Hot water system

Abstract

To provide a hot water system capable of restraining consumption of fuel gas relating to hot-water supply, and reducing an emission amount of carbon dioxide accompanied with combustion of a water heater, even when a tank is miniaturized.SOLUTION: A bath room use time zone in which hot water is used in a bath room is set to a controller 4. The controller 4 determines whether a current time is in the bath room use time zone and a temperature detected by a return temperature thermistor 11 is not less than a thermal insulation temperature, when detecting passage of water, actuates a water heater 3 in a second combustion capacity range lower than a first combustion capacity range when the time zone is the bath room use time zone and the temperature detected by the return temperature thermistor 11 is not less than the heat insulation temperature, and executes third hot water supply control for mixing tap water heated by the water heater 3 actuated in the second combustion capacity range with hot water in a tank 1, and then supplying hot water to a bath room.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, if the amount of hot water in the tank is low when filling the bathtub, the burner heating device is operated in addition to heating by the heat pump to make up for the lack 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 the hot water supply system described in Patent Document 1, the tank in which hot water is stored can be made smaller. However, when the tank is made smaller, the amount of hot water in the tank is likely to be insufficient during hot water supply operation in the bathroom, where hot water is used in large quantities, such as when filling the bathtub or using the shower. When the amount of hot water in the tank is insufficient, the water heater is operated as described above to make up for the lack of hot water. However, when tap water is heated to the set temperature for hot water supply, the consumption of fuel gas increases, which in turn increases the amount of carbon dioxide emitted by the combustion in the water heater. Therefore, when supplying hot water in the bathroom, the hot water stored in the tank is first supplied, and when the amount of hot water is insufficient, tap water is heated to supply hot water, which is a problem in terms of reducing carbon dioxide emissions. In particular, in a system using a small tank in which the amount of hot water in the tank is likely to be insufficient, the problem is more pronounced.

[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 reduce the amount of fuel gas consumed for hot water supply, even if the tank is made smaller, and ultimately reduce the amount of carbon dioxide emissions associated with combustion in the water heater. [Means for solving the problem]

[0006] In order to achieve the above object, the invention described in claim 1 of the present invention comprises 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 by heat of combustion of a fuel gas, a plurality of supply paths for supplying hot water to the points of use including a first supply path for supplying the hot water in the tank to a predetermined point of use and a second supply path for heating tap water in the water heater without passing through the tank and then supplying it to the point of use, and a control means for controlling the operation of the water heater and the selection of the supply paths, the control means performing a first hot water supply control for supplying the hot water in the tank to the points of use without heating it by the water heater, and a second supply path for operating the water heater within a predetermined first combustion capacity range and heating tap water in the water heater without passing through the tank and then supplying it to the point of use. a second hot water supply control in which the hot water in the tank is mixed with tap water heated by the water heater and then supplied to the point of use; a third supply path is provided as a supply path, which mixes hot water in the tank with tap water heated by the water heater and then supplies the mixed water to the point of use; a bathroom is included as a place of use, and a time zone determination means is provided for determining whether hot water is being supplied to the point of use during a bathroom usage time zone when hot water is used in the bathroom; and when the control means determines that hot water is being supplied during a bathroom usage time zone, it operates the water heater in a second combustion capacity range which is lower than the first combustion capacity range, and executes a third hot water supply control in which the tap water heated by the water heater operating in the second combustion capacity range is mixed with the hot water in the tank and then supplied to the point of use. In order to achieve the above object, the invention described in claim 2 of the present invention provides a water heater 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 by heat of combustion of a fuel gas, a first supply path for supplying the hot water in the tank to a predetermined point of use, and a plurality of supply paths for supplying the hot water to the points of use including a first supply path for supplying the hot water in the tank to a predetermined point of use and a second supply path for heating tap water in the water heater without passing through the tank and then supplying it to the point of use, and a control means for controlling the operation of the water heater and the selection of the supply paths, the control means controlling a first hot water supply control for supplying the hot water in the tank to the points of use without heating it by the water heater, and a second supply path for operating the water heater within a predetermined first combustion capacity range and heating tap water in the water heater without passing through the tank and then supplying it to the point of use. The hot water supply system performs hot water control, and includes a third supply path as a supply path that mixes hot water in a tank with tap water heated by a water heater and then supplies the mixed water to a point of use, while a bathroom is included as a point of use, and a time zone determination means is provided for determining whether hot water is being supplied to the point of use during a bathroom usage time zone when hot water is used in the bathroom.When the control means determines that hot water is being supplied during the bathroom usage time zone and a specified condition is satisfied, it operates the water heater in a second combustion capacity range which is lower than the first combustion capacity range, and performs a third hot water supply control in which the tap water heated by the water heater operating in the second combustion capacity range is mixed with the hot water in the tank and then supplied to the point of use. The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, a flow control means is provided in the third supply path between the tank and a point where the hot water in the tank and the tap water heated by the water heater are mixed, for controlling the flow rate of hot water flowing from inside the tank to the mixing point, and the control means operates the flow control means so that the flow rate of hot water flowing from inside the tank to the mixing point in the third hot water supply control is less than the flow rate of hot water flowing from inside the tank to the point of use in the first hot water supply control. Effect of the Invention

[0007] According to the present invention, a third supply path is provided as a supply path, which mixes hot water in the tank with tap water heated by the water heater and supplies the hot water to the place of use, while a bathroom is included as a place of use, and a time zone determination means is provided for determining whether hot water is being supplied to the place of use during a bathroom use time zone in which hot water is used in the bathroom. When the control means determines that hot water is being supplied during the bathroom use time zone (in the invention described in claim 2, it determines that hot water is being supplied during the bathroom use time zone and a predetermined condition is satisfied), it operates the water heater in a second combustion capacity range that is lower than the first combustion capacity range, and executes a third hot water supply control in which tap water heated by the water heater operating in the second combustion capacity range is mixed with hot water in the tank and then supplied to the place of use. In other words, when hot water is supplied during the bathroom use time zone, tap water heated by the water heater is mixed with hot water in the tank, so there is no need to heat the tap water to a temperature higher than the temperature set as the outlet temperature, and it is sufficient to operate the water heater in the second combustion capacity range. Therefore, it is possible to reduce the amount of carbon dioxide emissions associated with combustion in the water heater. According to the invention described in claim 3, a flow control means is provided in the third supply path between the tank and the place where the hot water in the tank and the tap water heated by the water heater are mixed, for controlling the flow rate of the hot water flowing from the tank to the mixing place. The control means operates the flow control means so that the flow rate of the hot water flowing from the tank to the mixing place in the third hot water supply control is less than the flow rate of the hot water flowing from the tank to the use place in the first hot water supply control. In other words, the amount of hot water used in the tank can be kept low. Therefore, it is possible to provide a hot water supply system that is less likely to cause a situation where the hot water in the tank runs out of hot water during shower use, causing a temporary change in the water temperature, and is less likely to cause discomfort to the user. [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] This is a table showing the start time of hot water supply, the amount of hot water produced, etc. for a typical four-person household. [Diagram 3] 4 is a flowchart showing control related to hot water supply operation by a controller. 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. A water supply pipe 6 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 forward 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 forward pipe 7 and the tank return pipe 8 form a circulation path 9 in 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 hot water and a return temperature thermistor 11 for detecting the temperature of the hot water in the tank return pipe 8. A relay pipe 12 is connected to the top of the tank 1 and is connected to a hot water heat exchanger 23 of the water heater 3, which will be described later. The relay pipe 12 is provided with a relay temperature thermistor 13 for detecting the temperature of the hot water flowing in the relay pipe 12, and a relay flow rate sensor 14 for detecting the flow rate of the hot water flowing in the relay pipe 12. A direct water supply pipe 15 is connected between the relay pipe 12 and the water supply pipe 6 to directly supply the water in the water supply pipe 6 to the hot water heat exchanger 23, bypassing the tank 1. Furthermore, at the connection between the relay pipe 12 and the direct water supply pipe 15, a switching solenoid valve 16 is provided for switching whether the hot water in the relay pipe 12 is supplied to the hot water heat exchanger 23 or the tap water in the direct water supply pipe 15 is supplied to the hot water heat exchanger 23. Note that the switching solenoid valve 16 is normally in a state in which the hot water in the tank 1 is supplied to the hot water heat exchanger 23.

[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] 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, and a hot water outlet temperature thermistor 27 for detecting the temperature of hot water and a hot water outlet flow rate sensor 32 for detecting the flow rate of hot water flowing through the hot water outlet pipe 26 are provided on the hot water outlet pipe 26. An external pipe 28 is connected to the hot water outlet pipe 26, and is provided with a plurality of hot water taps (including a shower head in the bathroom) 29, which are respectively provided in, for example, a washroom, a kitchen, a bathroom, etc. Furthermore, a mixing pipe 30 is connected between the hot water outlet pipe 26 and a point upstream of the switching solenoid valve 16 in the direct water supply pipe 15, to supply tap water into the hot water outlet pipe 26 to adjust the hot water outlet temperature. A water volume control valve 31 is provided at the connection between the direct water supply pipe 15 and the mixing pipe 30 to adjust the temperature of the hot water outlet by controlling the volume of water flowing from the direct water supply pipe 15 to the mixing pipe 30. A hot water supply pipe 18 is connected between the hot water outlet pipe 26 and a location on the relay pipe 12 upstream of the switching solenoid valve 16 to bypass the hot water heat exchanger 23 and supply hot water in the tank 1 to the hot water outlet pipe 26. A relay control valve 17 is provided at the connection between the relay pipe 12 and the hot water supply pipe 18 to switch the supply destination of hot water in the tank 1 between the hot water heat exchanger 23 side or the hot water outlet pipe 26 side, which will be described later, and 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 hot water outlet pipe 26 via the hot water supply pipe 18.

[0013] 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.

[0014] 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.

[0015] 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, etc., and a reheating button (not shown) for commanding the reheating of 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 hot water in the tank 1 warm, a hot water supply operation for supplying hot water from the hot water tap 29, and a reheating operation for reheating hot water in the bathtub 41, etc., according to a program stored in a non-transient computer-readable storage medium that is part of the storage means.

[0016] Before explaining the control of various operations by the controller 4, we will explain the actual hot water usage as disclosed in JIS2075, that is, a standard model of how 40°C hot water is used in a day in a typical household of four people, based on Figure 2. Figure 2 is a table showing the start time of hot water supply, the amount of hot water discharged, etc., in a typical household of four people.

[0017] JIS2075 is a regulation on the method of measuring the modal efficiency of domestic gas and oil hot water appliances, and is a method of measuring the efficiency of hot water appliances using a standard usage mode that reflects the way hot water is used in an ordinary household. Therefore, the hot water usage pattern disclosed in JIS2075 can be used as a standard model of how 40°C hot water is used in a day in a typical four-person household. Therefore, the time period from 19:00 to 24:00 is preset in the controller 4 as the time period for bathroom use.

[0018] The hot water supply operation by the controller 4 in which such a bathroom usage time zone is set will be described with reference to the flowchart shown in Fig. 3. Fig. 3 is a flowchart showing the control related to the hot water supply operation by the controller 4. When the hot water tap 29 is opened and the relay flow rate sensor 14 detects water flow (S1), the controller 4 judges whether the current time is within the learned bathroom use time zone (S2). If the current time is not within the bathroom use time zone (NO in S2), the controller 4 judges whether the temperature of the hot water in the circulation path 9, i.e., the temperature detected by the return temperature thermistor 11, is equal to or higher than a predetermined warming temperature (S6). If the temperature is equal to or higher than the warming temperature (YES in S6), the hot water burner 22 is not ignited and the hot water in the tank 1 is allowed to flow through the hot water heat exchanger 23 to the hot water outlet pipe 26. In other words, the hot water in the tank 1 is not heated by the hot water heat exchanger 23, but is allowed to flow directly to the hot water outlet pipe 26 and be discharged from the hot water tap 29 (S9). At this time, the switching solenoid valve 16 is controlled to prevent tap water from flowing directly from the water supply pipe 15 into the relay pipe 12. In addition, since the temperature of the hot water in the tank 1 flowing through the hot water outlet pipe 26 is relatively high, above the insulation temperature as described above, it is considered that it is often higher than the set temperature set by the remote control 5. Therefore, when the hot water temperature detected by the outlet hot water temperature thermistor 27 is higher than the set temperature set by the remote control 5, the water volume control valve 31 is controlled to a predetermined opening degree, and tap water is directly flowed from the water supply pipe 15 to the mixing pipe 30, and mixed with the hot water in the hot water outlet pipe 26 to adjust to the set temperature. This hot water supply control in which the hot water in the tank 1 is supplied without being heated by the water heater 3 is called the first hot water supply control. After that, the hot water supply tap 29 is closed and the stop of water flow is detected by the outlet hot water flow rate sensor 32 (S10), and the hot water supply operation under the first hot water supply control ends.

[0019] Also, if the temperature detected by the return temperature thermistor 11 is lower than the insulation temperature (determined as NO in S6), the switching solenoid valve 16 is controlled so that tap water is supplied directly from the water supply pipe 15 to the hot water heat exchanger 23. That is, the use of hot water in the tank 1 is stopped (S7). Then, the main solenoid valve 39 and the hot water gas switching valve 37 of the gas pipe 34 are opened, and the proportional control valve 40 is opened at a predetermined opening degree to supply fuel gas to the hot water burner 22. Also, the igniter is operated to ignite the hot water burner 22. Then, the tap water passes through the relay pipe 12 and the hot water heat exchanger 23 from the water supply pipe 6 via the direct water supply pipe 15, and is heated by heat exchange with the combustion exhaust gas in the hot water heat exchanger 23, and then flows into the hot water outlet pipe 26 and is discharged from the hot water tap 29 (S8). At this time, the temperature of the hot water after being heated by hot water heat exchanger 23 and flowing through hot water outlet pipe 26 becomes higher than the set temperature set by remote control 5. Therefore, when such a high hot water temperature is detected by outlet hot water temperature thermistor 27, water volume control valve 31 is controlled to a predetermined opening degree, tap water is directly flowed from water supply pipe 15 to mixing pipe 30, and mixed with the hot water in outlet hot water pipe 26 to adjust to the set temperature. This hot water supply control in which tap water is heated by hot water heater 3 before being discharged is called second hot water supply control. In this second hot water supply control, tap water is heated to a temperature equal to or higher than the set temperature set by remote control 5 or the like, so hot water supply burner 22 is burned within the first combustion capacity range. Thereafter, when the hot water tap 29 is closed and the water outlet flow rate sensor 32 detects the cessation of water flow (S10), the combustion of the hot water burner 22 is stopped and the switching solenoid valve 16 is controlled to return to the initial state, i.e., the state in which the hot water in the tank 1 is supplied to the hot water heat exchanger 23, and the hot water operation under the second hot water control is terminated.

[0020] On the other hand, when the result of the determination after checking the water flow in relay pipe 12 indicates that the bathroom is in use (YES in S2), it is determined whether the temperature detected by return temperature thermistor 11 is equal to or higher than the insulation temperature (S3). If it is equal to or higher than the insulation temperature (YES in S3), switching solenoid valve 16 is controlled so that tap water is supplied directly from water supply pipe 15 to hot water heat exchanger 23. Also, main solenoid valve 39 and hot water gas switching valve 37 of gas pipe 34 are opened to supply fuel gas to hot water burner 22, and an igniter is operated to ignite hot water burner 22. Then, the tap water is heated by heat exchange with the exhaust gas in hot water heat exchanger 23, and then flows to outlet pipe 26 (S4). In addition, the relay control valve 17 is controlled to pass the hot water in the tank 1 through the hot water supply pipe 18, and the hot water in the tank 1 is mixed with the hot water in the hot water outlet pipe 26, and then the hot water is discharged from the hot water tap 29 (S5). At this time, the temperature of the hot water obtained by mixing the hot water heated by the hot water heat exchanger 23 and the hot water in the tank 1 becomes higher than the set temperature set by the remote control 5. Therefore, when the outlet hot water temperature thermistor 27 detects such a high hot water temperature, the water amount control valve 31 is controlled to a predetermined opening degree, and tap water is directly flowed from the water supply pipe 15 to the mixing pipe 30, and mixed with the hot water in the hot water outlet pipe 26 to adjust to the set temperature. This hot water supply control in which the hot water generated by heating the tap water in the hot water heat exchanger 23 is mixed with the hot water in the tank 1 and then discharged is called the third hot water supply control. In this third hot water supply control, it is not necessary to heat the tap water to a temperature higher than the set temperature in the hot water heat exchanger 23. That is, hot water supply burner 22 may be burned in a second combustion capacity range that is lower than the first combustion capacity range. The amount of hot water that is passed from inside tank 1 through hot water supply pipe 18 and mixed with the hot water in outlet pipe 26 may be smaller than the amount of hot water supplied from inside tank 1 to hot water supply heat exchanger 23 in the first hot water supply control, and relay control valve 17 is controlled accordingly. After that, when hot water tap 29 is closed and the stop of water flow is detected by outlet water flow sensor 32 (S10), combustion of hot water supply burner 22 is stopped, and switching solenoid valve 16 and relay control valve 17 are controlled to return to the initial state, that is, the state in which hot water in tank 1 is supplied to hot water supply heat exchanger 23, and the hot water supply operation in the third hot water supply control is terminated.On the other hand, if the temperature is below the insulation temperature (determined as NO in S3), the second hot water supply control described above is executed. That is, the use of hot water in the tank 1 is stopped (S7), and the hot water supply burner 22 is combusted within the first combustion capacity range, and the tap water is heated to a set temperature or higher by the hot water supply heat exchanger 23 and supplied from the hot water tap 29 (S8).

[0021] The same is true for filling the bathtub 41. When the controller 4 detects water flow in response to a filling command from the remote control 5 or the like (S1), it determines whether the current time is within the bathroom use period (S2), and based on the result of that determination and the temperature of the hot water in the tank 1, it causes the hot water heated by the water heater 3, the hot water in the tank 1, or a mixture of the hot water heated by the water heater 3 and the hot water in the tank 1 to flow into the hot water outlet pipe 26. The controller 4 also opens the drop solenoid valve 48 of the drop pipe 47 to start dropping the hot water into the bathtub 41. Thus, the hot water heated by the water heater 3, the hot water in the tank 1, or a mixture of the hot water heated by the water heater 3 and the hot water in the tank 1 flows from the drop pipe 26 to the drop pipe 47, and is supplied to the bathtub 41 from the bath return pipe 42. Furthermore, when the controller 4 confirms that the flow rate detected by the drop-down flow sensor 49 has reached a preset set amount of hot water, 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.

[0022] Next, the reheating operation will be described. After filling the bath 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, the circulation pump 43 is operated, the bath gas switching valve 38 is opened, the bath burner 24 is ignited, 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.

[0023] According to the hot water supply system S having the above-mentioned configuration, a hot water supply pipe 18 is connected between a point on the relay pipe 12 upstream of the switching solenoid valve 16 and the hot water outlet pipe 26, bypassing the hot water heat exchanger 23, to supply hot water in the tank 1 to the hot water outlet pipe 26, and hot water generated by heating tap water in the hot water heat exchanger 23 and hot water in the tank 1 are mixed and then supplied to a place of use such as a bathroom. In addition, a bathroom use time period during which hot water is used in the bathroom is set in the controller 4. When the controller 4 detects water flow, it determines whether the current time is within the bathroom use time period and whether the temperature detected by the return temperature thermistor 11 is equal to or higher than the insulation temperature, and if it is within the bathroom use time period and the temperature detected by the return temperature thermistor 11 is equal to or higher than the insulation temperature, it operates the water heater 3 in a second combustion capacity range lower than the first combustion capacity range, and executes a third hot water supply control in which the tap water heated by the water heater 3 operating in the second combustion capacity range is mixed with the hot water in the tank 1 and then supplied to the bathroom. That is, when supplying hot water during the bathroom usage hours, tap water heated by the water heater 3 is mixed with hot water in the tank 1, so there is no need to heat the tap water to a set temperature or higher, and the water heater 3 can be operated within the second combustion capacity range. This makes it possible to reduce the amount of carbon dioxide emissions associated with combustion in the water heater 3.

[0024] In addition, a relay control valve 17 is provided at the connection between the relay pipe 12 and the hot water supply pipe 18 to switch the supply destination of the hot water in the tank 1 between the hot water heat exchanger 23 side and the hot water outlet pipe 26 side, and to control the amount of hot water used in the tank 1, that is, the amount of hot water flowing from the tank 1 to the hot water outlet pipe 26 through the hot water supply pipe 18. The controller 4 operates the relay control valve 17 so that the flow rate of hot water flowing from the tank 1 to the mixing location in the third hot water supply control is less than the flow rate of hot water flowing from the tank 1 to the usage location in the first hot water supply control. In other words, the amount of hot water used in the tank 1 can be kept low. Therefore, for example, a situation in which the hot water in the tank 1 runs out of hot water during shower use and the water temperature changes temporarily does not occur, and the hot water supply system S is less likely to cause discomfort to the user.

[0025] 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 configuration related to determining the bathroom usage time period can be appropriately modified as necessary.

[0026] In the above embodiment, the bathroom use time zone is set without taking into account the day of the week or whether it is a holiday, but the bathroom use time zone may be set in association with the date. For example, the bathroom use time zone may not be set on Saturdays, Sundays, and holidays. It is also possible to set the bathroom use time zone separately for Saturdays, Sundays, and holidays and for weekdays.

[0027] In the above embodiment, the bathroom use time period is set in advance in the control means, but it is also possible not to set the bathroom use time period in advance. For example, a configuration is conceivable in which the control means stores the usage history of the hot water supply system, learns the bathroom use time period based on the usage history (for example, learns the time period when hot and cold water usage is high as the bathroom use time period), and automatically determines whether or not the time period is a bathroom use time period based on the learning result. Another possible configuration is a configuration in which the control means determines that the bathroom use time period is a time period when a command to fill the bath is issued from a remote control, or a configuration in which the control means determines that the bathroom use time period is a time period when a bathroom priority button is operated on a remote control. Still another possible configuration is a configuration in which a human presence sensor is installed in the bathroom, and the control means determines that the bathroom use time period is a time period when the human presence sensor detects a person in the bathroom.

[0028] Furthermore, in the above embodiment, in addition to determining whether hot water is being supplied during the bathroom use time period, the third hot water supply control is executed by determining whether the temperature detected by the return temperature thermistor is equal to or higher than the insulation temperature, and if the temperature detected by the return temperature thermistor is equal to or higher than the insulation temperature, the third hot water supply control is executed as a predetermined condition is satisfied. However, it is also possible to determine the execution of the third hot water supply control only by determining whether hot water is being supplied during the bathroom use time period. Note that the satisfaction of the predetermined condition for the execution of the third hot water supply control can be achieved in other ways than by determining whether the temperature detected by the return temperature thermistor is equal to or higher than the insulation temperature as described above. For example, in a case where water is replenished in a tank after a certain amount of hot water stored in the tank is used, a sensor capable of measuring the amount of hot water remaining in the tank can be installed, and if the amount of hot water in the tank detected by the sensor is equal to or higher than a predetermined amount, it is determined that the predetermined condition is satisfied.

[0029] 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]

[0030] Reference Signs List: 1··Tank, 2··Heat pump, 3··Water heater, 4··Controller (control means, time zone determination means), 6··Water supply pipe, 12··Relay pipe (first supply path, second supply path, third supply path), 15··Direct water supply pipe (second supply path, third supply path), 16··Switching solenoid valve, 17··Relay control valve (flow rate control means), 18··Hot water supply pipe (third supply path), 20··Hot water heating section, 22··Hot water burner, 23··Hot water heat exchanger, 26··Outlet pipe (first supply path, second supply path, third supply path), 29··Hot water tap (point of use), 41··Bathtub (point of use), S··Hot water system.

Claims

1. The water heater comprises 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 by heat of combustion of fuel gas, a first supply path for supplying the hot water in the tank to a specified point of use, and a second supply path for heating tap water in the water heater without passing through the tank and then supplying it to the point of use, and a control means for controlling the operation of the water heater and the selection of the supply paths; The control means is a hot water supply system that executes a first hot water supply control for supplying hot water in the tank to the point of use without heating it by the hot water heater, and a second hot water supply control for operating the hot water heater within a predetermined first combustion capacity range and heating tap water in the hot water heater without passing through the tank and then supplying it to the point of use, As the supply path, a third supply path is provided for mixing the hot water in the tank with the tap water heated by the water heater and then supplying the resulting mixture to the point of use. a bathroom is included as the place of use, and a time zone determination means is provided for determining whether hot water is being supplied to the place of use during a bathroom usage time zone in which hot water is being used in the bathroom; This hot water supply system is characterized in that, when the control means determines that hot water is to be supplied during the bathroom usage time period, it operates the water heater at a second combustion capacity range lower than the first combustion capacity range, and executes a third hot water supply control, mixing the tap water heated by the water heater operating at the second combustion capacity range with the hot water in the tank and then supplying it to the point of use.

2. The water heater comprises 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 by heat of combustion of fuel gas, a first supply path for supplying the hot water in the tank to a specified point of use, and a second supply path for heating tap water in the water heater without passing through the tank and then supplying it to the point of use, and a control means for controlling the operation of the water heater and the selection of the supply paths; The control means is a hot water supply system that executes a first hot water supply control for supplying hot water in the tank to the point of use without heating it by the hot water heater, and a second hot water supply control for operating the hot water heater within a predetermined first combustion capacity range and heating tap water in the hot water heater without passing through the tank and then supplying it to the point of use, As the supply path, a third supply path is provided for mixing the hot water in the tank with the tap water heated by the water heater and then supplying the resulting mixture to the point of use. a bathroom is included as the place of use, and a time zone determination means is provided for determining whether hot water is being supplied to the place of use during a bathroom usage time zone in which hot water is being used in the bathroom; The hot water supply system is characterized in that the control means determines that hot water is being supplied during the bathroom usage time period and, when specified conditions are satisfied, operates the water heater at a second combustion capacity range which is lower than the first combustion capacity range, and executes a third hot water supply control in which the tap water heated by the water heater operating at the second combustion capacity range is mixed with the hot water in the tank and then supplied to the point of use.

3. In the third supply path, a flow control means is provided between the tank and a point where the hot water in the tank and the tap water heated by the water heater are mixed, for controlling a flow rate of the hot water flowing from the tank to the mixing point, The hot water supply system described in claim 1 or 2, characterized in that the control means operates the flow control means so that the flow rate of hot water flowing from the tank to the mixing point in the third hot water supply control is less than the flow rate of hot water flowing from the tank to the point of use in the first hot water supply control.

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