Water heater

Abstract

To provide a water heater capable of reducing an amount of water used for freezing prevention.SOLUTION: In a water heater (1) comprising a hot water supply passage that supplies heated hot water to a hot water supply plug (6), a flow control valve (27) disposed in the hot water supply passage, ambient temperature detection means (2a) that detects an ambient temperature, and control means (18) that controls an opening degree of the flow control valve, the control means is configured to be able to select a freezing prevention mode in which, when the temperature detected by the ambient temperature detection means is below a predetermined freezing prevention temperature, the flow control valve is opened and closed to periodically drain a predetermined amount of water from the open hot water supply plug and then stop draining, thereby preventing the hot water supply passage from being frozen. In the freezing prevention mode, the lower the temperature detected by the ambient temperature detection means, the shorter a closing time of the flow control valve is set.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a water heater that prevents freezing by running water. [Background technology]

[0002] Conventionally, some water heaters are configured to operate a resistance heater, for example, attached to the piping to prevent freezing when the outside air temperature drops and there is a risk of the hot water in the piping inside the water heater. Also, the hot water storage water heater of Patent Document 1 opens an antifreeze drain valve to drain water from the hot water supply passage connecting the hot water storage water heater and the hot water tap when the outside air temperature falls below a predetermined temperature, thereby preventing the hot water supply passage from freezing.

[0003] On the other hand, in the bathtub reheating device of Patent Document 2, the reheating circulation pump is operated intermittently depending on the outside air temperature to prevent the pipes in the reheating device from freezing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5318678 [Patent Document 2] Patent No. 3049951 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, to prevent pipes from freezing, the pipes are heated, the water is drained from the pipes, or hot and cold water is circulated through the pipes. However, the installation environment of the water heater varies, and there are cases where the hot water passage connecting the water heater and the hot water tap is not equipped with a heater or an antifreeze water drain valve.

[0006] In such cases, freezing can be prevented by allowing hot water to flow through the hot water supply passage. Generally, this is prevented by continuously running a small amount of water from the hot water tap that the user has turned on, but the water flowing out of the hot water tap is discarded without being used, resulting in waste. Therefore, the present invention aims to provide a hot water supply device that can reduce the amount of water used to prevent freezing. [Means for solving the problem]

[0007] The hot water supply device of the invention of claim 1 is a hot water supply device comprising a hot water outlet passage that outputs heated hot water to a hot water tap, a flow control valve arranged in the hot water outlet passage, an outside air temperature detection means that detects the outside air temperature, and a control means that controls the opening degree of the flow control valve, wherein the control means is configured to be able to select a freeze prevention mode in which, when the temperature detected by the outside air temperature detection means is below a predetermined freeze prevention temperature, the flow control valve is opened and closed, thereby periodically draining a predetermined amount of water from the open hot water tap and stopping the drainage to prevent the hot water outlet passage from freezing, and the freeze prevention mode is characterized in that the lower the temperature detected by the outside air temperature detection means, the shorter the closing time of the flow control valve is set.

[0008] According to the above configuration, when the outside air temperature is below the freezing prevention temperature, the flow control valve is opened to drain a predetermined amount of water from the open hot water tap, and then the flow control valve is closed to stop the drainage periodically. Since the drainage and drainage stop are periodically performed while the hot water tap remains open, freezing can be automatically prevented after the user opens the hot water tap, and the amount of water used for freezing prevention can be reduced. Furthermore, the lower the outside air temperature, the shorter the time the flow control valve is closed, so freezing of the hot water outlet passage can be prevented according to the outside air temperature.

[0009] The hot water supply device of the invention of claim 2 is characterized in that, in the invention of claim 1, the control means maintains the flow control valve in a closed state when the temperature detected by the outside air temperature detection means becomes equal to or higher than the anti-freeze temperature after switching to the anti-freeze mode. According to the above configuration, if the outside air temperature rises to a temperature where there is no risk of freezing during freeze prevention mode, the flow control valve remains closed and water is not drained from the hot water tap. Therefore, the amount of water that would be drained and wasted can be reduced regardless of the user's operation of the hot water tap.

[0010] The water heater of the invention of claim 3 is an invention of claim 1 or 2, which comprises a hot water storage tank that supplies heated and stored hot water to the hot water outlet passage, a water supply passage that supplies clean water to the hot water storage tank, a water supply bypass passage that branches off from the water supply passage and is connected to the hot water outlet passage upstream of the flow control valve, and a mixing valve arranged at the connection between the hot water outlet passage and the water supply bypass passage, and is characterized in that when a transition to the freeze prevention mode is selected, the control means maintains the mixing valve in a state where the water supply bypass passage side is fully open. According to the above configuration, the hot water supply device is a hot water supply device that supplies hot water by mixing hot water from the hot water storage tank and clean water from the water supply bypass passage that bypasses the hot water storage tank using a mixing valve. Freezing of the hot water outlet passage is prevented by fully opening the water supply bypass passage side of the mixing valve to prevent the hot water stored in the hot water storage tank from flowing out. Therefore, hot water can be stored in the hot water storage tank during the freeze prevention mode, and the stored hot water can be prevented from going to waste. [Effects of the Invention]

[0011] According to the hot water supply device of the present invention, a predetermined amount of water is drained periodically to prevent the hot water outlet passage from freezing, and the time for stopping drainage can be set according to the outside air temperature, so the amount of water used to prevent freezing can be reduced. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a water heater according to an embodiment of the present invention. [Figure 2] 4 is a control flowchart of the anti-freeze operation according to the embodiment of the present invention. [Figure 3] 10 is an example of setting the closing time of the flow control valve during freeze prevention operation. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the mode for carrying out the present invention will be described based on examples. [Example]

[0014] First, the configuration of a water heater 1 of the present invention will be described with reference to FIG. The hot water supply device 1 has a main heat source unit 2, such as a heat pump type heat source unit, a hot water storage unit 4 equipped with a hot water storage tank 3, and a combustion type auxiliary heat source unit 5 for heating the hot water supplied from the hot water storage unit 4. The hot water storage unit 4 performs a hot water storage operation in which hot water heated to a predetermined hot water storage set temperature by the main heat source unit 2 is stored in the hot water storage tank 3. The auxiliary heat source unit 5 supplies hot water to a hot water tap 6 by performing a heating operation or not, depending on the temperature of the hot water supplied from the hot water storage unit 4.

[0015] A main heat source unit supply passage 8 equipped with a pump 7 for supplying hot water from the hot water storage tank 3 to the main heat source unit 2 is connected to the bottom of the hot water storage tank 3. A main heat source unit return passage 9 for storing hot water heated by the main heat source unit 2 in the hot water storage tank 3 is connected to the top of the hot water storage tank 3. A changeover valve 10 for switching the hot water flow path is provided in the main heat source unit return passage 9, and a return branch passage 9a branched off from the main heat source unit return passage 9 by this changeover valve 10 is connected to a portion of the main heat source unit supply passage 8 upstream of the pump 7.

[0016] A return temperature sensor 9b that detects the temperature of the hot water heated by the main heat source unit 2 is disposed upstream of the switching valve 10 in the main heat source unit return passage 9. For example, if the temperature detected by the return temperature sensor 9b immediately after the main heat source unit 2 is started is lower than the predetermined hot water storage set temperature, the switching valve 10 is switched from the hot water storage tank 3 side to the return branch passage 9a side, and the hot water is circulated without being returned to the hot water storage tank 3 until it can be heated sufficiently.

[0017] A water supply passage 11, indicated by arrow CW, which supplies clean water, is connected to the bottom of the hot water storage tank 3. A hot water storage outlet passage 12, which allows hot water in the hot water storage tank 3 to be discharged from the hot water storage unit 4, is connected to the top of the hot water storage tank 3. A water supply bypass passage 11a, which branches off from the water supply passage 11, is connected to the hot water storage outlet passage 12 via a mixing valve 14 disposed in the middle of the hot water storage outlet passage 12, and is capable of supplying clean water to the hot water storage outlet passage 12, bypassing the hot water storage tank 3. A plurality of hot water temperature sensors 3a to 3d are disposed in the vertical direction of the hot water storage tank 3, which can detect the temperature and amount of hot water stored in the hot water storage tank 3.

[0018] The mixing valve 14 mixes the hot water dispensed from the hot water storage tank 3 with clean water from the water supply bypass passage 11a, adjusting the temperature and dispensing the hot water from the hot water storage unit 4. The mixing ratio of this mixing valve 14 is adjustable, and when the water supply bypass passage 11a side is fully open, the clean water from the water supply bypass passage 11a can be supplied from the hot water storage unit 4 without being mixed with the hot water in the hot water storage tank 3.

[0019] A water supply temperature sensor 11b is disposed in the water supply passage 11 to detect the temperature of clean water (water supply temperature) supplied from the water supply passage 11. A water supply flow rate sensor 12a is disposed in the water supply / outlet passage 12 to detect the flow rate of hot water discharged from the hot water storage unit 4, a tank outlet temperature sensor 12b is disposed in the water supply / outlet passage 12 to detect the temperature of hot water discharged from the hot water storage tank 3 (tank outlet temperature), and a water supply / outlet temperature sensor 12c is disposed in the water supply / outlet passage 12 to detect the outlet temperature of hot water from the hot water storage unit 4.

[0020] The hot water storage and outlet passage 12 of the hot water storage unit 4 and the water inlet 5a of the auxiliary heat source unit 5 are connected by a hot water passage 15. The hot water outlet 5b of the auxiliary heat source unit 5 is connected to a hot water supply passage 16 which is connected to the hot water tap 6. The hot water discharged from the hot water storage unit 4 is supplied to the hot water tap 6 via the auxiliary heat source unit 5, and is supplied from the hot water tap 6 as shown by the arrow HW.

[0021] The auxiliary heat source unit 5 has a burner 21, a heat exchanger 22 that heats hot water using the combustion heat of the burner 21, a water inlet passage 23 that connects the water inlet 5a to the heat exchanger 22, a heated hot water outlet passage 24 that connects the heat exchanger 22 to the hot water outlet 5b, and a heat exchange bypass passage 25 that bypasses the heat exchanger 22. The heat exchange bypass passage 25 branches off from the water inlet passage 23 at a distribution valve 26 installed midway along the water inlet passage 23 and is connected to the heated hot water outlet passage 24. The heated hot water outlet passage 24 downstream of this connection is equipped with a flow rate adjustment valve 27 that adjusts the flow rate of hot water supplied to the hot water tap 6 via the hot water supply passage 16, a hot water supply flow rate sensor 28 that detects the flow rate of the hot water, and a hot water supply temperature sensor 29 that detects the temperature of the hot water.

[0022] The hot water outlet passage of the hot water supply device 1 is composed of the hot water storage / outlet passage 12 of the hot water storage unit 4, the hot water passage 15 connecting the hot water storage unit 4 and the auxiliary heat source unit 5, the water inlet passage 23 of the auxiliary heat source unit 5, the heat exchanger 22, the heated hot water outlet passage 24, and the heat exchange bypass passage 25, and heated hot water is discharged to the hot water tap 6 via the hot water supply passage 16.

[0023] The hot water storage unit 4 has a control unit 18 (control means) that drives the main heat source unit 2 and pump 7 to circulate hot water between the hot water storage tank 3 and the main heat source unit 2, and controls a hot water storage operation in which hot water heated by the main heat source unit 2 is stored from the top of the hot water storage tank 3. The hot water storage operation by the control unit 18 is performed so as to increase operational efficiency based on the outdoor air temperature detected by an outdoor air temperature sensor 2a (outdoor air temperature detection means) equipped on the main heat source unit 2 and the hot water storage set temperature, and for example, the hot water storage tank 3 is filled with hot water at the hot water storage set temperature by a set time. The hot water storage operation may be performed so as to store the required amount of heat predicted based on the hot water supply history learned and stored by the control unit 18.

[0024] An operation terminal 19 is connected to the control unit 18 and the auxiliary heat source unit 5 so that the user can set, for example, the hot water supply setting temperature, etc. The operation terminal 19 has, for example, a display unit that displays operation information, an operation unit for performing various settings and operation operations, and an audio output unit that notifies, for example, operation information by voice.

[0025] The control unit 18 acquires (calculates) the stored hot water heat quantity based on the temperatures detected by the hot water storage temperature sensors 3a-3d. This control unit 18 adjusts the mixing ratio of the mixing valve 14 and dispenses hot water, for example, based on the tank outlet hot water temperature detected by the tank outlet hot water temperature sensor 12b, the feed water temperature detected by the feed water temperature sensor 11b, and the hot water outlet flow rate detected by the hot water storage outlet flow rate sensor 12a. At this time, the control unit 18 adjusts the mixing ratio so that the temperature detected by the hot water storage outlet temperature sensor 12c becomes the preset hot water supply temperature setting, thereby supplying hot water without performing heating operation by the auxiliary heat source unit 5. Furthermore, the control unit 18 adjusts the mixing ratio so that the temperature detected by the hot water storage outlet temperature sensor 12c becomes equal to or lower than the preset heating operation temperature, thereby supplying hot water with the heating operation of the auxiliary heat source unit 5 while also using the stored hot water heat quantity.

[0026] Normally, the control unit 18 supplies hot water by keeping the flow rate adjustment valve 27 fully open. In special cases where the heating capacity of the auxiliary heat source unit 5 is insufficient, the control unit 18 adjusts the flow rate adjustment valve 27 to reduce the hot water supply flow rate, thereby supplying hot water at the set temperature.

[0027] The water heater 1 is equipped with heaters that warm the pipes when there is a risk of the hot water in the pipes freezing. For example, the heat source unit supply path 8 is equipped with heater 8a, the water supply path 11 is equipped with heater 11c, and although not shown, heaters are also equipped in the pipes of the main heat source unit 2 and the auxiliary heat source unit 5. The hot water path 15 and the hot water supply path 16 are equipped with insulation made of, for example, foamed resin, but there is a risk of freezing when the outside air temperature is low. For this reason, the control unit 18 constantly monitors the outside air temperature as a freeze prevention operation and activates the heater when the outside air temperature is below a preset freeze prevention temperature (e.g., 0°C). The control unit 18 also warns the user about freezing by displaying and audibly warning the user from the operation terminal 19, and prompts the user to select a freeze prevention mode in which the water heater 1 flows water to prevent freezing.

[0028] Next, the control of the freeze prevention operation by the control unit 18 will be described based on the flowchart of Fig. 2. In the figure, Si (i = 1, 2, . . . ) represents a step.

[0029] First, in S1, the temperature (outside air temperature) detected by the outside air temperature sensor 2a is acquired, and the process proceeds to S2. Then, in S2, it is determined whether the outside air temperature is below the freezing prevention temperature. If the determination in S2 is No, the process returns to S1, and if the determination in S1 is Yes, the process proceeds to S3. The determination in S2 may be performed at appropriate time intervals (for example, every 1 to 5 minutes).

[0030] In S3, the heater of water heating apparatus 1 is activated, and the process proceeds to S4. Next, in S4, a freeze warning is issued by operation terminal 19 by display and sound, and the user is prompted to select transition to freeze prevention mode, and the process proceeds to S5. At this time, control unit 18 prompts the user in response to the freeze warning to open hot water tap 6 to flush water and prevent freezing. The freeze prevention mode is a mode in which water heating apparatus 1 automatically controls the flow (drainage) of water from hot water tap 6 that the user has opened.

[0031] In S5, it is determined whether or not transition to the freeze prevention mode has been selected. If transition to the freeze prevention mode has been selected and the determination in S5 is Yes, the process proceeds to S6. Then, in S6, mixing valve 14 disposed in the hot water outlet passage of water heater 1 is maintained in a state where the water supply bypass passage 11a side is fully open, and the process proceeds to S7. Note that in the freeze prevention mode, control unit 18 prohibits heating operation of auxiliary heat source unit 5.

[0032] Next, in S7, it is determined whether the flow rate (hot water outlet flow rate) detected by hot water supply flow rate sensor 28 installed in the hot water outlet passage of hot water supply device 1 is greater than 0 L / min. This makes it possible to determine whether hot water tap 6 has been opened. If the determination in S7 is No, the process proceeds to S8, where a notification is issued to prompt the user to open hot water tap 6, and the process proceeds to S9.

[0033] Next, in S9, it is determined whether the freeze prevention mode has been terminated. The freeze prevention mode selected by the user is terminated by the user's operation to terminate the freeze prevention mode on the operation terminal 19. For example, if the user wishes to use hot water, the freeze prevention mode is terminated and the system returns to the normal state in which hot water can be supplied. If the determination in S9 is No, the system returns to S7.

[0034] If the determination in S7 is Yes, the process proceeds to S10, where it is determined whether the hot water outlet flow rate has reached a preset cumulative flow rate (predetermined amount). The cumulative flow rate used as the determination criterion is, for example, a volume equivalent to the piping capacity from the inlet of the water supply passage 11 through the water supply bypass passage 11a and the hot water storage and outlet passage 12 to the hot water tap 6, and is set, for example, during the construction of the hot water supply device 1. Since the piping capacity within the hot water storage unit 4 and the auxiliary heat source unit 5 is determined by the specifications of the hot water supply device 1, the cumulative flow rate is set according to the lengths of the hot water passage 15 and the hot water supply passage 16 at the construction site. If the determination in S10 is No, the process returns to S7. If the determination in S10 is Yes, the process proceeds to S11. Note that in S7 and S10, the determination can also be made based on the flow rate detected by the hot water storage and outlet flow rate sensor 12a instead of the hot water supply flow rate sensor 28.

[0035] Next, in S11, the flow rate adjustment valve 27 is closed (fully closed), and the process proceeds to S12. Because the flow rate adjustment valve 27 is closed, water does not flow even if the hot water tap 6 is open (drainage is stopped).

[0036] Next, in S12, the outside air temperature is acquired, and the process proceeds to S13. In S13, the time (closing time) for maintaining the closed state of the flow control valve 27 is set according to the outside air temperature, and the process proceeds to S14. The closing time of the flow control valve 27 is set to be shorter as the outside air temperature decreases. For example, as shown in FIG. 3, the closing time may be set in stages according to the outside air temperature. Although not shown, the closing time may be set so that the outside air temperature and the closing time are proportional to each other below the freezing prevention temperature. Since the lower the outside air temperature, the easier it is for freezing to occur. Therefore, the lower the outside air temperature, the shorter the draining interval is to prevent freezing. At the same time, the amount of water used for freezing prevention (drainage amount) is reduced by not draining more water than necessary. Furthermore, when the outside air temperature is above the freezing prevention temperature, there is no need to drain water to prevent freezing. Therefore, the closing time is set to be constantly closed to maintain the closed state of the flow control valve 27, thereby reducing the amount of water to be drained.

[0037] Next, in S14 of FIG. 2, it is determined whether or not the anti-freeze mode has ended. The anti-freeze mode ends when the user performs an operation to end the anti-freeze mode. If the determination in S14 is No, the process proceeds to S15, where it is determined whether the closed state of the flow rate adjustment valve 27 has continued for the set closed time. If the determination in S15 is No, the process returns to S12. This makes it possible to reflect the closed time that has been updated in accordance with fluctuations in the outside air temperature. If the determination in S15 is Yes, the process proceeds to S16, where the flow rate adjustment valve 27 is opened so that water flows out of the hot water tap 6, and the process returns to S7. At this time, the flow rate adjustment valve 27 may be fully open, or may be opened to an extent that results in a predetermined flow rate (for example, 0.1 L / min).

[0038] On the other hand, if the user terminates the freeze prevention mode by operating to terminate the freeze prevention mode and the determination in S9 or S14 is Yes, the process proceeds to S17, where a notification is issued to the user to close the hot water tap 6, and the process proceeds to S18. Then, in S18, as the freeze prevention mode termination operation, if the flow rate adjustment valve 27 is closed, it is returned to its normal open state (fully open), and if the mixing valve 14 is fully open on the water supply bypass passage 11a side, it is set to the mixing ratio used during the previous hot water supply operation or a predetermined standby mixing ratio, and the process ends. Furthermore, the heater operation is stopped. This makes it possible to use hot water. The control unit 18 then starts freeze prevention operation and monitors the outside air temperature.

[0039] On the other hand, if the determination in S5 is No because the user did not select transition to the freeze prevention mode, the process proceeds to S19. For example, if the outside air temperature falls below the freeze prevention temperature while the user is asleep or out and transition to the freeze prevention mode cannot be selected, the determination in S5 is No and the process proceeds to S19. Then, in S19, the outside air temperature is acquired and the process proceeds to S20, where it is determined whether the outside air temperature is equal to or higher than the freeze prevention temperature. If the determination in S20 is No, the process returns to S5. For example, a user who has woken up or returned home can select transition to the freeze prevention mode. If the determination in S20 is Yes, the process proceeds to S21.

[0040] In S21, it is determined whether the hot water supply flow rate sensor 28 is not detecting a flow rate (the hot water outlet flow rate is 0 L / min). This is the step to determine whether the user has opened the hot water tap 6 without selecting the freeze prevention mode and is continuing to run water to prevent freezing. If the determination in S21 is No, proceed to S17, and if the determination in S21 is Yes, proceed to S18. S17 and S18 are the same as above, so explanations will be omitted.

[0041] As described above, when the outside air temperature falls below the freeze prevention temperature, the heater prevents the piping inside the water heater 1 from freezing. The water heater 1 then prompts the user to open the hot water tap 6 and to select whether or not to switch to freeze prevention mode. When the freeze prevention mode is switched to, if the hot water tap 6 is open, the flow control valve 27 is closed to stop the drainage after a predetermined amount of water is drained, and after the closing time has elapsed, the flow control valve 27 is opened to drain the water, and this process is repeated periodically to prevent the hot water outlet passage and the hot water supply passage 16 from freezing. Even when the freeze prevention mode is not switched to, the heater can prevent the piping inside the water heater 1 from freezing. The user can prevent the hot water outlet passage and the hot water supply passage 16 from freezing by opening the hot water tap 6 and continuing to run water at a small flow rate, as in the conventional case. The distribution valve 26 of the auxiliary heat source unit 5 may be adjusted so that water flows through both the heat exchanger 22 and the heat exchange bypass passage 25 to prevent freezing.

[0042] The operation and effects of the water heater 1 will be described. The hot water supply device 1 includes a hot water outlet passage that supplies heated hot water to the hot water tap 6, a flow rate adjustment valve 27 disposed in the hot water outlet passage, an outside air temperature sensor 2a (outside air temperature detection means) that detects the outside air temperature, and a control unit 18 (control means) that controls the opening degree of the flow rate adjustment valve 27. When the outside air temperature is below a preset anti-freeze temperature, the control unit 18 opens and closes the flow rate adjustment valve 27, allowing the user to select a freeze prevention mode in which a predetermined amount of water is drained from the open hot water tap 6 and then stopped from being drained periodically to prevent the hot water outlet passage from freezing.

[0043] In this anti-freeze mode, water is drained and stopped cyclically while the hot water tap 6 is open, so freezing can be prevented automatically after the user opens the hot water tap 6, and the amount of water used to prevent freezing can be reduced. The lower the outside temperature, the shorter the time that flow control valve 27 is closed (closing time), so freezing of the hot water outlet passage can be prevented according to the outside temperature, and the amount of water used to prevent freezing can be reduced by not draining more water than necessary.

[0044] If the outside air temperature becomes equal to or higher than the anti-freeze temperature after switching to the anti-freeze mode, the control unit 18 keeps the flow rate adjustment valve 27 closed and does not drain water from the hot water tap 6. Therefore, it is possible to reduce the amount of water that would be wasted by being drained without the user operating the hot water tap 6.

[0045] The hot water supply device 1 includes a hot water storage tank 3 that supplies heated and stored hot water to a hot water outlet passage, a water supply passage 11 that supplies clean water to the hot water storage tank 3, a water supply bypass passage 11a that branches off from the water supply passage 11 and is connected upstream of a flow rate adjustment valve 27 of the hot water outlet passage, and a mixing valve 14 that is disposed at the connection between the hot water outlet passage and the water supply bypass passage 11a. When a transition to the freeze prevention mode is selected, the control unit 18 maintains the mixing valve 14 in a state where the water supply bypass passage 11a side is fully open, preventing the hot water stored in the hot water storage tank 3 from flowing out. Therefore, hot water can be stored in the hot water storage tank 3 during the freeze prevention mode, and the stored hot water is not wasted.

[0046] The freeze prevention configuration of the present invention can also be applied to a combustion-type water heater equipped with an outside air temperature detection means. In addition, those skilled in the art can implement various modifications to the above embodiment without departing from the spirit of the present invention, and the present invention includes such modifications. [Explanation of symbols]

[0047] 1: Hot water supply equipment 2: Main heat source machine 2a: Outside air temperature sensor (outside air temperature detection means) 3: Hot water tank 4: Hot water storage unit 5:Auxiliary heat source machine 6: Hot water tap 7: Pump 8: Main heat source machine access passage 8a: Heater 9: Main heat source return passage 10: Switching valve 11:Water supply passage 11a: Water supply bypass passage 11b: Water supply temperature sensor 11c: Heater 12: Hot water storage and outlet passage 12a: Hot water storage and outlet flow rate sensor 12b: Tank outlet water temperature sensor 12c: Hot water storage and outlet temperature sensor 14: Mixing valve 15: Hot water passage 16: Hot water passage 18: Control unit (control means) 19: Operation terminal 21: Burner 22: Heat exchanger 23: Drowning passage 24: Heated hot water outlet passage 25: Heat exchange bypass passage 26: Distribution valve 27: Flow control valve 28: Hot water flow sensor 29: Hot water temperature sensor

Claims

1. A hot water supply device comprising a hot water outlet passage for discharging heated hot water to a hot water tap, a flow rate regulating valve disposed in the hot water outlet passage, an outside air temperature detecting means for detecting an outside air temperature, and a control means for controlling the opening of the flow rate regulating valve, the control means is configured to be able to selectively switch to a freeze prevention mode in which, when the temperature detected by the outside air temperature detection means is lower than a preset freeze prevention temperature, the flow rate adjustment valve is opened and closed to periodically drain and stop draining a predetermined amount of water from the open hot water tap to prevent freezing of the hot water outlet passage; The hot water supply apparatus is characterized in that in the freeze prevention mode, the closing time of the flow rate adjustment valve is set to be shorter as the temperature detected by the outside air temperature detection means is lower.

2. 2. The hot water supply device according to claim 1, wherein the control means maintains the flow control valve in a closed state when the temperature detected by the outside air temperature detection means becomes equal to or higher than the freeze prevention temperature after switching to the freeze prevention mode.

3. a hot water storage tank that supplies heated and stored hot water to the hot water outlet passage; a water supply passage that supplies clean water to the hot water storage tank; a water supply bypass passage that branches off from the water supply passage and is connected to the hot water outlet passage upstream of the flow rate regulating valve; and a mixing valve that is disposed at a connection between the hot water outlet passage and the water supply bypass passage, 3. The hot water supply apparatus according to claim 1, wherein the control means maintains the mixing valve in a state in which the water supply bypass passage side is fully open when the transition to the freeze prevention mode is selected.

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