JP7707515B2 - Hot water storage system - Google Patents

Description

The present invention relates to a hot water storage and hot water supply system that uses hot water heated by a main heat source unit and stored in a hot water tank for hot water supply.

Conventionally, hot water storage and hot water supply systems have been widely used as main heat source units with high heating operation efficiency, in which hot water heated by, for example, a heat pump type heat source unit is stored in a hot water tank and the hot water in the hot water tank is used to supply hot water. The hot water discharged from the hot water tank is mixed with tap water in a hot water mixing section, and the hot water adjusted to a preset hot water supply temperature is supplied to, for example, a hot water tap.

If there is no hot water in the hot water storage tank that can be supplied at the hot water supply setting temperature when hot water supply starts, the hot water discharged from the hot water storage tank through the hot water mixing unit is heated by the heating operation of an auxiliary heat source unit, such as a combustion-type heat source unit, to supply hot water. At this time, if the hot water temperature in the hot water storage tank is lower than the hot water supply setting temperature and close to the hot water supply setting temperature, there is a risk that the temperature will be higher than the hot water supply setting temperature even if heated with the minimum heating capacity of the auxiliary heat source unit. Therefore, when heating with the auxiliary heat source unit, the hot water in the hot water storage tank is mixed with clean water in the hot water mixing unit, and hot water whose temperature has been lowered to below the specified heating start temperature is supplied to the auxiliary heat source unit, and the hot water is supplied by adjusting the temperature to the hot water supply setting temperature by the heating operation of the auxiliary heat source unit.

For example, as in Patent Document 1, when hot water supply is resumed while high-temperature hot water is stored in the hot water tank, a technology is known in which the flow rate on the hot water tank side in the hot water mixing section is made smaller than the flow rate on the clean water side, thereby supplying low-temperature hot water to the auxiliary heat source unit, which then heats and supplies hot water. On the other hand, as in Patent Document 2, a technology is known in which, when hot water supply is stopped, the hot water mixing section is adjusted to a mixing ratio that results in a higher flow rate on the clean water side than during hot water supply, so that excessively high-temperature hot water is not supplied to the auxiliary heat source unit when hot water supply is resumed. Both technologies adjust the mixing ratio of the hot water mixing section to increase the flow rate on the low-temperature clean water side when hot water supply is resumed, preventing high-temperature hot water from being unexpectedly supplied.

Patent No. 6129033 Patent No. 6685135

The hot water supply temperature setting can be set by the user to a desired temperature before using the hot water supply, and can also be changed even while the hot water supply is in use. If the hot water supply temperature setting is changed while the hot water mixing unit is adjusting the temperature to the hot water supply temperature setting and supplying hot water, the auxiliary heat source unit will supply hot water at the changed hot water supply temperature, either without heating or by performing heating operation depending on the temperature of the hot water in the hot water storage tank, just as when hot water supply began. If the hot water supply temperature setting is changed during hot water supply involving heating operation by the auxiliary heat source unit, the heating capacity of the heating operation is adjusted to supply hot water at the changed hot water supply temperature.

Here, when a temperature reduction change is made to lower the hot water supply set temperature, the heating capacity of the heating operation is adjusted to be smaller, but if a heating capacity lower than the minimum heating capacity is requested, the heating operation will be stopped. If this happens, the auxiliary heat source unit will not heat the water, and the hot water will be lower than the hot water supply set temperature. For this reason, it is required that the hot water mixing unit supply hot water that has been adjusted to a different temperature from before the change to the hot water supply set temperature, to the auxiliary heat source unit.

However, when a temperature change is made that increases the hot water supply setting temperature, the heating capacity of the heating operation is increased to adjust the temperature. However, if the hot water mixing section supplies hot water that is hotter than before the temperature change to the auxiliary heat source unit in response to this temperature change, there is a risk that hot water that is hotter than the hot water supply setting temperature after the temperature change will be supplied. Therefore, there is a demand for a hot water storage and hot water supply system that can stably supply hot water at the changed hot water supply setting temperature even if the hot water supply setting temperature is changed during hot water supply involving heating operation by the auxiliary heat source unit.

The object of the present invention is to provide a hot water storage and hot water supply system that can stably supply hot water at the changed temperature when the hot water supply setting temperature is changed during hot water supply involving heating operation of an auxiliary heat source unit.

The hot water storage and hot water supply system of the invention of claim 1 has a main heat source machine, a hot water storage unit having a hot water storage tank for storing hot water heated by the main heat source machine, and an auxiliary heat source machine that adjusts the temperature of the hot water discharged from the hot water storage unit to a preset hot water supply setting temperature by heating operation when the hot water is equal to or lower than a predetermined heating start temperature, and supplies hot water, the hot water storage unit has a hot water storage temperature detection means for detecting the temperature of the hot water in the hot water storage tank, a hot water mixing means for mixing the hot water in the hot water storage tank with tap water to adjust the temperature, and a hot water mixing means for adjusting the temperature of the hot water in the hot water storage tank and tap water to adjust ... The control means controls the temperature adjustment, and when the temperature detected by the hot water storage temperature detection means is lower than the hot water supply setting temperature, the hot water mixing means adjusts the temperature to a target temperature equal to or lower than the heating start temperature and supplies hot water from the hot water storage unit, and when a temperature reduction change is made to reduce the hot water supply setting temperature during the heating operation of the auxiliary heat source unit, the control means reduces the target temperature so that the difference between the hot water supply setting temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change.

According to the above configuration, the hot water storage and hot water supply system includes a main heat source machine, a hot water storage unit having a hot water storage tank, and an auxiliary heat source machine that performs a heating operation to adjust the temperature to the hot water supply setting temperature and supply hot water when the hot water discharged from the hot water storage unit is equal to or lower than a predetermined heating start temperature. The hot water storage unit has a hot water storage temperature detection means for detecting the temperature of the hot water in the hot water storage tank, a hot water mixing means for mixing the hot water in the hot water storage tank with tap water to adjust the temperature, and a control means for controlling the temperature adjustment by the hot water mixing means. When there is no hot water in the hot water storage tank that can be supplied at the hot water supply setting temperature, this control means sets the target temperature of the hot water discharged from the hot water storage unit to a temperature equal to or lower than the heating start temperature of the auxiliary heat source machine and supplies hot water of adjusted temperature. The auxiliary heat source machine performs a heating operation to adjust the temperature of the hot water adjusted in the hot water storage unit to the hot water supply setting temperature and supplies hot water. If a temperature reduction change is made to reduce the hot water supply setting temperature during this heating operation, the control means reduces the target temperature of the hot water storage unit so that the difference in temperature between the hot water supply setting temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change. Therefore, since heating operation is necessary even after a temperature reduction change to reduce the hot water supply setting temperature, hot water at the hot water supply setting temperature can be stably supplied by continuing the heating operation. In particular, when hot water at a temperature lower than the hot water supply setting temperature but close to the hot water supply setting temperature is stored in the hot water storage tank, a temperature reduction change to reduce the hot water supply setting temperature during heating operation requires a heating capacity lower than the minimum heating capacity, which stops the heating operation, preventing hot water below the hot water supply setting temperature from being supplied.

The hot water storage and hot water supply system of the invention of claim 2 is characterized in that, in the invention of claim 1, the control means maintains the target temperature before the temperature increase change without changing it when a temperature increase change is made to increase the hot water supply set temperature during the heating operation.
According to the above configuration, when a temperature rise change is performed to raise the hot water supply set temperature during heating operation by the auxiliary heat source unit, the control means maintains the target temperature before the temperature rise change even after the temperature rise change. Therefore, since the temperature of the hot water supplied from the hot water storage unit to the auxiliary heat source unit is maintained, the heating capacity of the heating operation can be increased to correspond to the hot water supply set temperature after the temperature rise change, and hot water can be stably supplied at the changed hot water supply set temperature.

The hot water storage and hot water supply system of the present invention can stably supply hot water at the changed temperature when the hot water supply setting temperature is changed during hot water supply involving heating operation of the auxiliary heat source unit.

1 is an explanatory diagram of a hot water storage and supply system according to an embodiment of the present invention. 13 is a flowchart showing hot water discharge control of the hot water storage unit. 4 is a heating control flowchart of the auxiliary heat source unit.

The following describes the form for implementing the present invention based on examples.

First, the configuration of a hot water storage and supply system 1 of the present invention will be described with reference to FIG.
The hot water storage and hot water supply system 1 has a main heat source unit 2, for example a heat pump heat source unit, a hot water storage unit 4 equipped with a hot water storage tank 3 that stores hot water heated by the main heat source unit 2 through hot water storage operation, and an auxiliary heat source unit 5, for example a combustion type. When the temperature of the hot water in the hot water storage tank 3 is not sufficient to supply hot water at the set hot water supply temperature, the auxiliary heat source unit 5 heats the hot water supplied from the hot water storage unit 4 to the set hot water supply temperature through a heating operation and supplies the hot water to the hot water tap 6. When hot water at the set hot water supply temperature is supplied from the hot water storage unit 4, the auxiliary heat source unit 5 supplies hot water to the hot water tap 6 without performing a heating operation.

The lower part of the hot water storage tank 3 is connected to a main heat source unit forward passage 8 equipped with a pump 7 for supplying hot water from the hot water storage tank 3 to the main heat source unit 2. The upper part of the hot water storage tank 3 is connected to a main heat source unit return passage 9 for storing hot water heated by the main heat source unit 2 in the hot water storage tank 3. A switching valve 10 for switching the hot water flow path is provided midway in the main heat source unit return passage 9, and a return branch passage 9a branched off from the main heat source unit return passage 9 by this switching valve 10 is connected to a portion of the main heat source unit forward passage 8 upstream of the pump 7.

A return temperature sensor 9b is disposed upstream of the switching valve 10 in the main heat source unit return passage 9 to detect the temperature of the hot water heated by the main heat source unit 2. For example, if the temperature detected by the return temperature sensor 9b immediately after starting the main heat source unit 2 is lower than a predetermined hot water storage set temperature, the switching valve 10 is switched from the hot water storage tank 3 side to the return branch passage 9a side, and the hot water is circulated without being returned to the hot water storage tank 3 until it can be heated sufficiently.

A water supply passage 11 is connected to the bottom of the hot water tank 3, supplying clean water as indicated by the arrow CW. A hot water outlet passage 12 is connected to the top of the hot water tank 3, for discharging the hot water in the hot water tank 3 to the outside of the hot water storage unit 4. A water supply branch passage 11a, which branches off from the middle of the water supply passage 11, is connected to a mixing valve 14 (hot water mixing means) arranged in the middle of the hot water outlet passage 12. The hot water in the hot water tank 3 is mixed with clean water by the mixing valve 14 and discharged. Instead of the mixing valve 14, the hot water mixing means may be composed of a flow rate adjustment valve that adjusts the flow rate on the hot water tank 3 side and a flow rate adjustment valve that adjusts the flow rate on the water supply branch passage 11a side.

Multiple hot water temperature sensors 3a to 3d are arranged in the vertical direction in the hot water tank 3, and can detect the temperature (hot water temperature) and amount of hot water stored in the hot water tank 3. These multiple hot water temperature sensors 3a to 3d correspond to hot water temperature detection means that detect the hot water temperature in the hot water tank 3.

A water supply temperature sensor 11b is provided in the water supply passage 11 to detect the temperature (water supply temperature) of the clean water supplied from the water supply passage 11. A water outlet flow rate sensor 12a is provided in the hot water outlet passage 12 to detect the water outlet flow rate from the hot water storage unit 4, a hot water tank outlet temperature sensor 12b is provided to detect the temperature of the hot water being discharged from the hot water storage tank 3, and a hot water outlet temperature sensor 12c is provided to detect the temperature of the hot water being discharged from the hot water storage unit 4.

The hot water outlet passage 12 of the hot water storage unit 4 and the water supply port 5a of the auxiliary heat source unit 5 are connected by a hot water passage 15. The hot water supply port 5b of the auxiliary heat source unit 5 is connected to a hot water supply passage 16 connected to the hot water tap 6. The auxiliary heat source unit 5 has an inlet water temperature sensor 5c that detects the inlet water temperature of the hot water entering from the water supply port 5a, a hot water supply temperature sensor 5d that detects the hot water supply temperature of the hot water supplied from the hot water supply port 5b, and a hot water supply flow rate sensor 5e that detects the hot water supply flow rate. In order to supply hot water at a hot water supply setting temperature that is preset based on these detected temperatures and detected flow rates, an auxiliary heat source unit control unit 5f is equipped that controls the heating operation. The hot water discharged from the hot water storage unit 4 is supplied to the hot water tap 6 via the auxiliary heat source unit 5, and is supplied from the hot water tap 6 as shown by the arrow HW.

The hot water storage unit 4 has a hot water storage unit control unit 18 (control means) that drives the pump 7 to introduce hot water from the hot water storage tank 3 into the main heat source unit 2 and controls the hot water storage operation in which the hot water heated by the main heat source unit 2 is returned to the top of the hot water storage tank 3 and stored therein. An operation terminal 19 is connected to the hot water storage unit control unit 18 and the auxiliary heat source unit control unit 5f to allow the user to set, for example, the hot water supply setting temperature.

The hot water storage unit control unit 18 adjusts the mixing ratio of the mixing valve 14 to adjust the temperature of hot water to be discharged from the hot water storage unit 4 based on the supply water temperature detected by the supply water temperature sensor 11b, the hot water outlet flow rate detected by the hot water outlet flow rate sensor 12a, and the temperature of the hot water detected by the hot water storage tank outlet temperature sensor 12b, so that the temperature detected by the outlet water temperature sensor 12c becomes the target temperature of hot water to be discharged. The hot water storage unit control unit 18 also obtains (calculates) the amount of stored hot water heat based on the temperatures detected by the hot water storage temperature sensors 3a to 3d.

The hot water storage operation is performed, for example, so that the hot water storage tank 3 is filled with hot water at a preset hot water storage temperature at a set time. In addition, when the hot water storage heat amount falls below a reference heat amount, the hot water storage operation may be performed so that the hot water storage tank 3 is filled with hot water at the hot water storage temperature, or the hot water storage operation may be performed so that the required heat amount predicted based on the hot water supply usage learned and stored by the hot water storage unit control unit 18 is stored.

Next, the hot water supply operation control of the hot water storage unit control unit 18 during the hot water supply operation in which hot water adjusted in temperature by the hot water storage unit 4 is supplied to the auxiliary heat source unit 5 will be described based on the flowchart in Figure 2. In the figure, Si (i = 1, 2, ...) represents a step.

When hot water discharge operation control is started, in S1 it is determined whether the hot water discharge flow rate sensor 12a has detected a predetermined flow rate. This S1 is a step for determining whether hot water discharge has started, and is configured to repeatedly perform the determination in S1 in order to detect the start of hot water discharge from the hot water storage unit 4 accompanying the start of hot water supply at the hot water tap 6. If the determination in S1 is No, the determination in S1 is performed again, and if the determination in S1 is Yes, the process proceeds to S2.

In S2, it is determined whether the stored hot water temperature is equal to or higher than the hot water supply setting temperature. This is the step to determine whether heating operation by the auxiliary heat source unit 5 is necessary. The stored hot water temperature here is, for example, the temperature detected by the topmost stored hot water temperature sensor 3d. If the determination in S2 is Yes because hot water equal to or higher than the hot water supply setting temperature is stored in the hot water storage tank 3, the process proceeds to S3, where the hot water supply setting temperature is set as the target temperature for hot water discharged from the hot water storage unit 4, and the process proceeds to S4.

Next, in S4, hot water adjusted to the target temperature (hot water supply set temperature) is dispensed by adjusting the mixing ratio of the hot water dispensed from the hot water tank 3 in the mixing valve 14 and the clean water, and the process proceeds to S5. Then, in S5, it is determined whether the hot water discharge flow rate sensor 12a has detected no flow rate. This is the step for determining whether hot water discharge is stopped when hot water supply is stopped by closing the hot water tap 6. If the determination in S5 is No (hot water discharge continues), the process returns to S2. If the determination in S5 is Yes (hot water discharge stopped), the process proceeds to S6, where the hot water discharge operation is stopped and the process returns.

On the other hand, if the judgment in S2 is No, the process proceeds to S7, where the hot water tank 3 only contains hot water below the hot water supply setting temperature, so heating operation of the auxiliary heat source unit 5 is necessary. Therefore, in S7, a temperature equal to or lower than the heating start temperature of the auxiliary heat source unit 5 is set as the target temperature, and the process proceeds to S8. At this time, the hot water storage unit control unit 18 calculates a temperature that is lower than the hot water supply setting temperature by a predetermined temperature α based on the hot water supply setting temperature and the hot water outlet flow rate as the heating start temperature. The predetermined temperature α is set in advance according to, for example, the minimum heating capacity of the auxiliary heat source unit 5, and the hot water storage unit control unit 18 corrects the predetermined temperature α so that it is larger as the hot water outlet flow rate decreases. The target temperature is set to a temperature lower than the heating start temperature by a temperature β that the hot water storage unit control unit 18 adjusts in the range of, for example, 0 to 5°C according to the hot water outlet flow rate, so that the heating operation is not stopped when the heating start temperature is exceeded due to fluctuations in the hot water storage temperature, etc.

Next, in S8, hot water adjusted to the target temperature (a temperature below the heating start temperature) is dispensed by adjusting the mixing ratio of the hot water dispensed from the hot water tank 3 in the mixing valve 14 and tap water, and the process proceeds to S9. The temperature of the hot water supplied from the hot water storage unit 4 to the auxiliary heat source unit 5 only needs to be below the heating start temperature. Also, if the temperature of the hot water in the hot water tank 3 is below the target temperature, hot water at a temperature lower than the target temperature will be supplied to the auxiliary heat source unit 5 even if the mixing ratio is adjusted so that the hot water on the hot water tank 3 side is at its maximum.

In S9, it is determined whether the hot water outlet flow rate sensor 12a has detected no flow rate. Like S5, this is a step for determining whether hot water outlet has been stopped in response to the cessation of hot water supply by closing the hot water tap 6. If the determination in S9 is Yes (hot water outlet has been stopped), the process proceeds to S6, where the hot water outlet operation is stopped and the process returns. If the determination in S9 is No (hot water outlet will continue), the process proceeds to S10.

In S10, it is determined whether a temperature increase change has been made to increase the hot water supply setting temperature during heating operation of the auxiliary heat source unit 5. If the determination in S10 is Yes, the process proceeds to S11, where the target temperature is maintained without change and the process returns to S8. In S8, hot water at the same temperature before and after the temperature increase change is dispensed from the hot water storage unit 4.

On the other hand, if the determination in S10 is No, the process proceeds to S12, where it is determined whether a temperature reduction change has been made to lower the hot water supply set temperature during heating operation of the auxiliary heat source unit 5. If the determination in S12 is No, it is assumed that the hot water supply set temperature has not been changed and the process returns to S8. If the determination in S12 is Yes, the process proceeds to S13, where the target temperature is lowered by the same temperature as the temperature reduction change that lowers the hot water supply set temperature so that the temperature difference between the hot water supply set temperature before the temperature reduction change and the target temperature is maintained even after the temperature reduction change, and the process returns to S8. In S8, hot water adjusted to the lowered target temperature or at a temperature lower than that is dispensed from the hot water storage unit 4.

The auxiliary heat source unit 5 supplies hot water supplied from the hot water storage unit 4 to the hot water tap 6 with or without heating operation depending on the hot water temperature. The heating operation control by the auxiliary heat source unit control unit 5f at this time will be explained based on the flowchart in Figure 3.

When heating operation control is started, in S21 it is determined whether the hot water supply flow rate sensor 5e has detected a flow rate, i.e., hot water supply. This S21 is a step for determining whether hot water supply has started, and is configured to repeatedly perform the determination in S21 when hot water is not being supplied so that the start of hot water supply at the hot water tap 6 can be detected. If the determination in S21 is No, the determination in S21 is performed again, and if the determination in S21 is Yes, the process proceeds to S22.

In S22, it is determined whether the inlet water temperature detected by the inlet water temperature sensor 5c of the auxiliary heat source unit 5 is higher than the heating start temperature. This is a step to determine whether to perform heating operation in the auxiliary heat source unit 5. The heating start temperature is calculated by the auxiliary heat source unit control unit 5f based on the hot water supply set temperature and the hot water outlet flow rate as a temperature that is a predetermined temperature α lower than the hot water supply set temperature, but the heating start temperature may be shared by communication with the hot water storage unit control unit 18. If the determination in S22 is Yes, proceed to S23, where hot water is supplied without performing heating operation in S23, and proceed to S25.

On the other hand, if the judgment in S22 is No, the process proceeds to S24, where a heating operation is performed to adjust the heating capacity based on the inlet water temperature, hot water supply flow rate, and hot water supply set temperature to heat the hot water to the hot water supply set temperature, hot water adjusted to the hot water supply set temperature is supplied, and the process proceeds to S25. For example, if the hot water supply set temperature is changed to a lower temperature during heating operation, the target temperature is lowered by the same amount as the temperature change, and hot water adjusted to the temperature is supplied, so heating operation is necessary and heating operation is continued to supply hot water. On the other hand, if the hot water supply set temperature is changed to an upper temperature during heating operation, the target temperature is maintained before and after the temperature change to an upper temperature, and the inlet water temperature does not change, so the heating capacity of the heating operation is increased according to the changed hot water supply set temperature to supply hot water. Since the heating operation is continued, a smooth transition to hot water supply at the changed hot water supply set temperature can be made, and hot water can be stably supplied at the changed hot water supply set temperature.

Next, in S25, it is determined whether the hot water supply flow rate sensor 5e has detected no hot water supply flow rate. If the determination in S25 is No (hot water supply continues), the process returns to S22. If the determination in S25 is Yes (hot water supply ends), the process proceeds to S26, where hot water supply is stopped (heating operation is stopped if heating operation was being performed) and the process returns, and this heating operation control is started again from S21. Note that the auxiliary heat source unit control unit 5f of the auxiliary heat source unit 5 performs this heating operation control, but the hot water storage unit control unit 18 may be configured to perform the heating operation control of the auxiliary heat source unit 5.

The operation and effects of the hot water storage and supply system 1 will now be described.
When there is no hot water in the hot water tank 3 that can be supplied at the hot water supply setting temperature, the hot water storage unit control unit 18 (control means) sets the target temperature for the hot water discharge from the hot water storage unit 4 to a temperature equal to or lower than the heating start temperature of the auxiliary heat source unit 5, and supplies hot water of a regulated temperature. The auxiliary heat source unit 5 supplies the hot water whose temperature has been regulated in the hot water storage unit 4 by a heating operation, regulating the temperature to the hot water supply setting temperature.

When a temperature reduction change is made from the operation terminal 19 to reduce the hot water supply setting temperature during heating operation of the auxiliary heat source unit 5, the hot water storage unit control unit 18 reduces the target temperature of the hot water storage unit 4 so that the difference in temperature between the hot water supply setting temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change. Therefore, since heating operation is necessary even after a temperature reduction change to reduce the hot water supply setting temperature, hot water at the hot water supply setting temperature can be stably supplied by continuing the heating operation. In particular, when hot water at a temperature lower than the hot water supply setting temperature but close to the hot water supply setting temperature is stored in the hot water storage tank 3, a temperature reduction change to reduce the hot water supply setting temperature during heating operation requests a heating capacity smaller than the minimum heating capacity, stopping the heating operation and preventing hot water below the hot water supply setting temperature from being supplied.

On the other hand, when a temperature rise change is made to raise the hot water supply setting temperature during the heating operation of the auxiliary heat source unit 5, the hot water storage unit control unit 18 maintains the target temperature before the temperature rise change even after the temperature rise change, and adjusts the temperature to the hot water supply setting temperature after the temperature rise change in the heating operation of the auxiliary heat source unit 5 to supply hot water. Therefore, since the temperature of the hot water supplied from the hot water storage unit 4 to the auxiliary heat source unit 5 is maintained, the heating capacity of the heating operation can be increased to correspond to the hot water supply setting temperature after the temperature rise change, and hot water at the hot water supply setting temperature can be stably supplied.

In addition, those skilled in the art can implement the above-described embodiments in various modified forms without departing from the spirit of the present invention, and the present invention includes such modified forms.

1: Hot water storage and supply system 2: Main heat source unit 3: Hot water tank 3a to 3d: Hot water temperature sensor (hot water temperature detection means)
4: Hot water storage unit 5: Auxiliary heat source unit 5a: Water inlet 5b: Hot water supply port 5c: Inlet water temperature sensor 5d: Hot water supply temperature sensor 5e: Hot water supply flow rate sensor 5f: Auxiliary heat source unit control unit 6: Hot water tap 7: Pump 8: Main heat source unit forward passage 9: Main heat source unit return passage 9a: Return branch passage 10: Switching valve 11: Water supply passage 11a: Water supply branch passage 11b: Water supply temperature sensor 12: Hot water outlet passage 12a: Hot water outlet flow rate sensor 12b: Hot water storage tank outlet hot water temperature sensor 12c: Outlet hot water temperature sensor 14: Mixing valve (hot water and cold water mixing means)
15: Hot water passage 16: Hot water supply passage 18: Hot water storage unit control section (control means)
19: Operation terminal

Claims (2)

A hot water storage and hot water supply system having a main heat source unit, a hot water storage unit having a hot water storage tank for storing hot water heated by the main heat source unit, and an auxiliary heat source unit that adjusts the temperature of the hot water from the hot water storage unit to a preset hot water supply setting temperature by heating operation when the hot water is equal to or lower than a predetermined heating start temperature,
The hot water storage unit includes a hot water temperature detection means for detecting the temperature of the hot water in the hot water storage tank, a hot water mixing means for mixing the hot water in the hot water storage tank with clean water to adjust the temperature, and a control means for controlling the temperature adjustment by the hot water mixing means,
The control means, when the temperature detected by the hot water storage temperature detection means is lower than the hot water supply set temperature, adjusts the temperature to a target temperature below the heating start temperature using the hot water mixing means and supplies hot water from the hot water storage unit, and when a temperature reduction change is made to lower the hot water supply set temperature during the heating operation of the auxiliary heat source unit, the control means lowers the target temperature so that the difference temperature between the hot water supply set temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change. The hot water storage and hot water supply system according to claim 1, characterized in that, when a temperature increase change is made to increase the hot water supply set temperature during the heating operation, the control means maintains the target temperature before the temperature increase change without changing it.