JP6006063B2 - Hot water storage water heater - Google Patents

Description

  The present invention relates to a hot water storage type hot water heater that circulates hot water in a hot water storage tank to a primary side of a hot water supply external heat exchanger and heats flowing water flowing on a secondary side to supply hot water.

  Conventionally, in a hot water storage type water heater having an external heat exchanger of this type, as in Patent Document 1, a hot water storage tank for storing hot water, a heating means for heating the hot water in the hot water storage tank, and a primary side A hot water supply external heat exchanger that heats and supplies hot water flowing from the hot water in the hot water storage tank circulating through the hot water tank, and a primary side connecting the upper part of the hot water storage tank and the primary inlet of the hot water supply external heat exchanger A side return pipe, a primary return pipe connecting the primary outlet of the hot water supply external heat exchanger and the hot water storage tank, and a hot water in the hot water storage tank provided outside the hot water supply provided in the middle of the primary return pipe. A primary side pump that circulates to the primary side of the heat exchanger, a water supply pipe connected to the secondary side inlet of the hot water supply external heat exchanger, and a hot water supply pipe connected to the secondary side outlet of the hot water supply external heat exchanger There was something with.

JP 2012-107843 A

  However, in such a conventional system, in order to prevent freezing of the hot water heat exchanger and the surrounding pipes, freezing in which hot water from the hot water storage tank is circulated by driving the primary pump while hot water is stopped. Although it is conceivable to perform the prevention operation, the high temperature hot water in the hot water storage tank is consumed by this anti-freezing operation, and there is a lack of heat for hot water supply. When hot water is continuously supplied to the primary side of the hot water external heat exchanger for a long time, the residual water on the secondary side of the hot water external heat exchanger is overheated. There was a problem that the temperature overshooted significantly.

Therefore, in order to solve the above-described problems, the present invention provides a hot water storage tank for storing hot water, heating means for heating the hot water in the hot water storage tank, and hot water in the hot water storage tank circulating in the primary side as a heat source as a secondary source. A hot water external heat exchanger that heats and supplies hot water to the hot water, a primary forward pipe that connects the upper part of the hot water storage tank and the primary inlet of the hot water external heat exchanger, and a primary side of the hot water external heat exchanger A primary side return pipe connecting an outlet and the hot water storage tank, a primary side pump provided in the middle of the primary side return pipe for circulating hot water in the hot water storage tank to a primary side of the hot water supply external heat exchanger, In the hot water storage type hot water supply apparatus comprising: a hot water supply pipe connected to a secondary side inlet of the hot water supply external heat exchanger; and a hot water supply pipe connected to a secondary side outlet of the hot water supply external heat exchanger, the primary side pump Branching from the primary return pipe downstream of the A recirculation pipe connected to the secondary side forward pipe to join the hot water from the downstream side of the primary side pump to the primary side of the hot water supply external heat exchanger, and the hot water flowing out of the primary side pump is returned to the hot water storage tank side. Or a switching valve that switches whether to return to the primary inlet side of the hot water supply external heat exchanger via the recirculation pipe, and when there is a risk of freezing, the switching valve is switched to the primary inlet side, An anti-freezing control means for driving the primary pump, and the anti-freezing control means, when there is a risk of freezing, the switching valve when a predetermined short period of time elapses after the primary pump is started to drive. Is switched to the primary side inlet side, and when the predetermined freezing prevention time has elapsed, the primary side pump is stopped and the switching valve is returned to the hot water storage tank side .

According to the present invention, at the time of freeze prevention operation for preventing freezing of the hot water heat exchanger and the surrounding pipes, the switching valve is moved to the primary inlet side after a predetermined short period of time has elapsed after the primary pump has started to be driven. Therefore, it is possible to prevent freezing by transferring heat to the hot water heat exchanger and its surrounding piping, and to suppress unintentional hot water consumption by suppressing the consumption of heat in the hot water storage tank. Therefore, even if hot water is supplied during the freeze prevention operation, the hot water temperature does not significantly overshoot.

Schematic configuration diagram of one embodiment of the present invention Flow chart for explaining the operation of the same embodiment

Next, a hot water storage type water heater according to an embodiment of the present invention will be described with reference to the drawings.
1 is a tank unit having a hot water storage tank 2 for storing hot water, 3 is a hot water external heat exchanger composed of a plate heat exchanger for heating the hot water in the hot water tank 2 as a heat source, and 4 is a hot water tank 2. The primary side circulation circuit 4 circulates the hot water inside the hot water supply outside heat exchanger 3 to the primary side, and the primary side circulation circuit 4 connects the one side inlet 3 a of the hot water supply outside heat exchanger 3 and the upper part of the hot water storage tank 2. The primary side return pipe 5 is composed of a primary side return pipe 6 that connects the primary side outlet 3b of the hot water supply external heat exchanger 3 and the lower part of the hot water storage tank 2, and the upper part of the hot water storage tank 2 is in the middle of the primary side return pipe 6. A primary pump 7 is provided for circulating the hot water taken out from the primary side of the hot water supply external heat exchanger 3.

  8 is a water supply pipe connected to the secondary side inlet 3 c of the hot water supply external heat exchanger 3, and 9 is a hot water supply pipe connecting the secondary side outlet 3 d of the hot water supply external heat exchanger 3 and the hot water tap 10. Here, the water supply pipe 8 is directly connected from the city water to the hot water supply external heat exchanger 3 without going through the pressure reducing valve.

  Here, the hot water supply external heat exchanger 3 is arranged and fixed in the tank unit 1 in a posture in which a known plate type heat exchanger is set up, and a primary side inlet 3a and a secondary side outlet are provided at the lower part of one end plate. 3d is arranged, and the primary side outlet 3b and the secondary side inlet 3c are arranged at the upper part of the end plate on the same surface, and the primary side and the secondary side exchange heat in a substantially opposite flow. The hot water supply external heat exchanger 3 is not limited to a plate heat exchanger.

  11 is a heat pump unit as a heating means for heating the hot water in the hot water storage tank 2, and 12 is a heating circulation circuit for circulating the hot water in the hot water storage tank 2 to the heat pump unit 11, which is connected to the inlet of the heat pump unit 11. And a heating return pipe 14 connecting the outlet side of the heat pump unit 11 and the upper part of the hot water storage tank 2. The hot water storage tank 13 is located in the middle of the heating forward pipe 13. 2 A heating circulation pump 16 for circulating hot water taken out from the lower part to the water side of the refrigerant water heat exchanger 15 of the heat pump unit 11 is provided.

  17 is a compressor that compresses refrigerant, 18 is an expansion valve that decompresses and expands the pressure of the refrigerant, 19 is an evaporator that evaporates liquid refrigerant, 20 is a blower that blows outside air as a heat source to the evaporator 19, and 21 is refrigerant water. An incoming water temperature sensor 22 detects the temperature of hot water from the hot water storage tank 2 that flows into the water side of the heat exchanger 15, and 22 is the temperature of hot water boiled up by the heat pump unit 11 that flows out from the water side of the refrigerant water heat exchanger 15. The boiling temperature sensor 23 detects the outside air temperature, and the outside air temperature sensor 23 detects the outside air temperature. The heat pump unit 11 compresses the refrigerant absorbed by the evaporator 19 by the compressor 17 and supplies water via the refrigerant water heat exchanger 15. It is intended to be heated.

  Reference numeral 24 denotes a heating branch pipe branched from the middle of the heating return pipe 14 and connected to the primary return pipe 6, and 25 is provided at a branch point between the heating return pipe 14 and the heating branch pipe 24. This is a heating switching valve that switches between returning to the upper part of the hot water storage tank 2 or returning to the lower part of the hot water storage tank 2 via the heating branch pipe 24 and the primary return pipe 6.

  Reference numeral 26 denotes a recirculation pipe branched from the downstream side of the primary pump 7 of the primary return pipe 6 and connected to the primary forward pipe 5. The primary hot water whose temperature has dropped due to heat exchange in the hot water supply external heat exchanger 3. Is circulated again to the hot water supply external heat exchanger 3.

  27 adjusts the mixing ratio of the low temperature hot water from the recirculation pipe 26 flowing into the primary side of the hot water supply external heat exchanger 3 and the high temperature hot water from the primary side forward pipe 5, and flows out from the primary side pump 7. A primary side mixing valve that also functions as a switching valve that switches between returning hot water to the bottom of the hot water storage tank 2 or returning to the primary side inlet 3a side of the hot water supply heat exchanger 3 via a recirculation pipe 26, and a primary side forward pipe 5 and the recirculation pipe 26.

  28 is a supplementary water pipe branched from the hot water supply pipe 9 and connected in the middle of the primary side outgoing pipe 5, 29 is a pressure reducing valve provided in the middle of the supplementary water pipe 28 to reduce the feed water pressure, and 30 is connected in the middle of the primary side outgoing pipe 5. This is an overpressure relief valve that releases overpressure in the hot water storage tank 2.

  A water supply temperature sensor 31 is provided in the middle of the water supply pipe 8 to detect the temperature of the water supply, and 32 is provided in the middle of the hot water supply pipe 9 and is a hot water supply temperature at the secondary outlet of the hot water supply external heat exchanger 3 (secondary outlet temperature). A hot water supply temperature sensor as a secondary outlet temperature sensor for detecting the hot water, a hot water supply flow sensor 33 for detecting a hot water supply flow rate provided in the middle of the hot water supply pipe 9, and a junction 34 and a hot water supply of the primary forward pipe 5 and the recirculation pipe 26. A primary inlet temperature sensor 35 is provided between the external heat exchangers 3 to detect the temperature of hot water as a heat source flowing into the hot water supply external heat exchanger 3. A hot water supply external heat exchanger 3 is provided in the middle of the primary return pipe 6. A plurality of primary outlet temperature sensors 36 for detecting the temperature of the primary hot water flowing out from the hot water storage tank 2 are provided above and below the side surface of the hot water storage tank 2 to detect the hot water storage temperature.

  Reference numeral 37 denotes a remote controller including an operation switch for setting a desired hot water supply set temperature and a display unit for displaying the hot water set temperature.

  Reference numeral 38 denotes an incoming water temperature sensor 21, a boiling temperature sensor 22, an outside air temperature sensor 23, a feed water temperature sensor 31, a hot water supply temperature sensor 32, a hot water supply flow rate sensor 33, a primary inlet temperature sensor 34, a primary outlet temperature sensor 35, and a hot water storage temperature sensor 36. The detected value is input, and the operation of the primary side pump 7, heat pump unit 11, heating circulation pump 16, compressor 17, expansion valve 18, blower 20, heating switching valve 25, primary side mixing valve 27 is controlled, and remote control 37 And a control means connected so as to be communicable with each other. The control means 38 stores in advance a program for controlling the operation of the water heater, and has a calculation, comparison, storage function, and clock function.

  The control means 38 includes a primary side pump control means 39 for controlling the rotation speed of the primary side pump 7, a primary side mixing valve control means 40 for controlling the opening degree of the primary side mixing valve 27, and freezing while waiting for hot water supply. In such a case, the anti-freezing control means 41 that drives the primary pump 7 and switches the primary mixing valve 27 to the recirculation pipe 26 side is provided.

  The primary pump control means 39 detects the hot water supply temperature set by the remote controller 37 as the target temperature on the secondary side of the hot water supply external heat exchanger 3, the hot water temperature detected by the hot water temperature sensor 31, and the hot water flow rate sensor 33. Calculate the required amount of hot water supply from the hot water supply flow rate (heat exchange secondary side flow rate), and outside the hot water supply from the primary side outlet temperature (estimated primary side outlet temperature) of the hot water outside heat exchanger 3 estimated from the supply water temperature and the required hot water supply heat amount A flow rate (heat exchange primary side flow rate) flowing through the primary side of the heat exchanger 3 is calculated, and this heat exchange primary side flow rate is converted into the rotation speed (indicated rotation speed) of the primary side pump 7. Feed-forward control is performed so that the hot water supply temperature becomes the hot water supply set temperature by controlling the rotational speed to be the indicated rotational speed, and when the actual rotational speed of the primary pump 7 reaches the indicated rotational speed, With hot water temperature sensor 32 A temperature deviation is calculated from the supplied hot water temperature, and the rotation speed (instructed rotation speed) of the primary pump 7 is calculated from the temperature deviation by PI calculation of a predetermined control cycle. The rotation speed of the primary pump 7 is calculated as the instruction rotation speed. By performing such control, feedback control is performed so that the hot water supply temperature becomes the hot water supply set temperature.

  Further, the primary side mixing valve control means 40 has a specified rotational speed of the primary pump 7 instructed by the primary pump control means 39 to a predetermined minimum rotational speed, and a hot water temperature (secondary side) detected by the hot water temperature sensor 32. If the state in which the outlet temperature) exceeds the hot water supply set temperature (target outlet temperature) by a predetermined value (here, 1 ° C.) or more continues for a predetermined time (here, 1 second), the rotational speed of the primary pump 7 is set to the predetermined minimum rotational speed. The primary side pump control means 39 is instructed to maintain the temperature at the same time, and the opening degree of the primary side mixing valve 27 is controlled so that the hot water supply temperature coincides with the hot water supply set temperature. If the hot water supply temperature continues below a predetermined value (here, 1 ° C.) or more for a predetermined time (here, 1 second), the opening of the primary side mixing valve 27 becomes high. Fixed with 100% side At the same time, the instruction for maintaining the rotational speed of the primary pump 7 at the predetermined minimum rotational speed, which has been instructed to the primary pump control means 39, is canceled, and the primary pump 7 so that the hot water supply temperature matches the hot water supply set temperature. The number of rotations is controlled.

  In addition, the freeze prevention control means 41 is in the hot water supply standby state when the hot water supply flow rate sensor 33 detects less than the minimum operating flow rate (including no flow rate), and the hot water supply outside heat exchanger 3 and its surrounding piping (primary side circulation circuit). 4, the water supply pipe 8, and the hot water supply pipe 9), the primary side pump 7 is driven at a predetermined number of revolutions and the primary side mixing valve 27 is switched to 100% on the recirculation pipe 26 side. .

  Here, the case where there is a risk of freezing means that the outside air temperature detected by the heat pump unit 11 is equal to or lower than a predetermined temperature (here, 5 ° C.), and water supply is provided in a pipe connected to the hot water supply external heat exchanger 3. Although the case where the temperature detected by any of the temperature sensor 31, the hot water supply temperature sensor 32, the primary inlet temperature sensor 34, and the primary outlet temperature sensor 35 falls below a predetermined temperature (here, 5 ° C.) is illustrated, it is limited to this. Instead of this, the freeze prevention operation may be performed when one predetermined pipe temperature falls below a predetermined temperature.

<Boiling operation>
At the start time of a predetermined time zone (midnight time zone) at which the power unit price is cheap, the control means 36 drives the heat pump unit 11 and the heating circulation pump 16 so as to start boiling the hot water amount corresponding to the hot water supply load amount so far. The hot water taken out from the lower part of the hot water storage tank 2 is started and heated to the set temperature.

  At this time, the control means 38 keeps the heating switching valve 25 on the heating branch pipe 24 side while the boiling temperature detected by the boiling temperature sensor 22 is lower than a predetermined temperature lower than the boiling setting temperature, and the temperature is low. When hot water is prevented from flowing in from the upper part of the hot water storage tank 2 to lower the hot water storage temperature, and the boiling temperature reaches a predetermined temperature lower than the boiling temperature, the heating switching valve 25 is placed on the upper side of the hot water tank 2. The hot water that has been boiled so as to communicate with each other is returned to the upper part of the hot water storage tank 2, and hot water at the boiling set temperature is stored in a stacked manner from the upper part of the hot water storage tank 2.

  When the lowermost hot water storage temperature sensor 36 detects a predetermined boiling end determination temperature, the control means 38 stops driving the heat pump unit 11 and the heating circulation pump 16 and ends the boiling operation.

  At this time, the hot water stored as the temperature of the hot water in the hot water tank 2 rises, and when the pressure in the hot water tank 2 exceeds the set pressure of the overpressure relief valve 30, the overpressure relief valve 30 opens. When the expanded water is drained and the pressure in the hot water storage tank 2 becomes equal to or lower than the set pressure of the overpressure relief valve 30, the overpressure relief valve 30 is closed and the drainage is stopped to keep the inside of the hot water storage tank 2 at an appropriate pressure. Yes.

  Then, the hot water stored in the hot water storage tank 2 contracts due to the natural heat dissipation of the hot water in the hot water storage tank 2 over time and the temperature drop of the hot water in the hot water storage tank 2 due to the hot water supply described later, and the pressure in the hot water storage tank 2 is reduced. When the pressure falls below the set pressure of 29, the city water flows into the hot water storage tank 2 from the refill water pipe 28 via the pressure reducing valve 29, and when the pressure in the hot water storage tank 2 becomes equal to or higher than the set pressure of the pressure reducing valve 29, The inflow of water stops and the hot water storage tank 2 is kept in a full water state at an appropriate pressure.

<Hot-water supply operation>
Next, the hot water supply operation will be described. When the hot water tap 10 is opened, city water flows into the secondary side of the hot water supply external heat exchanger 3 from the water supply pipe 8 and passes through the secondary side of the hot water supply external heat exchanger 3. The discharged hot water flows out from the hot water supply pipe 9 toward the hot water tap 10. At this time, if the hot water supply flow sensor 33 detects a predetermined minimum working water amount or more, the primary pump control means 39 will detect the water supply temperature detected by the water supply temperature sensor 31, the hot water supply set temperature set by the remote control 37, The hot water supply required heat quantity is calculated from the hot water supply flow rate detected by the hot water supply flow rate sensor 33, the temperature of the primary hot water flowing out of the hot water supply external heat exchanger 3 (estimated primary side outlet temperature) is estimated from the hot water supply temperature, and hot water storage From the hot water storage temperature detected by the hot water storage temperature sensor 36 at the uppermost part of the tank 2, the estimated primary outlet temperature, and the required hot water supply amount, the flow rate of the hot water flowing through the primary side of the hot water supply heat exchanger 3 (primary flow rate) is calculated. The primary pump 7 is started to be driven at a rotation speed (instructed rotation speed) corresponding to the calculated primary flow rate.

  When the primary pump control means 39 detects that the actual rotational speed of the primary pump 7 has reached the indicated rotational speed, it calculates a temperature deviation from the hot water set temperature and the hot water temperature detected by the hot water temperature sensor 32. The rotation speed of the primary pump 7 (instructed rotation speed) is calculated from the temperature deviation by a predetermined PI calculation, and the hot water supply temperature is controlled so that the rotation speed of the primary pump 7 becomes the instruction rotation speed. The feedback control is performed so that the hot water supply temperature is reached.

  At this time, the hot water supply temperature may exceed the hot water supply set temperature even if the primary pump 7 is driven at the minimum number of revolutions in a situation where the required hot water supply amount is small and the hot water storage temperature is high. In this case, the designated rotational speed of the primary pump 7 designated by the primary pump control means 39 is a predetermined minimum rotational speed, and the hot water temperature detected by the hot water temperature sensor 32 is a predetermined value (here, the hot water temperature setting temperature). When the primary side mixing valve control means 40 detects that the state exceeding 1 ° C.) has been continued for a predetermined time (here, 1 second), the primary side mixing valve control means 40 sets the rotation speed of the primary side pump 7 to a predetermined value. The primary pump control means 39 is instructed to maintain the minimum number of revolutions, and the opening degree of the primary side mixing valve 27 is feedback-controlled so that the hot water temperature detected by the hot water temperature sensor 32 coincides with the hot water set temperature.

  In this way, when the required hot water supply amount is small and the hot water storage temperature is high, even if the primary pump 7 is driven at the minimum number of rotations, the hot water supply temperature exceeds the hot water supply set temperature. The control means 39 maintains the indicated rotational speed of the primary pump 7 at the minimum rotational speed, and the primary mixing valve control means 40 performs the primary side mixing by a predetermined PI calculation from the temperature deviation so as to coincide with the hot water supply temperature and the hot water supply set temperature. Since the opening degree of the valve 27 is feedback-controlled, the temperature-decreasing hot water flowing out from the primary side of the hot water supply external heat exchanger 3 is recirculated to the primary side inlet of the hot water supply heat exchanger 3 through the recirculation pipe 26. Therefore, the temperature of the hot water flowing from the primary side inlet of the hot water supply external heat exchanger 3 is lowered to an appropriate temperature, and the hot water supply external heat exchanger 3 is not reduced without reducing the rotational speed of the primary pump 7 below the minimum rotational speed. Reduce the amount of heating So that it is, the hot water supply heat value demand is small, and even when the hot water storage temperature is high, it is possible to stably hot water to hot water of a desired hot water temperature setting.

  At this time, since the hot water flowing through the primary side of the hot water supply external heat exchanger 3 is used to reduce the temperature of the hot water flowing into the primary side of the hot water supply heat exchanger 3, Even in a situation where the tank 2 is entirely filled with high-temperature hot water, the heating amount of the hot water supply external heat exchanger 3 can be reduced without reducing the rotational speed of the primary pump 7 below the minimum rotational speed, Even when the required hot water supply amount is small and the hot water storage temperature is high, hot water having a desired hot water supply set temperature can be stably supplied.

  Here, after the hot water supply temperature control by the primary side mixing valve control means 40 is started, the opening degree of the primary side mixing valve 27 becomes an opening degree of 100% on the high temperature side, and the hot water supply temperature is a predetermined value (here, If the temperature of the primary side mixing valve 27 is reduced to a state where the primary side pump 7 can be controlled at a higher rotational speed than the minimum rotational speed, While the opening degree is fixed at a high temperature side of 100%, the primary pump control means 39 cancels the instruction for maintaining the rotational speed of the primary pump 7 which has been instructed to the primary pump control means 39 at a predetermined minimum rotational speed. The means 39 controls the rotational speed of the primary pump 7 so that the hot water supply temperature matches the hot water supply set temperature.

  In this way, when the required amount of hot water supply becomes large and the opening of the primary side mixing valve 27 reaches 100% on the high temperature side, the temperature of the hot water flowing into the primary side of the hot water outside heat exchanger 3 is reduced again. Since there is no circulation, the temperature rises to the original hot water temperature in the hot water storage tank 2, so that the rotation speed of the primary pump 7 is reduced and the maximum rotation speed of the primary pump 7 can be suppressed.

  When the hot water flow rate detected by the hot water flow rate sensor 33 decreases to less than the minimum working water amount due to the hot water tap 10 being closed or the like, the control means 38 stops the operation of the primary side pump 7 and the primary side mixing valve 27 to supply hot water. Exit.

  In this way, the hot water after heat dissipation flowing out from the primary side of the hot water supply heat exchanger 3 is recirculated to the primary side of the hot water supply heat exchanger 3 via the recirculation pipe 26, so that the hot water in the hot water storage tank 2 is recirculated. Even if the total amount of water is high, the temperature of the hot water supplied to the primary side of the hot water supply external heat exchanger 3 can be lowered to the temperature required for heating the hot water, and even when the required amount of hot water supply is small, Hot water at a hot water supply set temperature can be stably supplied.

<Anti-freezing operation>
When the outside air temperature is low and there is a risk of freezing during the hot water supply standby in which the hot water supply flow rate sensor 33 detects that the hot water flow rate sensor 33 is less than the minimum operating flow rate (including no flow rate) after the hot water supply is stopped, as shown in the flowchart of FIG. When the outside air temperature detected by the outside air temperature sensor 23 is equal to or lower than a predetermined outside air temperature (here, 5 ° C.) (Yes in step S1), the prevention control unit 41 supplies the water temperature sensor 31, the hot water temperature sensor 32, and the primary inlet temperature sensor. 34 or the temperature of the water in the pipe detected by the primary outlet temperature sensor 35 is determined to be equal to or lower than a predetermined pipe temperature (here, 5 ° C.) (step S2). Is detected (step S3), the hot water storage tank is placed in the primary side forward pipe 5, the primary side of the hot water supply heat exchanger 3, the primary side return pipe 6, and the primary side pump 7. 2 Hot water is supplied, and hot water is circulated through the primary side, primary side forward pipe 5, primary side return pipe 6, and primary side pump 7 of the hot water supply heat exchanger 3, and the hot water supply heat exchange is performed. Heat is transferred to the water supply pipe 8 and the hot water supply pipe 9 in the vicinity of the secondary side of the hot water supply 3 and the hot water supply external heat exchanger 3 to prevent freezing of the hot water supply external heat exchanger 3 and the surrounding pipes.

  Then, when a predetermined short time (3 seconds in this case) has elapsed from the start of driving the primary side pump 7 (Yes in step S4), the primary side mixing valve 27 is set to 100% on the recirculation pipe 26 side (step S5), The entire amount of hot water flowing out from the primary side of the hot water supply heat exchanger 3 is recirculated to the primary side of the hot water supply heat exchanger 3 through the recirculation pipe 26.

  In this way, hot water is recirculated to the primary side of the hot water supply external heat exchanger 3 via the recirculation pipe 26, so that the hot water supply external heat exchanger 3 and the surrounding piping (the primary side forward pipe 5, the primary side return) Even if the pipe 6 and the hot water supply pipe 8 and the hot water supply pipe 8) in the vicinity of the hot water supply external heat exchanger 3 are prevented from freezing, consumption of heat in the hot water storage tank 2 can be suppressed to prevent unintentional hot water shortage, and hot water supply external heat The residual water on the secondary side of the exchanger 3 is not overheated.

  When a predetermined freezing prevention time (here, 10 minutes) has elapsed since the start of driving of the primary pump 7 (Yes in step S6), the driving of the primary pump 7 is stopped (step S7), and the primary mixing valve 27 is stopped. Is returned to 100% on the primary forward pipe 5 side (step S8), and the process returns to step S1 to determine again whether or not the freeze prevention operation is necessary.

  Thus, at the time of freeze prevention operation which prevents freezing of the hot water supply external heat exchanger 3 and the surrounding pipes, the primary side pump 27 is switched to the recirculation pipe 26 side while the primary side mixing valve 27 is switched to the recirculation pipe 26 side. 7 is driven, so that consumption of heat in the hot water storage tank 2 can be suppressed to prevent unintentional hot water shortage, and residual water on the secondary side of the hot water supply heat exchanger 3 is not overheated. Even if hot water is supplied during the freeze prevention operation, the hot water supply temperature does not significantly overshoot.

  In this embodiment, the primary side mixing valve 27 as a switching valve is arranged at the junction of the primary side forward pipe 5 and the recirculation pipe 26. However, the embodiment of the switching valve is not limited to this, and the primary side The mixing valve 27 may be arranged at a branch point between the primary return pipe 6 and the recirculation pipe 26. A three-way valve may be provided in place of the primary mixing valve 27, or the primary forward pipe before joining. 5 or the primary side return pipe 6 after branching and the recirculation pipe 26 may be provided with an on-off valve or a flow control valve that can be fully closed, equivalent to the primary side mixing valve 27 of this embodiment. The action can be exhibited.

  The present invention is not limited to the above-described embodiment, and can be modified without changing the gist of the invention. For example, the heating means is not limited to the heat pump unit 11, for example, by cogeneration. Exhaust heat, solar heat, or an electric heater may be used as the heating means.

DESCRIPTION OF SYMBOLS 2 Hot water storage tank 3 Hot water supply external heat exchanger 3a Primary side inlet 3b Primary side outlet 3c Secondary side inlet 3d Secondary side outlet 5 Primary side forward pipe 6 Primary side return pipe 7 Primary side pump 8 Water supply pipe 9 Hot water supply pipe 11 Heat pump unit (Heating means)
26 Recirculation pipe 27 Primary side mixing valve (switching valve)
41 Freezing prevention control means

Claims (1)

Hot water storage tank for storing hot water, heating means for heating the hot water in the hot water storage tank, and hot water outside heat exchange for supplying hot water by heating the running water on the secondary side using the hot water in the hot water tank circulating in the primary side as a heat source A primary side forward pipe connecting the upper part of the hot water storage tank and the primary inlet of the hot water supply external heat exchanger, and a primary return pipe connecting the primary outlet of the hot water supply external heat exchanger and the hot water storage tank A primary side pump provided in the middle of the primary side return pipe to circulate hot water in the hot water storage tank to a primary side of the hot water supply external heat exchanger, and connected to a secondary side inlet of the hot water supply external heat exchanger In the hot water storage type hot water heater having a hot water supply pipe and a hot water supply pipe connected to the secondary side outlet of the hot water supply external heat exchanger, a branch is made from the primary return pipe downstream of the primary pump. The hot water supply external heat exchanger connected to the primary side forward pipe A recirculation pipe that joins hot water from the downstream of the primary pump to the primary side, and returns the hot water flowing out of the primary pump to the hot water storage tank side or the hot water supply external heat exchanger via the recirculation pipe A switching valve that switches whether to return to the primary side inlet side, and an anti-freezing control means that switches the switching valve to the primary side inlet side and drives the primary side pump when there is a risk of freezing. The anti-freezing control means switches the switching valve to the primary side inlet side when a predetermined short time has elapsed after starting to drive the primary pump when there is a risk of freezing, and a predetermined anti-freezing time. A hot water storage type hot water supply machine that stops the primary pump when it has elapsed and returns the switching valve to the hot water storage tank side .

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