Hot water storage and supply system

Abstract

To provide a hot water storage hot water supply system enabling hot water supply with a stable temperature when a hot water supply set temperature is changed during hot water supply accompanied by heating operation of an auxiliary heat source machine.SOLUTION: A hot water storage hot water supply system (1) includes: a main heat source machine (2); a hot water storage unit (4) having a hot water storage tank (3) storing hot water by heating by the main heat source machine (2); and an auxiliary heat source machine (5) that when a temperature of hot water delivered from the hot water storage unit (4) is lower than a heating start temperature, controls the temperature to a hot water supply set temperature through heating operation for hot water supply. When a detection temperature obtained by hot water storage temperature detection means (3d) for detecting a temperature of hot water in the hot water storage tank (3) is lower than the hot water supply set temperature, control means (18) performs temperature control by using a temperature lower than the heating start temperature as a target temperature by hot water mixing means (14) mixing hot water in the hot water storage tank (3) and clean water for hot water delivery from the hot water storage unit (4). When a temperature lowering change for lowering the hot water supply set temperature is performed during the heating operation of the auxiliary heat source machine (5), the control means lowers the target temperature so that a temperature difference between the hot water supply set temperature before the temperature lowering change and the target temperature is maintained even after the temperature lowering change.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a hot water storage and supply system that uses hot water heated by a main heat source machine and stored in a hot water storage tank for hot water supply.

Background Art

[0002] Conventionally, as a main heat source machine with high heating operation efficiency, for example, a hot water storage and supply system that stores hot water heated by a heat pump type heat source machine in a hot water storage tank and uses the hot water in this hot water storage tank for hot water supply has been widely used. The hot water discharged from the hot water storage tank is mixed with makeup water in a hot water mixing section, and the hot water adjusted to a preset hot water supply set temperature is supplied to, for example, a hot water supply faucet.

[0003] When there is no hot water in the hot water storage tank that can be supplied at the hot water supply set temperature at the start of hot water supply, the hot water discharged from the hot water storage tank through the hot water mixing section is heated by the heating operation of, for example, a combustion type heat source machine as an auxiliary heat source machine and supplied for hot water supply. At this time, when the hot water temperature in the hot water storage tank is less than the hot water supply set temperature and close to the hot water supply set temperature, there is a risk that even if it is heated with the minimum heating capacity of the auxiliary heat source machine, it will become higher than the hot water supply set temperature. Therefore, when heating with the auxiliary heat source machine, makeup water is mixed with the hot water in the hot water storage tank in the hot water mixing section, and the hot water whose temperature has been lowered to a predetermined heating start temperature or lower is supplied to the auxiliary heat source machine, and it is configured to be heated to the hot water supply set temperature by the heating operation of the auxiliary heat source machine and then supplied for hot water supply.

[0004] For example, as in Patent Document 1, when hot water supply is restarted while high-temperature hot water is stored in the hot water storage tank, by making the flow rate on the hot water storage tank side smaller than the flow rate on the makeup water side in the hot water mixing section, low-temperature hot water is supplied to the auxiliary heat source machine, and a technique of heating with the auxiliary heat source machine and supplying hot water is known. On the other hand, as in Patent Document 2, when hot water supply is stopped, the mixing ratio of the hot water mixing section is adjusted to a mixing ratio in which the flow rate on the makeup water side is larger than that during hot water supply, so that excessively high-temperature hot water is not supplied to the auxiliary heat source machine when hot water supply is restarted. Both techniques adjust the mixing ratio of the hot water mixing section so as to increase the flow rate of the low-temperature makeup water side when hot water supply is restarted, and prevent hot water at an unexpectedly high temperature from being supplied for hot water supply.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, the hot water supply set temperature can be set by the user to a desired temperature before using the hot water supply, and can also be changed during the use of the hot water supply. When the hot water supply set temperature is changed while the temperature of the hot water is adjusted to the hot water supply set temperature in the hot and cold water mixing section, without performing the heating operation with the auxiliary heat source machine according to the temperature of the hot and cold water in the hot water storage tank as in the case of starting the hot water supply, or performing the heating operation, hot water supply is performed at the changed hot water supply set temperature. When the hot water supply set temperature is changed during the hot water supply accompanied by the heating operation of the auxiliary heat source machine, the heating capacity of the heating operation is adjusted in order to supply hot water at the changed hot water supply set temperature.

[0007] Here, when a temperature decrease change for decreasing the hot water supply set temperature is performed, the heating capacity of the heating operation is adjusted to be reduced, but if a heating capacity smaller than the minimum heating capacity is required, the heating operation will be stopped. Then, since the auxiliary heat source machine does not perform heating, hot water supply at a temperature lower than the hot water supply set temperature will result. Therefore, it is required to supply hot water adjusted to a temperature different from that before the change to the auxiliary heat source machine in the hot and cold water mixing section in accordance with the change in the hot water supply set temperature.

[0008] However, when a temperature increase change for increasing the hot water supply set temperature is performed, the heating capacity of the heating operation is increased for temperature adjustment. However, if the hot and cold water mixing section supplies hot water at a temperature higher than that before the temperature increase change to the auxiliary heat source machine following this temperature increase change, there is a risk that hot water at a temperature higher than the hot water supply set temperature after the temperature increase change will be supplied. Therefore, there is a demand for a hot water storage and supply system that can stably supply hot water at the changed hot water supply set temperature even when the hot water supply set temperature is changed during the hot water supply accompanied by the heating operation of the auxiliary heat source machine.

[0009] An object of the present invention is to provide a storage hot water supply system that can stably supply hot water at a changed temperature when the hot water supply set temperature is changed during hot water supply accompanied by the heating operation of an auxiliary heat source machine.

Means for Solving the Problems

[0010] In a storage hot water supply system having a main heat source machine, a storage hot water unit including a 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 storage hot water unit to a preset hot water supply set temperature by heating operation when the hot water temperature is below a predetermined heating start temperature, the storage hot water unit includes hot water storage temperature detection means for detecting the temperature of the hot water in the storage tank, hot water mixing means for mixing the hot water in the storage tank and make-up water to adjust the temperature, and control means for controlling the temperature adjustment by the hot water mixing means. When the detected temperature of the hot water storage temperature detection means is lower than the hot water supply set temperature, the control means adjusts the temperature with a temperature below the heating start temperature as the target temperature by the hot water mixing means and discharges hot water from the storage hot water unit. When a temperature reduction change is made to lower the hot water supply set temperature during the heating operation of the auxiliary heat source machine, the target temperature is lowered 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.

[0011] According to the above configuration, the hot water storage and supply system includes a main heat source unit, a hot water storage unit provided with a hot water storage tank, and an auxiliary heat source unit that performs a heating operation to adjust the temperature to the hot water supply set temperature and supply hot water when the hot water discharged from the hot water storage unit is below a predetermined heating start temperature. The hot water storage unit includes hot water temperature detection means for detecting the temperature of the hot water in the hot water storage tank, hot water mixing means for mixing the hot water in the hot water storage tank and the city water to adjust the temperature, and control means for controlling the temperature adjustment by the hot water mixing means. When there is no hot water that can supply hot water at the hot water supply set temperature in the hot water storage tank, this control means sets the target temperature of the hot water discharged from the hot water storage unit to a temperature below the heating start temperature of the auxiliary heat source unit and discharges the hot water whose temperature has been adjusted. The auxiliary heat source unit adjusts the temperature of the hot water adjusted by the hot water storage unit to the hot water supply set temperature by a heating operation and supplies hot water. When a temperature reduction change for lowering the hot water supply set temperature is made during this heating operation, the control means lowers the target temperature of the hot water storage unit so that the temperature difference between the hot water supply set temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change. Therefore, since heating operation is still required even after the temperature reduction change for lowering the hot water supply set temperature, the heating operation can be continued to stably supply hot water at the hot water supply set temperature. Especially when hot water with a temperature lower than the hot water supply set temperature but close to the hot water supply set temperature is stored in the hot water storage tank, it is possible to prevent a situation where the heating operation is stopped because a heating capacity smaller than the minimum heating capacity is required due to a temperature reduction change for lowering the hot water supply set temperature during the heating operation, and hot water with a temperature lower than the hot water supply set temperature is supplied.

[0012] The hot water storage and supply system according to the invention of claim 2 is, in the invention of claim 1, characterized in that when a temperature increase change for increasing the hot water supply set temperature is made during the heating operation, the control means maintains the target temperature before the temperature increase change without changing it. According to the above configuration, when a temperature increase change for increasing the hot water supply set temperature is made during the heating operation by the auxiliary heat source unit, the control means maintains the target temperature before the temperature increase change even after the temperature increase 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 increase change, and hot water can be stably supplied at the changed hot water supply set temperature.

Effects of the Invention

[0013] According to the hot water storage and supply system of the present invention, when the hot water supply set temperature is changed during hot water supply accompanied by the heating operation of the auxiliary heat source machine, hot water can be stably supplied at the changed temperature.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments for carrying out the present invention will be described based on examples.

Examples

[0016] First, the configuration of the hot water storage and supply system 1 of the present invention will be described with reference to FIG. 1. The hot water storage and supply system 1 includes, as a main heat source machine 2, for example, a heat pump heat source machine, a hot water storage unit 4 including a hot water storage tank 3 for storing the hot water heated by the main heat source machine 2 by this hot water storage operation, and, for example, a combustion-type auxiliary heat source machine 5. When the auxiliary heat source machine 5 cannot supply hot water at the hot water supply set temperature at the temperature of the hot water in the hot water storage tank 3, it heats the hot water supplied from the hot water storage unit 4 to the hot water supply set temperature by a heating operation and supplies the hot water to the hot water supply faucet 6. When hot water at the hot water supply set temperature is supplied from the hot water storage unit 4, the auxiliary heat source machine 5 supplies the hot water to the hot water supply faucet 6 without performing a heating operation.

[0017] At the bottom of the hot water storage tank 3, a main heat source machine incoming passage 8 equipped with a pump 7 for supplying the hot water in the hot water storage tank 3 to the main heat source machine 2 is connected. At the top of the hot water storage tank 3, a main heat source machine return passage 9 for storing the hot water heated by the main heat source machine 2 in the hot water storage tank 3 is connected. In the middle of the main heat source machine return passage 9, a switching valve 10 for switching the flow path of the hot water is arranged, and a return branch passage 9a branched from the main heat source machine return passage 9 by this switching valve 10 is connected to the upstream part of the pump 7 of the main heat source machine incoming passage 8.

[0018] Upstream of the switching valve 10 of the main heat source machine return passage 9, a return temperature sensor 9b for detecting the temperature of the hot water heated by the main heat source machine 2 is arranged. For example, when the detected temperature of the return temperature sensor 9b immediately after the start of the main heat source machine 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 returning to the hot water storage tank 3 until it can be sufficiently heated.

[0019] At the bottom of the hot water storage tank 3, a water supply passage 11 for supplying make-up water indicated by the arrow CW is connected. At the top of the hot water storage tank 3, a hot water discharge passage 12 for discharging the hot water in the hot water storage tank 3 to the outside of the hot water storage unit 4 is connected. A water supply branch passage 11a branched 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 discharge passage 12. The hot water in the hot water storage tank 3 is mixed with the make-up water by the mixing valve 14 and discharged. Incidentally, instead of the mixing valve 14, the hot water mixing means may be constituted by a flow rate adjusting valve for adjusting the flow rate on the hot water storage tank 3 side and a flow rate adjusting valve for adjusting the flow rate on the water supply branch passage 11a side.

[0020] In the hot water storage tank 3, a plurality of hot water storage temperature sensors 3a to 3d are arranged in the height direction, and the temperature (hot water storage temperature) and the hot water storage amount of the hot water stored in the hot water storage tank 3 can be detected. These plurality of hot water storage temperature sensors 3a to 3d correspond to hot water storage temperature detecting means for detecting the hot water storage temperature of the hot water storage tank 3.

[0021] In the water supply passage 11, a water supply temperature sensor 11b for detecting the temperature of the city water supplied from the water supply passage 11 (water supply temperature) is disposed. In the hot water supply passage 12, a hot water supply flow rate sensor 12a for detecting the hot water supply flow rate from the hot water storage unit 4, a storage tank hot water supply temperature sensor 12b for detecting the temperature of the hot water supplied from the storage tank 3, and a hot water supply temperature sensor 12c for detecting the hot water supply temperature from the hot water storage unit 4 are disposed.

[0022] The hot water supply passage 12 of the hot water storage unit 4 and the water supply port 5a of the auxiliary heat source machine 5 are connected by a hot water passage 15. A hot water supply passage 16 connected to the hot water supply faucet 6 is connected to the hot water supply port 5b of the auxiliary heat source machine 5. The auxiliary heat source machine 5 has an incoming water temperature sensor 5c for detecting the incoming water temperature of the hot water entering from the water supply port 5a, a hot water supply temperature sensor 5d for detecting 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 for detecting the hot water supply flow rate. And in order to supply hot water at a preset hot water supply set temperature based on these detected temperatures and detected flow rates, an auxiliary heat source machine control unit 5f for controlling the heating operation is provided. The hot water discharged from the hot water storage unit 4 is supplied to the hot water supply faucet 6 via the auxiliary heat source machine 5, and hot water is supplied from the hot water supply faucet 6 as indicated by the arrow HW.

[0023] The hot water storage unit 4 has a hot water storage unit control unit 18 (control means) for controlling a hot water storage operation of driving the pump 7 to introduce the hot water in the storage tank 3 into the main heat source machine 2, heating the hot water by the main heat source machine 2, and returning the heated hot water to the upper part of the storage tank 3 for hot water storage. An operation terminal 19 for the user to set, for example, the hot water supply set temperature is connected to the hot water storage unit control unit 18 and the auxiliary heat source machine control unit 5f.

[0024] The hot water storage unit control unit 18 adjusts the mixing ratio of the mixing valve 14 based on the water supply temperature detected by the water supply temperature sensor 11b, the hot water supply flow rate detected by the hot water supply flow rate sensor 12a, and the temperature of the hot water detected by the storage tank hot water supply temperature sensor 12b, so that the temperature detected by the hot water supply temperature sensor 12c becomes the target temperature of the hot water discharged from the hot water storage unit 4, and then adjusts the temperature and discharges hot water. Further, the hot water storage unit control unit 18 acquires (calculates) the hot water storage heat amount based on the detected temperatures of the hot water storage temperature sensors 3a to 3d.

[0025] The hot water storage operation is executed so that, for example, the hot water storage tank 3 is filled with hot water at a preset hot water storage set temperature at a set time. Also, when the amount of heat for hot water storage becomes less than the reference amount of heat, the hot water storage operation may be executed so that the hot water storage tank 3 is filled with hot water at the hot water storage set temperature, or the hot water storage operation may be executed so as to store the necessary amount of heat predicted based on the hot water supply use learned and memorized by the hot water storage unit control unit 18.

[0026] Next, the hot water discharge operation control of the hot water storage unit control unit 18 in the hot water discharge operation of discharging the hot water whose temperature has been adjusted by the hot water storage unit 4 to the auxiliary heat source machine 5 will be described based on the flowchart of FIG. 2. Si (i = 1, 2, ···) in the figure represents a step.

[0027] When the hot water discharge operation control is started, it is determined in S1 whether the hot water discharge flow rate sensor 12a has detected a predetermined flow rate. This S1 is a determination step for the start of hot water discharge, and is configured to repeatedly perform the determination of 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 supply faucet 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.

[0028] In S2, it is determined whether the hot water storage temperature is equal to or higher than the hot water supply set temperature. This is a step of determining whether heating operation by the auxiliary heat source machine 5 is necessary. The hot water storage temperature here is, for example, the temperature detected by the topmost hot water storage temperature sensor 3d. Since hot water at a temperature equal to or higher than the hot water supply set temperature is stored in the hot water storage tank 3, if the determination in S2 is Yes, the process proceeds to S3, and in S3, the hot water supply set temperature is set as the target temperature for hot water discharge from the hot water storage unit 4, and the process proceeds to S4.

[0029] Next, in S4, by adjusting the mixing ratio of the hot water discharged from the hot water storage tank 3 and the make-up water in the mixing valve 14, hot water adjusted to the target temperature (hot water supply set temperature) is discharged and the process proceeds to S5. Then, in S5, it is determined whether or not the hot water discharge flow rate sensor 12a has detected no flow rate. This is a determination step for stopping the hot water discharge accompanying the closing of the hot water supply faucet 6. If the determination in S5 is No (when the hot water discharge continues), the process returns to S2. If the determination in S5 is Yes (when the hot water discharge stops), the process proceeds to S6, and in S6, the hot water discharge operation is stopped and the process returns.

[0030] On the other hand, if the determination in S2 is No, the process proceeds to S7. Since there is only hot water below the hot water supply set temperature in the hot water storage tank 3 and heating operation of the auxiliary heat source machine 5 is necessary, in S7, a temperature equal to or lower than the heating start temperature of the auxiliary heat source machine 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, based on the hot water supply set temperature and the hot water discharge flow rate, a temperature that is lower than the hot water supply set temperature by a predetermined temperature α 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 machine 5, and the hot water storage unit control unit 18 corrects it so that the predetermined temperature α increases as the hot water discharge flow rate decreases. The target temperature is set to a temperature lower than the heating start temperature by a temperature β adjusted by the hot water storage unit control unit 18 in the range of, for example, 0 to 5°C according to the hot water discharge flow rate so that the heating operation is not stopped exceeding the heating start temperature due to fluctuations in the hot water storage temperature, etc.

[0031] Next, in S8, by adjusting the mixing ratio of the hot water discharged from the hot water storage tank 3 and the make-up water in the mixing valve 14, hot water adjusted to the target temperature (a temperature equal to or lower than the heating start temperature) is discharged 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 machine 5 only needs to be equal to or lower than the heating start temperature. Also, when the temperature of the hot water in the hot water storage tank 3 is lower than the target temperature, even if the mixing ratio is adjusted so that the hot water storage tank 3 side is maximized, hot water at a temperature lower than the target temperature will be supplied to the auxiliary heat source machine 5.

[0032] In S9, it is determined whether or not the hot water flow rate sensor 12a has detected no flow rate. Similar to S5, this is a determination step for the stop of hot water supply accompanying the closing of the hot water supply faucet 6. If the determination in S9 is Yes (in the case of hot water supply stop), it proceeds to S6, where the hot water supply operation is stopped and returns. If the determination in S9 is No (in the case of continuous hot water supply), it proceeds to S10.

[0033] In S10, it is determined whether or not a temperature increase change for raising the hot water supply set temperature has been performed during the heating operation of the auxiliary heat source unit 5. If the determination in S10 is Yes, it proceeds to S11, where it is maintained without changing the target temperature and returns to S8. In S8, hot water of the same temperature before and after the temperature increase change is discharged from the hot water storage unit 4.

[0034] On the other hand, if the determination in S10 is No, it proceeds to S12, where it is determined whether or not a temperature decrease change for lowering the hot water supply set temperature has been performed during the heating operation of the auxiliary heat source unit 5. If the determination in S12 is No, it returns to S8 assuming there is no change in the hot water supply set temperature. If the determination in S12 is Yes, it proceeds to S13, where the target temperature is lowered by the same temperature as the temperature decrease change for lowering the hot water supply set temperature so that the temperature difference between the hot water supply set temperature and the target temperature before the temperature decrease change is maintained, and then it returns to S8. In S8, hot water adjusted to the lowered target temperature or hot water of a temperature lower than that is discharged from the hot water storage unit 4.

[0035] The auxiliary heat source unit 5 supplies the hot water supplied from the hot water storage unit 4 to the hot water supply faucet 6 with or without performing a heating operation according to the temperature of the hot water. The heating operation control by the auxiliary heat source control unit 5f at this time will be described based on the flowchart of FIG. 3.

[0036] When the heating operation control is started, it is determined in S21 whether the hot water supply flow rate sensor 5e has detected the flow rate, that is, the hot water supply. This S21 is a determination step for starting the hot water supply. In order to be able to detect the start of the hot water supply at the hot water supply faucet 6, when there is no hot water supply, the determination of S21 is repeatedly performed. If the determination in S21 is No, the determination in S21 is performed again. If the determination in S21 is Yes, the process proceeds to S22.

[0037] In S22, it is determined whether the incoming water temperature detected by the incoming water temperature sensor 5c of the auxiliary heat source unit 5 is higher than the heating start temperature. This is a step for determining whether to perform the heating operation with the auxiliary heat source unit 5. The heating start temperature is calculated by the auxiliary heat source unit control unit 5f as a temperature that is lower than the hot water supply set temperature by a predetermined temperature α based on the hot water supply set temperature and the hot water flow rate. However, 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, the process proceeds to S23. In S23, hot water is supplied without performing the heating operation, and the process proceeds to S25.

[0038] On the other hand, if the determination in S22 is No, the process proceeds to S24. Based on the incoming water temperature, the hot water supply flow rate, and the hot water supply set temperature, the heating capacity is adjusted, and a heating operation is performed to heat the hot water to the hot water supply set temperature. The hot water adjusted to the hot water supply set temperature is supplied, and the process proceeds to S25. For example, when the hot water supply set temperature is decreased during the heating operation, the target temperature is decreased by the same amount as this decrease, and the heated hot water enters, so the heating operation is necessary, and the heating operation is continued to supply hot water. On the other hand, when the hot water supply set temperature is increased during the heating operation, the target temperature is maintained before and after the increase, and the incoming water temperature does not change. Therefore, the heating capacity of the heating operation is increased according to the hot water supply set temperature after the change to supply hot water. Since the heating operation is continued, it is possible to smoothly shift to the supply of hot water at the changed hot water supply set temperature, and it is possible to stably supply hot water at the hot water supply set temperature after the change.

[0039] Next, in S25, it is determined whether or not the hot water supply flow rate sensor 5e has detected no hot water supply flow rate. If the determination in S25 is No (when hot water supply continues), the process returns to S22. If the determination in S25 is Yes (when hot water supply ends), the process proceeds to S26, where the hot water supply is stopped (if a heating operation was being performed, the heating operation is stopped) and then returns, and this heating operation control starts 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.

[0040] The operation and effects of the hot water storage and supply system 1 will be described. When there is no hot water that can be supplied at the hot water supply set temperature in the hot water storage tank 3, the hot water storage unit control unit 18 (control means) sets the target temperature of the hot water discharged 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 discharges the temperature-controlled hot water. The auxiliary heat source unit 5 heats the hot water temperature-controlled by the hot water storage unit 4 to the hot water supply set temperature by a heating operation and then supplies the hot water.

[0041] When a temperature reduction change to lower the hot water supply set temperature is made from the operation terminal 19 during the heating operation of the auxiliary heat source unit 5, the hot water storage unit control unit 18 lowers the target temperature of the hot water discharged from the hot water storage unit 4 so that the temperature difference between the hot water supply set temperature and the target temperature before the temperature reduction change is maintained even after the temperature reduction change. Therefore, since heating operation is still required even after the temperature reduction change to lower the hot water supply set temperature, the heating operation can be continued to stably supply hot water at the hot water supply set temperature. In particular, when hot water at a temperature lower than the hot water supply set temperature and close to the hot water supply set temperature is stored in the hot water storage tank 3, a temperature reduction change to lower the hot water supply set temperature during the heating operation can prevent a situation where the heating operation is stopped because a heating capacity smaller than the minimum heating capacity is required and hot water at a temperature lower than the hot water supply set temperature is supplied.

[0042] On the other hand, when a temperature increase change for raising the hot water supply set temperature is performed during the heating operation of the auxiliary heat source machine 5, the hot water storage unit control unit 18 maintains the target temperature before the temperature increase change even after the temperature increase change, and adjusts the temperature to the hot water supply set temperature after the temperature increase change by the heating operation of the auxiliary heat source machine 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 machine 5 is maintained, the heating capacity of the heating operation is increased so as to correspond to the hot water supply set temperature after the temperature increase change, and hot water at the hot water supply set temperature can be stably supplied.

[0043] In addition, those skilled in the art can implement the above embodiments in various modified forms without departing from the spirit of the present invention, and the present invention includes such modified forms.

Explanation of Reference Numerals

[0044] 1: Hot water storage and supply system 2: Main heat source machine 3: Hot water storage tank 3a~3d: Hot water storage temperature sensor (hot water storage temperature detection means) 4: Hot water storage unit 5: Auxiliary heat source machine 5a: Water inlet 5b: Hot water supply port 5c: Water inlet temperature sensor 5d: Hot water supply temperature sensor 5e: Hot water supply flow sensor 5f: Auxiliary heat source machine control unit 6: Hot water faucet 7: Pump 8: Passage to the main heat source machine 9: Return passage from the main heat source machine 9a: Return branch passage 10: Changeover valve 11: Water supply passage 11a: Water supply branch passage 11b: Water supply temperature sensor 12: Hot water discharge passage 12a: Hot water discharge flow sensor 12b: Hot water storage tank hot water discharge temperature sensor 12c: Hot water discharge 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

1. In a hot water storage and supply system having a main heat source unit, a hot water storage unit including 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 discharged from the hot water storage unit to a preset hot water supply set temperature by heating operation when the hot water temperature is below a predetermined heating start temperature and then supplies the hot water, the hot water storage unit includes hot water temperature detection means for detecting the temperature of the hot water in the hot water storage tank, hot water mixing means for mixing the hot water in the hot water storage tank and make-up water to adjust the temperature, and control means for controlling the temperature adjustment by the hot water mixing means. The control means is configured to adjust the temperature by using the hot water mixing means with a temperature below the heating start temperature as a target temperature and discharge hot water from the hot water storage unit when the detected temperature by the hot water temperature detection means is lower than the hot water supply set temperature. When a temperature decrease change for lowering the hot water supply set temperature is performed during the heating operation of the auxiliary heat source unit, the target temperature is lowered so that the temperature difference between the hot water supply set temperature and the target temperature before the temperature decrease change is maintained even after the temperature decrease change. A hot water storage and supply system characterized by this.

2. The hot water storage and supply system according to claim 1, wherein when a temperature increase change for increasing the hot water supply set temperature is performed during the heating operation, the control means maintains the target temperature before the temperature increase change without changing it.

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