JP2002181381A - Hot water supply system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Even if the critical temperature of the refrigerant of a heat pump is low, C
Provided is a hot water supply system capable of storing hot water in a hot water storage tank in an operation state with a high OP. SOLUTION: The heat pump 20 of the system 1 has an external air heat collecting section 24A and a water heat collecting section 24B as the evaporator 24. The upstream end of the main flow path portion 31 of the flow passage 30 is continuous with the lower portion of the hot water storage tank 10, and the downstream end is connected to the hot water storage tank 1.
0 is connected to the upper part. The main flow path section 31 is provided with a cooling section 33 that is cooled by the heat collection of the water heat collection section 24B, and a heating section 35 that receives the heat radiation of the condenser 22 and is heated. One end 31a of the sub flow path 31 is connected to the main flow path 31 between the cooling unit 33 and the heating unit 35.
The other end of the sub flow path 31 is connected to the lower end of the hot water storage tank 10 (below the upstream end of the main flow path 31). The sub flow path 31 is provided with a reversible pump 36 that can flow water from one end 31a to the other end 31b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot water supply system in which a hot water storage tank is heated by a heat pump having an outside air heating section and a water heating section.

[0002]

BACKGROUND OF THE INVENTION For example, Japanese Patent Application Laid-Open No. H8-303884
The publication describes a heat pump in which a refrigerant circulates in the order of a compressor, a condenser, an expansion valve, and an evaporator. The refrigerant radiates heat while passing through the condenser, and collects heat while passing through the evaporator. The evaporator is composed of an outside air sampling unit that extracts heat from outside air, and a water sampling unit that extracts heat from water. The water is cooled by the heat collection of the water sampling unit. However, the above publication does not specify how to treat the cooled water.

[0003] In recent years, it has been desired to employ a substance that does not destroy the ozone layer as a refrigerant for a heat pump. Representative of such materials include R
410A (a mixture of 50% by weight of difluoromethane and pentafluoroethane) and carbon dioxide. However, their critical temperatures are relatively low (R41
0A is about 75 ° C. Carbon dioxide is about 30 ° C). for that reason,
The coefficient of performance (hereinafter referred to as “COP”) was not good.

The present invention has been made in view of the above circumstances, and applies a heat pump having an outside air heat collecting section and a water heat collecting section to a hot water supply system. It is another object of the present invention to effectively utilize the water that has been collected and to realize a heat pump operation with a high COP even when the critical temperature of the refrigerant is low.

[0005]

In order to achieve the above object, a hot water supply system according to a first aspect of the present invention comprises a heat pump, a hot water storage tank for storing hot water, and the hot water storage tank. To the heat pump, and then return to the hot water storage tank. The heat pump has a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring shape, and the refrigerant circulating in the refrigerant circuit radiates heat in the condenser, and the refrigerant circulates in the evaporator. Collect heat. The evaporator includes an outside air heat collecting unit that collects heat from outside air, and a water heat collecting unit. The flow passage has a main flow path and a sub flow path. The upstream end of the main flow path is connected to the lower part of the hot water storage tank, and the downstream end is connected to the upper part of the hot water storage tank. One end of the sub flow path is connected to a middle part of the main flow path, and the other end is connected to a lower side of an upstream end of the main flow path in the hot water storage tank. The main flow path portion is provided with a cooling unit that is cooled by heat collection of the water heat collection unit on the upstream side of one end of the sub flow path unit, and dissipates heat of the condenser downstream from the one end. A heating unit for receiving and heating is provided. Water supply means is provided in the sub-channel portion. This water supply means creates a water flow from one end of the sub flow path to the other end.

According to a second feature of the present invention, a detecting means for detecting a water temperature of a lower portion of the hot water storage tank is further provided. The first and second modes are selectively executed based on the detection value of the detection means. In the first mode, the water is taken from the hot water storage tank into the other end of the sub flow path, and is returned to the hot water storage tank via the sub flow path and the downstream portion of the main flow path. In the second mode,
The water is taken from the hot water storage tank into an upstream portion of the main flow path, a part of which is returned to the hot water storage tank through the sub flow path by the driving of the water supply means, and the remainder is the main flow path. Is returned to the hot water storage tank through a downstream portion of the hot water storage tank.

[0007] According to a third aspect of the present invention, in the first or second aspect, the outside air heat collecting section and the water heat collecting section are arranged in series in the refrigerant circuit.

According to a fourth aspect of the present invention, in the second aspect, the outside air heat collecting section and the water heat collecting section are arranged in series in the refrigerant circuit. Time,
The opening degree of the expansion valve is adjusted so that the refrigerant temperature in the outside air heat collecting section becomes substantially equal to the outside air temperature.

In a fifth aspect of the present invention, in the first or second aspect, the outside air heat collecting section and the water heat collecting section are arranged in parallel in the refrigerant circuit.

According to a sixth aspect of the present invention, in the fifth aspect, the expansion valve is an outside air heat expansion valve connected to the outside air heat section, and a water heat expansion valve connected to the water heat section. An expansion valve is provided, and the opening degree of each of these two expansion valves is adjusted, so that the amount of heat taken by the outside air sampling unit and the water sampling unit is controlled.

According to a seventh aspect of the present invention, in the second aspect, the refrigerant circuit is provided with the outside air sampling section and the water sampling section in parallel, and in the first mode, An opening / closing means is provided for opening the outside air sampling unit and shutting off the water sampling unit, and for shutting off the outside air sampling unit and opening the water sampling unit in the second mode.

According to an eighth aspect of the present invention, the first to seventh aspects are described.
In any of the features of the above, in the upper part of the hot water storage tank,
A heating heat receiving unit that receives the heat of the water and sends the water to a heater is accommodated therein.

According to a ninth feature of the present invention, the first to eighth aspects described above.
In any of the features of the above, on the lower side of the hot water storage tank,
The solar heat supply part which gives the solar heat sent from the solar heat collector to the said water is accommodated.

According to a tenth aspect of the present invention, in the ninth aspect, the upstream end of the main flow path and the other end of the sub flow path are vertically arranged with the solar heat supply unit interposed therebetween. I have. And the hot water supply system is in the middle of the night (for example,
At 4:00 am), a predetermined mode is executed. In this mode, the sub flow path is closed, and the water is returned from the hot water storage tank to the hot water storage tank through the main flow path.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hot water supply / room heating system 1 according to a first embodiment of the present invention. The hot water supply / room heating system 1 includes a hot water storage tank 10 and a heat pump 20.

A water supply pipe 11 is provided at the lower end of the hot water storage tank 10.
Is connected. The hot water storage tank 10 is filled with the water supplied from the water supply pipe 11. As described below,
The water in the upper part of the hot water storage tank 10 is hot water of 80 ° C. to 90 ° C. This hot water is supplied to the hot water through a hot water supply pipe 12 extending from the upper end of the hot water storage tank 10.

A heating circuit 40 and a solar heat supply circuit 50 are connected to the hot water storage tank 10. Heating circuit 40
Has a floor heater 41 and a heating heat receiving portion 42 composed of a heat transfer tube housed in the upper portion of the hot water storage tank 10, and a heat medium such as brine is supplied between the heater 41 and the heat receiver 42. It is being circulated. The heat medium is heated by hot water in the process of passing through the heat receiver 42 and radiates heat in the process of passing through the heater 41. (The heat receiving section 42 receives the heat of the hot water and sends it to the heater 41.) Thus, the floor is heated.

The solar heat supply circuit 50 includes a solar heat collector 51.
And a solar heat supply unit 52 composed of a heat transfer tube accommodated in a lower portion of the hot water storage tank 10 so that a heat medium such as brine is circulated between the heat collector 51 and the supply unit 52. Has become. The heat medium is heated by the solar heat collected by the heat collector 51 while passing through the heat collector 51, and radiates heat while passing through the supply unit 52. Thereby, the hot water storage tank 1
The water in the lower part of 0 is warmed. (The supply unit 52 gives the solar heat sent from the heat collector 51 to the water in the hot water storage tank 10.) The warmed water moves toward the upper part of the hot water storage tank 10 by natural convection.

Next, the heat pump 20 will be described. The heat pump 20 has a refrigerant circuit 20X in which a compressor 21, a condenser 22, an expansion valve 23, and an evaporator 24 are sequentially connected in a ring shape. The refrigerant circulating in the refrigerant circuit 20X uses, for example, carbon dioxide as a substance that does not have a risk of destroying the ozone layer. The refrigerant is adiabatically compressed by the compressor 21 and sent out to the condenser 22. Then, it is condensed, liquefied and radiated in the process of passing through the condenser 22. Next, adiabatic expansion is performed by the expansion valve 23.
Then, in the process of passing through the evaporator 24, it is evaporated and vaporized,
Collect heat.

The evaporator 24 is composed of an outside air heat collecting section 24A for collecting heat from outside air, and a water heat collecting section 24B for collecting heat from water in a main flow path section 31 which will be described later. These heat collecting units 24
A and 24B are arranged in series in the refrigerant circuit 20X.
The outside air heat collecting unit 24A is arranged on the expansion valve 23 side, and the water heat collecting unit 24B is arranged on the compressor 21 side.

The system 1 further includes a flow passage 30 for guiding water from the hot water storage tank 10 to the heat pump 20 and thereafter returning the water to the hot water storage tank 10. The flow passage 30 has a main flow path 31 and a sub flow path 32.

The upstream end of the main flow path 31 is connected to the hot water storage tank 10.
And a portion slightly above the solar heat supply section 52. The downstream end of the main flow path 31 is connected to the upper end of the hot water storage tank 10. In the main flow path section 31, a cooling section 33 composed of a heat transfer tube and a pump 3
4, and a heating section 35 composed of a heat transfer tube.
The heating unit 35 constitutes the first heat exchanger 1a together with the condenser 22 of the heat pump 20. The cooling unit 33 constitutes the second heat exchanger 1b together with the water heat collecting unit 24B.

One end 32 a of the sub flow path 32 is connected to a cooling section 33.
And the other end 32b
Is connected to the lower end of the hot water storage tank 10 (below the solar heat supply unit 52). The sub flow path 32 is provided with a reversible pump 36 capable of reversing the flow direction.

Further, the hot water supply / room heating system 1 includes a controller 60 (control means). Controller 60
, A detection signal is input from a water temperature sensor 61 (detection means) provided in the hot water storage tank 10 near the upstream end of the main flow path portion 31. The controller 60 determines the input value from the sensor 61 and the time by the built-in timer (whether it is midnight or not).
By operating the compressor 21, the pumps 34, 36, and the like based on the above, the first to third modes are selectively executed,
The hot water storage tank 10 is heated. Hereinafter, the control contents will be described.

It is assumed that the season is winter. The controller 60 executes the first mode when the water temperature detected by the water temperature sensor 61 falls below a predetermined range of, for example, about 40 ° C. in a time zone other than midnight.

In this mode, the compressor 21 is driven. As a result, the refrigerant circulates through the refrigerant circuit 20X, collects heat from the outside air at the outside air heat collection unit 24A, and radiates heat at the condenser 35, that is, the heat exchanger 1a.

Also, the pumps 34 and 36 are driven. The pump 36 supplies water from the other end 32b of the sub-flow path portion 32 to one end 3b.
2a. Thereby, the water near the lower end of the hot water storage tank 10 passes through the sub flow path 32 and the main flow path 31 b downstream of one end 32 a of the sub flow path 32, and the heating unit 35, that is, the heat exchanger 1 a It is led to. In the heat exchanger 1a, the refrigerant is heated by the radiation of the refrigerant, and is turned into hot water. This hot water is returned from the downstream end of the main flow path 31 to the upper part of the hot water storage tank 10. Thereby, the area of the hot water in the hot water storage tank 10 expands downward, and the water temperature detected by the water temperature sensor 61 rises.

The pumping flow rates of the two pumps 34 and 36 are adjusted so as to be the same. As a result, water does not flow through the main flow path 31a upstream of the one end 32a of the sub flow path 32. Therefore, heat exchange (refrigeration and radiation of the refrigerant) in the heat exchanger 1b is not performed.

The controller 60 adjusts the water temperature detected by the water temperature sensor 61 in the predetermined range (40
The second mode is executed when the temperature falls within (approximately 0 C).

In this mode, the compressor 21 is driven,
The refrigerant is circulated as in the first mode. In addition, the pump 34 is driven, and the pump 36 is driven in a direction opposite to the first mode, that is, in a direction in which water flows from one end 32a of the sub flow path 32 to the other end 32b. (The pump 36 at this time functions as "water supply means" in the claims.)

As a result, hot water of about 40 ° C. is taken from the hot water storage tank 10 into the upstream portion 31a of the main flow path portion 31 and guided to the cooling section 33, that is, the heat exchanger 1b.
Then, in the heat exchanger 1b, heat is collected by the refrigerant passing through the water heat collecting section 24B and cooled. The cooled water is supplied to the downstream portion 31b of the main flow path 31 and the sub flow path 3
And two. The water that has entered the downstream portion 31b is guided to the heat exchanger 1a, turned into hot water by heat exchange with the refrigerant, and then returned to the upper portion of the hot water storage tank 10. On the other hand, the water diverted to the sub flow path 32 is kept cold while the hot water storage tank 1
It is returned to the lower end of 0. Thereby, the hot water storage tank 10
A hot water region can be clearly formed on the upper side and a cold water region can be clearly formed on the lower side.

In the second mode, as described above, the refrigerant takes heat from hot water, so that the evaporation temperature can be increased. Thereby, the load on the compressor 21 can be reduced. As a result, a heat pump operation with a high COP can be realized despite the use of carbon dioxide having a low critical temperature (about 30 ° C.) as a refrigerant.

When the evaporating temperature is to be increased, it is desirable that the temperature of the refrigerant in the outside air sampling section 24A be made substantially equal to the outside air temperature by adjusting the opening of the expansion valve 23. As a result, the refrigerant radiates heat at the outside air heat collecting section 24A (generation of heat loss).
Can be prevented. On the other hand, although the heat can be hardly collected in the outside air heat collecting section 24A, there is no problem because the water is collected in the water heat collecting section 24B.

Generally, the amount of hot water taken out of the hot water supply pipe 12 increases from the evening until late at night. Therefore, in the hot water storage tank 10, the upper hot water region becomes narrower,
That much cold winter water is newly supplied from the water supply pipe 11,
The cold water region extends far above the upstream end of the main flow path portion 31.

At midnight, the controller 60
Executes the third mode (midnight mode). In this mode, the pump 36 is stopped. Pump 36 stopped
Functions as a valve that closes the sub-channel portion 32. Further, the compressor 21 is driven to circulate the refrigerant, and the pump 34 is driven. As a result, the cold water in the hot water storage tank 10 is taken into the main flow path 31 and the heat exchanger 1b
In this case, the heat is collected by the refrigerant and further cooled, and is guided to the heat exchanger 1a at a lower temperature. Therefore, the condenser 22
Heat can be efficiently received from the refrigerant. on the other hand,
Since the refrigerant can take heat from the outside air at the outside air sampling unit 24A and then further take heat from the water at the water sampling unit 24B, the amount of heat radiation in the condenser 22 can be increased. As a result, the COP of the heat pump 20 can be increased. In addition, since the operation is performed at midnight, the electricity usage fee is low.

The water after passing through the heat exchanger 1a becomes hot water,
It is returned to the upper part of hot water storage tank 10. As a result, the hot water area of the tank 10 can be expanded downward,
It can extend to near the upstream end of the main flow path portion 31. As a result, a sufficient amount of hot water can be secured before dawn.

On the other hand, the water temperature below the upstream end of the main flow path section 31 can be maintained at a low temperature. Therefore, during the daytime, the solar heat supply from the solar heat supply unit 52 can be efficiently performed. Eventually, the temperature of the heat medium flowing back from the supply unit 52 to the heat collector 51 can be lowered, and the heat collector 51
The solar heat collection efficiency can be increased.

Next, another embodiment of the present invention will be described.
In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

FIG. 2 shows a hot water supply / room heating system 1A according to a second embodiment of the present invention. This system 1
In the refrigerant circuit 20X of A, an outside air heat collecting unit 24A and a water heat collecting unit 24B are arranged in parallel. Two heat collecting units 24A,
An electromagnetic three-way valve 25 (opening / closing means) is provided at the branch to 24B.

The three-way valve 25 is controlled by the controller 60, and in the first mode, opens the outside air sampling unit 24A and shuts off the water sampling unit 24B. As a result, heat is collected only in the outside air heat collecting unit 24A. The same applies to the third mode.

On the other hand, in the second mode, the three-way valve 25 shuts off the outside air heat collecting portion 24A and opens the water heat collecting portion 24B. Thereby, heat is collected only in the water sampling unit 24B. Therefore, there is no risk of heat radiation from the outside air heat collecting unit 24A, and the evaporation temperature of the refrigerant is set higher than the outside air temperature, so that CO 2
P can be further improved.

FIG. 3 shows a hot water supply / room heating system 1B according to a third embodiment of the present invention. This system 1
In B, as in the second embodiment, the two heat collecting sections 24
A and 24B are arranged in parallel. In addition, the expansion valve
Two of them are arranged in parallel, and are composed of an expansion valve 23A for external air heat collection connected to the external air heat collection unit 24A and an expansion valve 23B for water heat collection connected to the water heat collection unit 24B.

The controller 60 adjusts the opening of each of the two expansion valves 23A and 23B. Thereby, the heat collecting units 24A and 24B are set according to the mode to be executed.
, The amount of heat taken can be controlled. That is, in the first mode, it is possible to close the water-heat-collecting expansion valve 23B substantially, and to collect heat only in the outside-air heat collecting unit 24A. In the second mode, the outside air heat collection expansion valve 23A is almost closed, or the opening degree is adjusted so that the refrigerant temperature is substantially equal to the outside air temperature, so that heat collection and heat dissipation in the outside air heat collection unit 24A is eliminated, and water sampling is performed. The COP can be further improved by adjusting the opening of the expansion valve 23B for water collection so that the refrigerant temperature of the heating part 24A becomes higher. In the third mode, the heat collection ratio between the heat collection units 24A and 24B can be set to be optimal.

The present invention is not limited to the above embodiment, but can adopt various forms. For example, an on-off valve that is closed in the first mode may be provided on the upstream side portion 31a of the main flow path portion 31. The sub flow path 32 is provided with a bypass passage which bypasses the pump 36 and is opened in the first mode and closed in the second mode, and the pump 36 is not reversible but is directed in a direction from one end 32a to the other end 32b. A pump for flowing only water may be used. Sub flow path 32
Alternatively, an on-off valve that is closed in the third mode may be provided. In the first embodiment, the outside air heat collecting section 24A may be arranged on the compressor 21 side, and the water heat collecting section 24B may be arranged on the expansion valve 23 side. In the second embodiment, the electromagnetic three-way valve 25 may be provided at a junction downstream of the two heat sampling units 24A and 24B. In addition, instead of the electromagnetic three-way valve 25,
A pair of on-off valves may be provided in each branch for A and 24B.

[0045]

As described above, according to the first aspect of the present invention, in a hot water supply system, a heat pump operation with a high COP can be realized even when the critical temperature of the refrigerant is low, and the hot water is placed on the upper side of the hot water storage tank. Regions can be formed. Further, the water cooled in the cooling section can be returned to the hot water storage tank below the upstream end of the main flow path section to form a cold water area. According to the second feature of the present invention, the hot water region and the cold water region can be formed more reliably and efficiently. According to the third aspect of the present invention, it is possible to cause the refrigerant to sequentially perform the outside air heat collection and the water heat collection. According to the fourth feature of the present invention, it is possible to prevent the refrigerant from radiating heat in the outside air heat collecting section, and it is possible to more reliably improve the COP. According to the fifth aspect of the present invention, the refrigerant is allowed to perform only one of external air heat collection and water heat collection,
A part of the refrigerant can be heated with outside air, and the rest can be heated with water. According to the sixth aspect of the present invention, it is possible to separately adjust the amount of external air heat and the amount of water heat. According to the seventh aspect of the present invention, in the first mode, the heat radiation in the water heat collecting section can be prevented, and in the second mode, the heat radiation in the outside air heat collecting section can be prevented. Further improvement can be achieved. According to the eighth aspect of the present invention, the hot water in the hot water storage tank can be used for heating. According to the ninth feature of the present invention, solar heat can be efficiently supplied to the lower portion of the hot water storage tank having a low water temperature. Tenth aspect of the present invention
According to the feature described above, a sufficient amount of hot water can be secured in the hot water storage tank by using inexpensive electric power at midnight. On the other hand, the temperature around the solar heat supply unit can be reliably maintained at a low temperature, and the efficiency of daytime solar heat supply can be more reliably improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hot water supply / room heating system according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a hot water supply / room heating system according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a hot water supply / room heating system according to a third embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B Hot water supply / heating system 10 Hot water storage tank 20 Heat pump 20X Refrigerant circuit 21 Compressor 22 Condenser 23 Expansion valve 23A Expansion valve for collecting external air 23B Expansion valve for collecting water 24 Evaporator 24A External air sampling section 24B Water sampling Heating part 25 Electromagnetic three-way valve (opening / closing means) 30 Flow path 31 Main flow path part 31a Upstream side part 31b Downstream side part 32 Sub flow path part 32a One end 32b Other end 33 Cooling unit 35 Heating unit 41 Floor heater 42 Heating Heating part 51 Solar heat collector 52 Solar heat supply part 61 Water temperature sensor (detection means)

Claims (10)

[Claims] (A) a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring shape; a refrigerant circulating in the refrigerant circuit radiates heat in the condenser; A heat pump for collecting heat by the evaporator; (b) a hot water storage tank for storing water for hot water supply; and (c) a flow passage for guiding the water from the hot water storage tank to the heat pump and then returning the water to the hot water storage tank. A hot water supply system, wherein the evaporator has an outside air sampling unit for sampling heat from outside air and a water sampling unit, and the flow passage has an upstream end connected to a lower side of the hot water storage tank, A main flow passage portion having a downstream end connected to the upper portion of the hot water storage tank; and a sub flow passage having one end connected to a middle portion of the main flow passage portion and the other end connected to a lower side of the upstream end of the main flow passage portion in the hot water storage tank. The main flow path portion has an upper end than one end of the sub flow path portion. On the side,
A cooling unit that is cooled by heat collection of the water heat collecting unit is provided, and a heating unit that receives and discharges heat from the condenser is provided downstream of the one end. And a water supply means for producing a water flow from the one end to the other end. 2. A detecting means for detecting a water temperature of a lower portion of the hot water storage tank, and based on a detection value of the detecting means,
The first mode and the second mode are selectively executed. In the first mode, the water is returned from the hot water storage tank to the hot water storage tank through the sub flow path portion and the downstream portion of the main flow path portion. In the second mode, the water passes from the hot water storage tank to an upstream portion of the main flow path portion, and then a part of the water returns to the hot water storage tank through the sub flow path portion by driving of the water supply means. 2. The remaining portion is returned to the hot water storage tank through a downstream portion of the main flow path portion. 3.
The hot water supply system according to 1. 3. The hot water supply system according to claim 1, wherein the outside air heat collecting section and the water heat collecting section are arranged in series in the refrigerant circuit. 4. The outside air sampling section and the water sampling section are arranged in series in the refrigerant circuit, and in the second mode, the temperature of the refrigerant in the outside air sampling section is equal to the outside air temperature. The hot water supply system according to claim 2, wherein the opening degree of the expansion valve is adjusted so as to be substantially equal to. 5. The hot water supply system according to claim 1, wherein the outside air heat collecting section and the water heat collecting section are arranged in parallel in the refrigerant circuit. 6. The expansion valve comprises an outside air heating expansion valve connected to the outside air heating unit, and a water heating expansion valve connected to the water heating unit. The hot water supply system according to claim 5, wherein the amounts of heat collected by the outside air sampling unit and the water sampling unit are respectively controlled by adjusting the degrees. 7. In the refrigerant circuit, the outside air sampling unit and the water sampling unit are arranged in parallel, and in the first mode, the outside air sampling unit is opened and the water sampling unit is opened. 3. The hot water supply system according to claim 2, further comprising: an opening / closing unit that shuts off the outside air heat collecting unit and opens the water heat collecting unit in the second mode. 4. 8. The hot water supply according to claim 1, wherein a heating heat receiving unit that receives heat of the water and sends the heat to a heater is accommodated in an upper portion of the hot water storage tank. system. 9. A solar heat supply unit for supplying solar heat sent from a solar heat collector to the water is accommodated in a lower portion of the hot water storage tank. Hot water supply system as described. 10. The upstream end of the main flow passage and the other end of the sub flow passage are disposed vertically above and below the solar heat supply unit. At midnight, the sub flow passage is closed. , The water
The hot water supply system according to claim 9, wherein a midnight mode in which the hot water storage tank is returned to the hot water storage tank through the main flow path portion is executed.