to 60 ° C or higher when it is detected that this has not been done. Was going to use.

JP 2010-236713 A JP 2007-10244 A Japanese Patent No. 4559307 Japanese Patent No. 3935416

  In the conventional hot water storage system, since the heating function of the gas water heater is used for avoiding microcomputer meter shut-off and sterilization, a gas water heater having a heating function is essential as a backup heat source machine. However, a gas water heater with a heating function is more expensive than a gas water heater without the function. In addition, in a configuration in which the heating function is used to avoid microcomputer meter shut-off and reheating for sterilization, a heat exchanger for reheating is required in the hot water storage tank unit, and further, a gas water heater and a hot water storage tank unit are connected. Since heating piping is required in between, the entire system will increase in cost.

  An object of the present invention is to provide a hot water storage system that can avoid microcomputer meter interruption without using a gas water heater having a heating function as a backup heat source device.

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

[1] A case in which a hot water storage tank to which hot water is supplied and a heating device that recovers exhaust heat from a heat source and heats the water in the hot water storage tank are provided, and the hot water storage in the hot water storage tank is insufficient for hot water at a set temperature In a hot water storage system that uses a gas water heater to heat the shortage,
A drain pipe branched from a hot water pipe connected to the hot water outlet of the gas water heater;
A drainage control valve for opening and closing the drainage pipe;
As an operation of avoiding that the gas meter shuts off the gas supply due to long-term continuous use of a small amount of gas by the heat source, the hot water obtained by opening the drain control valve and burning the gas with the gas water heater from the drain pipe A hot water storage system comprising: a control unit that performs an operation of draining water.

  In the above-described invention, gas hot water supply is performed as an operation for preventing the gas meter from shutting off the supply of gas due to long-term continuous use of a small amount of gas by a heat source such as a fuel cell (gas engine generator, fuel processing device (reformer), etc.). The operation of draining the hot water obtained by burning the gas in the vessel from the drain pipe.

[2] A second drain pipe communicating with the hot water outlet of the hot water storage tank, and a second drain control valve for opening and closing the second drain pipe,
The hot water storage system according to [1], wherein the control unit opens the second drainage control valve when performing an operation of replacing water in the hot water storage tank.

  In the above invention, when the operation of replacing the water in the hot water storage tank is performed, the accumulated water in the hot water storage tank is drained by opening the second drainage control valve and replaced with new water supply.

[3] A mixer that connects the hot water supply pipe, a first tank hot water pipe connected to the hot water outlet of the hot water storage tank, and a water supply pipe, mixes hot water from these at a set mixing ratio, and supplies hot water;
A first state including a first inlet, a second inlet, and an outlet, wherein the first inlet and the outlet are in communication with each other and the second inlet is closed; and the second inlet and the outlet are in communication with each other. A three-way valve that switches to the second state with the inlet closed;
Further comprising
The gas water heater is supplied with water from a water supply pipe,
The drain pipe is divided into an upstream drain pipe on the hot water supply pipe side and a downstream drain pipe,
The drainage control valve opens and closes the downstream drainage pipe;
The upstream drain pipe is connected to the first inlet of the three-way valve, the second tank outlet pipe connected to the outlet of the hot water storage tank is connected to the second inlet, and the downstream drain pipe is connected to the outlet. ,
The controller is
While controlling the heating by the gas water heater and the mixing ratio of the mixer so that hot water at a set temperature is supplied from the outlet side of the mixer,
In the avoidance operation, the three-way valve is set to the first state, the drainage control valve is opened, and when the operation of replacing the water in the hot water storage tank is performed, the three-way valve is set to the second state, The hot water storage system according to [1], wherein the drainage control valve is opened.

  The hot water storage system of the above invention employs a system (post-mixing system) in which hot water from a gas water heater, hot water from a hot water storage tank, and hot water from a water supply pipe are mixed in a mixer to supply hot water at a set temperature. . Also, in the avoidance operation of the gas meter shutting off the gas supply due to long-term continuous use of a small amount of gas by a fuel cell or the like, the gas water heater can be operated by setting the three-way valve to the first state and opening the drainage control valve. The operation of draining hot water obtained by burning gas. Further, in the operation of replacing the water in the hot water storage tank, the water in the hot water storage tank is drained and replaced with new water supply by setting the three-way valve to the second state and opening the drainage control valve.

[4] A first tank hot water pipe connected to the hot water outlet of the hot water storage tank and a water supply pipe are connected to mix hot water from these at a set mixing ratio, and the outlet side to the water hot water outlet of the gas water heater. A piped mixer;
A first state including a first inlet, a second inlet, and an outlet, wherein the first inlet and the outlet are in communication with each other and the second inlet is closed; and the second inlet and the outlet are in communication with each other. A three-way valve that switches to the second state with the inlet closed;
Further comprising
The drain pipe is divided into an upstream drain pipe on the hot water supply pipe side and a downstream drain pipe,
The drainage control valve opens and closes the downstream drainage pipe;
The upstream drain pipe is connected to the first inlet of the three-way valve, the second tank outlet pipe connected to the outlet of the hot water storage tank is connected to the second inlet, and the downstream drain pipe is connected to the outlet. And
The controller is
While controlling the mixing ratio of the mixer so that hot water at a set temperature is performed from the gas water heater without additional heating by the gas water heater or by adding heating by the gas water heater,
In the avoidance operation, the three-way valve is set to the first state and the drainage control valve is opened,
The hot water storage system according to [1], wherein when performing the operation of replacing water in the hot water storage tank, the three-way valve is set to the second state and the drainage control valve is opened.

  The hot water storage system of the above invention is a system for supplying hot water by mixing hot water from a hot water storage tank and water supplied from a water supply pipe with a mixer to the gas water heater and heating the shortage with the gas water heater (water supply preheating system) ) Is adopted. Also, in the avoidance operation of the gas meter shutting off the gas supply due to long-term continuous use of a small amount of gas by a fuel cell or the like, the gas water heater can be operated by setting the three-way valve to the first state and opening the drainage control valve. The operation of draining hot water obtained by burning gas. Further, in the operation of replacing the water in the hot water storage tank, the water in the hot water storage tank is drained and replaced with new water supply by setting the three-way valve to the second state and opening the drainage control valve.

[5] The hot water storage system according to [4], wherein in the avoidance operation, the mixer is set so that water is supplied to the gas water heater.

  In the above invention, in the operation of avoiding the interruption of the gas supply by the gas meter, the feed water is sent to the gas water heater and the hot water heated by the gas water heater is drained, so that the hot water in the hot water storage tank is consumed for the avoidance operation. Is prevented.

[6] Measure the amount of feed water flowing into the hot water storage tank during the replacement operation,
Any one of [2] to [5], wherein the control unit terminates the replacement operation after confirming that all of the hot water storage tank has been replaced with new water supply from the measured amount of water. The hot water storage system according to item 1.

  In the above-described invention, it is confirmed that the water in the hot water storage tank has been completely replaced with new water supply, and the replacement operation ends. It should be noted that complete replacement can be performed without waste if the replacement operation is terminated when the amount of water is equal to or greater than the capacity of the hot water storage tank plus the piping capacity of the drainage path.

[7] The upstream drain pipe is branched from a location near the mixer in the hot water pipe from the gas water heater to the mixer,
The controller is
As a hot water supply control mode, there are a first mode in which hot water and hot water from a hot water storage tank are mixed to supply hot water of a set temperature, and hot water and hot water heated to a temperature higher than the set temperature by the gas water heater. And at least a second mode of mixing and supplying hot water at a set temperature,
When switching to the second mode during the hot water supply operation in the first mode, the hot water heated by the gas water heater with the three-way valve in the first state and the drain control valve opened is drained from the downstream drain pipe. The hot water storage system according to [3], wherein after the elapse of a predetermined time since the setting is made, the drainage control valve is closed to shift to the hot water supply operation in the second mode.

  In the above invention, in the hot water storage system of the post-mixing type, as the hot water control mode, the first mode in which hot water and hot water from the hot water storage tank are mixed to supply hot water at a set temperature and the hot water from the set temperature with the backup heat source machine. A second mode in which hot water heated to a high temperature and water supply are mixed to supply hot water at a set temperature. When switching to the second mode during the hot water supply operation in the first mode, the drain control valve is opened, and the hot water heated by the gas water heater is set to be discharged from the drain pipe. Control is performed to return to the second mode hot water supply operation by returning the drainage control valve to the closed state after the cold water in the pipe from the gas water heater to the mixer is drained while continuing this state for a predetermined time. .

[8] The hot water storage system according to [7], wherein after the predetermined time has elapsed, at least hot water heated by the gas water heater has reached the upstream drain pipe.

  In the above invention, drainage is continued until at least all the water accumulated in the pipe from the gas water heater to the branching point when switching from the first mode to the second mode flows out to the upstream drainage pipe.

[9] The control unit
As a hot water supply control mode, there are a first mode in which hot water and hot water from a hot water storage tank are mixed to supply hot water of a set temperature, and hot water and hot water heated to a temperature higher than the set temperature by the gas water heater. A second mode in which hot water at a set temperature is mixed and hot water heated by the gas water heater, hot water from the hot water storage tank and hot water are mixed to supply hot water at a set temperature; Have
In the hot water supply operation, the first mode is preferentially selected, and when the hot water having the set temperature cannot be supplied in the first mode and hot water not lower than the predetermined temperature by the predetermined temperature or higher can be supplied from the hot water storage tank, the third mode is selected. The hot water storage system according to [3], [7], or [8], wherein a mode is selected and the second mode is selected when the third mode cannot be selected.

  In the above invention, the hot water in the hot water storage tank heated by the exhaust heat is effectively used by preferentially using the first mode in which hot water from the hot water storage tank and the hot water are mixed to supply hot water at the set temperature. The Furthermore, although the hot water temperature in the hot water storage tank is lower than the set temperature and hot water supply in the first mode is not possible, if there is hot water in the hot water storage tank that is not lower than the set temperature by a predetermined temperature or more, the third hot water is used. Since hot water is supplied in the mode, hot water supply using hot water in the hot water storage tank is possible even when the set temperature is not reached, and the hot water utilization rate of the hot water storage tank can be increased.

  According to the hot water storage system according to the present invention, it is possible to prevent the gas meter from shutting off the gas supply due to long-term continuous use of a small amount of gas by the fuel cell without using a gas water heater having a heating function as a backup heat source device. can do. In addition, when performing the operation of replacing the water in the hot water storage tank, the accumulated water in the hot water storage tank is drained by opening the second drainage control valve and replaced with new water supply. Since it is not necessary to reheat and sterilize the water with the heating function of the gas water heater, a gas water heater without a heating function can be used as a backup heat source.

It is a figure which shows schematic structure of the bath hot-water supply system (water-supply preheating system) which concerns on 1st Embodiment. It is a figure which shows the structural example of a bath water heater. It is explanatory drawing which shows the flow of the hot water in the waste heat recovery operation | movement of the bath hot-water supply system which concerns on 1st Embodiment. It is explanatory drawing which shows the flow of the hot water in the hot water supply operation | movement of the bath hot water system which concerns on 1st Embodiment. It is explanatory drawing which shows the flow of the hot water in the microcomputer meter interruption | blocking avoidance operation | movement of the bath hot-water supply system which concerns on 1st Embodiment. It is explanatory drawing which shows the flow of the hot water in the tank retention water drainage operation | movement of the bath hot-water supply system which concerns on 1st Embodiment. It is a figure which shows schematic structure of the bath hot-water supply system (post-mixing system) which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water in the hot water supply operation | movement of the 1st mode of the bath hot-water supply system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water in the hot water supply operation | movement of the 2nd mode of the bath hot water system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water in the hot water supply operation | movement of the 3rd mode of the bath hot water system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water at the time of switching from a 1st mode to a 2nd mode in the bath hot-water supply system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water of the state in the middle of the transition which gradually increased the mixing ratio of the hot water from a bath water heater at the time of switching from the 1st mode to the 2nd mode in the bath hot water system which concerns on 2nd Embodiment. is there. It is explanatory drawing which shows the flow of the hot water in the microcomputer meter interruption | blocking avoidance operation | movement of the bath hot-water supply system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water in the tank retention water drainage operation | movement of the bath hot-water supply system which concerns on 2nd Embodiment. It is explanatory drawing which shows the flow of the hot water in the pouring operation | movement of the bath hot-water supply system which concerns on 2nd Embodiment. It is a figure which shows the conventional hot water storage system which uses the gas water heater provided with the heating function as a backup heat source machine.

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

  The basic concept of the present invention will be described.

  The hot water storage system according to the present invention includes a path for draining hot water from a gas water heater as a backup heat source unit, and as an avoidance operation for shutting down the microcomputer meter, an operation for draining hot water obtained by heating the water with the gas water heater. I do. In addition, when the water (or hot water) in the hot water storage tank stays without being used for a long period of time, the hot water in the hot water storage tank is drained and replenished with water to be replaced with new water.

  Next, a first embodiment of the present invention will be described.

  FIG. 1 shows a configuration of a bath hot water supply system 10 according to a first embodiment to which a hot water storage system of the present invention is applied. In the hot water supply system 10 according to the first embodiment, when the hot water temperature in the hot water storage tank 13 is sufficiently high, the hot water from the hot water storage tank 13 is mixed with the hot water and the hot water at the set temperature is discharged and the hot water is set to the set temperature. In the case where it is not sufficient, a system (water supply preheating system) is employed in which the hot water in the hot water storage tank 13 is heated to a set temperature by the bath water heater 70 at the subsequent stage.

  The bath hot water supply system 10 includes a hot water storage tank unit 11, a heat source unit 4 including a fuel cell, an exhaust heat recovery device 50, and a bath water heater 70 as a backup heat source unit. In the figure, piping between apparatuses and external piping are indicated by double arrows.

  The hot water storage tank unit 11 includes a hot water storage tank 13 that stores water supplied from a water supply pipe 12. The hot water storage tank 13 is a hollow, substantially cylindrical tank, with a water supply port 14 provided at the lower part and a hot water outlet 15 provided at the upper part. Further, a water intake port 16 is provided at the lower part of the hot water storage tank 13 and a return port 17 is provided at the upper part.

  The hot water storage tank 13 has, for example, a capacity of about 100 liters, and a first temperature sensor 18a for detecting the water temperature at the water level of 20 liters from the bottom has a water level of 40 liters from the bottom. A second temperature sensor 18b for detecting the water temperature at the location is located at a location where the water level is 60 liters from the bottom, and a third temperature sensor 18c for detecting the water temperature at the location is located at a location where the water level is 80 liters from the bottom. A hot water temperature sensor 18d for detecting the water temperature is further provided, and a tank upper temperature sensor 18e for detecting the water temperature at the location is provided at the uppermost part of the hot water storage tank 13, respectively.

  The exhaust heat recovery device 50 is provided in the heat source unit 4 or the like and recovers the exhaust heat of the heat source unit 4. The exhaust heat recovery device 50 includes an exhaust heat recovery heat exchanger 51 and an exhaust heat recovery pump 52. The exhaust heat recovery heat exchanger 51 of the hot water storage tank 13 and the exhaust heat recovery device 50 has a heat recovery pipe 53 (53a, 53b) so that an exhaust heat recovery circulation path for circulating the water of the hot water storage tank 13 is formed between them. ). Specifically, one end of a heat recovery pipe (low temperature) 53 a is connected to the water intake 16 of the hot water storage tank 13, and the other end of the heat recovery pipe (low temperature) 53 a is connected to the inlet side of the exhaust heat recovery heat exchanger 51. ing. The exhaust heat recovery pump 52 is inserted into a heat recovery pipe (low temperature) 53a in the vicinity of the entrance side of the exhaust heat recovery heat exchanger 51, and the exhaust heat recovery pump 52 uses the water in the heat recovery pipe (low temperature) 53a. Water is fed from the intake 16 side of the hot water storage tank 13 toward the entrance side of the exhaust heat recovery heat exchanger 51.

  One end of a heat recovery pipe (high temperature) 53 b is connected to the outlet side of the exhaust heat recovery heat exchanger 51, and the other end of the heat recovery pipe (high temperature) 53 b is a first of the first three-way valve 21 in the hot water storage tank unit 11. It is connected to the connection port 21a.

  The first three-way valve 21 includes the first connection port 21a, the second connection port 21b, and the third connection port 21c, and connects the first connection port 21a and the second connection port 21b to form a third connection port. The connection state can be switched between the A direction for closing 21c and the B direction for connecting the first connection port 21a and the third connection port 21c and closing the second connection port 21b. The first three-way valve 21 is controlled by the control unit 20 so as to be in the A direction if the temperature of the water flowing in from the first connection port 21a is equal to or higher than the predetermined temperature, and to be switched to the B direction if the temperature is lower than the predetermined temperature.

  The second connection port 21 b of the first three-way valve 21 is connected to the return port 17 of the hot water storage tank 13. One end of the bypass pipe 54 is connected to the third connection port 21 c of the first three-way valve 21, and the other end of the bypass pipe 54 joins the heat recovery pipe (low temperature) 53 a in the hot water storage tank unit 11.

  A heat recovery pipe high temperature side temperature sensor 22a is provided in the heat recovery pipe (high temperature) 53b in the vicinity of the first connection port 21a of the first three-way valve 21, and a junction between the water intake 16 of the hot water storage tank 13 and the bypass pipe 54 is provided. The heat recovery pipe low temperature side sensor 22b is provided in the heat recovery pipe (low temperature) 53a until the above.

  The hot water storage tank unit 11 includes a mixer 23 that mixes hot water from the hot water outlet 15 of the hot water storage tank 13 and water supply. This mixer 23 is actually a first mixer 23 a that adjusts the amount of hot water supplied from the hot water outlet 15 of the hot water storage tank 13 and a second mixer 23 b that adjusts the amount of mixed water supplied from the water supply pipe 12. And is configured.

  The inlet side of the first mixer 23a is connected to a hot water outlet 15 of the hot water storage tank 13 by piping, and an overpressure relief valve 24, an intake valve 25, and a tank outlet temperature sensor 26 are provided in the middle of the piping. . A water supply pipe 12 is connected to the entrance side of the second mixer 23b.

  The outlet side of the first mixer 23 a and the outlet side of the second mixer 23 b merge to communicate with the outlet of the mixer 23. A connection pipe 61 that leads to a water supply connection port of the bath water heater 70 is connected to the outlet of the mixer 23. The connecting pipe 61 in the vicinity of the outlet side of the mixer 23 is provided with a tapping temperature sensor 32 and a high cut temperature sensor 33.

  The water supply pipe 12 inside the hot water storage tank unit 11 is provided with a flow rate sensor 34, a water supply temperature sensor 35, and a pressure reducing valve 36. The water supply pipe 12 branches into two downstream of these, one of which is connected to the inlet side of the second mixer 23b via a check valve 37a, and the other is connected to the hot water storage tank 13 via the check valve 37b. It is connected to the water supply port 14.

  Further, a drain pipe 41 leading to a predetermined drainage point is connected to the water intake 16 of the hot water storage tank 13, and a drain plug 42 for opening and closing the pipe line is provided in the middle of the drain pipe 41.

  A hot water supply pipe 62 leading to a hot water tap or the like is connected to the hot water supply connection port of the bath water heater 70. A second connection pipe 63 branched in the middle of the hot water supply pipe 62 is connected to a second connection port 43 b of a second three-way valve 43 provided in the hot water storage tank unit 11. The second three-way valve 43 includes a first connection port 43a, a second connection port 43b, and a third connection port 43c, and connects the first connection port 43a and the second connection port 43b to connect the third connection port 43c. The connection state can be switched between the E direction to be closed and the F direction to connect the first connection port 43a and the third connection port 43c and close the second connection port 43b.

  The pipe connected to the hot water outlet 15 of the hot water storage tank 13 is bifurcated, one of which is connected to the inlet of the first mixer 23 a described above, and the other is connected to the third connection port 43 c of the second three-way valve 43. It is connected.

  Further, one end of the drainage guide pipe 46 is connected to the first connection port 43 a of the second three-way valve 43, and the other end of the drainage guide pipe 46 joins downstream from the drain plug 42 of the drain pipe 41. . In the middle of the drainage guide pipe 46, a check valve 44 and a drainage electromagnetic valve 45 for opening and closing the drainage guide pipe 46 are provided.

  The hot water storage tank unit 11 includes a control unit 20 that performs overall control of the operation of the hot water storage tank unit 11. The control unit 20 includes a CPU (Central Processing Unit), a flash ROM (Read Only Memory) 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. (Random Access Memory) and an I / F (Interface) unit for inputting / outputting various signals and the like. Detection signals from various sensors of the hot water tank unit 11 are input to the control unit 20. A control signal is output from the control unit 20 to each valve and other controlled objects. The control unit 20 further exchanges various information and commands with the heat source unit 4 and the bath water heater 70.

  Next, a configuration example of the bath water heater 70 as a backup heat source device will be described. The bath water heater 70 has a function of heating and discharging water flowing from the water supply connection port, a function of pouring (filling) the bath (tub) 2, and a function of chasing hot water in the bath (tub) 2. This is a gas-fired bath water heater.

  As shown in FIG. 2, the bath water heater 70 includes a one-can two-water channel type heat exchanger 72 through which a first heat exchange water pipe 72 a and a second heat exchange water pipe 72 b pass, and a burner that heats the heat exchanger 72. 73 is provided. A gas supply pipe 73a is connected to the burner 73, and a gas valve for switching supply / cutoff of gas and a proportional valve for adjusting the amount of supply gas are provided in the middle of the gas supply pipe 73a.

  The inlet side of the first heat exchange water pipe 72 a is connected to a water supply connection port by a water inlet pipe 74, and the outlet side of the first heat exchange water pipe 72 a is connected to a hot water supply connection port by a hot water outlet pipe 75. Further, a bath return pipe 76 leading to the bath (tub) 2 is provided on the entry side of the second heat exchange water pipe 72b, and a bath return pipe 77 similarly leading to the bath (tub) 2 is provided on the exit side of the second heat exchange water pipe 72b. Each is connected.

  The hot water outlet pipe 75 and the bath return pipe 76 are connected by a connecting pipe 78, and a hot water electromagnetic valve 79 for switching between closing and opening of the connecting pipe 78 is provided in the middle of the connecting pipe 78. In addition, a water amount servo 81 capable of adjusting the opening degree from a substantially closed state to a fully open state is provided in the middle of the hot water discharge pipe 75 upstream from the connection point of the connecting pipe 78 to adjust the amount of hot water discharged. A tapping temperature sensor 82 for detecting tapping temperature is provided on the downstream side of the water amount servo 81.

  Furthermore, a bypass pipe 83 branched from the water intake pipe 74 and joined to and connected to the hot water discharge pipe 75 at a predetermined location on the first heat exchange water pipe 72a side from the water quantity servo 81 is provided. A bypass adjustment valve 84 whose opening degree can be adjusted until it is fully opened is provided. The bypass adjustment valve 84 is adjusted so that hot water from the first heat exchange water pipe 72a and water via the bypass pipe 83 are mixed to become hot water at a set temperature. The inlet pipe 74 upstream of the branching point of the bypass pipe 83 is provided with a flow rate sensor 85 that detects the flow rate in the inlet pipe 74 and an incoming water temperature sensor 86 that detects the incoming water temperature.

  In the middle of the bath return pipe 76, a bath circulation pump 87 for circulating the water in the bath (tub) 2 through the recirculation circulation path (bath return pipe 76, second heat exchange water pipe 72 b, bath going-out pipe 77). Is provided. A flowing water switch 88 provided in the bath return pipe 76 detects whether water is actually circulating in the recirculation circulation path when the bath circulation pump 87 is operated.

  In addition, the bath return pipe 76 and the bath return pipe 77 are provided with a bath return temperature sensor 89a and a bath return temperature sensor 89b, respectively, for detecting the temperature in the pipe.

  The control unit 91 includes a CPU, a flash ROM that stores a program executed by the CPU, fixed data, and the like, and a RAM that temporarily stores various types of information when the CPU executes the program. Has been. Various sensors, valves, a bath circulation pump 87, and the like that the bath water heater 70 has are connected to the control unit 91.

  Further, normally, the remote controller 92 is directly connected to the control unit 91 via a wiring. Here, however, the control unit is configured to operate the bath water heater 70 under the control of the control unit 20 on the hot water storage tank unit 11 side. 91 is connected to the control unit 20 via wiring, and a remote control (a common remote control for the hot water storage tank unit 11 side and the bath water heater 70) 92 is connected to the control unit 20 via wiring. The remote control 92 is a switch for receiving various operations from the user, such as designation of hot water supply set temperature and bath set temperature, start / end instruction of hot water filling and reheating operation, power on / off, operation state and set temperature, etc. It is comprised with the display part etc. which display.

  In the hot water supply operation for supplying hot water to the hot water supply pipe 62, the controller 91 of the bath water heater 70 turns on the burner 73 so that hot water at the hot water supply set temperature set by the common remote controller 92 connected to the hot water storage tank unit 11 is discharged. / OFF, the combustion amount thereof, the opening degree of the bypass adjustment valve 84, and the like are controlled. Specifically, if the temperature of the hot water supplied from the hot water storage tank unit 11 through the connection pipe 61 is equal to or higher than the hot water supply set temperature, the hot water is supplied to the hot water supply pipe 62 without burning the burner 73 of the apparatus itself. If the temperature of the hot water supplied from the hot water storage tank unit 11 side is lower than the hot water supply set temperature, the burner 73 of the own apparatus is burned so as to reach the hot water supply set temperature, and the amount of combustion and the opening of the bypass adjustment valve 84 are controlled. .

  In the operation of pouring (hot water) into the bath (tub) 2, the opening of the water quantity servo 81 is adjusted while the burner 73 is burned by opening the pouring solenoid valve 79, thereby flowing from the water supply connection port. The hot water is heated through the first heat exchange water pipe 72a of the heat exchanger 72, and further from the hot water pipe 75 to the bath (tub) 2 through both (or one) of the connecting pipe 78, the bath return pipe 76 and the bath outlet pipe 77. Flow in (this path is a pouring circuit). At this time, the combustion amount of the burner 73, the opening degree of the bypass adjustment valve 84, and the like are controlled so that hot water having a bath setting temperature set by the user is poured by the remote controller 92. If the hot water supplied from the hot water storage tank unit 11 through the connection pipe 61 has already reached the bath set temperature and no additional heating is required in the bath water heater 70, the hot water pouring operation is performed without burning the burner 73. Do. The bath water heater 70 checks the water level in the bath (tub) 2, and the hot water pouring operation ends when the set water level is reached.

  In the reheating operation, the hot water solenoid valve 79 is closed, and the burner 73 is burned with the bath circulation pump 87 activated. As a result, hot water in the bath (tub) 2 is taken into the bath water heater 70 through the bath return pipe 76 and heated while passing through the second heat exchange water pipe 72 b of the heat exchanger 72, and the heated hot water is heated to the bath outlet pipe 77. It is returned to the bath (tub) 2 through.

  Next, various operations of the bath hot water supply system 10 will be described.

<Exhaust heat recovery operation>
FIG. 3 shows the flow of hot water in the exhaust heat recovery operation. A path through which hot water flows in the exhaust heat recovery operation is indicated by a thick line. In the exhaust heat recovery operation for recovering the exhaust heat of the heat source unit 4 and heating the hot water in the hot water storage tank 13, the control unit 20 instructs the heat source unit 4 to operate the exhaust heat recovery pump 52. As a result, the hot water in the hot water storage tank 13 exits from the water intake 16 and is connected to the heat recovery pipe (low temperature) 53a, the exhaust heat recovery heat exchanger 51, the heat recovery pipe (high temperature) 53b, and the first three-way valve 21 in the A direction. It circulates in the circulation path which returns to the upper part of the hot water storage tank 13 from the return port 17 via. In addition, since the hot water heated by the exhaust heat recovery heat exchanger 51 and reaching a high temperature reaches the first connection port 21a of the first three-way valve 21, the control unit 20 sets the first three-way valve 21 in the A direction. .

  The hot water is supplied from the water supply port 14 at the lower part of the hot water storage tank 13 and the hot water heated by the exhaust heat recovery operation is returned to the upper part of the hot water storage tank 13, so that the lower part of the hot water storage tank 13 has a low temperature and the upper part has a high temperature. Such a temperature gradient is formed. By continuing the exhaust heat recovery operation, the amount of hot water that accumulates in the upper portion gradually increases.

<Hot-water supply operation>
Hot water is supplied in the following control mode (1) or (2).

(1) Combustion off mode The combustion off mode is a hot water supply operation in the case where the hot water storage tank 13 has sufficiently stored heat. FIG. 4 shows the flow of hot water in the hot water supply operation. In the figure, the path through which hot water flows is indicated by a bold line. In the combustion off mode, the hot water and hot water from the hot water storage tank 13 are mixed in the mixer 23 to set the hot water supply temperature + α ° C. (α ° C. is a temperature taking into account the temperature drop in the connecting pipe 61, for example, 2 ° C.). The hot water is made and supplied to the bath water heater 70 through the connecting pipe 61. The bath water heater 70 is supplied with hot water at the set temperature of the hot water supply, and does not perform additional heating by itself, turns off the burner 73 and supplies the hot water supplied from the hot water storage tank unit 11 side to the hot water supply pipe 62 as it is. To do.

(2) Additional heating mode This is a hot water supply operation in the case where the amount of heat stored in the hot water storage tank 13 is insufficient and hot water having a hot water supply set temperature cannot be supplied in the combustion off mode, and additional heating is performed by the bath water heater 70. The flow of hot water in the hot water supply operation in the follow-up heating mode is the same as that in FIG. However, the bath water heater 70 is turned on.

  More specifically, when the hot water in the hot water storage tank 13 is slightly lower than the hot water supply set temperature and is sent to the bath water heater 70 as it is, the hot water temperature exceeds the hot water set temperature even if the bath water heater 70 is operated with the minimum capacity. The hot water from the hot water tank 13 mixed with hot water from the hot water storage tank 13 by the mixer 23 is sent to the bath water heater 70, and the hot water hot water is heated to the set hot water temperature by the bath water heater 70. When the temperature of the hot water in the hot water storage tank 13 is sufficiently lower than the hot water supply set temperature and the above-described intentional temperature reduction is not necessary, hot water (or water) having a temperature sufficiently lower than the hot water supply set temperature in the hot water storage tank 13 is bathed. The hot water is supplied to the hot water heater 70 and heated to the set hot water temperature by the bath water heater 70 to supply hot water.

<Pouring operation>
In the pouring operation, similarly to the hot water supply operation, hot water is supplied to the bath water heater 70, and the bath water heater 70 performs additional heating if the temperature of the hot water supplied from the hot water storage tank unit 11 is lower than the bath set temperature. If the temperature is higher than the bath set temperature, hot water is poured into the bath (tub) 2 without additional heating. It should be noted that all the functions used for the fully automatic bath such as water level detection and reheating use the functions of the bath water heater 70 as they are.

<Microcomputer meter cutoff avoidance operation>
In the microcomputer meter cutoff avoiding operation, the control unit 20 fully closes the first mixer 23a, sets the second three-way valve 43 in the E direction, and opens the drainage electromagnetic valve 45. Further, the control unit 20 instructs the hot water heater 70 about the hot water temperature at which the burner 73 is burned. For example, the hot water supply at a temperature 15 ° C. higher than the temperature of the water supply is instructed.

  FIG. 5 shows the flow of hot water in the microcomputer meter shut-off avoiding operation. By setting the second three-way valve 43 in the E direction and opening the drain electromagnetic valve 45, water flows into the bath water heater 70, and the bath water heater 70 that has detected this water flow is the temperature instructed by the control unit 20. Burner 73 is burned so that hot water is supplied. Hot water discharged from the bath water heater 70 is drained to the outside through the second connection pipe 63, the drain guide pipe 46, and the drain pipe 41.

  Since gas is consumed by the hot water supply combustion operation of the bath water heater 70, it can be determined that the gas flow rate has changed on the gas meter side, and microcomputer meter shut-off can be avoided. In order for the gas meter to determine the gas flow rate fluctuation, the hot water supply combustion operation by the bath water heater 70 may be continued for about 2 minutes.

  The avoidance operation of the microcomputer meter cutoff is performed when it is detected that the microcomputer meter cutoff is about to occur. For example, it is performed when the power generation operation of the fuel cell continues for a certain time or more. Alternatively, when the power generation operation of the fuel cell has continued for a certain time or longer, other uses under the control of the control unit 20 (for example, use of the bath water heater 70 as a reheating use or instead of the bath water heater 70) This is performed when gas is not used in the heating application when a hot water heater is provided. Note that even if a gas stove, a gas stove, or the like is used, it corresponds to a microcomputer meter cutoff avoidance operation. However, since they are not under the control of the control unit 20, the control unit 20 cannot recognize the use of these gas appliances. The determination of the timing for performing the microcomputer meter shut-off avoidance operation may be performed by the hot water storage tank unit 11 or the fuel cell. In the former case, the hot water storage tank unit 11 receives a signal indicating that the power generation operation is in progress from the fuel cell, and determines the timing at which the microcomputer meter shutoff avoidance operation should be started based on the duration of this signal and the presence or absence of combustion in the own device. In the latter case, the hot water storage tank unit 11 may execute the microcomputer meter cutoff avoiding operation when receiving a request for executing the microcomputer meter cutoff avoiding operation from the fuel cell.

<Draining operation of tank accumulated water>
The tank accumulated water draining operation is an operation for replacing the hot water remaining in the hot water storage tank 13 with new water supply. When the control unit 20 determines that the hot water in the hot water storage tank 13 is not used for a long period of time, the control unit 20 performs a tank accumulated water draining operation. FIG. 6 shows the flow of hot water in the tank accumulated water draining operation. In the tank accumulated water draining operation, the control unit 20 sets the second three-way valve 43 in the F direction and controls the drain electromagnetic valve 45 to open, so that the accumulated water in the hot water storage tank 13 is discharged to the drain guide pipe 46 or the drainage. Water is drained along a path indicated by a thick line in FIG. Then, when it is confirmed from the measured amount of water that the entire hot water storage tank 13 has been replaced with new water supply, the replacement operation is terminated. Here, when the measured amount of drainage exceeds the total amount of the capacity of the hot water storage tank 13 and the piping capacity of the drainage path, the drainage electromagnetic valve 45 is closed and the tank accumulated water drainage operation is terminated.

  Note that the check valve 44 is provided so as not to suck air from the drain electromagnetic valve 45 because the line of the second connection pipe 63 may become negative pressure during downstairs hot water supply.

  As described above, in the hot water supply system 10 according to the first embodiment, the microcomputer meter shut-off avoidance operation and the tank accumulated water drainage operation are performed. Therefore, a gas water heater without a heating function is used as a backup heat source device. Can do. A gas water heater without a heating function is cheaper than a gas water heater with a heating function. Also, the reheat heat exchanger is not required in the hot water storage tank unit 11, and the apparatus configuration is simplified such that no heating pipe is required between the bath water heater and the hot water storage tank unit 11, thereby reducing the cost of the entire system. it can.

  Next, a second embodiment of the present invention will be described.

  FIG. 7 shows a configuration of a bath hot water supply system 10B according to a second embodiment to which the hot water storage system of the present invention is applied. The bath hot water system 10B according to the second embodiment mixes hot water obtained by heating the hot water with the bath water heater, hot water from the hot water storage tank, and the hot water with the mixer 30 to create hot water at a preset hot water temperature. The hot water supply system (post-mixing system) is used.

  In a bath hot water system that uses a hot water storage tank, pressure loss in the hot water storage tank and pressure loss in the connecting piping are added, compared to when hot water is supplied directly from a gas water heater or the like. Further, depending on the construction conditions, it is necessary to install the hot water storage tank unit and the gas water heater as a backup heat source machine apart from each other, and the pressure loss further increases when the connecting pipe from the hot water storage tank unit to the gas hot water heater becomes longer.

  In the case of the hot water supply hot water bath system 10 shown in the first embodiment, since the entire amount of hot water to be supplied always passes through the connection pipe 61 and the bath water heater 70, it is easily affected by pressure loss. In the post-mixing method shown in the second embodiment, the pressure loss is reduced. Thereby, the fall of the amount of hot water supply in a low water pressure area is prevented.

  As shown in FIG. 7, a bath water heater system 10B according to the second embodiment includes a hot water storage tank unit 11B, a heat source unit 4, an exhaust heat recovery device 50, and a bath water heater 70 as a backup heat source unit. It is prepared for. In this example, the heat source unit 4 is a fuel cell. In addition, the same code | symbol is attached | subjected to the same location as 1st Embodiment. In the figure, piping between apparatuses and external piping are indicated by double arrows.

  The hot water storage tank unit 11 </ b> B includes a hot water storage tank 13 that stores water supplied from the water supply pipe 12. The structure of the hot water storage tank 13 and the internal temperature sensors 18a to 18e are the same as those in the first embodiment, and a description thereof will be omitted. Further, the exhaust heat recovery device 50 and the connection between the exhaust heat recovery device 50 and the hot water storage tank 13 are the same as those in the first embodiment, and the description thereof is omitted.

  The hot water storage tank unit 11 </ b> B includes a mixer 30 that mixes hot water from the hot water outlet 15 of the hot water storage tank 13, hot water from the bath water heater 70, and water supply. This mixer 30 is actually a first mixer 30 a that adjusts the amount of hot water supplied from the outlet 15 of the hot water storage tank 13 and a second mixer that adjusts the amount of hot water supplied from the bath water heater 70. 30 b and a third mixer 30 c that adjusts the amount of water supplied from the water supply pipe 12.

  The inlet side of the first mixer 30a is connected to a hot water outlet 15 of the hot water storage tank 13 by piping, and an overpressure relief valve 24, an intake valve 25, and a tank outlet temperature sensor 26 are provided in the middle of the piping. . The entrance side of the second mixer 30 b is connected to the hot water supply connection port of the bath water heater 70 by a connection pipe (high temperature) 65. A connecting pipe high temperature side temperature sensor 28 that detects the temperature of hot water in the connecting pipe (high temperature) 65 is provided at a predetermined location in the hot water storage tank unit 11B in the connecting pipe (high temperature) 65. The water supply pipe 12 is connected to the entrance side of the third mixer 30c.

  The outlet side of the first mixer 30a and the outlet side of the second mixer 30b join together, and after passing through the pipe provided with the hot water supply high temperature sensor 29, join the pipe from the outlet side of the third mixer 30c. It leads to the outlet of the mixer 30. A hot water supply pipe 31 is connected to the outlet of the mixer 30. A hot water supply temperature sensor 32 and a high cut temperature sensor 33 are provided in the hot water supply pipe 31 in the vicinity of the outlet side of the mixer 30.

  The water supply pipe 12 inside the hot water storage tank unit 11B is provided with a flow rate sensor 34, a water supply temperature sensor 35, and a pressure reducing valve 36. The water supply pipe 12 branches into three downstream of these, one of which is connected to the inlet side of the third mixer 30c via a check valve 37a, and the other one via the check valve 37b. The other one is connected to the second connection port 38b of the third three-way valve 38 via the check valve 37c.

  The third three-way valve 38 includes a first connection port 38a, a second connection port 38b, and a third connection port 38c, connects the first connection port 38a and the second connection port 38b, and closes the third connection port 38c. The connection state can be switched between the C direction and the D direction in which the first connection port 38a and the third connection port 38c are connected and the second connection port 38b is closed. A pipe 31b branched from the hot water supply pipe 31 on the downstream side of the high cut temperature sensor 33 is connected to the third connection port 38c. A check valve 39 is provided in the middle of the pipe 31b. The first connection port 38 a of the third three-way valve 38 is connected to the water supply connection port of the bath water heater 70 through a connection pipe (low temperature) 66.

  Further, a drain pipe 41 leading to a predetermined drainage point is connected to the water intake 16 of the hot water storage tank 13, and a drain plug 42 for opening and closing the pipe line is provided in the middle of the drain pipe 41.

  In addition, in the hot water storage tank unit 11B, a pipe branched from a location closer to the mixer 30 than the connection pipe high temperature side temperature sensor 28 of the connection pipe (high temperature) 65 is connected to the second connection port 43b of the second three-way valve 43. ing. In addition, this branch location is a location closer to the mixer 30 in the entire length of the connection pipe (high temperature) 65, and the length of the pipe from the branch location to the mixer 30 is the hot water outlet of the bath water heater 70 from the branch location. It is sufficiently shorter than the pipe length up to.

  Similarly to the first embodiment, the second three-way valve 43 includes a first connection port 43a, a second connection port 43b, and a third connection port 43c, and the first connection port 43a and the second connection port 43b. The connection state can be switched between the E direction in which the third connection port 43c is closed and the F direction in which the first connection port 43a and the third connection port 43c are connected and the second connection port 43b is closed. ing.

  The pipe connected to the hot water outlet 15 of the hot water storage tank 13 is bifurcated, one of which is connected to the inlet of the first mixer 30a described above, and the other is connected to the third connection port 43c of the second three-way valve 43. It is connected.

  Further, the first connection port 43 a of the second three-way valve 43 is connected to one end of the drainage guide pipe 46, and the other end of the drainage guide pipe 46 joins downstream from the drain plug 42 of the drainage pipe 41. In the middle of the drainage guide pipe 46, a check valve 44 and a drainage electromagnetic valve 45 for opening and closing the drainage guide pipe 46 are provided.

  The configuration of the control unit 20 and the transmission / reception of signals are the same as those in the first embodiment, and a description thereof will be omitted.

  The bath water heater 70 as a backup heat source machine has the same configuration as that of the first embodiment. However, the controller 91 of the bath water heater 70 according to the second embodiment has a temperature instructed by the controller 20 on the hot water storage tank unit 11B side in the operation of discharging hot water from the hot water supply connection port to the connection pipe (high temperature) 65. The combustion amount of the burner 73 and the opening degree of the bypass adjustment valve 84 are controlled so that the hot water is discharged to the connection pipe (high temperature) 65.

  In the operation of pouring (filling) the bath (tub) 2, the combustion amount of the burner 73, the opening degree of the bypass adjustment valve 84, etc. are set so that hot water at the bath set temperature set by the user with the remote controller 92 is poured. Control. If the hot water supplied from the hot water storage tank unit 11B side through the connection pipe (low temperature) 66 has already reached the bath set temperature and no additional heating is required in the bath water heater 70, the burner 73 is not burned. Perform hot water operation. The bath water heater 70 checks the water level in the bath (tub) 2, and the hot water pouring operation ends when the set water level is reached. The chasing operation is the same as that in the first embodiment.

  Next, various operations of the bath hot water supply system 10B will be described.

<Exhaust heat recovery operation>
The exhaust heat recovery operation is the same as in the first embodiment, and a description thereof is omitted.

<Hot-water supply operation>
The hot water storage tank unit 11B may be installed near the bath water heater 70 or may be installed far away. For example, in a house with a bath on the second floor, there is a case where the bath water heater 70 is installed on the outer wall of the second floor, and the hot water storage tank unit 11B and the heat source unit 4 are installed on the first floor. The connection pipe (high temperature) 65 and the connection pipe (low temperature) 66 connecting the apparatuses become long, resulting in an installation situation where the pressure loss is large. In the hot water supply system 10B according to the second embodiment of the present invention, an increase in pressure loss is suppressed so that a sufficient amount of hot water can be secured even in an installation situation where the piping is long and the pressure loss is large in a low water pressure region. It is supposed to do hot water supply.

  Hot water is supplied in one of the following three control modes.

(1) First mode (tank hot water mode)
The first mode is a hot water supply operation in the case where the hot water storage tank 13 has sufficiently stored heat. FIG. 8 shows the flow of hot water in the hot water supply operation in the first mode. In the figure, the path through which hot water flows is indicated by a bold line. In the first mode, hot water and hot water from the hot water storage tank 13 are mixed by the mixer 30 to create hot water at a hot water supply set temperature and hot water is supplied. No water is sent to the bath water heater 70, no heating is performed in the bath water heater 70, and no combustion operation is performed.

  Specifically, the second mixer 30b of the mixer 30 is closed, the opening degree of the first mixer 30a and the third mixer 30c is adjusted, and the outlet side of the mixer 30 detected by the tapping temperature sensor 32 is adjusted. The hot water temperature is controlled so as to become the hot water supply set temperature. Here, for example, the detection temperature of the hot water temperature sensor 18d provided in the hot water storage tank 13 is equal to or higher than the hot water supply set temperature (actually, for example, the hot water supply set temperature + 1 ° C. in consideration of a temperature drop in the hot water supply pipe or the like). In this case, hot water is supplied in the first mode.

(2) Second mode (hot water supply hot water mode)
The second mode is a hot water supply operation when there is no hot water available in the hot water storage tank 13. FIG. 9 shows the flow of hot water in the hot water supply operation in the second mode. In the figure, the path through which hot water flows is indicated by a bold line. In the second mode, hot water heated to a temperature higher than the hot water supply set temperature by the bath water heater 70 and hot water are mixed by the mixer 30 to supply hot water at the hot water set temperature.

  Specifically, the third three-way valve 38 is set in the C direction, and water is supplied to the bath water heater 70. Also, the first mixer 30a of the mixer 30 is closed, the opening degree of the second mixer 30b and the third mixer 30c is adjusted, and the hot water on the outlet side of the mixer 30 detected by the hot water temperature sensor 32 is adjusted. The temperature is controlled so as to become the hot water supply set temperature.

  Note that the control unit 20 instructs the bath water heater 70 to provide a hot water temperature so that the hot water temperature of the bath water heater 70 is sufficiently higher than the hot water supply set temperature. Thereby, the amount of hot water from the bath water heater 70 necessary for mixing with the water supply to obtain the hot water supply set temperature is reduced, and passes through the connection pipe (low temperature) 66, the bath water heater 70, and the connection pipe (high temperature) 65. The pressure loss caused by this can be kept small. For example, if the hot water supply set temperature is 40 ° C., hot water at 55 ° C. is obtained from the bath water heater 70. If the hot water supply set temperature is 60 ° C., 75 ° C. hot water is obtained from the bath water heater 70.

[Calculation of effect]
When the hot water supply temperature is 15 ° C, the hot water supply set temperature is 40 ° C, and the hot water supply flow rate is 8L / min. ) 65 and connecting pipe (low temperature) 66 will flow hot water at 8 L / min. On the other hand, when 55 ° C. hot water is received from the bath water heater 70, the flow rate through the connecting pipe (high temperature) 65 and the connecting pipe (low temperature) 66 may be 5 L / min, and the water supply is 3 L / min in the hot water storage tank unit 11B. To make 8L / min of 40 ° C hot water. Since the pressure loss increases as the flow velocity (proportional to the flow rate when the pipe diameter is the same) is increased, reducing the flow rate greatly contributes to pressure loss reduction.

  In the case of the hot water preheating method, even if there is heat storage in the hot water storage tank, hot water of 40 ° C and 8L / min is made with the hot water tank unit, and the entire amount is connected to the water supply connection port of the hot water heater as a backup heat source and hot water supply Will flow into the vessel. Even when there is no heat storage in the hot water storage tank, 8 L / min of water is sent from the hot water storage unit to the water heater and heated to 40 ° C. In any case, it is necessary to flow 8 L / min through the pipe to the water heater and the water heater.

  According to the experimental results using a cross-linked polyethylene pipe having an inner diameter of 16 mm, when the pipe length is 25 m (when the pipe is reciprocated to 25 m, it corresponds to a case where the bath water heater 70 and the hot water storage tank unit 11B are installed 12.5 m apart). As a result, the pressure loss of the pipe connected to the bath water heater 70 is 8 L / min and the pipe pressure loss is 11 kPa, and 5 L / min is 5 kPa. The pressure loss is reduced by 55%.

(3) Third mode (post-mixing hot water mode)
The third mode is a hot water supply operation in the case where heat is stored in the hot water storage tank 13 but the temperature is low and the hot water in the hot water storage tank 13 is not sufficient. FIG. 10 shows the flow of hot water in the hot water supply operation in the third mode. In the figure, the path through which hot water flows is indicated by a bold line. The third mode is selected, for example, when the temperature detected by the hot water temperature sensor 18d of the hot water storage tank 13 is lower than the hot water supply set temperature but not lower than a predetermined temperature (for example, 10 ° C.) above the hot water supply set temperature.

  In the third mode, the hot water heated by the bath water heater 70, the hot water from the hot water storage tank 13 and the hot water are mixed to make hot water having a hot water supply set temperature. More specifically, hot water produced by heating the third three-way valve 38 in the C direction and heating the hot water in the bath water heater 70, hot water from the hot water storage tank 13, and hot water from the hot water storage tank 13 are mixed in the hot water supply set temperature. Make hot water and supply hot water. Even if the temperature of the hot water in the hot water storage tank 13 is low, the heat stored in the hot water storage tank 13 can be used up more by mixing with the hot water received from the bath water heater 70, so the first and second Energy savings are higher than when controlling only in the mode.

  The controller 20 preferentially selects the first mode, and hot water that is not lower than the hot water set temperature by a predetermined temperature (for example, 10 ° C.) from the hot water storage tank 13 when hot water at the set temperature cannot be supplied in the first mode. When the supply is possible, the third mode is selected, and when the third mode cannot be selected, the second mode is selected.

<Switching operation from the first mode to the second mode>
Next, after starting hot water supply in the first mode (tank hot water), the transition operation in the case where the heat storage (hot water amount) in the hot water storage tank 13 is insufficient and the hot water control mode is switched to the second mode (hot water supply hot water). explain.

  Note that the position at which the hot water temperature sensor 18d is attached is determined from the amount of retained water in the connection pipe (high temperature) 65, the maximum hot water flow rate, and the like. That is, the amount of water in the hot water storage tank 13 above the position where the hot water temperature sensor 18d is attached is equal to or greater than the maximum amount of hot water from the hot water storage tank 13 consumed while switching from the first mode to the second mode. The attachment position of the hot water temperature sensor 18d is set.

  After determining that there is sufficient heat storage in the hot water storage tank 13 and starting hot water supply in the first mode (tank hot water), if there is no longer any heat storage (hot water that can be discharged at the set temperature) from the temperature detected by the hot water temperature sensor 18d. If it is determined, the third three-way valve 38 is set to the C direction, the drain electromagnetic valve 45 is opened, and the water supply starts from the connecting pipe (low temperature) 66 to the bath water heater 70, the connecting pipe (high temperature) 65, and the second three-way valve in the E direction. 43, the drainage electromagnetic valve 45 is opened, and the drainage guide pipe 46 and the drainage pipe 41 are allowed to drain to the outside. FIG. 11 shows the flow of hot water when the drain electromagnetic valve 45 is opened. The thick line portion in the figure indicates the drainage route, and the thick broken line indicates the discharge route for the first mode (tank discharge).

  When water flows into the bath water heater 70 due to drainage through the drainage guide pipe 46 and the drain pipe 41, the bath water heater 70 that detects this by the flow rate sensor 85 starts combustion heating. The bath water heater 70 discharges hot water at a temperature instructed by the control unit 20 of the hot water storage tank unit 11B. Thereby, the inside of the pipe of the connection pipe (high temperature) 65 is gradually warmed by the hot water from the bath water heater 70. The drainage state is continued until the temperature detected by the connecting pipe high temperature side temperature sensor 28 rises to a predetermined temperature. Here, when the detected temperature of the connecting pipe high temperature side temperature sensor 28 becomes higher than the detected temperature of the tank upper temperature sensor 18e of the hot water storage tank 13, the drain electromagnetic valve 45 is closed to switch to the second mode (hot water supply hot water).

  Specifically, when the detected temperature of the connecting pipe high temperature side temperature sensor 28 becomes higher than the detected temperature of the tank upper temperature sensor 18e of the hot water storage tank 13, the mixer 30 is controlled to maintain the hot water supply set temperature. The second mixer 30b is gradually opened while the mixer 30a is gradually closed, so that the mixing ratio of hot water from the bath water heater 70 gradually increases.

  FIG. 12 shows the flow of hot water at this time. If the water to be squeezed in the connecting pipe (high temperature) 65 in the portion of the second mixer 30b side from the branching point of the drainage guide pipe 46, the second mixer 30b is gradually opened to squeeze that portion. Although water flows into the second mixer 30b (path indicated by a thick dashed line in FIG. 12), initially, the hot water at the hot water supply set temperature is maintained by slightly opening the second mixer 30b. Then, the first mixer 30a is fully closed when the water to be filled is used up and the inside of the connection pipe (high temperature) 65 becomes hot water heated by the bath water heater 70.

  When the mixing ratio of hot water from the hot water storage tank 13 becomes zero (the first mixer 30a is fully closed), that is, when the transition to the second mode is completed, the drainage electromagnetic valve 45 is closed to end the drainage state. The state after shifting to the second mode is as shown in FIG. Note that when the flow rate of the second mixer 30b exceeds the minimum flow rate at which the bath water heater 70 can continue to burn, the drainage electromagnetic valve 45 may be closed to end the drainage state.

  Further, instead of the condition that the detected temperature of the connecting pipe high temperature side temperature sensor 28 is higher than the detected temperature of the tank upper temperature sensor 18e of the hot water storage tank 13, the hot water heated by the bath water heater 70 is connected to the connecting pipe high temperature side temperature sensor. It is good also as a condition that it was confirmed that 28 places were reached. Specifically, taking into account the temperature drop in the connecting pipe (high temperature) 65, the temperature detected by the connecting pipe high temperature side temperature sensor 28 is the tapping temperature set in the bath water heater 70 by the controller 20 of the hot water storage tank unit 11B. When the temperature reaches −3 ° C., the control may be such that the mixing ratio of the mixer 30 is changed and the transition to the second mode is started.

  Since the above transition control is performed, even when the water in the connection pipe (high temperature) 65 is cold when switching from the first mode (tank hot water) to the second mode (hot water heater hot water), the hot water supply set temperature The hot water supply for the street can be continued and the user is not uncomfortable.

  In addition, since the line of the connection pipe (high temperature) 65 may become negative pressure during downstairs hot water supply in the second mode (hot water supply hot water), the check valve 44 is set so as not to suck air from the drain electromagnetic valve 45. It is provided.

<Microcomputer meter cutoff avoidance operation>
In the microcomputer meter shut-off avoiding operation, the control unit 20 fully closes the second mixer 30b, sets the third three-way valve 38 in the C direction, sets the second three-way valve 43 in the E direction, and discharges the electromagnetic valve 45. open. In addition, the control unit 20 instructs the bath water heater 70 to the hot water temperature at which the burner 73 is burned. For example, the hot water is instructed at a temperature 15 ° C. higher than the temperature of the water supply.

  FIG. 13 shows the flow of hot water in the avoidance operation of microcomputer meter interruption. The second mixer 30b is fully closed, the third three-way valve 38 is set in the C direction, the second three-way valve 43 is set in the E direction, and the drain electromagnetic valve 45 is opened, so that water flows into the bath water heater 70. The bath water heater 70 that detects this causes the burner 73 to burn so as to discharge hot water at a temperature instructed by the control unit 20. Hot water discharged from the bath water heater 70 is drained to the outside through the connection pipe (high temperature) 65, the second three-way valve 43 in the E direction, the drain guide pipe 46, and the drain pipe 41.

  Since the gas is consumed by the hot water supply combustion operation of the bath water heater 70, it is possible to cause the gas meter to determine that the gas flow rate has changed, and the microcomputer meter can be prevented from being shut off. In order for the gas meter to determine the fluctuation of the gas flow rate, the hot water supply combustion operation by the bath water heater 70 may be continued for about 2 minutes.

  The start timing of the microcomputer meter shut-off avoidance operation is the same as in the first embodiment, and a description thereof is omitted.

<Draining operation of tank accumulated water>
When the control unit 20 determines that the hot water in the hot water storage tank 13 has remained without being used for a long period of time, the control unit 20 performs a tank accumulated water draining operation. FIG. 14 shows the flow of hot water in the tank accumulated water draining operation. In the tank accumulated water draining operation, the control unit 20 sets the second three-way valve 43 in the F direction and controls the drain electromagnetic valve 45 to open, so that the accumulated water in the hot water storage tank 13 is discharged to the drain guide pipe 46 or The water is drained by a route through the drain pipe 41 and the amount of drainage is measured by the flow sensor 34. Then, when it is confirmed from the measured amount of water that the entire hot water storage tank 13 has been replaced with new water supply, the replacement operation is terminated. Here, when the measured amount of drainage exceeds the total amount of the capacity of the hot water storage tank 13 and the piping capacity of the drainage path, the drainage electromagnetic valve 45 is closed and the tank accumulated water drainage operation is terminated.

  As described above, in the hot water supply system 10B according to the second embodiment, the microcomputer meter shut-off avoidance operation and the tank accumulated water drainage operation are performed. Therefore, a gas water heater without a heating function is used as a backup heat source device. Can do. A gas water heater without a heating function is cheaper than a gas water heater with a heating function, and there is no need for a reheating heat exchanger in the hot water tank unit 11B, and between the hot water heater and the hot water tank unit 11B. Therefore, the apparatus configuration is simplified such that no heating pipe is required, and the cost of the entire system can be reduced.

<Pouring operation>
FIG. 15 illustrates the flow of hot water in the pouring operation of the hot water supply system 10B according to the second embodiment. In the figure, the path through which hot water flows is indicated by a bold line. In the pouring operation, the hot water on the outlet side of the mixer 30 is supplied to the water supply connection port of the bath water heater 70, and the hot water from the hot water storage tank 13 or the hot water from the hot water storage tank 13 and the hot water are mixed. The hot water at the bath set temperature is poured from the bath water heater 70 to the bath (tub) 2 with the addition of heating by the bath water heater 70 to the hot water produced from the outlet side of the mixer 30 or without additional heating. To control.

  Specifically, when pouring (hot water filling) with hot water stored in the hot water storage tank 13, the third three-way valve 38 is set in the D direction, and the hot water and hot water from the hot water storage tank 13 are mixed by the mixer 30. Then, the hot water having the set temperature of the bath is sent to the bath water heater 70 and filled with the pouring circuit of the bath water heater 70. The control unit 20 of the hot water storage tank unit 11B instructs the bath water heater 70 to open the pouring electromagnetic valve 79 while the burner 73 is in a combustion off state. Hot water from the outlet side of the mixer 30 of the hot water storage tank unit 11B is supplied from a connecting pipe (low temperature) 66 to a hot water supply circuit of the bath water heater 70, that is, a water inlet pipe 74 and a first heat exchange water pipe 72a in the bath water heater 70. After passing through the hot water solenoid valve 79 and the connecting pipe 78, the hot water flows out into the bath (tub) 2 through both or one of the bath going-out pipe 77 and the bath return pipe 76, and is poured.

  When the hot water storage tank 13 does not store heat, the second three-way valve 38 is set in the D direction, hot water having a temperature lower than the bath setting temperature in the hot water storage tank 13, water supply, or a bath setting temperature obtained by mixing them. The low temperature hot water is sent to the bath water heater 70, heated to the bath set temperature in the bath water heater 70, and poured through the pouring circuit in the bath water heater 70.

  It should be noted that all the functions used for the fully automatic bath such as detection of water level and reheating use the functions of the bath water heater 70 as they are.

  In this way, the third three-way valve 38 is switched in the D direction to supply hot water from the outlet side of the mixer 30 to the bath water heater 70, so that hot water in the hot water storage tank can be used for pouring.

  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.

  If the hot water storage system of the present invention includes the hot water storage tank unit 11 (or 11B) of the bath hot water system, the exhaust heat recovery device 50, the bath water heater 70, and the heat source unit 4 may or may not be included. For example, the exhaust heat recovery device 50 may be included in the heat source unit 4, or the bath water heater 70 may be an existing one.

  In 2nd Embodiment, although the suitable example which made the control mode of hot water supply the 1st mode, the 2nd mode, and the 3rd mode was shown, if there exists at least the 1st and 2nd mode, the structure without the 3rd mode But it doesn't matter.

  In the second mode, how much hot water is produced by the bath water heater 70 from the set temperature of the hot water supply may be determined as appropriate. However, the connection pipe 61 (high temperature), the connection pipe 62 (low temperature), and the bath water heater 70 are used. In order to reduce the pressure loss by reducing the amount of water flowing through the water, it is desirable that the temperature be sufficiently high as long as it is mixed with the feed water to obtain hot water at the hot water set temperature. When the backup heat source device is an instrument that requires water flow exceeding a predetermined minimum operating flow rate to perform a heating operation, such as a gas-fired bath water heater 70, the backup heat source device If the temperature of the hot water to be obtained is raised too much, the amount of hot water may fall below the minimum operating flow rate of the backup heat source machine. For this reason, in the second mode, it is desirable to control the temperature of hot water produced by the backup heat source device in a range where the amount of hot water supplied from the backup heat source device does not fall below the minimum operating flow rate of the backup heat source device.

  In addition, in the bath water heater 70 of the embodiment, the configuration including the incoming water temperature sensor 86 that detects the incoming water temperature is shown, but the incoming water temperature may be estimated by calculation without providing the incoming water temperature sensor 86. That is, an estimated value of the incoming water temperature Ti is calculated from Ti = To− (ηQ / W) from the hot water temperature To, the flow rate W, the gas amount (heating amount) Q measured at the last time when the hot water temperature was stabilized, and the efficiency η at this time. ), Etc. may be obtained by back calculation. In addition, efficiency (eta) measures and memorize | stores beforehand the value (efficiency (eta)) in each condition by changing tapping temperature and flow volume variously. Then, at the time of calculation, it is only necessary to obtain and use the efficiency η corresponding to the hot water temperature and the flow rate to be substituted for the calculation with reference to this memory.

  In the embodiment, the bath water heater 70 is a single-can two-water channel type, but it may be a water heater of a type in which the reheating of the bath and the hot water supply are performed by separate heat exchangers. Further, the heat source for exhaust heat recovery is not limited to the fuel cell 4, and may be, for example, a gas engine generator, a fuel processing device (reformer), or the like.

2 ... Bath (tub)
4 ... Heat source machine (fuel cell)
DESCRIPTION OF SYMBOLS 10, 10B ... Bath hot water supply system 11, 11B ... Hot water storage tank unit 12 ... Water supply pipe 13 ... Hot water storage tank 14 ... Water supply port 15 ... Outlet 16 ... Intake port 17 ... Return port 18a ... First temperature sensor 18b ... Second temperature sensor 18c ... third temperature sensor 18d ... hot water temperature sensor 18e ... tank upper temperature sensor 20 ... control unit 21 ... first three-way valve 21a ... first connection port 21b ... second connection port 21c ... third connection port 22a ... heat recovery Pipe high temperature side sensor 22b ... Heat recovery pipe low temperature side sensor 23 ... Mixer 23a ... First mixer 23b ... Second mixer 24 ... Overpressure relief valve 25 ... Intake valve 26 ... Tank outlet temperature sensor 28 ... Connection piping High temperature side temperature sensor 29 ... Hot water supply high temperature sensor 30 ... Mixer 30a ... First mixer 30b ... Second mixer 30c ... Third mixer 31 ... Hot water supply piping DESCRIPTION OF SYMBOLS 1b ... Piping 32 ... Hot water temperature sensor 33 ... High cut temperature sensor 34 ... Flow rate sensor 35 ... Feed water temperature sensor 36 ... Pressure reducing valve 37a ... Check valve 37b ... Check valve 37c ... Check valve 38 ... Third three-way valve 38a ... First 1 connection port 38b ... 2nd connection port 38c ... 3rd connection port 39 ... Check valve 41 ... Drain pipe 42 ... Drain plug 43 ... 2nd 3 way valve 43a ... 1st connection port 43b ... 2nd connection port 43c ... 3rd Connection port 44 ... Check valve 45 ... Drainage solenoid valve 46 ... Drainage guide pipe 50 ... Waste heat recovery device 51 ... Waste heat recovery heat exchanger 52 ... Waste heat recovery pump 53 ... Heat recovery pipe 53a ... Heat recovery pipe (low temperature)
53b ... Heat recovery piping (high temperature)
54 ... Bypass pipe 61 ... Connection pipe 62 ... Hot water supply pipe 63 ... Second connection pipe 65 ... Connection pipe (high temperature)
66 ... Connection piping (low temperature)
70 ... Bath water heater 72 ... Heat exchanger 72a ... First heat exchange water pipe 72b ... Second heat exchange water pipe 73 ... Burner 73a ... Gas supply pipe 74 ... Inlet pipe 75 ... Outlet pipe 76 ... Bath return pipe 77 ... Bath return pipe 77 78 ... Connecting pipe 79 ... Pouring solenoid valve 81 ... Water volume servo 82 ... Outflow temperature sensor 83 ... Bypass pipe 84 ... Bypass adjustment valve 85 ... Flow sensor 86 ... Incoming water temperature sensor 87 ... Bath circulation pump 88 ... Flow water switch 89a ... Bath going out Temperature sensor 89b ... Bath return temperature sensor 91 ... Control unit 92 ... Remote control (common remote control)

Claims (9)

A hot water storage tank to which hot water is supplied, and a heating device that recovers the exhaust heat of the heat source and heats the water in the hot water storage tank, and the shortage is insufficient when the hot water storage in the hot water storage tank is insufficient for the hot water at the set temperature In a hot water storage system that heats the minute with a gas water heater,
A drain pipe branched from a hot water pipe connected to the hot water outlet of the gas water heater;
A drainage control valve for opening and closing the drainage pipe;
As an operation of avoiding that the gas meter shuts off the gas supply due to long-term continuous use of a small amount of gas by the heat source, the hot water obtained by opening the drain control valve and burning the gas with the gas water heater from the drain pipe A hot water storage system comprising: a control unit that performs an operation of draining water. A second drain pipe communicating with the hot water outlet of the hot water storage tank; and a second drain control valve for opening and closing the second drain pipe;
The hot water storage system according to claim 1, wherein the control unit opens the second drainage control valve when performing an operation of replacing water in the hot water storage tank. A mixer for connecting the hot water supply pipe, a first tank hot water supply pipe leading to the hot water outlet of the hot water storage tank, and a water supply pipe, and mixing and supplying hot water from these at a set mixing ratio;
A first state including a first inlet, a second inlet, and an outlet, wherein the first inlet and the outlet are in communication with each other and the second inlet is closed; and the second inlet and the outlet are in communication with each other. A three-way valve that switches to the second state with the inlet closed;
Further comprising
The gas water heater is supplied with water from a water supply pipe,
The drain pipe is divided into an upstream drain pipe on the hot water supply pipe side and a downstream drain pipe,
The drainage control valve opens and closes the downstream drainage pipe;
The upstream drain pipe is connected to the first inlet of the three-way valve, the second tank outlet pipe connected to the outlet of the hot water storage tank is connected to the second inlet, and the downstream drain pipe is connected to the outlet. ,
The controller is
While controlling the heating by the gas water heater and the mixing ratio of the mixer so that hot water at a set temperature is supplied from the outlet side of the mixer,
In the avoidance operation, the three-way valve is set to the first state, the drainage control valve is opened, and when the operation of replacing the water in the hot water storage tank is performed, the three-way valve is set to the second state, The hot water storage system according to claim 1, wherein the drainage control valve is opened. A first tank hot water pipe connected to the hot water outlet of the hot water storage tank and a water supply pipe were connected to mix hot water from these at a set mixing ratio, and the outlet side was piped to the water hot water outlet of the gas water heater. A mixer;
A first state including a first inlet, a second inlet, and an outlet, wherein the first inlet and the outlet are in communication with each other and the second inlet is closed; and the second inlet and the outlet are in communication with each other. A three-way valve that switches to the second state with the inlet closed;
Further comprising
The drain pipe is divided into an upstream drain pipe on the hot water supply pipe side and a downstream drain pipe,
The drainage control valve opens and closes the downstream drainage pipe;
The upstream drain pipe is connected to the first inlet of the three-way valve, the second tank outlet pipe connected to the outlet of the hot water storage tank is connected to the second inlet, and the downstream drain pipe is connected to the outlet. And
The controller is
While controlling the mixing ratio of the mixer so that hot water at a set temperature is performed from the gas water heater without additional heating by the gas water heater or by adding heating by the gas water heater,
In the avoidance operation, the three-way valve is set to the first state and the drainage control valve is opened,
2. The hot water storage system according to claim 1, wherein when performing the operation of replacing water in the hot water storage tank, the three-way valve is set to the second state and the drainage control valve is opened. The hot water storage system according to claim 4, wherein in the avoiding operation, the mixer is set so that water is supplied to the gas water heater. Measure the amount of water supplied to the hot water storage tank during the replacement operation,
The said control part complete | finishes the said replacement | exchange operation | movement, after confirming that all the inside of the said hot water storage tank was replaced by the new water supply from the measured amount of water. The hot water storage system described in 1. The upstream drain pipe is branched from a location near the mixer in the hot water pipe from the gas water heater to the mixer,
The controller is
As a hot water supply control mode, there are a first mode in which hot water and hot water from a hot water storage tank are mixed to supply hot water of a set temperature, and hot water and hot water heated to a temperature higher than the set temperature by the gas water heater. And at least a second mode of mixing and supplying hot water at a set temperature,
When switching to the second mode during the hot water supply operation in the first mode, the hot water heated by the gas water heater with the three-way valve in the first state and the drain control valve opened is drained from the downstream drain pipe. 4. The hot water storage system according to claim 3, wherein after a predetermined time has elapsed since the setting was made, the drainage control valve is closed to shift to the hot water supply operation in the second mode. The hot water storage system according to claim 7, wherein the predetermined time has elapsed after at least hot water heated by the gas water heater has reached the upstream drain pipe. The controller is
As a hot water supply control mode, there are a first mode in which hot water and hot water from a hot water storage tank are mixed to supply hot water of a set temperature, and hot water and hot water heated to a temperature higher than the set temperature by the gas water heater. A second mode in which hot water at a set temperature is mixed and hot water heated by the gas water heater, hot water from the hot water storage tank and hot water are mixed to supply hot water at a set temperature; Have
In the hot water supply operation, the first mode is preferentially selected, and when the hot water having the set temperature cannot be supplied in the first mode and hot water not lower than the predetermined temperature by the predetermined temperature or higher can be supplied from the hot water storage tank, the third mode is selected. The hot water storage system according to claim 3, 7 or 8, wherein a mode is selected and the second mode is selected when the third mode cannot be selected.

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