Hot water supply system

Abstract

To provide a hot water supply system capable of efficiently using hot water stored in a tank.SOLUTION: A controller 4 can execute a first mixing control for generating hot water at a set temperature by mixing hot water in the tank 1 with tap water, and a second mixing control for generating hot water below the set temperature by mixing the hot water in the tank 1 with the tap water, as operation control of a mixing control valve 16 and a tank flow control valve 17. The controller is configured to, when supplying hot water from a hot water tap 29, execute the first mixing control to supply the generated hot water to the hot water tap 29 without being heated by a water heater 3, while when filling the bathtub 41 with hot water, execute the second mixing control to heat the generated hot water to a set temperature by the water heater 3 and then supply it to the bathtub 41.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hybrid hot water supply system comprising a hot water heater equipped with a burner and capable of heating passing water, and a tank equipped with a heat pump and storing the heated hot water. [Background technology]

[0002] Conventionally, a heat pump-type hot water supply system has been put into practical use, which includes a heat pump and a tank for storing hot water heated by the heat pump, and supplies hot water in the tank to a kitchen, a bathroom, etc. However, in the conventional heat pump-type hot water supply system, there is a problem that the tank must be very large in size in order to store a large amount of hot water required when filling a bathtub. Therefore, as described in Patent Document 1, for example, a hybrid hot water supply system has been devised in which a burner heating device, which is a hot water heater, is installed in the supply path downstream of the tank in which the hot water is stored. In the hybrid hot water supply system described in Patent Document 1, when the amount of hot water in the tank is low during hot water supply operation, the burner heating device is operated in addition to heating by the heat pump to make up for the shortage of hot water, and as a result, the tank can be made smaller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-224762 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a hybrid hot water supply system such as that described in Patent Document 1, it is possible to reduce the size of the tank in which hot water is stored. However, when the tank is reduced in size in this way, the efficient use of the hot water stored in the tank becomes an issue.

[0005] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a hot water supply system that can efficiently use the hot water stored in the tank. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the invention described in claim 1 of the present invention is a hot water supply system comprising a tank for storing hot water, a heat pump for heating the hot water in the tank, a water heater for heating the supplied hot water using the heat of combustion of fuel gas, a supply path for supplying the hot water in the tank to a predetermined point of use via the water heater, a mixing means for mixing the hot water in the tank and tap water at a predetermined mixing ratio upstream of the water heater in the supply path, and a control means for controlling the operation of the water heater and the mixing means, wherein the control means is capable of executing, as operation control of the mixing means, a first mixing control for mixing the hot water in the tank and tap water to produce hot water of a predetermined set temperature or higher, and a second mixing control for mixing the hot water in the tank and tap water to produce hot water below the set temperature, and when the first mixing control is executed, the produced hot water is supplied to the point of use without being heated by the water heater, while when the second mixing control is executed, the produced hot water is heated to a temperature above the set temperature by the water heater before being supplied to the point of use. The invention described in claim 2 is characterized in that, in the invention described in claim 1, a bathtub is included as a place of use, and a command means is provided that commands the control means to fill the bathtub with water, and when the command means commands the bathtub to be filled with water, the control means executes a second mixed control. The invention described in claim 3 is characterized in that, in the invention described in claim 1, a bathtub is included as a place of use, and a command means is provided that commands the control means to fill the bathtub with water, and when the command means commands filling the bathtub with water and predetermined conditions are satisfied, the control means executes a second mixed control. The invention described in claim 4 is characterized in that, in the invention described in claim 2 or 3, a filling discrimination means is provided for discriminating the end of filling the bathtub with water, and the control means, during a trial run of filling the bathtub with water, measures and stores the filling time from the start to the end of filling the bathtub with water based on the discrimination result by the filling discrimination means, and uses the filling time and the capacity of the tank to set the amount of hot water and water used per unit time in the tank in the second mixing control. Effect of the Invention

[0007] According to the present invention, the control means can execute, as operation control of the mixing means, a first mixing control for producing hot water at a predetermined set temperature or higher by mixing the hot water in the tank with tap water, and a second mixing control for producing hot water below the set temperature by mixing the hot water in the tank with tap water, and when the first mixing control is executed, the produced hot water is supplied to the point of use without being heated by the water heater, whereas when the second mixing control is executed, the produced hot water is heated to a set temperature or higher by the water heater before being supplied to the point of use. By selectively using the mixing mode of the hot water in the tank and tap water in this way, the hot water in the tank can be used efficiently. According to the inventions of claims 2 and 3, a bathtub is included as a place of use, and a command means is provided that commands the control means to fill the bathtub with hot water, and the control means executes the second mixing control when the command means commands filling the bathtub with hot water (claim 2) or when the command means commands filling the bathtub with hot water and a predetermined condition is met (claim 3).In this way, when filling the bathtub, where a large amount of hot water is expected to be used, the second mixing control is executed, which uses a relatively small amount of hot water in the tank, so that the hot water in the tank can be used very efficiently, resulting in a hot water supply system that is less likely to run out of hot water in the tank while filling the bathtub. Furthermore, according to the invention described in claim 4, a filling determination means is provided for determining the end of filling the bathtub with hot water, and the control means measures and stores the filling time from the start to the end of filling the bathtub based on the determination result by the filling determination means during a trial run for filling the bathtub with hot water, and sets the amount of hot water used in the tank per unit time in the second mixing control using the filling time and the tank capacity. Therefore, for example, when the amount of hot water in the tank is close to the maximum amount, it is possible to set the amount of use so that the hot water in the tank can be used continuously from the start to the end of filling the bathtub. By setting such an amount of use, it is possible to prevent the temperature of the hot water from fluctuating greatly during filling, and ultimately to stabilize the combustion in the water heater. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram showing an outline of a hot water supply system. [Diagram 2] 4 is a flowchart showing control related to hot water supply operation by a controller. [Diagram 3] 4 is a flowchart showing control of the filling operation by the controller. [Figure 4] 1 is a graph showing the correlation between the rotation speed of an air supply fan and gas input in a water heater for each combustion stage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hot water supply system according to an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a hot water supply system S. As shown in FIG. The hot water supply system S comprises a tank 1 for storing hot water, a heat pump 2 for heating the hot water in the tank 1, a water heater 3 for heating the supplied hot water by burning a fuel gas, a controller 4, and a remote control 5. The capacity of the tank 1 is 20 L, which is sufficiently smaller than the capacity of a typical bathtub 41 (for example, 100 L). A water supply pipe 6 that is connected to an external water pipe is also connected to the tank 1. The heat pump 2 is a known device that includes an evaporator, a compressor, a heat exchanger, etc., and heats the passing water by heat exchange between a heat medium and the passing water, and has an output of 2.0 kW.

[0010] A tank supply pipe 7 is connected between the top of the tank 1 and the outlet of the heat pump 2, and a tank return pipe 8 is connected between the bottom of the tank 1 and the inlet of the heat pump 2. The tank supply pipe 7 and the tank return pipe 8 form a circulation path 9 through which hot water circulates between the tank 1 and the heat pump 2. The tank return pipe 8 is provided with a pump 10 for circulating the hot water, and a return temperature thermistor 11 for detecting the temperature of the hot water in the tank return pipe 8.

[0011] When the remote control 5 is operated to instruct heat-retention operation by the heat pump 2, the controller 4 operates the heat pump 2 and the pump 10. Then, the hot water in the tank 1 circulates through the circulation path 9 and is heated as it passes through the heat pump 2. The hot water in the tank 1 is once heated to a high temperature (e.g., 75°C) in the heat pump 2, and then the heat pump 2 is turned ON / OFF based on the temperature detected by the return temperature thermistor 11, thereby maintaining the water at a predetermined heat-retention temperature (e.g., 65°C).

[0012] Furthermore, a relay pipe 12 connected to a hot water heat exchanger 23 of the water heater 3 described later is connected to the upper part of the tank 1. A direct water supply pipe 15 is connected between a portion of the relay pipe 12 upstream of the water heater 3 and the water supply pipe 6 to bypass the tank 1 and directly supply water in the water supply pipe 6 to the water heater 3 side, and a water supply temperature thermistor 19 is provided in the direct water supply pipe 15 to detect the temperature of tap water. A mixing control valve 16 is provided at the connection between the relay pipe 12 and the direct water supply pipe 15 to control the amount of water flowing from the direct water supply pipe 15 to the relay pipe 12 and to control the mixing ratio of the hot water and tap water sent from the tank 1. Furthermore, a tank flow control valve 17 is provided at a portion upstream of the mixing control valve 16 in the relay pipe 12 to control the amount of hot water used in the tank 1, i.e., the amount of hot water flowing from the tank 1 to the mixing control valve 16, and a usage sensor 14 is provided to detect the amount of hot water flowing from the tank 1 to the mixing control valve 16. Meanwhile, downstream of the mixing control valve 16 in the relay pipe 12, there are provided a supply temperature thermistor 13 for detecting the temperature of the hot water supplied to the hot water heat exchanger 23, and a supply amount sensor 18 for detecting the amount of hot water supplied per unit time to the hot water heat exchanger 23. Note that the tank flow control valve 17 is normally in a state where the hot water in the tank 1 can flow toward the hot water heat exchanger 23.

[0013] On the other hand, the water heater 3 includes a water heater 20 and a bath heater 21. The water heater 20 includes a water burner 22 and a water heat exchanger 23, and the relay pipe 12 is connected to the inlet of the water heat exchanger 23. A hot water outlet pipe 26 is connected to the outlet of the water heat exchanger 23. The hot water outlet pipe 26 is provided with a hot water outlet temperature thermistor 27 for detecting the temperature of the hot water outlet, and a hot water outlet flow rate sensor 32 for detecting the flow rate of the hot water flowing through the hot water outlet pipe 26. The hot water outlet pipe 26 is also connected to an external pipe 28 provided with a plurality of hot water taps 29 that are arranged in, for example, a washroom, a kitchen, a bathroom, etc.

[0014] The bath heating section 21 has a bath burner 24 and a bath heat exchanger 25. A bath return pipe 42 is connected between the inlet of the bath heat exchanger 25 and the external bathtub 41. A circulation pump 43 and a bath temperature thermistor 44 are provided in the bath return pipe 42. A bath supply pipe 45 is connected between the outlet of the bath heat exchanger 25 and the bathtub 41. The bath return pipe 42 and the bath supply pipe 45 form a reheating circulation path 46 in which hot water circulates between the bath heat exchanger 25 and the bathtub 41. A drop pipe 47 is connected between the bath return pipe 42 and the hot water outlet pipe 26. A drop solenoid valve 48 and a drop flow rate sensor 49 are provided in the drop pipe 47.

[0015] Furthermore, gas pipe 34, which supplies fuel gas to hot water burner 22 and bath burner 24, branches into hot water branch pipe 35 on the hot water heating section 20 side and bath branch pipe 36 on the bath heating section 21 side. Hot water branch pipe 35 supplies fuel gas to hot water burner 22, and bath branch pipe 36 supplies fuel gas to bath burner 24. Hot water branch pipe 35 is provided with hot water gas switching valve 37, and bath branch pipe 36 is provided with bath gas switching valve 38. In addition, a main solenoid valve 39 and a proportional control valve 40 are provided from the upstream side in gas pipe 34 before branching.

[0016] In addition, water heater 3 is provided with air supply fan 33 for mixing fuel gas and air and supplying the mixture to hot water burner 22 and bath burner 24. In Fig. 1, air supply fan 33 is shown only in the combustion chamber in which hot water burner 22 is installed, but air supply fan 33 also supplies air to the combustion chamber in which bath burner 24 is installed.

[0017] The remote control 5 is operated by the user as appropriate, and is provided with, for example, a setting button (not shown) for setting the hot water temperature, a filling button (not shown) for commanding filling the bathtub 41 with hot water, and a reheating button (not shown) for commanding reheating of the hot water in the bathtub 41. The controller 4 is composed of a CPU, a storage means, a timer, etc., and is electrically connected to each thermistor, each sensor, and each valve. Based on operation commands from the remote control 5, the set temperature set by the remote control 5, information obtained from each thermistor and each sensor, etc., the controller 4 executes an operation for keeping the hot water in the tank 1 warm, a hot water supply operation for supplying hot water from the hot water tap 29, a hot water filling operation for filling the bathtub 41 with hot water, and a reheating operation for reheating the hot water in the bathtub 41, in accordance with a program stored in a non-transient computer-readable storage medium that is a part of the storage means.

[0018] The hot water supply operation and hot water filling operation by the controller 4 will be described below with reference to the flowcharts and graphs shown in Figures 2 to 4. Figure 2 is a flowchart showing the control of the hot water supply operation by the controller 4. Figure 3 is a flowchart showing the control of the hot water filling operation by the controller 4. Figure 4 is a graph showing the correlation between the rotation speed of the air supply fan 33 in the water heater 3 and the gas input for each combustion stage.

[0019] First, the hot water supply operation will be described. When the hot water tap 29 is opened and the usage sensor 14 detects the flow of water (S1), the controller 4 judges whether the temperature of the hot water in the circulation path 9, that is, the temperature detected by the return temperature thermistor 11, is equal to or higher than a predetermined warming temperature (S2). If the temperature is equal to or higher than the warming temperature (YES in S2), the mixing control valve 16 and the tank flow control valve 17 are controlled by the first mixing control to mix the hot water in the tank 1 with the tap water (S5). This first mixing control is a control to mix the hot water in the tank 1 with the tap water to generate hot water at the set temperature for hot water supply set by the remote control 5. That is, for example, if the set temperature required for hot water output is 40°C, the temperature of the hot water in the tank 1 is 65°C, and the temperature of the tap water is 15°C, hot water at 40°C can be generated by mixing the hot water in the tank 1 with the tap water at a ratio of 1:1. Therefore, the tank flow control valve 17 is controlled to an opening corresponding to the degree to which the hot water tap 29 is opened, while the mixing control valve 16 is controlled to an opening calculated based on the temperature detected by the return temperature thermistor 11, the temperature detected by the supply water temperature thermistor 19, the set temperature set in the remote control 5, and the amount of hot and cold water detected by the usage sensor 14, and the control of the mixing control valve 16 and the tank flow control valve 17 at this time becomes the first mixing control.

[0020] Furthermore, as described above, in order to generate hot water at the set temperature by mixing the hot water in the tank 1 with tap water, the hot water burner 22 is not ignited, i.e., the generated hot water is not heated by the hot water heat exchanger 23, but is instead flowed from the hot water heat exchanger 23 to the hot water outlet pipe 26 (S6). After that, when the hot water tap 29 is closed and the outlet water flow rate sensor 32 detects that water flow has stopped (YES is determined in S7), the mixing control valve 16 and the tank flow rate control valve 17 are returned to their original states, and the hot water supply operation with the first mixing control is terminated. Whether or not the temperature of the hot water generated by mixing the hot water in the tank 1 with tap water is the set temperature is determined by the temperature detected by the supply temperature thermistor 13 or the outlet water temperature thermistor 27, and if the temperature is higher or lower than the set temperature, the opening of the mixing control valve 16 is finely adjusted according to the determination result.

[0021] On the other hand, if the temperature detected by the return temperature thermistor 11 is below the warming temperature when hot water supply starts, or if the temperature detected by the return temperature thermistor 11 becomes below the warming temperature during hot water supply (determined as NO in S2), the tank flow control valve 17 is controlled so that the hot water in the tank 1 is not supplied to the hot water heat exchanger 23. That is, the use of the hot water in the tank 1 is stopped (S3). Also, the mixing control valve 16 is controlled to an opening degree corresponding to the degree of opening of the hot water tap 29, so that only tap water is supplied directly from the water supply pipe 15 to the hot water heat exchanger 23. Furthermore, the main solenoid valve 39 and the hot water gas switching valve 37 of the gas pipe 34 are opened, and further the proportional control valve 40 is opened at a predetermined opening degree, and the air supply fan 33 is rotated and driven to supply the fuel gas mixed with air to the hot water burner 22. In addition, the igniter is operated to ignite the hot water burner 22. Then, tap water flows from water supply pipe 6 directly through water supply pipe 15, relay pipe 12, and hot water heat exchanger 23, where it is heated to the set temperature for hot water supply by heat exchange with the combustion exhaust gas and then flows into hot water outlet pipe 26 (S4). This mixing control in which only tap water is supplied to water heater 3 without supplying hot water in tank 1 to water heater 3 is called third mixing control. After that, when hot water tap 29 is closed and the stop of water flow is detected by outlet water flow sensor 32 (YES is determined in S7), the combustion of hot water burner 22 is stopped, and mixing control valve 16 and tank flow control valve 17 are returned to their original states, and hot water supply operation with the third mixing control is terminated.

[0022] Next, the filling operation will be described. When the filling operation is performed, after the hot water supply system S is installed, the trial operation described below is performed in advance, and the controller 4 measures the filling time required for filling the water, calculates the amount of hot water used per minute in the tank 1 during filling (hereinafter referred to as the filling amount), and stores each in the storage means. This trial operation is performed, for example, by operating a filling setting button (not shown) provided on the remote control 5. When the filling setting button is operated, the controller 4 opens the drop solenoid valve 48 and starts dropping hot water into the bathtub 41 at a preset drop amount per unit time, i.e., filling the bathtub, and determines the end of filling the bathtub 41 based on the detection value by the pressure sensor 30 provided in the bathtub 41, and measures the filling time from the start to the end of filling the bathtub. The controller 4 also calculates and stores the amount of hot water used using the capacity of the tank 1 and the filling time. This filling amount is set so that the hot water in the tank 1 can be used continuously from the start to the end of filling when the amount of hot water in the tank 1 is close to the maximum amount, because the capacity of the tank 1 is sufficiently smaller than that of the bathtub 41. This is because if hot water is poured into the bathtub 41 at a typical amount per unit time (for example, 5 L / min), the hot water in the tank 1 will run out before the filling is completed by 50%. Therefore, for example, the filling amount is calculated by dividing 80% of the capacity of the tank 1 by the filling time, and if the capacity of the tank 1 is 20 L and the filling is completed in 20 minutes, the filling amount is 0.8 L / min. The capacity of the tank 1 is input in advance to the controller 4 by the remote control 5 or the like by the operator. The controller 4 also detects the amount of hot water required for filling using the pouring flow rate sensor 49 and stores it as the set amount of hot water.

[0023] After such a test run, when the filling button on the remote control 5 is operated to start filling the water (S11), the controller 4 judges whether the temperature detected by the return temperature thermistor 11 is equal to or higher than the predetermined warming temperature (S12). If it is equal to or higher than the warming temperature (YES in S12), the controller 4 controls the mixing control valve 16 and the tank flow control valve 17 in the second mixing control to mix the hot water in the tank 1 with the tap water (S15). This second mixing control is a control in which the opening of the tank flow control valve 17 is set to an opening corresponding to the amount of filling used, and the opening of the mixing control valve 16 is set to an opening corresponding to the amount of filling used minus the amount of filling used from the amount of drop per unit time, and hot water in the tank 1 is mixed with tap water to generate hot water that is lower than the set temperature for filling set on the remote control 5 but higher than tap water. Depending on the set temperature and the amount of drop per unit time, it is possible that the second mixing control cannot generate hot water that is lower than the set temperature for filling the water but higher than tap water. However, considering the generally expected set temperature and drop amount per unit time, the above-mentioned second mixing control will produce hot water that is lower than the set temperature for filling the tub, but hotter than tap water.

[0024] Furthermore, the main solenoid valve 39, hot water gas switching valve 37, and proportional control valve 40 of the gas pipe 34 are opened, and the air supply fan 33 is rotated to supply fuel gas mixed with air to the hot water burner 22. In addition, the igniter is operated to ignite the hot water burner 22. Then, the hot water generated by the second mixing control passes through the hot water heat exchanger 23 from the relay pipe 12, and flows into the hot water outlet pipe 26 after being heated to the set temperature for filling the bath by heat exchange with the combustion exhaust. Furthermore, the controller 4 opens the drop solenoid valve 48 of the drop pipe 47 to start dropping the hot water into the bathtub 41. Therefore, the hot water heated by the water heater 3 flows from the hot water outlet pipe 26 to the drop pipe 47, and is supplied to the bathtub 41 from the bath return pipe 42 (S16). Thereafter, when the controller 4 confirms that the flow rate detected by the drop-down flow sensor 49 has reached the preset hot water volume (determines YES in S17), it closes the drop-down solenoid valve 48 and stops the combustion of the hot water burner 22, thereby terminating the supply of hot water to the bathtub 41, i.e., the filling operation.

[0025] However, when the water filling starts, the temperature detected by the return temperature thermistor 11 may be below the warming temperature, or the water in the tank 1 may run out during the filling process, causing the temperature detected by the return temperature thermistor 11 to be below the warming temperature (NO in S12). In this case, the mixing control valve 16 and the tank flow control valve 17 are controlled by the third mixing control. That is, the use of hot water in the tank 1 is stopped, and only tap water is supplied to the hot water heat exchanger 23 (S13). In addition, the hot water burner 22 is ignited or kept burning, and the tap water is heated to the set temperature for filling by the hot water heat exchanger 23, and then supplied to the bathtub 41 via the outlet pipe 26, drop pipe 47, and bath return pipe 42 (S14).

[0026] Here, the combustion control of water heater 3 during filling with the second mixing control and hot water supply or filling with the third mixing control will be described. When igniting hot water burner 22 during filling or supplying hot water as described above, controller 4 detects the temperature of hot water or tap water supplied to hot water heat exchanger 23 with supply temperature thermistor 13. Also, the amount of hot water supplied to hot water heat exchanger 23 per unit time with supply amount sensor 18. Then, the gas input related to the combustion of hot water burner 22 is calculated based on the set temperature, detected temperature, and supply amount related to filling or supplying hot water, and the rotation speed of air supply fan 33 is determined based on the graph shown in FIG. 4, and the rotation drive of air supply fan 33 is controlled.

[0027] In addition, when filling water with the second mixing control is compared with hot water supply with the third mixing control, the temperature of the hot water supplied to the hot water heat exchanger 23 in filling water with the second mixing control is higher than the temperature of the tap water supplied to the hot water heat exchanger 23 in hot water supply with the third mixing control. Therefore, when comparing a situation where heating is performed to the same temperature as filling water in hot water supply with the third mixing control, filling water with the second mixing control requires less gas input during combustion of the hot water burner 22 than hot water supply with the third mixing control. Therefore, the consumption of fuel gas is reduced, and the amount of carbon dioxide emissions associated with combustion in the water heater 3 is reduced. In addition, when comparing cases where the number of combustion stages of the hot water burner 22 is the same, the rotation speed of the air supply fan 33 is reduced due to the reduced gas input. Therefore, when compared with a situation in which heating is performed to the same temperature as when filling water with the third mixing control, when filling water with the second mixing control, the driving power of the air supply fan 33 is reduced compared to when filling water with the third mixing control. Furthermore, since the combustion heat of the hot water burner 22 remains longer around the hot water heat exchanger 23 due to the reduced rotation speed of the air supply fan 33, when filling water with the second mixing control, the thermal efficiency is improved compared to when filling water with the third mixing control.

[0028] Finally, the reheating operation will be explained. After filling the bathtub as described above, when the reheating button on the remote control 5 is operated, the controller 4 executes the reheating operation to heat the hot water in the bathtub 41. That is, while activating the circulation pump 43, the bath gas switching valve 38 is opened and the air supply fan 33 is rotated and driven to ignite the bath burner 24, and the hot water in the bathtub 41 is circulated through the reheating circulation path 46 for reheating. When the temperature detected by the bath temperature thermistor 44 reaches the preset reheating temperature, the circulation pump 43 is stopped and the combustion of the bath burner 24 is stopped, and the reheating operation is terminated.

[0029] According to the hot water supply system S having the above configuration, the controller 4 can execute, as the operation control of the mixing control valve 16 and the tank flow control valve 17, a first mixing control for mixing the hot water in the tank 1 with tap water to generate hot water at a set temperature, and a second mixing control for mixing the hot water in the tank 1 with tap water to generate hot water below the set temperature. When supplying hot water from the hot water tap 29, the first mixing control is executed, and the generated hot water is supplied to the hot water tap 29 without being heated by the water heater 3. On the other hand, when filling the bathtub 41 with hot water, if the temperature detected by the return temperature thermistor 11 is equal to or higher than a predetermined insulation temperature, the second mixing control is executed as a predetermined condition is satisfied, and the generated hot water is heated to the set temperature by the water heater 3 before being supplied to the bathtub 41. By using the mixing mode of the hot water in the tank 1 and the tap water in this way, the hot water in the tank 1 can be used efficiently. In addition, particularly during filling the water, when a large amount of hot water is expected to be used, the second mixing control is executed, which uses a relatively small amount of hot water in the tank 1, so that the hot water in the tank 1 can be used very efficiently, resulting in a hot water supply system S in which it is unlikely that there will be a situation where there is not enough hot water in the tank 1 during filling the water.

[0030] In addition, a pressure sensor 30 is provided to determine the end of filling the bathtub 41 with hot water, and the controller 4 measures and stores the time from the start to the end of filling the bathtub 41 with hot water based on the value detected by the pressure sensor 30 during a trial run for filling the bathtub 41 with hot water, and sets the amount of hot water used per minute in the tank 1 in the second mixing control using the time of filling the bathtub 41 and the capacity of the tank 1. Therefore, for example, when the amount of hot water in the tank 1 is close to the maximum amount, it is possible to set the amount of use so that the hot water in the tank 1 can be used continuously from the start to the end of filling the bathtub. By setting such an amount of use, it is possible to prevent the temperature of the hot water from fluctuating greatly during filling the bathtub, and it is also possible to stabilize the combustion in the water heater 3.

[0031] The hot water supply system of the present invention is not limited to the above-described embodiment, and the overall configuration of the hot water supply system as well as the configurations relating to the first mixing control, the second mixing control, and the third mixing control can be appropriately modified as necessary.

[0032] In the above embodiment, in the first mixing control, the hot water in the tank and tap water are mixed to produce hot water at the set temperature, but taking into consideration that the temperature of the hot water drops in the supply path until it is supplied to the place of use, the hot water in the tank and tap water may be mixed to produce hot water at a temperature higher than the set temperature. Similarly, in the above embodiment, in the second mixing control and the third mixing control, the mixed hot water is heated to the set temperature by heat exchange with the combustion exhaust gas in the hot water supply heat exchanger, but there is no problem if it is heated to a temperature higher than the set temperature.

[0033] It is also possible to draw water from the water supply pipe into the hot water outlet pipe and mix it with tap water to adjust the temperature of the hot water flowing through the hot water outlet pipe. By adopting such a configuration, it is possible to accurately and easily adjust the temperature of the hot water supplied to the point of use. Furthermore, in the above embodiment, in addition to a command to fill the water, the second mixing control is executed only when the temperature detected by the return temperature thermistor is equal to or higher than the insulation temperature, but it is also possible to configure the system to mix the hot water and cold water in the tank with the second mixing control even if the temperature detected by the return temperature thermistor is below the insulation temperature when filling the water starts, or if there is not enough hot water in the tank during filling and the temperature detected by the return temperature thermistor falls below the insulation temperature. In other words, the system may be configured to execute the second mixing control automatically without determining whether or not a certain condition is met when a command to fill the water is issued.

[0034] Furthermore, as described in the embodiment, it is possible to switch from the second mixing control to the third mixing control during filling, but it is desirable to set the mixing ratio of the hot water and tap water in the tank in the second mixing control so that the number of combustion stages of the hot water burner does not change due to the change in the fuel gas input at this time, that is, so that the gas input in the second mixing control is equal to or greater than the minimum gas input on the same line as the number of combustion stages assumed in the third mixing control. By setting the mixing ratio in this way, even if the control switches from the second mixing control to the third mixing control during filling, the number of combustion stages of the hot water burner does not change, so there is an effect of stabilizing the combustion operation of the water heater during filling.

[0035] Furthermore, in the above embodiment, the filling time is measured by a trial run for the filling operation and the filling usage amount is calculated, but there is no problem with a hot water supply system that does not measure the filling time. That is, the filling usage amount in the second mixing control may be set separately, regardless of the filling time, etc. Also, in the above embodiment, a pressure sensor is used as the filling determination means for determining the end of filling, but other means such as a drop flow rate sensor can be used as the filling determination means. If a drop flow rate sensor is used as the filling determination means, the bathtub volume can be input in advance to the controller, etc.

[0036] In addition, the capacity of the tank is not limited to 20 L as in the above embodiment, but may be set appropriately between 10.00 L and 25.00 L. The heat exchanger of the water heater may be provided with both a primary heat exchanger for recovering sensible heat and a secondary heat exchanger for recovering latent heat. Furthermore, although the water heater of the above-described embodiment is equipped with a bath heating section, it is also possible to adopt a water heater without a bath heating section. [Explanation of symbols]

[0037] Description of the Reference Numerals 1··Tank, 2··Heat pump, 3··Water heater, 4··Controller (control means), 5··Remote control (command means), 6··Water supply pipe, 12··Relay pipe (supply path), 13··Supply temperature thermistor (supply temperature detection means), 14··Usage sensor, 15··Direct water supply pipe (second supply path), 16··Mixing control valve (mixing means), 17··Tank flow control valve (mixing means), 18··Supply amount sensor (supply amount detection means), 19··Water supply temperature thermistor, 20··Water supply heating section, 22··Water supply burner, 23··Water supply heat exchanger, 26··Outlet pipe (supply path, second supply path), 29··Water supply tap (point of use), 30··Pressure sensor (means for determining whether water is filled), 33··Air supply fan, 41··Bathtub (point of use), S··Water supply system.

Claims

1. A hot water supply system comprising a tank for storing hot water, a heat pump for heating the hot water in the tank, a water heater for heating the supplied hot water with heat of combustion of fuel gas, a supply path for supplying the hot water in the tank to a specified point of use via the water heater, a mixing means for mixing the hot water in the tank and tap water at a specified mixing ratio upstream of the water heater in the supply path, and a control means for controlling the operation of the water heater and the mixing means, The control means is capable of executing, as an operation control of the mixing means, a first mixing control for producing hot water of a predetermined set temperature or higher by mixing the hot water in the tank with tap water, and a second mixing control for producing hot water of a temperature lower than the set temperature by mixing the hot water in the tank with tap water, When the first mixing control is executed, the generated hot water is supplied to the use point without being heated by the hot water heater, A hot water supply system characterized in that, when the second mixing control is executed, the produced hot water is heated by the water heater to a temperature equal to or higher than the set temperature and then supplied to the point of use.

2. The place of use includes a bathtub, and a command means is provided for commanding the control means to fill the bathtub with water, The hot water supply system according to claim 1, characterized in that the control means executes the second mixing control when the command means issues a command to fill the tub with hot water.

3. The place of use includes a bathtub, and a command means is provided for commanding the control means to fill the bathtub with water, The hot water supply system according to claim 1, characterized in that the control means executes the second mixing control when the command means issues a command to fill the tub with hot water and a predetermined condition is satisfied.

4. A bathtub filling determination means is provided for determining when the bathtub has been filled with water, The control means measures and stores a time from the start to the end of filling the bathtub with water based on the result of the determination by the filling determination means during a test operation of filling the bathtub with water, and The hot water supply system according to claim 2 or 3, characterized in that the amount of hot water and cold water used per unit time in the tank in the second mixing control is set using the water filling time and the capacity of the tank.

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