JP2011208839A - Hot water supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot water supply system capable of sterilizing hot water within a hot water storage tank even during defrosting operation by a heat pump.SOLUTION: The hot water supply system includes: the hot water storage tank 10; a stored hot water temperature sensor 31 detecting the temperature of hot water in the hot water storage tank 10; the heat pump 9 heating the hot water within the hot water storage tank 10 via a tank circulation passage 11; and a combustion water heater 3 heating the hot water from the hot water storage tank 10. A heating water pipe 33 connected to a heating circuit 32 of the combustion water heater 3 is provided within the hot water storage tank 10. The hot water supply system further includes a first sterilizing process control means 34 heating the hot water within the hot water storage tank 10 by the heat pump 9 when a state where the temperature of the hot water within the hot water storage tank 10 is less than a sterilization necessity determination temperature is continued for sterilization necessity determination time or longer. The hot water supply system further includes a second sterilizing process control means 35 heating the hot water within the hot water storage tank 10 by the heating circuit 32 of the combustion water heater 3 via the heating water pipe 33 when the state where the temperature of the hot water within the hot water storage tank 10 is less than the sterilization necessity determination temperature is continued for the sterilization necessity determination time or longer and outside air temperature is a defrosting process determination temperature of lower.

Description

  The present invention relates to a hot water supply system in which a hot water storage tank unit is connected to an instantaneous heating combustion water heater.

  2. Description of the Related Art Conventionally, there is known a hot water supply system in which an instantaneous heating type combustion hot water heater is connected to a hot water storage tank unit that heats hot water in a hot water storage tank by a heat pump (see, for example, Patent Document 1).

  Generally, a heat pump is configured by connecting a compressor, a water heat exchanger (condenser), an expansion valve (decompressor), and an air heat exchanger (evaporator) through a refrigerant circuit. In the refrigerant circuit, after the refrigerant discharged from the compressor is circulated to the water heat exchanger, it is circulated to the air heat exchanger through an expansion valve whose opening is adjustable, and heat is supplied from the atmosphere by the air heat exchanger. Inhaled into the compressor. The water heat exchanger is connected to the tank circulation path connected to the upper and lower parts of the hot water storage tank, and the hot water in the tank circulation path is heated by heat exchange between the refrigerant in the refrigerant circulation path and the hot water in the tank circulation path. Is done.

  In this type of hot water supply system, when hot water is supplied using hot water stored in the hot water storage tank, when the temperature of the hot water in the hot water storage tank continues to be low, bacteria such as Legionella bacteria are present in the hot water in the hot water storage tank. It will be easy to breed. In view of this, a hot water supply system has been proposed in which hot water in a hot water storage tank is boiled to a high temperature in the midnight hours to sterilize the hot water so that clean hot water is supplied (see, for example, Patent Document 2).

JP 2000-329401 A Japanese Patent Laid-Open No. 2003-130452

  By the way, if the outside air temperature is low in winter, frost may form on the evaporator of the heat pump. If the evaporator is in a frosted state, the heat supply from the atmosphere will be insufficient and the hot water in the hot water storage tank will be heated to a high temperature. Can not boil.

  Therefore, in the heat pump, for example, when the outside air temperature or the refrigerant temperature in the air heat exchanger is extremely low, the refrigerant outlet direction is reversed by switching the outlet of the compressor to the air heat exchanger side by a four-way valve or the like, A defrosting operation for heating and defrosting the air heat exchanger by sending a high-temperature refrigerant from the compressor to the air heat exchanger is performed.

  However, during the defrosting operation that heats the air heat exchanger, the circulation of hot water in the tank circuit is stopped to prevent low temperature refrigerant from flowing into the water heat exchanger and lowering the temperature of the water in the tank circuit. The hot water boiling operation of the hot water storage tank cannot be performed. In addition, the evaporator often frosts during the midnight hours in winter, and even when trying to boil up for sterilization during the midnight hours, the defrosting operation is performed in the heat pump. Cannot be sterilized.

  The present invention has been made in view of the above background, and an object thereof is to provide a hot water supply system capable of sterilizing hot water in a hot water storage tank even when a heat pump is in a defrosting operation.

  The present invention includes a hot water storage tank for storing hot water therein, a water supply pipe connected to the hot water storage tank for supplying water to the hot water storage tank, and a hot water discharge pipe connected to the hot water storage tank for deriving hot water from the hot water storage tank. A tank circulation path whose start and end are connected to the hot water tank to circulate hot water in the hot water storage tank, a heat pump for heating the hot water in the hot water storage tank through the tank circulation path, and hot water in the hot water storage tank A hot water storage temperature sensor for detecting the temperature, a hot water supply circuit connected to the hot water discharge pipe, a combustion hot water heater that heats hot water flowing through the hot water discharge pipe by a burner, and a combustion water heater that is provided in the combustion hot water supply and is heated by the burner A heating circuit in which the heating water circulates, and is connected to the heating circuit and is provided in the hot water storage tank to heat the hot water in the hot water storage tank by exchanging heat with the heating water in the heating circuit. A water pipe for heating, an outside air temperature sensor for detecting outdoor air temperature, and a defrosting process control means for stopping heating of hot water in the hot water storage tank by the heat pump and instructing the heat pump to perform a defrosting operation when frosting the heat pump. The state where the detected temperature of the hot water storage temperature sensor is lower than the sterilization necessity determination temperature set assuming the temperature at which various germs propagate in the hot water of the hot water storage tank continues for a predetermined sterilization necessity determination time. The first sterilization processing control means for instructing heating of the hot water in the hot water storage tank to be equal to or higher than a sterilization temperature set by assuming the temperature at which the hot water in the hot water storage tank is sterilized by the heat pump; A state in which the temperature detected by the hot water storage temperature sensor is lower than the sterilization necessity determination temperature continues for a preset sterilization necessity determination time and is detected by the outside air temperature sensor. The heating water heated by the combustion water heater is supplied to the heating circuit when the temperature is equal to or lower than the defrosting determination temperature set assuming the outside air temperature at which the defrosting operation of the heat pump is performed by the defrosting control means. And a second sterilization process control means for instructing heating of the hot water in the hot water storage tank so as to be supplied to the heating water pipe and to be at or above the sterilization temperature.

  According to the present invention, not only the hot water storage tank can be sterilized by the first sterilization processing control means, but also the second sterilization processing can be performed even when the sterilization processing by the first sterilization processing control means cannot be performed. Since the hot water in the hot water storage tank can be sterilized by the control means, it is possible to reliably prevent the propagation of germs in the hot water in the hot water storage tank and supply clean hot water from the hot water storage tank.

  That is, when the defrosting operation of the heat pump is performed by the defrosting processing control means, the hot water in the hot water storage tank cannot be heated by the heat pump, and the heat pump cannot be operated for sterilization.

  Therefore, in the present invention, when the temperature detected by the hot water storage temperature sensor is lower than the sterilization necessity determination temperature for a sterilization necessity determination time or longer, the second sterilization processing control means detects the temperature detected by the outside air temperature sensor. To determine whether or not the heat pump performs a defrosting operation. Next, when it is assumed that the heat pump performs the defrosting operation, the second sterilization processing control means operates the heating circuit of the combustion water heater, and stores the hot water storage tank through the heating water pipe connected to the heating circuit. Is heated above the sterilization temperature. By doing so, the hot water in the hot water storage tank can be sterilized even when the heat pump is in the defrosting operation.

  For example, when the defrosting operation of the heat pump is performed when the refrigerant temperature is extremely low, the defrosting operation of the heat pump is not performed unless the refrigerant temperature is extremely decreased even if the outside air temperature is low. On the other hand, the 2nd sterilization process control means judges the presence or absence of the defrost operation of a heat pump based on the detected temperature of an outside temperature sensor. As a result, even if the heat pump is not performing the defrosting operation even though the outside air temperature is low, the second sterilization processing control means is such that the temperature of the hot water in the hot water storage tank is lower than the sterilization necessity determination temperature. If a certain state continues for the sterilization necessity determination time or more, the hot water storage tank is instructed to be heated by the heating circuit of the combustion water heater.

  According to this, when the hot water of the hot water storage tank is heated by the heat pump by the first sterilization processing control means without performing the defrosting operation, the heating by the heating circuit of the combustion water heater is simultaneously performed. The hot water in the hot water storage tank is heated to the sterilization temperature or higher extremely quickly, so that the hot water in the hot water storage tank can be quickly sterilized and the time required for the sterilization process can be shortened.

The block diagram of the hot-water supply system of this invention.

  An embodiment of the present invention will be described with reference to FIG. The hot water supply system of the present embodiment is configured by further connecting an instantaneous heating combustion water heater 3 to a tank unit 2 to which a heat pump unit 1 is connected.

  The heat pump unit 1 includes a compressor 4, a water heat exchanger (condenser) 5, an expansion valve (decompressor) 6, and an air heat exchanger (evaporator) 7 connected by a refrigerant circulation path 8. It has. The refrigerant circulation path 8 is provided with a four-way valve 8a and an electromagnetic valve 8b. The water heat exchanger 5 is connected to a tank circulation path 11 connected to an upper part and a lower part of a hot water storage tank 10 to be described later, and performs heat exchange between the refrigerant in the refrigerant circulation path 8 and the hot water in the tank circulation path 11. Hot water in the circulation path 11 is heated.

  The tank circulation path 11 includes a circulation pump 12 for circulating hot water stored in the hot water storage tank 10 to the tank circulation path 11, and a thermistor 13 for detecting the temperature of the hot water flowing from the water heat exchanger 5 to the hot water storage tank 10. A thermistor 14 for detecting the temperature of hot water from the hot water storage tank 10 toward the water heat exchanger 5 is provided.

  In addition, the heat pump unit 1 includes a heat pump controller 15 configured by a microcomputer or the like, and operations of the heat pump 9 and the circulation pump 12 are controlled by a control signal output from the heat pump controller 15.

  The heat pump controller 15 is communicably connected to a tank controller 16 to be described later, and when receiving a heating instruction signal from the tank controller 16, based on the detected temperature of the thermistors 13 and 14 provided in the tank circulation path 11. The circulation pump 12 and the heat pump 9 are operated, and the hot water in the hot water storage tank 10 is heated to a predetermined boiling set temperature (for example, 60 ° C.).

  Further, the heat pump controller 15 is functionally provided with a defrosting process control means 17 that performs a defrosting operation in order to prevent the air heat exchanger 7 of the heat pump 9 from frosting and insufficient heat supply from the atmosphere. In preparation. When the outside air temperature or the refrigerant temperature in the air heat exchanger 7 is extremely low, the defrosting process control means 17 switches the outlet of the compressor 4 to the air heat exchanger 7 side by the four-way valve 8a to change the flow direction of the refrigerant. The high-temperature refrigerant by the compressor 4 is sent to the air heat exchanger 7 for defrosting. At this time, the solenoid valve 8b is further opened to reduce the amount of low-temperature refrigerant toward the water heat exchanger 5. When the defrosting operation is being performed, the heat pump controller 15 does not perform an operation for heating the hot water in the hot water storage tank 10 even if it receives a heating instruction signal from the tank controller 16.

  The tank unit 2 includes a hot water storage tank 10 filled with hot water and a tank controller 16 configured by a microcomputer or the like. A hot water discharge pipe 18 is connected to the upper part of the hot water storage tank 10. The hot water discharge pipe 18 has a start end connected to the hot water storage tank 10 and a terminal end connected to a hot water tap such as a curan (not shown). A water supply pipe 19 is connected to the lower part of the hot water storage tank 10. The water supply pipe 19 has a start end connected to the water supply, a downstream side branched into two, one end connected to the hot water storage tank 10, and the other end connected to the middle of the hot water discharge pipe 18.

  The hot water discharge pipe 18 extends from the downstream of the connection point X to the water supply pipe 19 to the outside of the tank unit 2, passes through a hot water supply circuit 20 to be described later of the combustion water heater 3, and then extends into the tank unit 2 again. The hot water bypass pipe 21 is connected. The hot water bypass pipe 21 is provided with a bypass valve 22. When the bypass valve 22 is closed, hot water from the hot water storage tank 10 flows through the hot water supply circuit 20 of the combustion water heater 3, and the bypass valve 22 is opened. When the hot water is stored, the hot water from the hot water storage tank 10 goes to the end of the hot water outlet pipe 18 via the hot water bypass pipe 21.

  The tank unit 2 includes a hot water thermistor 23 provided on the upstream side of the connection point X between the hot water pipe 18 and the water supply pipe 19, a water amount sensor 24 that detects the water flow rate of the water supply pipe 19, and the hot water pipe 18. The water thermistor 25 provided in the water supply pipe 19 extending toward the connection point X, the hot water variable valve 26 for changing the flow rate of hot water supplied from the hot water storage tank 10 to the hot water discharge pipe 18, and the hot water supply pipe 18 from the water supply pipe 19. A water amount variable valve 27 for changing the flow rate of water supplied to the water supply, a pressure reducing valve 28 with a check valve provided in the water supply pipe 19, a connection point X between the hot water pipe 18 and the water supply pipe 19, and a hot water bypass pipe 21 The mixing thermistor 29 provided between the upstream end of the hot water supply and the hot water supply outlet thermistor 30 for detecting the temperature of hot water supplied to the downstream side of the connection point Y between the downstream end of the hot water bypass pipe 21 and the hot water discharge pipe 18. Have

  A hot water storage thermistor 31 (corresponding to the hot water storage temperature sensor of the present invention) for detecting the temperature of the hot water stored in the hot water storage tank 10 is provided at an upper position of the hot water storage tank 10. Further, inside the hot water storage tank 10, a heating water pipe 33 that is connected to a heating circuit 32 to be described later and heats the hot water in the hot water storage tank 10 by exchanging heat with the heating water in the heating circuit 32 is provided.

  The tank controller 16 includes a hot water storage thermistor 31, a tapping hot water thermistor 23, a incoming water thermistor 25, a mixing thermistor 29, a hot water supply outlet thermistor 30, and a temperature detected by the thermistor 14 of the tank circulation path 11 and a water supply pipe detected by the water amount sensor 24. The operation of the hot water variable valve 26, the water variable valve 27, and the bypass valve 22 is controlled based on the 19 water flow rate.

  The tank controller 16 monitors the temperature detected by the hot water storage thermistor 31 and transmits a heating instruction signal to the heat pump controller 15 according to the time zone.

  Further, the tank controller 16 functionally includes a first sterilization process control unit 34 and a second sterilization process control unit 35 that perform a process for sterilizing germs (Legionella bacteria, etc.) in the hot water of the hot water storage tank 10. I have.

  The tank controller 16 has a plurality of operation switches (not shown) such as a temperature switch for setting a desired hot water supply temperature (temperature of hot water supplied from the outlet of the hot water outlet pipe 18) in accordance with a user operation. ) Is connected.

  Further, the tank controller 16 can monitor the outside air temperature by an external thermistor 37 (corresponding to the outside air temperature sensor of the present invention) installed outdoors.

  Here, the state of the hot water filled in the hot water storage tank 10 will be described. Since the hot water discharge pipe 18 is connected to the upper part of the hot water storage tank 10 and the water supply pipe 19 is connected to the lower part of the hot water storage tank 10, When 10 hot water is used for hot water supply, the hot water is led out from the hot water discharge pipe 18 and the hot water in the hot water storage tank 10 is reduced. As a result, water is supplied from the water supply pipe 19 below the hot water storage tank 10. Accordingly, in the hot water storage tank 10, a hot water layer is formed at the top and a water layer is formed at the bottom.

  When the hot water layer at the upper part of the hot water storage tank 10 decreases and the water layer comes to the upper part of the hot water storage tank 10, the detected temperature of the hot water storage thermistor 31 is set to the target hot water temperature set by the remote controller 36 (set by the remote controller 36). The temperature becomes lower than the set temperature of the hot water supply), and when this happens, the hot water runs out. Whether or not the hot water storage tank 10 is in a hot water condition is determined when the detected temperature of the hot water storage thermistor 31 is equal to or lower than the hot water temperature determination temperature set near the target hot water supply temperature. It can be judged.

  When the detected temperature of the hot water storage thermistor 31 is higher than the target hot water supply temperature (in a state where no hot water has run out), the tank controller 16 detects that the water flow sensor 24 detects water flow exceeding a predetermined lower limit flow rate. 22 is opened, and the opening temperature of the hot water amount variable valve 26 and the water amount variable valve 27 is adjusted so that the detected temperature of the mixing thermistor 29 or the hot water supply outlet thermistor 30 becomes the target temperature. Execute adjustment control.

  On the other hand, when the detected water temperature of the hot water storage thermistor 31 is equal to or lower than the target hot water supply temperature (a state where hot water has run out), if the water amount sensor 24 detects water flow exceeding the lower limit water amount, the tank controller 16 22 is closed. Accordingly, the hot water in the hot water storage tank 10 flows through the hot water supply circuit 20 of the combustion hot water heater 3 and is heated by the combustion hot water heater 3.

  The combustion water heater 3 may employ a known configuration as an instantaneous heating type. The combustion water heater 3 employed in the present embodiment includes a hot water supply circuit 20 connected to the hot water discharge pipe 18 and a heating circuit 32 connected to a heating water pipe 33 inside the hot water storage tank 10. In this embodiment, the heating water pipe 33 inside the hot water storage tank 10 is connected without connecting the heating terminal to the heating circuit 32. However, as long as the heating circuit 32 has a configuration in which a plurality of branches are provided. The hot water heating can be performed by connecting the heating water pipe 33 and the heating terminal in parallel.

  The hot water supply circuit 20 and the heating circuit 32 are provided independently of each other, and each is provided with a gas burner and a heat exchanger (not shown). When the bypass valve 22 of the tank unit 2 is closed, the hot water in the hot water storage tank 10 flows through the hot water supply circuit 20 and is heated.

  The heating circuit 32 is filled with heating water. This heating water is circulated through the heating circuit 32 by a heating circulation pump (not shown) provided inside the combustion water heater 3. That is, high-temperature heating water heated by the combustion water heater 3 is sent to the heating water pipe 33 inside the hot water storage tank 10 through the heating forward pipe 38, and the hot water in the hot water storage tank 10 is heated by the heating water pipe 33 ( After liquid-liquid heat exchange), it returns to the combustion water heater 3 through the heating return pipe 39.

  The combustion water heater 3 includes a hot water controller 40 configured by a microcomputer or the like. The hot water controller 40 supplies hot water in the hot water supply circuit 20 (hot water from the hot water storage tank 10) to a target hot water temperature. While temperature control is performed, heating temperature control is performed so that the heating water in the heating circuit 32 becomes the target heating temperature.

  Further, the hot water supply controller 40 is communicably connected to the tank controller 16, and the tank controller 16 is instructed to permit or prohibit heating of hot water for the hot water supply circuit 20.

  Next, the operation of the first sterilization processing control means 34 and the second sterilization processing control means 35 according to the gist of the present invention will be described.

  The first sterilization processing control means 34 is a heat pump controller when the detected temperature of the hot water storage thermistor 31 is less than 53 ° C. (sterilization necessity determination temperature) for 96 hours (sterilization necessity determination time) or more. A signal instructing sterilization heating is sent to 15. The heat pump controller 15 that has received this signal starts heating the hot water in the hot water storage tank 10 by the heat pump 9 unless the defrosting operation is being performed.

  Then, the first sterilization processing control means 34 maintains the state where the detected temperature of the hot water storage thermistor 31 is heated to 58 ° C. (sterilization temperature) or more for 1 hour (sterilization time), and then causes the heat pump controller 15 to stop sterilization heating. An instructing signal is transmitted, and the sterilization process by the heat pump 9 is terminated.

  Here, the condition that the temperature detected by the hot water storage thermistor 31 is lower than 53 ° C. continues for 96 hours or more, because low temperature hot water has been stored in the hot water storage tank 10 for a long time. It is a condition that is assumed to have a risk of breeding.

  The condition that the temperature detected by the hot water storage thermistor 31 is maintained at a temperature of 58 ° C. or higher for 1 hour or longer is a condition in which miscellaneous bacteria in the hot water in the hot water storage tank 10 are supposed to be killed by heating.

  Note that the sterilization necessity determination temperature, the sterilization necessity determination time, the sterilization temperature, and the sterilization time are not limited to the above-described specific values, and are appropriately selected and set according to the hot water usage status of the hot water storage tank 10 and the like. It is what is done.

  By performing the sterilization process by the first sterilization process control unit 34 as described above, the hot water in the hot water storage tank 10 can be sterilized efficiently, and clean hot water can be supplied from the hot water storage tank 10.

  Unlike the first sterilization process control unit 34, the second sterilization process control unit 35 executes the sterilization process only when it is assumed that the heat pump 9 is performing a defrosting operation. That is, the second sterilization processing control unit 35 continues the state where the detected temperature of the hot water storage thermistor 31 is lower than the sterilization necessity determination temperature for the sterilization necessity determination time and the detected temperature of the outside air thermistor 37 is 5 ° C. When the temperature is equal to or lower than the frost treatment determination temperature), a signal instructing sterilization heating is transmitted to the hot water supply controller 40. Receiving this signal, the hot water supply controller 40 heats the heating water in the heating circuit 32 to about 80 ° C. and starts circulation with the heating water pipe 33. Thereby, the hot water in the hot water storage tank 10 is heated by the high-temperature heating water in the heating water pipe 33.

  Here, when the detected temperature of the outside air thermistor 37 is 5 ° C. (defrosting determination temperature) or lower, the condition that the outside air temperature is extremely low may cause frost on the air heat exchanger 7 of the heat pump 9. Therefore, the condition is assumed that the heat pump 9 is performing the defrosting operation. In addition, the defrost process determination temperature is appropriately set based on the generation temperature of frost, and usually any temperature between 5 ° C. and −5 ° C. is selected.

  Then, the second sterilization processing control means 35 transmits a signal instructing the hot water supply controller 40 to stop the sterilization heating after maintaining the state where the temperature detected by the hot water storage thermistor 31 is heated above the sterilization temperature for the sterilization time. Then, the sterilization process by the combustion water heater 3 is terminated.

  By doing so, even when sterilization cannot be performed because the heat pump 9 is performing the defrosting operation, the hot water in the hot water storage tank 10 is sterilized, so clean hot water is supplied from the hot water storage tank 10. It becomes possible.

  Note that the sterilization necessity determination temperature, the sterilization necessity determination time, the sterilization temperature, and the sterilization time in the second sterilization process control unit 35 are the same as those in the first sterilization process control unit 34.

  In addition, since the second sterilization process control means 35 starts the sterilization process based on the temperature detected by the outside air thermistor 37, the first sterilization process control means 34 is performing the sterilization process by the heat pump 9 (ie, Even when the heat pump is not performing a defrosting operation), the sterilization process by the combustion water heater 3 is performed at the same time. Thereby, the hot water of the hot water storage tank 10 can be sterilized very quickly by both the heating circuit 32 and the heat pump 9 of the combustion water heater 3, and the time required for the sterilization process can be shortened.

  Furthermore, since the hot water sterilization of the hot water storage tank 10 can be performed using the existing heating circuit 32 provided in the combustion water heater 3 as in the present embodiment, it can be configured relatively inexpensively.

  In addition, in this embodiment, although the hot water supply system provided with the hot water bypass pipe 21 which bypasses the combustion hot water heater 3 and the bypass valve 22 which opens and closes the hot water bypass pipe 21, the hot water supply bypass pipe 21 and the bypass valve 22 are provided. The present invention can be applied to a hot water supply system that does not have this effect.

  In the present embodiment, the tank unit 2 is provided with the outside air thermistor 37, and the tank controller 16 includes the second sterilization processing control means 35, and the sterilization heating is started and stopped from the tank controller 16 to the hot water supply controller 40. In addition to this configuration, if the hot water supply controller 40 is configured to collect the detected temperature of the hot water storage thermistor 31 by communication with the tank controller 16, the outdoor hot water thermistor 3 is provided to the combustion hot water heater 3. 37 and the hot water supply controller 40 can be provided with the second sterilization processing control means 35. In this case as well, the effects of the present invention can be obtained.

  DESCRIPTION OF SYMBOLS 3 ... Combustion water heater, 9 ... Heat pump, 10 ... Hot water storage tank, 11 ... Tank circulation path, 17 ... Defrosting control means, 18 ... Hot water pipe, 19 ... Water supply pipe, 20 ... Hot water supply circuit, 31 ... Hot water storage thermistor (hot water storage) Temperature sensor), 32 .. heating circuit, 33... Heating water pipe, 34... First sterilization process control means, 35... Second sterilization process control means, 37 .. outdoor thermistor (outside air temperature sensor).

Claims (1)

A hot water storage tank for storing hot water inside,
A water supply pipe connected to the hot water storage tank to supply water to the hot water storage tank;
A hot water outlet pipe connected to the hot water storage tank and leading out hot water of the hot water storage tank;
A tank circulation path having a start end and an end connected to the hot water storage tank for circulating hot water in the hot water storage tank;
A heat pump for heating the hot water in the hot water storage tank through the tank circuit;
A hot water storage temperature sensor for detecting the temperature of the hot water in the hot water storage tank;
A combustion water heater that includes a hot water supply circuit connected to the hot water pipe and heats hot water flowing through the hot water pipe with a burner;
A heating circuit which is provided in the combustion water heater and in which heating water heated by a burner circulates;
A heating water pipe connected to the heating circuit, provided inside the hot water storage tank, for heating the hot water in the hot water storage tank by heat exchange with the heating water in the heating circuit;
An outside temperature sensor for detecting the outdoor temperature;
Defrosting control means for stopping heating of hot water in the hot water storage tank by the heat pump when the heat pump is frosted and instructing the heat pump to perform a defrosting operation;
When the state where the temperature detected by the hot water storage temperature sensor is lower than the sterilization necessity determination temperature set in consideration of the temperature at which various germs propagate in the hot water of the hot water storage tank continues for a predetermined sterilization necessity determination time. A first sterilization processing control means for instructing heating of the hot water in the hot water storage tank so as to be equal to or higher than a sterilization temperature set by assuming the temperature at which the hot water in the hot water storage tank is sterilized by the heat pump;
The state where the detected temperature of the hot water storage temperature sensor is lower than the sterilization necessity determination temperature continues for a predetermined sterilization necessity determination time, and the detected temperature of the outside air temperature sensor is controlled by the defrosting process control means. When the temperature is equal to or lower than the defrosting determination temperature set assuming the outside air temperature at which the defrosting operation is performed, the heating water heated by the combustion water heater is supplied to the heating water pipe of the heating circuit, and the sterilization temperature A hot water supply system comprising: a second sterilization processing control unit that instructs heating of the hot water in the hot water storage tank as described above.

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