JP2024080904A - Hot water storage and supply system - Google Patents

Abstract

To provide a hot water storage and supply system capable of reducing overshooting of hot water supply temperature that occurs when temperature of inflow water of an auxiliary heat source machine increases rapidly.SOLUTION: A hot water storage and supply system (1) includes: a hot water storage unit (3) equipped with a hot water storage tank (2) for storing hot water heated by a main heat source machine (4) and a mixing valve (14) for mixing the hot water in the hot water storage tank (2) with clean water, and supplying hot water; an auxiliary heat source machine (5) for supplying the hot water supplied from the hot water storage unit (3) after heating it according to the inflow water temperature, or without heating it; and control means for controlling a hot water supply operation by the hot water storage unit (3) and the auxiliary heat source machine (5). The hot water storage and supply system includes a stored hot water temperature detection means (2d) for detecting hot water temperature of the hot water storage tank (2). When the mixing valve (14) is in a state that the clean water side is opened to a prescribed opening degree or more, and the hot water temperature of the hot water storage tank (2) is a prescribed reference temperature or higher at the start of the hot water supply operation, the control means executes control to set a target heating temperature of the auxiliary heat source machine (5) for a temperature lower than when the mixing valve is in a state that the clean water side is not opened to a prescribed opening degree or more.SELECTED DRAWING: Figure 4

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 storage tank for hot water supply.

Conventionally, hot water storage and hot water supply systems have been widely used, in which hot water heated by, for example, a heat pump unit is stored in a hot water storage tank as a main heat source unit with high heating operation efficiency, and the hot water in the hot water storage tank is used to supply hot water. The hot water storage and hot water supply system includes a main heat source unit, a hot water storage unit equipped with a hot water storage tank, and an auxiliary heat source unit, for example a combustion type, that has a greater heating capacity than the main heat source unit.

As in Patent Document 1, for example, some hot water storage and hot water supply systems are configured so that hot water dispensed from a hot water storage unit is supplied to a hot water tap via an auxiliary heat source unit. In this hot water storage and hot water supply system, when hot water supply is started by opening the hot water tap, high-temperature hot water from the hot water storage tank is mixed with tap water in the hot water mixing section of the hot water storage unit, and hot water with adjusted temperature is dispensed from the hot water storage unit. The hot water dispensed from the hot water storage unit is then supplied to the hot water tap via the auxiliary heat source unit.

At this time, the auxiliary heat source unit supplies hot water with or without heating depending on the temperature of the hot water dispensed from the hot water storage unit. Heating operation by the auxiliary heat source unit is performed when there is no hot water in the hot water storage tank at a temperature that can be supplied at the hot water supply set temperature, and hot water dispensed from the hot water storage unit is heated and supplied at the hot water supply set temperature. On the other hand, when hot water dispensed from the hot water storage unit is adjusted to the hot water supply set temperature, the auxiliary heat source unit supplies hot water without heating.

Patent Document 1 describes delaying the timing of the auxiliary heat source unit's start of heating until an amount of hot water equivalent to the piping capacity of the connecting passage connecting the hot water storage unit and the auxiliary heat source unit is supplied to the hot water supply destination. This ensures that the time it takes for hot water at the hot water supply setting temperature to be supplied to the hot water supply destination is the same whether hot water drawn from the hot water storage unit is heated by the auxiliary heat source unit and supplied as hot water or not heated.

Patent Document 2 also describes calculating the piping capacity of the connecting passage connecting the hot water storage unit and the auxiliary heat source unit during trial operation, and if the hot water in the hot water storage tank cannot be supplied from the hot water storage unit at the hot water supply setting temperature, the auxiliary heat source unit heats the water to supply hot water at the hot water supply setting temperature. Then, during hot water supply involving heating by the auxiliary heat source unit, if hot water that can be supplied at the hot water supply setting temperature is stored in the hot water storage tank, when hot water at the hot water supply setting temperature is supplied from the hot water storage unit and the auxiliary heat source unit switches to unheated hot water supply, the auxiliary heat source unit heats the water until an amount equivalent to the piping capacity of the connecting passage has been supplied, and then the hot water is supplied unheated. This makes effective use of the hot water in the hot water storage tank.

Meanwhile, Patent Document 3 describes how, before the high-temperature water in the hot water storage tank runs out and clean water is discharged, clean water is mixed with the high-temperature water from the hot water storage tank to lower the temperature of the hot water that is discharged, and this hot water is heated by an auxiliary heat source unit to supply hot water. This reduces the drop in hot water temperature when the auxiliary heat source unit starts heating, and reduces the drop in hot water temperature when the high-temperature water in the hot water storage tank runs out and clean water enters the auxiliary heat source unit.

Patent No. 6385071 Japanese Patent No. 5309061 JP 2016-44949 A

When hot water at the set hot water supply temperature is dispensed from the hot water storage unit, the auxiliary heat source unit dispenses unheated hot water. When hot water at the set hot water supply temperature cannot be dispensed from the hot water storage unit, hot water or clean water adjusted to a temperature below a specified level is dispensed from the hot water storage unit, and the auxiliary heat source unit heats this water to supply hot water. At this time, the auxiliary heat source unit adjusts the temperature to the set hot water supply temperature by mixing unheated hot water with hot water that has been heated to a post-heating hot water temperature (target heating temperature) set based on the temperature of the hot water dispensed from the hot water storage unit (inlet water temperature), and supplies hot water.

If the auxiliary heat source unit was not heated during the previous hot water supply use, and hot water at the hot water supply setting temperature can be dispensed from the hot water storage unit during the next hot water supply use, the temperature of the hot water stagnating in the connecting passage will decrease as time passes since the previous hot water supply use. At this time, the auxiliary heat source unit is supplied with hot water whose temperature has decreased while stagnating in the connecting passage until hot water at the hot water supply setting temperature is supplied from the hot water storage unit. Also, if the previous hot water supply use was accompanied by heating by the auxiliary heat source unit, and hot water that can be dispensed at the hot water supply setting temperature is stored in the hot water storage tank by the subsequent hot water storage operation, hot water at the hot water supply setting temperature will be dispensed from the hot water storage unit during the next hot water supply use. At this time, low-temperature hot water stagnating in the connecting passage will be supplied to the auxiliary heat source unit until the hot water at the hot water supply setting temperature dispensed from the hot water storage unit reaches the auxiliary heat source unit.

The auxiliary heat source unit heats low-temperature hot water so that it can supply hot water at the hot water supply setting temperature based on the inlet water temperature, and so heats the hot water stagnating in the connecting passage to supply hot water. However, when hot water at the hot water supply setting temperature is discharged from the hot water storage unit, the inlet water temperature rises suddenly to the hot water supply setting temperature during heating, so the adjustment of the hot water supply temperature by heating and mixing in the auxiliary heat source unit cannot keep up with the sudden rise in the inlet water temperature, and an overshoot in the hot water supply temperature occurs.

As in Patent Documents 1 and 2, if the auxiliary heat source unit is not used to heat water when hot water that can be dispensed at the hot water supply setting temperature is stored in the hot water storage tank at the start of hot water supply use, the above-mentioned overshoot does not occur. However, the longer the connecting passage, the longer it takes to dispense hot water at the hot water supply setting temperature, which reduces convenience. To improve this convenience, it is required that the auxiliary heat source unit heats and dispenses hot water according to the inlet water temperature when hot water supply use starts, so there was a need for technology that reduces the overshoot in hot water supply temperature that occurs when the inlet water temperature rises suddenly, as opposed to Patent Document 3.

The present invention aims to provide a hot water storage and hot water supply system that can reduce the overshoot in hot water temperature that occurs when the inlet water temperature of the auxiliary heat source unit rises suddenly.

The hot water storage and hot water supply system of the invention of claim 1 has a hot water storage unit equipped with a hot water storage tank for storing hot water heated by a main heat source unit and a mixing valve for mixing the hot water in the hot water storage tank with tap water and discharging the hot water, an auxiliary heat source unit for heating or unheating the hot water discharged from the hot water storage unit depending on the inlet water temperature, and a control means for controlling the hot water supply operation by the hot water storage unit and the auxiliary heat source unit, the hot water storage system is equipped with a hot water temperature detection means for detecting the hot water temperature in the hot water storage tank, and the control means is characterized in that, when the hot water supply operation starts, if the mixing valve is open to the tap water side by a predetermined degree or more and the hot water temperature in the hot water storage tank is equal to or higher than a predetermined reference temperature, the target heating temperature of the auxiliary heat source unit is limited to a lower temperature than when the mixing valve is not open to the tap water side by the predetermined degree or more.

According to the above configuration, the hot water from the hot water storage tank and clean water are mixed by the mixing valve, and the hot water discharged from the hot water storage unit is supplied via the auxiliary heat source unit. The auxiliary heat source unit sets a target heating temperature, which is the temperature of the hot water after heating, and supplies the heated hot water by adjusting it to the hot water supply setting temperature, or supplies hot water without heating. When this hot water supply operation starts, if the mixing valve of the hot water storage unit is in a state where the clean water side is opened to a predetermined opening degree or more and there is hot water in the hot water storage tank at a temperature above the reference temperature, the target heating temperature of the auxiliary heat source unit is restricted to be set to a lower temperature than when the mixing valve is not opened to the clean water side to the predetermined opening degree or more. Therefore, since the hot water is heated by the auxiliary heat source unit at the start of hot water supply, hot water at the hot water supply setting temperature can be supplied quickly. And, since the target heating temperature at this time is restricted to be set to a low temperature, even if the hot water discharged from the hot water storage unit reaches the auxiliary heat source unit and the inlet water temperature rises sharply, it is possible to reduce the overshoot of the hot water supply temperature that occurs when the temperature adjustment of the hot water to be supplied cannot keep up.

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 releases the restriction on the target heating temperature when the accumulated hot water flow rate from the hot water storage unit when the target heating temperature is restricted reaches an amount equivalent to the passage volume of the connecting passage connecting the hot water storage unit and the auxiliary heat source unit.
According to the above configuration, after all the hot water that has been stagnating in the connecting passage has flowed into the auxiliary heat source unit, the hot water discharged from the hot water storage unit flows in, at which point the restriction on the target heating temperature is released. When hot water at the hot water supply setting temperature is discharged from the hot water storage unit and the inlet water temperature of the auxiliary heat source unit rises sharply, heating is stopped, but because the target heating temperature was restricted, it is possible to reduce overshooting of the hot water supply temperature. When hot water that is below the hot water supply setting temperature but at or above the reference temperature flows into the auxiliary heat source unit, heating continues, but because the target heating temperature was restricted, it is possible to reduce fluctuations in the hot water supply temperature even if the target heating temperature is changed.

The hot water storage and hot water supply system of the invention of claim 3 is characterized in that, in the invention of claim 1 or 2, it is possible to select a normal mode in which the target heating temperature of the auxiliary heat source unit is set according to the hot water supply setting temperature, and a restriction mode in which the target heating temperature is restricted to be set at a temperature lower than in the normal mode, and the control means restricts the target heating temperature when the restriction mode is selected.
According to the above configuration, for example, by selecting the restriction mode when the connecting pipe is long, hot water heated by the auxiliary heat source unit can be supplied quickly, and the overshoot of the hot water temperature can be reduced if the inlet water temperature of the auxiliary heat source unit suddenly rises during heating.

The hot water storage and hot water supply system of the present invention can reduce the overshoot in hot water supply temperature that occurs when the inlet water temperature of the auxiliary heat source unit rises suddenly.

1 is an explanatory diagram of the overall configuration of a hot water storage and supply system according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of the internal configuration of the auxiliary heat source unit of FIG. 1 . 4 is a flowchart of hot water discharge control of a hot water storage unit according to an embodiment of the present invention. 4 is a flowchart of heating operation control of the auxiliary heat source unit according to the embodiment of the present invention. 1 is a graph showing an example of overshooting of hot water temperature due to a conventional heating operation.

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 hot water storage unit 3 equipped with a hot water storage tank 2, a main heat source unit 4 such as a heat pump unit, and an auxiliary heat source unit 5 such as a combustion type. This hot water storage and hot water supply system 1 performs a hot water storage operation in which hot water heated to a target hot water storage temperature by the main heat source unit 4 is stored in the hot water storage tank 2. The target hot water storage temperature is set, for example, based on a hot water supply setting temperature and a prediction of hot water usage. The auxiliary heat source unit 5 supplies the hot water discharged from the hot water storage unit 3 to a hot water tap 6 with or without heating depending on the temperature of the hot water.

Next, the hot water storage unit 3 will be described.
A main heat source unit forward passage 8 equipped with a pump 7 is connected to the bottom of the hot water storage tank 2 in order to supply hot water from the hot water storage tank 2 to the main heat source unit 4. A main heat source unit return passage 9 is connected to the top of the hot water storage tank 2 in order to store hot water heated by the main heat source unit 4 in the hot water storage tank 2. A changeover valve 10 for switching the hot water flow path is disposed 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 at this changeover 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 that detects the temperature of the hot water heated by the main heat source unit 4 is disposed upstream of the switching valve 10 in the main heat source unit return passage 9. For example, since sufficient heating cannot be achieved immediately after the main heat source unit 4 is started up by starting the hot water storage operation, the switching valve 10 can be switched from the hot water storage tank 2 side to the return branch passage 9a side, and the hot water can be circulated without being returned to the hot water storage tank 2 until it can be heated sufficiently.

The bottom of the hot water storage tank 2 is connected to a water supply passage 11 that supplies clean water indicated by an arrow CW. The top of the hot water storage tank 2 is connected to a hot water outlet passage 12 that allows hot water in the hot water storage tank 2 to be discharged from the hot water storage unit 3. A mixing valve 14 (hot water mixing section) is provided in the middle of the hot water outlet passage 12. A water supply branch passage 11a that branches off from the middle of the water supply passage 11 is connected to this mixing valve 14. The hot water from the hot water storage tank 2 and the clean water from the water supply branch passage 11a are mixed by the mixing valve 14 and discharged from the hot water storage unit 3. Instead of the mixing valve 14, the hot water mixing section may be composed of a flow rate adjustment valve that adjusts the flow rate on the hot water storage tank 2 side and a flow rate adjustment valve that adjusts the flow rate on the water supply branch passage 11a side.

The hot water storage tank 2 is provided with multiple hot water temperature sensors 2a-2d (hot water temperature detection means) arranged at a predetermined interval in the vertical direction, and can detect the temperature of the hot water stored in the hot water storage tank 2 and the amount of hot water stored at that temperature. In order to prevent the temperature of the stored hot water from dropping, a heat insulating material (not shown) is arranged to cover the hot water temperature sensors 2a-2d and the hot water storage tank 2.

A supply water temperature sensor 11b is provided in the supply water passage 11 to detect the temperature of the tap water (supply water temperature). A hot water outlet passage 12 is provided with an outlet water flow rate sensor 12a to detect the outlet water flow rate of the hot water from the hot water storage unit 3, a hot water storage tank outlet water temperature sensor 12b to detect the temperature of the hot water from the hot water storage tank 2, and an outlet water temperature sensor 12c (outlet water temperature detection means) to detect the outlet water temperature from the hot water storage unit 3.

The hot water outlet passage 12 of the hot water storage unit 3 and the water supply port 5a of the auxiliary heat source unit 5 are connected by a connecting 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 hot water discharged from the hot water storage unit 3 is supplied to the hot water tap 6 via the auxiliary heat source unit 5.

In hot water storage operation, the main heat source unit 4 and pump 7 are driven to circulate hot water between the hot water storage tank 2 and the main heat source unit 4, and hot water introduced into the main heat source unit 4 from the bottom of the hot water storage tank 2 is heated and returned to the top of the hot water storage tank 2 for storage. This creates a temperature stratification in the hot water storage tank 2, consisting of hot water at the target hot water storage temperature in the upper layer and hot water before heating in the lower layer. The hot water storage unit 3 has a hot water storage unit control unit 18 that controls this hot water storage operation and the temperature adjustment of the hot water discharged from the hot water storage unit 3.

Next, the auxiliary heat source unit 5 will be described.
As shown in Fig. 2, the auxiliary heat source unit 5 has a hot water supply passage 21 connecting the water supply port 5a and the hot water supply port 5b, a heat exchanger 22 arranged in the hot water supply passage 21, a blower fan 23, and a burner 24 that burns fuel gas using air sent from the blower fan 23. Hot water flowing through the hot water supply passage 21 is heated in the heat exchanger 22 using heat (combustion heat) of the combustion gas of the burner 24 sent to the heat exchanger 22 by the blower fan 23. The heat exchanger 22 is composed of a primary heat exchanger that uses sensible heat of the combustion gas and a secondary heat exchanger that uses latent heat of the combustion gas. A heat exchange outlet temperature sensor 22a that detects the temperature of the hot water heated by the heat exchanger 22 is provided at the outlet of the heat exchanger 22 in the hot water supply passage 21.

The hot water supply passage 21 has a distribution valve 25 between the water supply port 5a and the heat exchanger 22, and a bypass passage 26 that bypasses the heat exchanger 22 is branched off from the hot water supply passage 21 by the distribution valve 25. The hot water supply passage 21 also has a hot water supply flow rate adjustment valve 27 between the heat exchanger 22 and the hot water supply port 5b, and the bypass passage 26 is connected between the heat exchanger 22 and the hot water supply flow rate adjustment valve 27. The distribution valve 25 distributes the hot water received from the water supply port 5a to the hot water supply passage 21 on the heat exchanger 22 side and the bypass passage 26 by adjusting the distribution ratio. The hot water supply flow rate adjustment valve 27 adjusts the flow rate of the hot water supplied from the auxiliary heat source unit 5.

The auxiliary heat source unit 5 can supply hot water to the bathtub through a water filling passage 28 that branches off from the hot water supply passage 21 at the hot water supply flow rate adjustment valve 27. In addition, the auxiliary heat source unit 5 has a function for reheating hot water in the bathtub and a hot water heating function, although explanations are omitted.

The hot water supply passage 21 has an inlet water temperature sensor 5c, a hot water supply temperature sensor 5d, and a hot water supply flow rate sensor 5e. The inlet water temperature sensor 5c detects the inlet water temperature of the hot water entering through the water supply port 5a. The hot water supply temperature sensor 5d detects the supply temperature of the hot water supplied via the auxiliary heat source unit 5. The hot water supply flow rate sensor 5e detects the flow rate of the hot water distributed to the heat exchanger 22 side by the distribution valve 25, and the flow rate of the hot water supplied via the auxiliary heat source unit 5 is calculated based on this flow rate and the distribution ratio of the distribution valve 25.

When the temperature of the hot water stored in the hot water storage tank 2 is not sufficient to supply hot water at the hot water supply setting temperature, the auxiliary heat source unit 5 performs a heating operation in which the hot water discharged from the hot water storage unit 3 is heated in the heat exchanger 22 using the combustion heat of the burner 24. The heating capacity of the heating operation is adjusted by adjusting the amount of combustion in the burner 24 according to the temperature of the hot water discharged from the hot water storage unit 3. The hot water heated in the heat exchanger 22 is then mixed with unheated hot water from the bypass passage 26, and hot water adjusted to the hot water supply setting temperature is supplied.

To control the heating operation and the hot water supply caused by this heating operation, the auxiliary heat source unit 5 is equipped with an auxiliary heat source unit control unit 29 that controls the operation of the blower fan 23, distribution valve 25, and hot water supply flow rate adjustment valve 27 based on the temperatures detected by the inlet water temperature sensor 5c and the hot water supply temperature sensor 5d. The auxiliary heat source unit control unit 29 is connected to an operation terminal 19 that is connected to the hot water storage unit control unit 18 as shown in FIG. 1, and the hot water storage unit control unit 18 and the auxiliary heat source unit control unit 29 are connected so as to be able to communicate with each other. The hot water storage unit control unit 18 and the auxiliary heat source unit control unit 29 constitute a control means that coordinates various controls of the hot water storage and hot water supply system 1.

The operation terminal 19 is for the user to set and operate, for example, the hot water supply temperature setting, and multiple units may be connected. In addition, the operation terminal 19 corresponding to the hot water storage unit 3 may be connected to the hot water storage unit control unit 18, and the operation terminal corresponding to the auxiliary heat source unit 5 may be connected to the auxiliary heat source unit control unit 29, and the hot water storage unit control unit 18 and the auxiliary heat source unit control unit 29 may be connected by a communication line.

Next, the control of the hot water supply operation of the hot water storage and hot water supply system 1 will be described based on the flowcharts of Figures 3 and 4. In the figures, Si (i = 1, 2, ...) represents a step. This control is performed by the hot water storage unit control unit 18, which is the control means, and the auxiliary heat source unit control unit 29 in cooperation with each other, and the detection information such as hot water temperature and flow rate, as well as the judgment results and calculation results required for control, are shared between the hot water storage unit control unit 18 and the auxiliary heat source unit control unit 29.

When the hot water tap 6 is opened, for example, the flow rate is detected by the hot water supply flow rate sensor 5e of the auxiliary heat source unit 5 and the hot water outlet flow rate sensor 12a of the hot water storage unit 3, and hot water outlet control of the hot water storage unit 3 and heating operation control of the auxiliary heat source unit 5 are started as hot water supply operation control. In the hot water outlet control, as shown in FIG. 3, the hot water storage temperature, water supply temperature, and hot water outlet flow rate are obtained in S1, and the process proceeds to S2.

Next, 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 of determining whether the hot water tank 2 contains hot water at a temperature that can be supplied without heating. The stored hot water temperature in this determination is the temperature detected by the hot water temperature sensor 2d in the topmost level of the hot water tank 2. Considering that the temperature of the hot water in the hot water tank 2 drops before it reaches the hot water tap 6, a temperature higher than the hot water supply setting temperature may be used as the determination criterion.

If the storage hot water temperature is equal to or higher than the hot water supply set temperature and the judgment in S2 is Yes, proceed to S3, where the opening degree of the mixing valve 14 is set so that the outlet hot water temperature is equal to the hot water supply set temperature in S3, and proceed to S5. On the other hand, if the judgment in S2 is No, proceed to S4, where the opening degree of the mixing valve 14 is set so that the outlet hot water temperature is equal to or lower than the target outlet hot water temperature that requires heating, and proceed to S5. The opening degree of the mixing valve 14 is set so that the outlet hot water temperature is equal to or lower than the hot water supply set temperature or the target outlet hot water temperature that requires heating, based on the temperature detected by the hot water storage tank outlet hot water temperature sensor 12b and the water supply temperature.

The target outlet temperature that needs to be heated is set to a predetermined temperature (e.g., 7°C) lower than the hot water supply setting temperature. This target outlet temperature that needs to be heated is the inlet water temperature of the auxiliary heat source unit 5 that can be adjusted to the hot water supply setting temperature when the auxiliary heat source unit 5 has its minimum heating capacity, and can also be set based on the hot water supply flow rate and the hot water supply setting temperature.

Next, in S5, it is determined whether the hot water discharge flow rate has reached zero. This is the step to determine whether hot water supply use has ended. If the determination in S5 is No, the process returns to S1. If the determination in S5 is Yes, the process proceeds to S6, where the process waits in preparation for re-dispensing hot water, and then proceeds to S7.

Next, in S7, it is determined whether hot water discharge has been resumed. If the determination in S7 is Yes, the process returns to S1. If the determination in S7 is No, the process proceeds to S8, where it is determined whether a predetermined waiting time has elapsed in S8. The waiting time can be set appropriately, for example, to 10 minutes. If the determination in S8 is No, the process returns to S6. If the determination in S8 is Yes, the process proceeds to S9, where the opening degree of the mixing valve 14 is set to a state in which the clean water side is opened to a predetermined opening degree or more (above the predetermined opening degree of the clean water side), and hot water discharge control is terminated. The predetermined opening degree is, for example, 90% opening degree when the clean water side is fully open to 100% and the clean water side is fully closed to 0%, and more clean water is mixed than the hot water from the hot water storage tank 2. When hot water supply use is started after high-temperature hot water is stored by the hot water storage operation, the mixing valve 14 opens the hot water storage tank side from a state in which the clean water side is opened to a predetermined opening degree or more, so that high-temperature hot water is prevented from being discharged and safety is improved.

In heating operation control, as shown in FIG. 4, the inlet water temperature and hot water supply flow rate of the auxiliary heat source unit 5 are acquired in S11, and the process proceeds to S12. The hot water supply flow rate is calculated based on the flow rate detected by the hot water supply flow rate sensor 5e and the distribution ratio of the distribution valve 25, but the flow rate detected by the hot water supply flow rate sensor 12a of the hot water storage unit 3 may also be used.

In S12, it is determined whether the normal mode is currently selected. In the normal mode, a target heating temperature of the hot water heated by the heat exchanger 22 of the auxiliary heat source unit 5 is set according to the hot water supply setting temperature, and the combustion amount (heating capacity) of the burner 24 is adjusted so that the temperature detected by the heat exchange outlet temperature sensor 22a becomes this target heating temperature based on the inlet water temperature and the hot water supply flow rate.

If normal mode is selected and the judgment in S12 is Yes, proceed to S13, where it is judged whether the inlet water temperature is equal to or lower than the target outlet water temperature that needs to be heated. If the judgment in S13 is Yes, proceed to S14, where the target heating temperature is set based on the hot water supply setting temperature, and proceed to S15. Then, in S15, heated water and unheated water are mixed to reach the target heating temperature to supply hot water, and proceed to S17. On the other hand, if the judgment in S13 is No, since the inlet water temperature is the hot water supply setting temperature, the hot water that has entered the auxiliary heat source unit 5 is supplied without being heated, and proceed to S17.

Next, in S17, the inlet water temperature and hot water supply flow rate are obtained, and the process proceeds to S18. Then, in S18, it is determined whether the hot water supply flow rate has decreased below the minimum operating flow rate. This is the step to determine whether the hot water tap 6 has been closed and hot water supply use has ended. If the determination in S18 is No, the process returns to S13. If the determination in S18 is Yes, the process proceeds to S19, where a hot water supply end operation is performed in S19, and hot water supply operation control is terminated.

When the auxiliary heat source unit 5 is supplying hot water by heating, the hot water supply termination operation stops the fuel supply to the burner 24, purges the combustion gas, and then stops the blower fan 23, terminating the heating operation control. When the auxiliary heat source unit 5 is supplying hot water without heating, there is no combustion, so the heating operation control is terminated.

On the other hand, if the determination in S12 is No (if the restriction mode described below is selected), the process proceeds to S20. Then, in S20, it is determined whether the mixing valve 14 of the hot water storage unit 3 is opened to a predetermined opening degree or more on the clean water side, and whether the stored hot water temperature is higher than a preset reference temperature. This is the step for determining whether the inlet water temperature will suddenly rise midway because the hot water storage tank 2 contains hot water that is hotter than the reference temperature, but a predetermined waiting time or more has passed since the end of the previous hot water supply, and clean water or cooled, low-temperature hot water is stagnating in the connecting passage 15.

As described above, the opening of the mixing valve 14 is set to a specified opening on the clean water side or higher for safety when a specified waiting time has elapsed after the end of hot water supply. The reference temperature is preset to a temperature at which the heating capacity does not increase when heated by the auxiliary heat source unit 5, for example, 30°C.

If the determination in S20 is No (the inlet water temperature does not rise suddenly during operation), proceed to S13 and supply hot water with or without heating, as in normal mode. If the mixing valve 14 is not open to the specified opening degree or more on the clean water side, the inlet water temperature at the start of hot water supply will be roughly the same as the previous hot water supply because the time that has elapsed since the previous hot water supply ended is short, and the previous hot water supply operation will be reproduced. Also, if the stored hot water temperature does not exceed the reference temperature, the inlet water temperature will not rise suddenly during operation. Therefore, overshooting of the hot water supply temperature will not occur.

If the inlet water temperature rises sharply during the process and the determination in S20 is Yes, proceed to S21. Then, in S21, in order to heat the hot water stagnating in the connecting passage 15 and bring the hot water temperature closer to the hot water supply set temperature, a limited target heating temperature is set based on the hot water supply set temperature so as to be lower than the target heating temperature in normal mode (target heating temperature in S14), and proceed to S22. The limited target heating temperature is set to a temperature that is a predetermined temperature (e.g., 10°C) lower than the target heating temperature set in normal mode.

Next, in S22, the hot water heated to the limited target heating temperature is mixed with unheated hot water from the bypass passage 26 to supply hot water, and the process proceeds to S23. Then, in S23, the inlet water temperature and hot water supply flow rate are obtained, and the process proceeds to S24.

Next, in S24, it is determined whether the hot water supply flow rate is equal to or greater than the minimum operating flow rate. This is the step for determining whether hot water supply use should be terminated. If the determination in S24 is No, the process proceeds to S19, where a hot water supply termination operation is performed and hot water supply operation control is terminated. If the determination in S24 is Yes, hot water supply use continues, so the process proceeds to S25.

Next, in S25, it is determined whether the accumulated hot water flow rate since the start of the current hot water supply operation, i.e., the accumulated hot water flow rate of the hot water storage unit 3, has reached an amount equivalent to the passage volume of the connecting passage 15. This is the step to determine whether all of the hot water that was stagnating in the connecting passage 15 before the start of the hot water supply operation has entered the auxiliary heat source unit 5. If the determination in S25 is No, the process returns to S21. If the determination in S25 is Yes, the process proceeds to S26, where the restriction on the target heating temperature is released and the process proceeds to S13. Then, hot water is supplied with or without heating by the auxiliary heat source unit 5, and when hot water supply use ends as described above, hot water supply is stopped and heating operation control is terminated.

In the limited mode, the control of S20 to S26 is carried out in addition to the normal mode control of S13 to S18 to minimize overshoot, and either the normal mode or the limited mode can be selected by operating the operation terminal 19. When the limited mode is selected, the heating target temperature may be limited based on the state of the mixing valve 14 and the hot water temperature.

For example, the transition of the hot water temperature, etc. will be explained using an example in which the hot water discharged from the hot water storage unit 3 was supplied without heating during the previous hot water supply, and then hot water supply use was started with the mixing valve 14 of the hot water storage unit 3 fully open on the clean water side. Figure 5 shows an example of the transition of the hot water supply flow rate, inlet water temperature, target heating temperature, and hot water supply temperature in the conventional normal mode heating operation control with the hot water supply set temperature set to 40°C. Before the start of hot water supply use, the hot water temperature in the connecting passage 15 is not uniform, but some of it has dropped to below 30°C, and the hot water storage tank 2 is in a state where hot water that can be supplied at the hot water supply set temperature is stored. In addition, since the inlet water temperature sensor 5c that detects the inlet water temperature is located inside the auxiliary heat source unit 5 where heat radiation is prevented to a certain extent, the inlet water temperature before the start of hot water supply use is less likely to drop than the hot water temperature in the connecting passage 15, and is about 38°C in this case.

At time t0, hot water supply begins and the hot water flow rate increases, and from time t1, the temperature of the low-temperature hot water in the connecting passage 15 is detected as the inlet water temperature, the set target heating temperature rises to 55°C, and heating begins. It takes a little time, but the hot water temperature begins to rise according to the target heating temperature. At time t2, the inlet water temperature begins to rise and rises sharply, and the target heating temperature is set low accordingly. The hot water adjusted to the hot water supply set temperature in the hot water storage unit 3 reaches the auxiliary heat source unit 5 at time t3, the inlet water temperature becomes the hot water supply set temperature, and combustion in the burner 24 is stopped.

At this time, the hot water heated between times t1 and t3, when the inlet water temperature is low, becomes hotter than the hot water supply set temperature because it mixes with the unheated hot water. However, the temperature of the unheated hot water (inlet water temperature) rises suddenly to the hot water supply set temperature, so the heating capacity and temperature adjustments cannot keep up, and an overshoot occurs in which the hot water supply temperature becomes higher than the hot water supply set temperature even after mixing, and the hot water supply temperature rises to a maximum of 45°C after heating is stopped.

Therefore, when the restricted mode is selected and it is known that hot water at a temperature equal to or higher than the reference temperature will be dispensed from the hot water storage unit 3 after low-temperature hot water is introduced (when the determination in S20 in FIG. 4 is Yes), the target heating temperature is restricted to be lower than in the normal mode. In the case of FIG. 5, the restricted target heating temperature is set to, for example, 45°C.

By limiting the target heating temperature, the heating capacity of the auxiliary heat source unit 5 can be reduced, thereby reducing overshooting of the hot water temperature. In particular, the longer the connecting passage 15 is, the more the hot water that has been stagnating in this passage is heated and the hot water is steadily supplied at the hot water supply setting temperature, which is useful when subsequent overshooting of the hot water temperature becomes noticeable.

In the case of FIG. 5, hot water that can be dispensed at the hot water supply setting temperature is stored in the hot water storage tank 2, so after all of the hot water that was stagnating in the connecting passage 15 enters the auxiliary heat source unit 5, the restriction on the target heating temperature is lifted and hot water is supplied without heating, as in normal mode. Even if hot water that is below the hot water supply setting temperature but higher than the reference temperature is stored in the hot water storage tank 2, the heating capacity of the auxiliary heat source unit 5 is reduced by restricting the target heating temperature after hot water supply use begins. And after the restriction on the target heating temperature is lifted, the inlet water temperature is higher than the reference temperature, so hot water can be supplied without large fluctuations in heating capacity, and the hot water supply temperature can be stabilized.

The operation and effects of the above-described hot water storage and supply system 1 will now be described.
The hot water and clean water from the hot water storage tank 2 are mixed by the mixing valve 14, and the hot water discharged from the hot water storage unit 3 is supplied to a hot water supply destination, such as the hot water tap 6, via the auxiliary heat source unit 5. The auxiliary heat source unit 5 supplies hot water heated or unheated depending on the inlet temperature of the hot water from the hot water storage unit 3. When heating, a target heating temperature is set and heated hot water is mixed with unheated hot water distributed to the bypass passage 26 by the distribution valve 25, and the hot water is adjusted to the hot water supply set temperature and supplied. When this hot water supply operation starts, if the mixing valve 14 is in a state where the clean water side is opened to a predetermined opening degree or more and there is hot water in the hot water storage tank 2 at a temperature above the reference temperature, the target heating temperature is limited to be set lower than when the mixing valve is not opened to the clean water side to the predetermined opening degree or more as described above.

Therefore, when hot water supply starts, the hot water to be supplied is heated by the auxiliary heat source unit 5, so that hot water at the hot water supply setting temperature can be supplied quickly. In addition, since the target heating temperature at this time is limited to a low temperature, even if the hot water discharged from the hot water storage unit 3 reaches the auxiliary heat source unit 5 and the inlet water temperature rises suddenly, the temperature adjustment of the hot water to be supplied cannot keep up and an overshoot in the hot water supply temperature can be reduced. When the mixing valve 14 is not open to the mains water side to a predetermined opening degree or more, no time has passed since the previous hot water supply use, and the temperature drop of the hot water in the connecting passage 15 is small, so that the previous hot water supply operation can be reproduced without limiting the target heating temperature, and hot water can be supplied without an overshoot in the hot water supply temperature. When there is no hot water at or above the reference temperature in the hot water storage tank 2, the inlet water temperature does not rise suddenly during heating by the auxiliary heat source unit 5, so hot water can be supplied without an overshoot in the hot water supply temperature.

After all the hot water that had been stagnating in the connecting passage 15 enters the auxiliary heat source unit 5, the hot water discharged from the hot water storage unit 3 enters, at which point the restriction on the target heating temperature is lifted. If hot water at the hot water supply setting temperature is discharged from the hot water storage unit 3 and the inlet water temperature of the auxiliary heat source unit 5 rises sharply, heating is stopped, but because the target heating temperature was restricted, overshooting of the hot water supply temperature can be reduced. If hot water that is below the hot water supply setting temperature but at or above the reference temperature enters the auxiliary heat source unit 5, heating continues, but because the target heating temperature was restricted, fluctuations in the hot water supply temperature can be reduced even if the target heating temperature is changed.

For example, by selecting the restricted mode when the connecting passage 15 is long, hot water heated by the auxiliary heat source unit 5 can be supplied quickly, and an overshoot in the hot water supply temperature can be reduced if the temperature of the water entering the auxiliary heat source unit 5 rises suddenly during heating. On the other hand, for example, if the connecting passage 15 is short and hot water in the hot water storage tank 2 is supplied before the auxiliary heat source unit 5 can heat it sufficiently, an overshoot in the hot water supply temperature is unlikely to occur, so by selecting the normal mode, hot water can be supplied quickly at the hot water supply setting temperature even if there is no high-temperature hot water in the hot water storage tank 2.

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: Hot water storage tanks 2a to 2d: Hot water storage temperature sensor (hot water storage temperature detection means)
3: Hot water storage unit 4: Main heat source unit 5: Auxiliary heat source unit 5a: Water inlet 5b: Hot water supply port 5c: Inlet water temperature sensor 5d: Hot water temperature sensor 5e: Hot water flow rate sensor 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 water temperature sensor 12c: Outlet water temperature sensor (outlet water temperature detection means)
14: Mixing valve 15, 16: Hot and cold water passage 18: Hot water storage unit control section (control means)
19: Operation terminal 21: Hot water supply passage 22: Heat exchanger 22a: Heat exchange outlet temperature sensor 23: Blower fan 24: Burner 25: Distribution valve 26: Bypass passage 27: Hot water supply flow rate adjustment valve 28: Hot water filling passage 29: Auxiliary heat source unit control section (control means)

Claims (3)

A hot water storage and hot water supply system having a hot water storage unit equipped with a hot water storage tank for storing hot water heated by a main heat source unit and a mixing valve for mixing the hot water in the hot water storage tank with tap water and discharging the hot water, an auxiliary heat source unit for supplying the hot water discharged from the hot water storage unit with or without heating depending on the inlet water temperature, and a control means for controlling the hot water supply operation by the hot water storage unit and the auxiliary heat source unit,
A hot water temperature detection means is provided for detecting the temperature of the hot water in the hot water tank.
The hot water storage and hot water supply system is characterized in that, when the hot water supply operation starts, the control means limits the target heating temperature of the auxiliary heat source unit to a lower temperature than when the mixing valve is open to the tap water side by a predetermined degree or more and the hot water temperature in the hot water storage tank is above a predetermined reference temperature. The hot water storage and hot water supply system according to claim 1, characterized in that the control means releases the restriction on the target heating temperature when the accumulated hot water flow rate from the hot water storage unit while the target heating temperature is restricted reaches an amount equivalent to the passage volume of the connecting passage connecting the hot water storage unit and the auxiliary heat source unit. The hot water storage and hot water supply system according to claim 1 or 2, characterized in that a normal mode in which the target heating temperature of the auxiliary heat source unit is set according to the hot water supply setting temperature and a restricted mode in which the target heating temperature is restricted to be set to a temperature lower than that in the normal mode can be selected, and the control means restricts the target heating temperature when the restricted mode is selected.

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