Hot water supply tank, hot water supply tank unit, and heat-pump water heater

Abstract

Provided is a hot water generation apparatus that can perform an efficient operation or an operation that maintains user comfort, in accordance with conditions, without using a plurality of pumps. A hot water supply tank (12) includes: a tank (51) storing supply water; a water supply pipe (53) having an outlet (52) disposed in a bottom portion inside the tank (51) and pouring the supply water into the tank (51); a coil (55) provided inside the tank (51) and circulating water for heating the supply water in the tank (51); a hot water supply pipe (56) guiding hot water which is the supply water heated in the tank (51) to an outside of the tank (51); and a heat insulation material (58) covering an outer surface of the tank (51) above a vicinity of a height of the outlet (52) of the water supply pipe (53) or a vicinity of a height of a lower end (55d) of the coil (55).

Description

TECHNICAL FIELD

[0001] Embodiments of the present invention relate to a hot water supply tank, a hot water supply tank unit, and a heat pump water heater.BACKGROUND

[0002] There is known a hot water storage tank unit including a stainless steel or enamel hot water storage tank and a plurality of heat insulation members covering the surface of the hot water storage tank to keep it warm. The hot water storage tank is a cylindrical tank extending in the up-down direction, and has a center cylindrical portion, an upwardly protruding lid portion closing the upper end of the cylindrical portion, and a downwardly protruding bottom portion closing the lower end of the cylindrical portion. The plurality of heat insulation members include a front heat insulation member and a rear heat insulation member combined together to surround the cylindrical portion of the hot water storage tank from the front-rear direction, an upper heat insulation member covering the lid portion of the hot water storage tank from above, and a lower heat insulation member covering the bottom portion of the hot water storage tank from below. The plurality of heat insulation members are combined together to surround the hot water storage tank.PRIOR ART DOCUMENTPATENT DOCUMENT

[0003] [Patent Document 1] JP 2020-139588 ASUMMARYPROBLEMS TO BE SOLVED BY INVENTION

[0004] A hot water supply tank of a heat pump water heater includes a tank that stores hot water, a water supply pipe that pours supply water into the tank, a coil that circulates a heating medium such as water to heat the supply water in the tank, a hot water supply pipe that guides the hot water which is the supply water heated in the tank to the outside of the tank, and an heat insulation material that covers the periphery of the tank.

[0005] The supply water supplied to this type of hot water supply tank flows into the bottom portion of the tank through a water supply pipe, and is heated by the coil disposed above the portion where the water flows in. The hot water which is the heated supply water rises in the tank by natural convection and collects in an upper portion of the tank. Therefore, the temperature of the supply water that collects in a lower portion of the tank is lower than the temperature of the hot water which is heated water that collects in the upper portion of the tank, and is closer to the temperature of the atmosphere in the environment where the hot water supply tank is installed, or the temperature of the supply water supplied to the hot water supply tank, i.e., the temperature of tap water. Hence, the heat insulation material provided in the lower portion of the hot water supply tank has a low heat retention effect on the hot water inside the hot water supply tank. Such a hot water supply tank further includes a supporting member that is attached to a lower portion of the tank to support the tank. The heat insulation material provided in the lower portion has a special structure to avoid the supporting member supporting the tank. When the supporting member is fixed to the hot water supply tank unit, the heat insulation material provided in the lower portion gets in the way, which reduces the manufacturability of the device, the workability of device installation, and the maintainability of the device.

[0006] Therefore, an object of the present invention is to provide a hot water supply tank, a hot water supply tank unit, and a heat pump water heater that can favorably suppress heat dissipation of heated supply water, i.e., hot water, so as to match the temperature distribution of the supply water that collects in a tank, are excellent in controlling the costs of raw materials of the heat insulation material, and facilitate the manufacturability of the device, the workability of device installation, and the maintainability of the device.MEANS FOR SOLVING PROBLEM

[0007] In order to solve the above-mentioned problems, a hot water supply tank according to an embodiment of the present invention includes: a tank that can store supply water; a water supply pipe that has an outlet disposed in a bottom portion inside the tank and pours the supply water into the tank; a coil that is provided inside the tank and circulates circulating water for heating the supply water in the tank; a hot water supply pipe that guides hot water which is the supply water heated in the tank to an outside of the tank; and a heat insulation material that covers an outer surface of the tank above a vicinity of a height of the outlet of the water supply pipe or a vicinity of a height of a lower end of the coil.

[0008] The hot water supply tank according to the embodiment of the present invention is preferably configured such that the heat insulation material covers at least a portion of the outer surface of the tank having a height equal to or greater than the height of the lower end of the coil.

[0009] The hot water supply tank according to the embodiment of the present invention is preferably configured such that the outlet of the water supply pipe is disposed below the lower end of the coil, and the heat insulation material has a lower end on the outer surface of the tank in a range equal to or greater than the height of the outlet of the water pipe and below the height of the lower end of the coil.

[0010] The hot water supply tank according to the embodiment of the present invention is preferably configured such that the tank is a cylindrical tank extending in an up-down direction and including an upper mirror plate disposed on an upper side, a lower mirror plate disposed on a lower side, and a cylindrical body portion connecting the upper mirror plate and the lower mirror plate. The hot water supply tank according to the embodiment of the present invention is preferably configured such that the outlet of the water supply pipe is disposed below an upper end of the lower mirror plate. The hot water supply tank according to the embodiment of the present invention is preferably configured such that the heat insulation material covers all or a part of the body portion.

[0011] The hot water supply tank according to the embodiment of the present invention is preferably configured such that an upper portion of the heat insulation material has higher heat insulation performance than a lower portion of the heat insulation material.

[0012] The hot water supply tank according to the embodiment of the present invention is preferably configured such that a material of the upper portion has higher heat insulation performance than a material of the lower portion, and a thickness of the heat insulation material is substantially a same in the upper and lower portions.

[0013] The hot water supply tank according to the embodiment of the present invention is preferably configured such that a thickness of the upper portion is thicker than a thickness of the lower portion, and a material of the heat insulation material is substantially a same in the upper and lower portions.

[0014] The hot water supply tank according to the embodiment of the present invention is preferably configured such that the hot water supply tank further includes a temperature sensor that measures a representative value of a temperature of the hot water in the tank, and a height of a switching portion of the heat insulation performance of the heat insulation material is substantially a same as a height at which the temperature sensor is installed.

[0015] A hot water supply tank unit according to an embodiment of the present invention includes the hot water supply tank, and a water heat exchanger that heats the circulating water with a circulating refrigerant.

[0016] The hot water supply tank unit according to the embodiment of the present invention preferably further includes: a housing that has a bottom plate and accommodates the hot water supply tank; a leg portion provided on a bottom surface of the tank; and a fixing member that fixes the leg portion to the bottom plate.

[0017] A hot water supply tank unit according to an embodiment of the present invention includes: the hot water supply tank; a water heat exchanger that heats the circulating water with a circulating refrigerant; a housing that has a bottom plate and accommodates the hot water supply tank; a leg portion that is provided on a bottom surface of the lower mirror plate; and a fixing member that fixes the leg portion to the bottom plate.

[0018] A heat pump water heater according to an embodiment of the present invention includes the hot water supply tank unit, and a refrigeration circuit that circulates the refrigerant to the water heat exchanger.EFFECTS OF INVENTION

[0019] The present invention can provide a hot water supply tank, a hot water supply tank unit, and a heat pump water heater that can favorably suppress heat dissipation of heated supply water, i.e., hot water, so as to match the temperature distribution of the supply water that collects in a tank, are excellent in controlling the costs of raw materials of the insulation material, and facilitate the manufacturability of the device, the workability of device installation, and the maintainability of the device.BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a system configuration diagram of a heat pump water heater according to an embodiment of the present invention. Fig. 2 is a perspective view of a hot water supply tank unit according to the embodiment of the present invention. Fig. 3 is a side view a lower portion of the hot water supply tank unit according to the embodiment of the present invention. Fig. 4 is a schematic longitudinal sectional view of a hot water supply tank according to the embodiment of the present invention. Fig. 5 is a schematic planar sectional view of the hot water supply tank according to the embodiment of the present invention. Fig. 6 is a schematic sectional view of a second aspect of the hot water supply tank according to the embodiment of the present invention. Fig. 7 is a schematic sectional view of a third aspect of the hot water supply tank according to the embodiment of the present invention. DETAILED DESCRIPTION

[0021] Embodiments of a hot water supply tank, a hot water supply tank unit, and a heat pump water heater according to the present invention will be described with reference to Fig. 1 to Fig. 7. The same reference signs are given to identical or equivalent components in each figure.

[0022] As illustrated in Fig. 1, a heat pump water heater 1 according to the present embodiment heats supply water supplied from the outside using the heat of outside air, and supplies the hot water to the outside. Note that the supply water supplied from the outside is generally tap water supplied through water pipes.

[0023] The heat pump water heater 1 includes: an outdoor unit 2 that serves as a heat source unit for exchanging heat between outdoor air and a refrigerant; a hot water supply tank unit 3 that exchanges heat between circulating water as a use-side heat medium and the refrigerant to exchange heat between the circulating water and supply water and heat the supply water to boiling point; a remote controller 5 as an input device that accepts operations from the user; and a control unit 6 that controls the outdoor unit 2 and the hot water supply tank unit 3 on the basis of the operations input to the remote controller 5. Note that the circulating water which is the use-side heat medium is not limited to water, and may be other heat mediums such as antifreeze.

[0024] The heat pump water heater 1 circulates the refrigerant between the outdoor unit 2 and the hot water supply tank unit 3, exchanges heat between the refrigerant and the circulating water in a water heat exchanger 11 in the hot water supply tank unit 3, and exchanges heat between the circulating water and the supply water in a hot water supply tank 12 in the hot water supply tank unit 3.

[0025] The water circulating inside the hot water supply tank unit 3 is used for heating, so-called boiling up, of the supply water stored in the hot water supply tank 12. The supply water heated in the hot water supply tank 12, i.e., hot water is supplied to hot water supply destinations, such as the washroom, the kitchen, and the bathroom.

[0026] The outdoor unit 2 is installed outside and the hot water supply tank unit 3 is installed inside. The outdoor unit 2 and the hot water supply tank unit 3 are connected by crossover pipes 17 and 18 that refrigerant piping 13 includes and communication lines (not illustrated). That is, only the refrigerant flows between the outdoor unit 2 and the hot water supply tank unit 3, so that the heat pump water heater 1 does not need piping for water supply outside. Accordingly, the heat pump water heater 1 can avoid freezing water in outdoor piping for water supply during low temperatures in winter.

[0027] Note that the heat pump water heater 1 may be configured to heat circulating water and circulate the circulating water of a first temperature such as 40 to 50 degrees Celsius to an outside device without passing through the hot water supply tank 12. The outside device is, for example, a radiator (heat exchanger) for an underfloor heating system or a radiator for an air conditioning system. The first temperature depends on the type of the refrigerant. In a case of circulating R410A refrigerant between the outdoor unit 2 and the hot water supply tank unit 3, the first temperature reaches a maximum of around 55 degrees Celsius. If R32 refrigerant or CO2 refrigerant is used, the first temperature can be raised even higher.

[0028] The heat pump water heater 1 may be configured to heat supply water to a second temperature higher than the first temperature, such as around 70 degrees Celsius, by using a combination of heat exchange between the refrigerant and circulating water in the water heat exchanger 11 and heating of the supply water by a backup heater (not illustrated) installed in the hot water supply tank 12, and store the hot water in the hot water supply tank 12.

[0029] The heat pump water heater 1 includes a refrigeration circuit 21. The heat source of the refrigeration circuit 21 is outside air. The refrigeration circuit 21 includes a compressor 22 that compresses and discharges a refrigerant, an air heat exchanger 23 that serves as an evaporator, an expansion valve 25, the water heat exchanger 11 that serves as a condenser, and the refrigerant piping 13 that connects the compressor 22, the air heat exchanger 23, the expansion valve 25, and the water heat exchanger 11 to circulate the refrigerant. The water heat exchanger 11 is a plate-type heat exchanger or a heat exchanger with double pipes that conducts heat exchange between the refrigerant and circulating water, for example. The refrigeration circuit 21 transfers heat from the air heat exchanger 23, which is a low-temperature part, to the water heat exchanger 11, which is a high-temperature part, by means of the circulating refrigerant. The refrigeration circuit 21 heats circulating water by the heat of the high-temperature refrigerant circulating through the water heat exchanger 11.

[0030] The refrigeration circuit 21 includes: a four-way valve 26 that sends the refrigerant discharged from the compressor 22 to one of the air heat exchanger 23 and the water heat exchanger 11, and then sends the refrigerant that has passed through the other of the air heat exchanger 23 and the water heat exchanger 11 back to the compressor 22; and an accumulator 27 provided in the refrigerant piping 13 between the four-way valve 26 and the compressor 22.

[0031] The water heat exchanger 11 and a part of the refrigerant piping 13 are accommodated in the hot water supply tank unit 3. Other components of the refrigeration circuit 21 are accommodated in the outdoor unit 2.

[0032] In a case where circulating water is heated by the refrigeration circuit 21, the air heat exchanger 23 functions as an evaporator (also referred to as "heat absorber"), and the water heat exchanger 11 functions as a condenser (also referred to as "radiator").

[0033] The compressor 22 compresses the refrigerant, increases the pressure, and discharges it. It is preferable that the compressor 22 can change its operating frequency using known inverter control. Increasing the speed of the compressor 22 increases the amount of heat transferred to the high-temperature part, and decreasing the speed of the compressor 22 decreases the amount of heat transferred to the high-temperature part.

[0034] As the expansion valve 25, for example, an electronically controlled expansion valve (pulse motor valve, PMV) that can adjust the valve opening is used.

[0035] The refrigerant piping 13 connects the compressor 22, the accumulator 27, the four-way valve 26, the air heat exchanger 23, the expansion valve 25, and the water heat exchanger 11.

[0036] The four-way valve 26 switches the direction of flow of the refrigerant circulating through the compressor 22, the air heat exchanger 23, the expansion valve 25, and the water heat exchanger 11. In the case where circulating water is heated by the refrigeration circuit 21, the four-way valve 26 circulates the refrigerant discharged from the compressor 22 in the order of the water heat exchanger 11, the expansion valve 25, and the air heat exchanger 23 (flow of refrigerant indicated by solid line in Fig. 1).

[0037] When heating the circulating water, the refrigeration circuit 21 that is a refrigeration cycle discharges a compressed high-temperature high-pressure refrigerant from the compressor 22. The refrigerant is sent to the hot water supply tank unit 3 through the four-way valve 26 and the crossover pipe 17 to enter the water heat exchanger 11. The water heat exchanger 11 heats the circulating water passing through the water heat exchanger 11 with the refrigerant passing through the water heat exchanger 11. In the water heat exchanger 11, the circulating water is heated, and the refrigerant is cooled and becomes a high-pressure liquid state. That is, when heating the circulating water, the water heat exchanger 11 functions as a radiator. The refrigerant having passed through the water heat exchanger 11 returns to the outdoor unit 2 through the crossover pipe 18, passes through the expansion valve 25 to be decompressed and become a lowpressure gas-liquid two-phase refrigerant, and reaches the air heat exchanger 23. The air heat exchanger 23 is ventilated with outside air by a blower (not illustrated). This outside air heats the refrigerant flowing through the air heat exchanger 23. At this time, the air heat exchanger 23 functions as a heat absorber that evaporates the refrigerant and turns it into a gaseous state. The refrigerant having passed through the air heat exchanger 23 and become a gas is sucked into the compressor 22.

[0038] The outdoor air heat exchanger 23 frosts over on its surface when the outside temperature drops. Therefore, the refrigeration circuit 21 switches the direction of the flow of the refrigerant in the refrigerant piping 13 using the four-way valve 26 to perform defrosting. When performing defrosting, the heat pump water heater 1 reverses the four-way valve 26 to create a refrigerant flow in the opposite direction to the refrigerant flow that heats the circulating water in the refrigeration circuit 21. In the case of defrosting, the four-way valve 26 circulates the refrigerant discharged from the compressor 22 in the order of the air heat exchanger 23, the expansion valve 25, and the water heat exchanger 11 (flow of refrigerant indicated by broken line in Fig. 1).

[0039] When defrosting, the air heat exchanger 23 functions as a condenser, and the water heat exchanger 11 functions as an evaporator. The heat pump water heater 1 cools the circulating water by circulating the refrigerant in the same direction as defrosting, and takes heat from the supply water in the hot water supply tank 12. However, the frequency of defrosting is low, and the duration of defrosting is short, lasting only about 10 minutes. Accordingly, defrosting only slightly lowers the temperature of water stored in the hot water supply tank 12, and does not largely affect the use of hot water.

[0040] Next, the hot water supply tank unit 3 includes the water heat exchanger 11 that is a part of the refrigeration circuit 21 and heats circulating water with the circulating refrigerant, the hot water supply tank 12 that can store supply water, and a use-side heat medium circulation circuit 41 that circulates the circulating water heated by the water heat exchanger 11 between the water heat exchanger 11 and the hot water supply tank 12. The hot water supply tank unit 3 is also referred to as a water heat exchange unit (hydro unit).

[0041] The use-side heat medium circulation circuit 41 includes the use side of the water heat exchanger 11, a pump 42 that circulates circulating water, circulating water piping 43 that circulates the circulating water which is the use-side heat medium. The circulating water is circulated in one direction in the use-side heat medium circulation circuit 41.

[0042] The circulating water heated in the water heat exchanger 11 is sucked into the driving pump 42 and is discharged toward the hot water supply tank 12. The circulating water whose temperature has dropped after heating the supply water in the hot water supply tank 12 is returned to the water heat exchanger 11. The circulating water having returned to the water heat exchanger 11 is heated again by the refrigerant circulating through the refrigeration circuit 21. The circulating water heated by the water heat exchanger 11 is sucked into the pump 42 again.

[0043] The hot water supply tank 12 stores supply water heated and boiled up by the circulating water circulating through the use-side heat medium circulation circuit 41, that is, hot water, and supplies it to the user as required. The hot water supply tank 12 includes a stainless steel tank 51 that can store supply water, a water supply pipe 53 that has an outlet 52 disposed in a bottom portion inside the tank 51 and pours the supply water into the tank 51, a coil 55 provided in the tank 51 to circulate the circulating water that heats the supply water in the tank 51, a hot water supply pipe 56 that guides the hot water, which is the supply water that has been heated inside the tank 51, to the outside of the tank 51, and a heat insulation material 58 that covers most of an outer surface of the tank 51. The tank 51 is airtight, except for an opening portion of the hot water supply pipe 56 and an opening portion of the water supply pipe 53. When hot water is used at the hot water supply destination which is connected to the hot water supply pipe 56, in the hot water supply tank 12, supply water is fed into the tank 51 from the water supply pipe 53 to replenish the amount of hot water supplied. As a result, the tank 51 is filled with water. The hot water supply pipe 56 that supplies the hot water in the tank 51 to the outside is provided in a top portion of the tank 51. In general, the hot water supply tank 12 supplies hot water from the tank 51 to the outside by the water pressure of tap water acting on a water pipe, which is the connection destination, of the water supply pipe 53. For this reason, the same amount of water as that supplied to the outside via the hot water supply pipe 56 is supplied from the water supply pipe 53 into the tank 51.

[0044] The hot water supply tank 12 also includes a temperature sensor 59 that measures the representative value of the temperature of the hot water in the tank 51. The output of the temperature sensor 59 is input to the control unit 6.

[0045] Although not illustrated, the heat pump water heater 1 includes, in addition to the temperature sensor 59, sensors including various temperature sensors necessary for controlling operation of the refrigeration circuit 21 and boiling up the hot water in the hot water supply tank 12.

[0046] The circulating water piping 43 includes an outgoing pipe 61 that sends the circulating water heated in the water heat exchanger 11 to the coil 55 in the hot water supply tank 12, and a return pipe 62 that returns the circulating water whose temperature has dropped after heating the supply water in the tank 51 by the coil 55 from the hot water supply tank 12 to the water heat exchanger 11. The pump 42 is provided in the middle of the outgoing pipe 61. In a case where the circulating water is used in an outside device, the heated circulating water is sent to the outside device using piping that branches from the outgoing pipe 61 between the water heat exchanger 11 and the hot water supply tank 12. Then, the circulating water that has been used in the outside device is returned to the return pipe 62 between the hot water supply tank 12 and the water heat exchanger 11.

[0047] There is at least one remote controller 5. The remote controller 5 may include a remote controller provided in the hot water supply tank unit 3, for example, and a remote controller installed on an indoor wall surface, for example (not illustrated).

[0048] As illustrated in Fig. 2, the remote controller 5 provided in a front center portion of the hot water supply tank unit 3 is an input device into which a boiling up setting temperature of hot water in the hot water supply tank 12 can be input. In a case where the heat pump water heater 1 is configured to circulate circulating water to an outside device, the remote controller 5 can preferably receive input of the setting temperature of circulating water to be circulated to the outside device. The remote controller 5 transmits the boiling up setting temperature of hot water in the hot water supply tank 12 and the setting temperature of circulating water to be circulated to the outside device as a control signal to the control unit 6.

[0049] The control unit 6 includes a microprocessor (not illustrated), and a storage device (not illustrated) that stores various calculation programs executed by the microprocessor and parameters. The control unit 6 reads various control programs from an auxiliary storage device into a main storage device, and executes the various control programs read into the main storage device in a central processing unit.

[0050] The control unit 6 performs operation control of the heat pump water heater 1, including operation of the refrigeration circuit 21 and operation of the pump 42 of the use-side heat medium circulation circuit 41, on the basis of control signals received from the remote controller 5 via wired or wireless communication lines and the output of the sensors including the temperature sensor 59. For example, the control unit 6 performs operation control of the heat pump water heater 1 so that the measured temperature of the temperature sensor 59 is the boiling up setting temperature of hot water in the hot water supply tank 12.

[0051] In a case where the heat pump water heater 1 is configured to circulate circulating water to an outside device, the control unit 6 switches the circulating route of the circulating water to one of the hot water supply tank 12 and the outside device, or alternately switches the circulating route of the circulating water between the hot water supply tank 12 and the outside device, and balances the supply of the circulating water to the outside device with the boiling up of the hot water in the hot water supply tank 12. The remote controller 5 preferably includes a function of switching between these operational states.

[0052] As illustrated in Figs. 2 to 5, the tank 51 of the hot water supply tank 12 according to the present embodiment is a so-called cylindrical tank. For the sake of explanation, it is hereinafter assumed that the hot water supply tank 12 is installed with a center line C of the tank 51 erected in the up-down direction. In an installed state of the hot water supply tank 12, the extending direction of the center line C of the tank 51 substantially coincides with the height direction of the hot water supply tank 12.

[0053] As illustrated in Fig. 2, the hot water supply tank 12 is accommodated in the hot water supply tank unit 3 including a vertical rectangular housing 81. The housing 81 of the hot water supply tank unit 3 includes a bottom plate 82 in a bottom portion and a top plate 100 as a ceiling surface. The top plate 100 is fixed by four support pillars 101 rising from the four corners of the bottom plate 82. The four sides of the housing 81 are each covered with an outer plate 83, which is a flat sheetmetal panel. The outer plate 83 is fixed to the support pillar 10, the bottom plate 82, and the top plate 100 using fastening members such as screws. During maintenance and inspection, one or a plurality of screws fixing the outer plate 83 are removed, and the outer plate 83 is removed to allow inspection and confirmation operation to be carried out on the various devices inside the hot water supply tank unit 3. The tank 51 is fixed to the substantial center of the bottom plate 82 and accommodated in the hot water supply tank unit 3. Although not illustrated in Fig. 2, the water heat exchanger 11, the pump 42, and other pipes are accommodated above the tank 51 in the housing 81. A plurality of pipes penetrate through holes in the top plate 100 and protrude to the outside of the housing 81. Each pipe includes a connection port 103 exposed to the outside of the housing 81. The connection ports 103 are couplers that are connectable to a refrigeration cycle piping, an external water supply piping, and hot water piping. The hot water supply tank unit 3 is installed on an indoor floor or the like by four support legs 104 protruding downward from the four corners of the bottom plate 82. The hot water supply tank unit 3 is installed so that the bottom plate 82 is as horizontal as possible. For this reason, the support leg 104 may include a screw that can adjust the height in the up-down direction to keep the hot water supply tank unit 3 horizontal.

[0054] As illustrated in Fig. 4, the tank 51 includes a lower mirror plate 71 that is disposed on the lower side, an upper mirror plate 72 that is disposed on the upper side, and a cylindrical body portion 73 that connects the lower mirror plate 71 and the upper mirror plate 72. The lower mirror plate 71 has a downwardly protruding dome shape, the upper mirror plate 72 has an upwardly protruding dome shape, and the body portion 73 is a cylinder having a substantially uniform diameter and extending in the up-down direction. The center line C of the tank 51 substantially coincides with the center line of the body portion 73. The lower mirror plate 71, the upper mirror plate 72, and the body portion 73 are made of stainless steel. The thickness of the lower mirror plate 71, the thickness of the upper mirror plate 72, and the thickness of the body portion 73 are substantially the same. The border between the body portion 73 and the lower mirror plate 71 and the border between the body portion 73 and the upper mirror plate 72 are both welded in an airtight manner.

[0055] A plane that is perpendicular to the center line C of the hot water supply tank 12 is substantially the horizontal plane in the installed state of the hot water supply tank 12. The cross-sectional shape of the lower mirror plate 71, the upper mirror plate 72, and the body portion 73 on this plane is substantially circular. The diameter of an upper end 71u of the lower mirror plate 71 is the maximum diameter of the lower mirror plate 71, and the diameter of a lower end 72d of the upper mirror plate 72 is the maximum diameter of the upper mirror plate 72. The maximum diameter of the lower mirror plate 71, the maximum diameter of the upper mirror plate 72, and the diameter of the body portion 73 are substantially the same, and correspond to a diameter D of the tank 51.

[0056] In the height direction of the tank 51, the body portion 73 is longer than the lower mirror plate 71 and also longer than the upper mirror plate 72. A height H of the tank 51 is larger than the diameter D of the tank 51. In other words, the tank 51 is a vertical cylindrical tank.

[0057] The lower mirror plate 71 of the hot water supply tank 12 is fixed to the bottom plate 82 of the housing 81 of the hot water supply tank unit 3. Specifically, as illustrated in Fig. 4 and Fig. 2 in which a lower portion of the outer plate 83 of the housing 81 covering the hot water supply tank unit 3 is partially cut out to show the structure inside the hot water supply tank unit 3, the tank 51 includes a ring-shaped leg portion 75 having a smaller diameter than the maximum diameter of the lower mirror plate 71 and fixed to an outer surface of the lower mirror plate 71 which is a bottom surface of the tank 51. The leg portion 75 is welded to the lower mirror plate 71. As illustrated in Fig. 3 showing a lower structure of the hot water supply tank unit 3 from which the outer plate 83 of the housing 81 covering the hot water supply tank unit 3 is removed, the leg portion 75 attached to the lower mirror plate 71 is fixed to the bottom plate 82 of the housing 81 of the hot water supply tank unit 3 via a plurality of angle materials 78 having an L-shaped cross section and a plurality of fastening members 79 (fixing members) such as bolts. Note that the leg portion 75 may have a tongue piece corresponding to the angle material 78 as one body. That is, the angle material 78 may be omitted. In other words, the hot water supply tank unit 3 includes a plurality of fastening members 79 that fix the leg portion 75 to the bottom plate 82 of the housing 81.

[0058] The hot water supply tank 12 also includes the temperature sensor 59 that measures the representative value of the temperature of hot water in the tank 51. The output of the temperature sensor 59 is input to the control unit 6.

[0059] A tank upper structure will further be described with reference to the cross-sectional view of Fig. 5. Fig. 5 illustrates the cross-sectional shape of only the tank 51 and the heat insulation material 58 of the hot water supply tank 12, and illustrates non-cross-sectional shapes of other portions including the water supply pipe 53, the coil 55, and the hot water supply pipe 56. The water supply pipe 53 penetrates the upper mirror plate 72 in the up-down direction to enter the tank 51, extends downward inside the tank 51, and reaches the bottom portion inside the tank 51. The water supply pipe 53 has a curved portion 53a curving toward the center line C of the tank 51 inside the tank 51, and a straight portion 53b extending toward the lower side of the tank 51 at a position closer to the center line C of the tank 51 than the position where the water supply pipe 53 penetrates the upper mirror plate 72. The curved portion 53a is located above a spiral portion 55a where the coil 55 is wound in a spiral shape. The straight portion 53b passes through the inside of the spiral formed by the spiral portion 55a of the coil 55.

[0060] A lower end portion 53d of the water supply pipe 53 located in the bottom portion inside the tank 51 has the outlet 52 disposed in the bottom portion of the tank 51. The outlet 52 opens in a direction facing the lower mirror plate 71, i.e., opens downward. Therefore, supply water flowing out of the outlet 52 of the water supply pipe 53 flows into the tank 51 toward an inner surface (upper surface) of the lower mirror plate 71 which is a bottom surface inside the tank 51. The supply water flowing out of the outlet 52 of the water supply pipe 53 has a higher specific gravity than supply water heated in the tank 51, that is, hot water, and flows into the tank 51 so as to fill the bottom portion of the tank 51 which is a region BA below the outlet 52 of the water supply pipe 53.

[0061] Note that the region BA may be a part or all of the region defined in a bowl shape by the lower mirror plate 71. Alternatively, the region BA may be a part of a region defined in a columnar shape by the body portion 73 of the tank 51 and include a region adjacent to the lower mirror plate 71.

[0062] In the height direction of the tank 51, the outlet 52 of the water supply pipe 53 is disposed below a lower end 55d of the coil 55 through which circulating water flows. The outlet 52 of the water supply pipe 53 is disposed below the upper end 71u of the lower mirror plate 71. Accordingly, in the height direction of the tank 51, the region BA below the outlet 52 of the water supply pipe 53 is below the lower end 55d of the coil 55. Note that the lower end 55d of the coil 55 corresponds to the lowermost end of the spiral portion 55a of the coil 55.

[0063] The coil 55 has a circulating water introduction portion 55b that penetrates the upper mirror plate 72 in the up-down direction to enter the tank 51 and extends downward inside the tank 51 in a straight line, the spiral portion 55a that is wound in a spiral shape subsequent to the circulating water introduction portion 55b, and a circulating water returning portion 55c that extends upward inside the tank 51 in a straight line from the end of the spiral portion 55a and penetrates the upper mirror plate 72 in the up-down direction to protrude out of the tank 51. The spiral portion 55a extends toward the bottom portion of the tank 51 while spiraling along an inner peripheral surface of the body portion 73 away from the center line C of the tank 51. This spiral portion 55a increases the surface area of the coil 55, thereby increasing the amount of heat transferred between the circulating water flowing through coil 55 and the supply water in the tank 51. The gap between the spiral portion 55a and the inner peripheral surface of the body portion 73 is separated to the extent that it does not interfere with the natural convection of the supply water boiled up in the tank 51, i.e., hot water. As illustrated in Fig. 5, the spiral portion 55a is fixed to the inner peripheral surface of the body portion 73 by an appropriate number of clamps 74. The circulating water introduction portion 55b is disposed directly above the spiral portion 55a and is connected to the spiral portion 55a. The position where the circulating water introduction portion 55b penetrates the upper mirror plate 72 is directly above the spiral portion 55a. The circulating water returning portion 55c bends upward at the lowermost end of the spiral portion 55a and extends toward the upper mirror plate 72 so as to pass through the inside of the spiral portion 55a. The position where the circulating water returning portion 55c penetrates the upper mirror plate 72 is closer to the center line C of the tank 51 than the circulating water introduction portion 55b or the spiral portion 55a.

[0064] The hot water supply pipe 56 protrudes upward from the upper mirror plate 72. The hot water supply pipe 56 is closer to the center line C of the tank 51 than the water supply pipe 53, and is disposed so that the distance between the circulating water returning portion 55c and the center line C of the tank 51 and the distance between the hot water supply pipe 56 and the center line C of the tank 51 are substantially the same, for example. The hot water supply pipe 56 is a short piping, and an opening portion 56a of the hot water supply pipe 56 located inside the tank 51 opens in an upper portion of the tank 51. Therefore, high-temperature water in the upper portion inside the tank 51 is supplied to the outside device.

[0065] The temperature sensor 59 is provided inside a thin cylindrical temperature sensor holder 86 protruding downward from the upper mirror plate 72. The temperature sensor holder 86 extends downwards from the upper mirror plate 72 toward a part suitable for measuring the temperature of hot water inside the tank 51 such as a center portion of the tank 51. An inner peripheral surface of the temperature sensor holder 86 is connected to the outer surface of the tank 51, and an outer peripheral surface of the temperature sensor holder 86 is connected to the inner surface of the tank 51. The temperature sensor 59 is adhered to the inner surface of the temperature sensor holder 86, and measures the temperature of hot water transmitted from the outer surface of the temperature sensor holder 86 to the inner surface of the temperature sensor holder 86.

[0066] The heat insulation material 58 prevents the temperature of hot water in the tank 51 from dropping by reducing direct heat dissipation from the hot water supply tank 12 to the atmosphere. The heat insulation material 58 is either expanded polystyrene or expanded polyurethane, which has better heat insulation performance than expanded polystyrene. Vacuum heat insulation material, which has even better heat insulation performance, can also be used.

[0067] The heat insulation material 58 has a middle heat insulation portion 91 that mainly covers all or a part of the body portion 73, and an upper heat insulation portion 92 that covers the upper mirror plate 72.

[0068] The middle heat insulation portion 91 is obtained by filling a space between a mold disposed around the body portion 73 with a gap therebetween and the body portion 73 with foam insulation material before foaming, and foaming and hardening it. The material is brought into contact with and adhered to the outer surface of the body portion 73 without any gaps. After the foam insulation material has hardened, the middle heat insulation portion 91 is removed from the mold. The middle heat insulation portion 91 covers the outer shape of the columnar body portion 73 in a cylindrical shape. Note that the middle heat insulation portion 91 may be obtained by combining and integrating a plurality of members.

[0069] The upper heat insulation portion 92 covers the upper mirror plate 72 of the tank 51 from above, and is combined with the middle heat insulation portion 91 while being brought into contact with the upper mirror plate 72 and the middle heat insulation portion 91 without any gaps. The upper heat insulation portion 92 has a plurality of through holes in which the water supply pipe 53, the circulating water introduction portion 55b and the circulating water returning portion 55c of the coil 55, and the hot water supply pipe 56 are disposed. The upper heat insulation portion 92 is obtained by filling a mold that combines a male mold (core) and a female mold (cavity) with foam insulation material before foaming, then releasing it from the mold after foaming and hardening. That is, the heat insulation material 58 is a combination of the middle heat insulation portion 91 integrated with the tank 51 and the foamed and hardened upper heat insulation portion 92. Note that the upper heat insulation portion 92 may be obtained by combining a plurality of members.

[0070] Incidentally, in the tank 51, the supply water heated by circulating water moves to the upper side of the tank 51 by natural convection of the supply water. That is, high-temperature hot water collects in a center portion and upper portion above the center portion of the tank 51, and low-temperature supply water before being boiled up to hot water collects in a lower portion below the center portion of the tank 51. Supply water before being boiled up to hot water is generally tap water. Therefore, low-temperature tap water before heating having flowed in from the water supply pipe 53 concentrate in the region BA of the bottom portion of the tank 51. The low-temperature supply water collected in a lower portion of the tank 51 is not affected by natural convection of supply water in the tank 51 heated by circulating water, and the temperature of the supply water in the region BA is kept at a low temperature closest to the temperature of the atmosphere in the supply water in the tank 51.

[0071] Hence, the heat insulation material 58 of the hot water supply tank 12 according to the present embodiment covers the outer surface of the tank 51 above the vicinity of a height h1 of the outlet 52 of the water supply pipe 53 or the vicinity of a height h2 of the lower end 55d of the coil 55. The heat insulation material 58 only needs to cover at least a portion 51a having a height equal to greater than the height h2 of the lower end 55d of the coil 55 of the outer surface of the tank 51. That is, the vicinity of the height h1 of the outlet 52 of the water supply pipe 53 and the vicinity of the height h2 of the lower end 55d of the coil 55 only need to include at least a height equal to or greater than the height h2 of the lower end 55d of the coil 55 and include a region having a height equal to or greater than a height position where supply water in the tank 51 is thermally affected by circulating water circulating through the coil 55 and having a higher temperature than the supply water in the region BA. That is, the heat insulation material 58 may have its lower end located at a height equal to or greater than the height h1 of the outlet 52 of the water supply pipe 53 and lower than the height h2 of the lower end 55d of the coil 55 on the outer surface of the tank 51. Note that the height h1 of the outlet 52 of the water supply pipe 53 and the height h2 of the lower end 55d of the coil 55 may be based on an installation surface IL of the leg portion 75 of the hot water supply tank 12, or may be based on a ground surface GL on which the hot water supply tank unit 3 is installed.

[0072] Note that for the sake of explanation, the region having a height equal to or greater than a height position where supply water in the tank 51 is thermally affected by circulating water circulating through the coil 55 is hereinafter referred to as "boiling up region BoA".

[0073] In other words, the heat insulation material 58 does not cover the outer surface of the tank 51 below the boiling up region BoA. That is, the hot water supply tank 12 has an uninsulated portion 95 where the heat insulation material 58 is not provided below the boiling up region BoA. The uninsulated portion 95 is mainly all or a part of the outer surface of the lower mirror plate 71. From the perspective of manufacturability, it is desirable to cover the entire body portion 73 with the heat insulation material 58, and to make the entire lower mirror plate 71 an uninsulated portion 95 with no insulation material 58 on the outside.

[0074] The temperature of the uninsulated portion 95 is closer to the temperature of supply water flowing in from the water supply pipe 53 (temperature of tap water) or the temperature of the atmosphere than that of other portions of the tank 51. Therefore, there is almost no heat dissipation from the uninsulated portion 95 to the outside of the tank 51. Accordingly, the temperature drop in the hot water stored in the hot water supply tank 12 due to the uninsulated portion 95 is small enough to be almost negligible.

[0075] Note that in the height direction of the tank 51, the outlet 52 of the water supply pipe 53 may be disposed above the lower end 55d of the coil 55. In other words, the outlet 52 of the water supply pipe 53 may be disposed in the boiling up region BoA. In this case, in the height direction of the tank 51, the lower end 55d of the coil 55 enters the region BA below the outlet 52 of the water supply pipe 53, and a part of the coil 55 overlaps the region BA. The heat insulation material 58 only needs to cover the outer surface of the tank 51 above the vicinity of the height h2 of the lower end 55d of the coil 55 including the height h1 of the outlet 52 of the water supply pipe 53. Of the outer surface of the tank 51, the heat insulation material 58 only needs to cover at least the portion 51a having a heigh equal to or greater than the height h2 of the lower end 55d of the coil 55.

[0076] As described above, the hot water supply tank 12 according to the present embodiment includes the heat insulation material 58 that covers the outer surface of the tank 51 in the vicinity of the height h1 of the outlet 52 of the water supply pipe 53 or above the vicinity of the height h2 of the lower end 55d of the coil 55. The hot water supply tank 12 has the uninsulated portion 95 where the heat insulation material 58 is not provided below the heat insulation material 58. That is, the hot water supply tank 12 covers, with the heat insulation material 58, the outer surface of the tank 51 of a portion which may lower the temperature of hot water boiled up by circulating water passing through the hot water supply tank 12, but does not cover, with the heat insulation material 58, the outer surface of the tank 51 of a portion where supply water before heating and flowing into the tank 51 from the water supply pipe 53 concentrates.

[0077] Thus, the hot water supply tank 12 according to the present embodiment can reduce the use amount of the heat insulation material 58 as compared to the conventional hot water supply tank that covers the entire outer surface of the tank 51 with the heat insulation material 58. The insulation material that can be reduced in the hot water supply tank 12 according to the present embodiment corresponds to the insulating member covering the lower mirror plate in the conventional hot water supply tank. The heat insulation member to be reduced is obtained by filling a mold with foam insulation material before foaming, and foaming and hardening it to remove it from the mold as in the upper heat insulation portion 92 according to the present embodiment. Thus, the hot water supply tank 12 according to the present embodiment not only can simply reduce the insulating member covering the lower mirror plate 71, but can also eliminate the processes of designing and manufacturing the mold for manufacturing the insulating member covering the lower mirror plate 71, and manufacturing the insulating member covering the lower mirror plate 71 using the mold.

[0078] In the hot water supply tank 12 according to the present embodiment, the volume around the lower mirror plate 71 is not occupied by the insulating member covering the lower mirror plate 71, so that the leg portion 75, the angle material 78, and the fastening member 79 provided in this part and supporting the tank 51 can be viewed more clearly. Thus, the hot water supply tank 12 can improve the workability in the assembly process of the hot water supply tank unit 3 and enhance the manufacturability of the hot water supply tank unit 3. The hot water supply tank 12 according to the present embodiment can also improve maintainability in a lower space of the tank 51 after installation.

[0079] The hot water supply tank 12 according to the present embodiment further includes the heat insulation material 58 that covers at least the portion 51a of the outer surface of the tank 51 having a height equal to or greater than the height of the lower end 55d of the coil 55. Therefore, the hot water supply tank 12 is not only advantageous in including the uninsulated portion 95, but can also reliably prevent a temperature drop in supply water heated by circulating water.

[0080] In a case where the outlet 52 of the water supply pipe 53 is disposed below the lower end 55d of the coil 55, the hot water supply tank 12 according to the present embodiment only needs to have the heat insulation material 58 having the lower end in a position equal to or greater than the height of the outlet 52 of the water supply pipe 53 and below the height of the lower end 55d of the coil 55. Thus, the hot water supply tank 12 can increase the freedom of the range of the uninsulated portion 95.

[0081] The hot water supply tank 12 according to the present embodiment only needs to include the cylindrical tank 51, the water supply pipe 53 that has the outlet 52 disposed below the uppermost end 71u of the lower mirror plate 71 of the tank 51, and the heat insulation material 58 that covers all or some of the body portion 73. In this case, the hot water supply tank 12 according to the present embodiment can improve the manufacturability of the middle heat insulation portion 91 which is a part of the heat insulation material 58 even more.

[0082] Next, another aspect of the hot water supply tank 12 according to the present embodiment will be described. Note that in hot water supply tanks 12A and 12B illustrated in each aspect, the same configuration as the hot water supply tank 12 of the first aspect is assigned the same reference signs and overlapping description is omitted.

[0083] Fig. 6 is a schematic sectional view of a second aspect of the hot water supply tank according to the embodiment of the present invention.

[0084] As illustrated in Fig. 6, a hot water supply tank 12A of a second aspect according to the embodiment of the present invention (hereinafter simply referred to as "hot water supply tank 12A") includes a heat insulation material 58A of the second example (hereinafter simply referred to as "heat insulation material 58A"). The heat insulation material 58A is a combination of a middle heat insulation portion 91A and an upper heat insulation portion 92.

[0085] An upper portion 91u of the middle heat insulation portion 91A has higher heat insulation performance than a lower portion 91d of the middle heat insulation portion 91A. For example, the material of the lower portion 91d of the middle heat insulation portion 91A is expanded polystyrene, while the material of the upper portion 91u of the middle heat insulation portion 91A is expanded polyurethane, which has better heat insulation performance than expanded polystyrene. The thickness of the upper portion 91u of the middle heat insulation portion 91A and the thickness of the lower portion 91d of the middle heat insulation portion 91A are substantially the same. Therefore, the outer diameter of the upper portion 91u and the outer diameter of the lower portion 91d of the middle heat insulation portion 91A are the same, and the diameter of the hot water supply tank 12A in an upper portion of the body portion 73 of the tank 51 and the diameter of the hot water supply tank 12A in a lower portion of the body portion 73 of the tank 51 are the same.

[0086] A height hc of a switching portion 96 of the heat insulation performance of the middle heat insulation portion 91A is substantially the same as the height at which a temperature sensor 59 is installed. That is, the height hc of the switching portion 96 between the upper portion 91u and the lower portion 91d of the middle heat insulation portion 91A is substantially the same as the height at which the temperature sensor 59 is installed. The height hc of the switching portion 96 may be lower than the height at which the temperature sensor 59 is installed.

[0087] Note that the material of the upper heat insulation portion 92 is preferably the same as the material of the upper portion 91u of the middle heat insulation portion 91A. The thickness of the upper heat insulation portion 92 and the thickness of the upper portion 91u of the middle heat insulation portion 91A may be substantially the same. Alternatively, the thicknesses of the upper heat insulation portion 92 and the portion in the vicinity of the border with the middle heat insulation portion 91A may be the same, while the thickness of other portions of the upper heat insulation portion 92, such as the thickness of a top portion may be thicker than the thickness of the middle heat insulation portion 91A.

[0088] As described above, the heat insulation performance of an upper portion 58u of the heat insulation material 58A of the hot water supply tank 12A according to the present embodiment is higher than the heat insulation performance of a lower portion did of the heat insulation material 58A.

[0089] High-temperature hot water collects in a center portion and upper portion above the center portion of the tank 51, and low-temperature supply water before being boiled up to hot water collects in a lower portion of the tank 51 below the center portion thereof. That is, the amount of heat dissipation in the lower portion of the tank 51 is smaller than the amount of heat dissipation in the center portion and upper portion of the tank 51. Therefore, the hot water supply tank 12A can impart heat insulation performance suitable for the amount of heat dissipation of the outer surface of the tank 51 in the up-down direction to the heat insulation material 58A and suppress the cost of the entire heat insulation material 58A. Specifically, the cost of the entire heat insulation material 58A is suppressed by using an expensive material with excellent heat insulation performance for the upper portion 58u of the heat insulation material 58A requiring high heat insulation performance, while using an inexpensive material with lower heat insulation performance for the lower portion 58d of the heat insulation material 58A not requiring high insulation performance.

[0090] The hot water supply tank 12A according to the present embodiment also imparts heat insulation performance suitable for the amount of heat dissipation of the outer surface of the tank 51 in the up-down direction to the heat insulation material 58 having substantially the same thickness. Therefore, the hot water supply tank 12A does not waste the storage volume of the housing 81 of the hot water supply tank unit 3, especially the footprint (downward projection area of housing 81) of the housing 81.

[0091] Fig. 7 is a schematic sectional view of a third aspect of the hot water supply tank according to the embodiment of the present invention.

[0092] As illustrated in Fig. 7, a hot water supply tank 12B of a third aspect according to the embodiment of the present invention (hereinafter simply referred to as "hot water supply tank 12B") includes a heat insulation material 58B of the third aspect (hereinafter simply referred to as "heat insulation material 58B"). The heat insulation material 58B is a combination of a middle heat insulation portion 91B and an upper heat insulation portion 92.

[0093] The thickness of an upper portion 91u of the middle heat insulation portion 91B is thicker than the thickness of a lower portion 91d of the middle heat insulation portion 91B. Therefore, the outer diameter of the upper portion 91u of the middle heat insulation portion 91B is larger than the outer diameter of the lower portion 91d of the middle heat insulation portion 91B, and the diameter of the hot water supply tank 12B in an upper portion of a body portion 73 of a tank 51 is larger than the diameter of the hot water supply tank 12B in a lower portion of the body portion 73 of the tank 51. The material of the upper portion 91u of the middle heat insulation portion 91B is the same as the material of the lower portion 91d of the middle heat insulation portion 91B.

[0094] A height hc of a switching portion 96 of the thickness of the middle heat insulation portion 91B, that is, the height hc of the switching portion 96 of heat insulation performance is substantially the same as the height at which a temperature sensor 59 is installed. That is, the height hc of the switching portion 96 between the upper portion 91u and the lower portion 91d of the middle heat insulation portion 91B is substantially the same as the height at which the temperature sensor 59 is installed. The height hc of the switching portion 96 may be lower than the height at which the temperature sensor 59 is installed.

[0095] Note that the material of the upper heat insulation portion 92 may be the same as the material of the middle heat insulation portion 91B, or may be a material having higher heat insulation performance than the material of the middle heat insulation portion 91B. The thickness of the upper heat insulation portion 92 and the thickness of the upper portion 91u of the middle heat insulation portion 91B may be substantially the same. Alternatively, the thicknesses of the upper heat insulation portion 92 and a portion in the vicinity of the border with the middle heat insulation portion 91B may be the same, while the thickness of other portions of the upper heat insulation portion 92, such as the thickness of a top portion may be thicker than the thickness of the middle heat insulation portion 91B.

[0096] As described above, the heat insulation performance of an upper portion 58u of the heat insulation material 58B of the hot water supply tank 12B according to the present embodiment is higher than the heat insulation performance of a lower portion 58d of the heat insulation material 58B. Therefore, the hot water supply tank 12B can impart heat insulation performance suitable for the amount of heat dissipation of the outer surface of the tank 51 in the up-down direction to the heat insulation material 58B and suppress the cost of the entire heat insulation material 58B. Specifically, the cost of the entire heat insulation material 58B is suppressed by reducing the material of the lower portion 58d of the heat insulation material 58B not requiring high heat insulation performance as compared to the upper portion 58u of the heat insulation material 58B requiring high heat insulation performance.

[0097] The hot water supply tank 12B according to the present embodiment can secure a gap between the lower portion 58d of the heat insulation material 58B and an outer plate 83 of a housing 81, with respect to the storage volume of the housing 81 of the hot water supply tank unit 3, especially the footprint of the housing 81. This gap creates a space for installing piping and wiring inside the hot water supply tank unit 3, improving workability during the assembly process.

[0098] The height hc of the switching portion 96 of heat insulation performance of the heat insulation materials 58A and 58B of the hot water supply tank 12A of the second aspect and the hot water supply tank 12B of the third aspect according to the present embodiment is substantially the same as the height at which the temperature sensor 59 is installed. Therefore, the hot water supply tanks 12A and 12B can measure the temperature of hot water in the tank 51 accurately, and even if it has the uninsulated portions 95 of the heat insulation materials 58A and 58B, it can boil up the supply water to the boiling up setting temperature in the same way as the conventional hot water supply tank that covers the entire tank 51 with heat insulation material.

[0099] Hence, according to the hot water supply tanks 12, 12A, and 12B , the hot water supply tank unit 3 including any one of the hot water supply tanks 12, 12A, and 12B, and the heat pump water heater 1 including this hot water supply tank unit 3 of the present embodiment, it is possible to favorably suppress heat dissipation of supply water heated so as to match the temperature distribution of supply water stored in the tank 51, i.e., hot water, achieve control of the costs of raw materials of the heat insulation materials 58, 58A, and 58B, and facilitate the manufacturability of the device, the workability of device installation, and the maintainability of the device.

[0100] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.REFERENCE SIGNS LIST

[0101] 1... heat pump water heater, 2... outdoor unit, 3... hot water supply tank unit, 5... remote controller, 6... control unit, 11... water heat exchanger, 12, 12A, 12B... hot water supply tank, 13... refrigerant piping, 17, 18... crossover pipe, 21... refrigeration circuit, 22... compressor, 23... air heat exchanger, 25...expansion valve, 26... four-way valve, 27... accumulator, 41... use-side heat medium circulation circuit, 42...pump, 43... circulating water piping, 51... tank, 51a... portion equal to or higher than lower end of coil, 52... outlet, 53... water supply pipe, 53a... curved portion, 53b... straight portion, 53d... lower end portion, 55... coil, 55a... spiral portion, 55b... circulating water introduction portion, 55c... circulating water returning portion, 55d... lower end of coil, 56... hot water supply pipe, 58, 58A, 58B... heat insulation material, 58u... upper portion of heat insulation material, 58d... lower portion of heat insulation material, 59... temperature sensor, 61... outgoing pipe, 62... return pipe, 71... lower mirror plate, 71u... upper end of lower mirror plate, 72... upper mirror plate, 72d... lower end of upper mirror plate, 73... body portion, 74... clamp, 75... leg portion, 78... angle material, 79... fastening member (fixing member), 81... housing, 82... bottom plate, 83... outer plate, 86... temperature sensor holder, 91, 91A, 91B... middle heat insulation portion, 92... upper heat insulation portion, 95... uninsulated portion, 96... switching portion of heat insulation performance, 100... top plate, 101... support pillar.

Claims

1. A hot water supply tank comprising: a tank that can store supply water; a water supply pipe that has an outlet disposed in a bottom portion inside the tank and pours the supply water into the tank; a coil that is provided inside the tank and circulates circulating water for heating the supply water in the tank; a hot water supply pipe that guides hot water which is the supply water heated in the tank to an outside of the tank; and a heat insulation material that covers an outer surface of the tank above a vicinity of a height of the outlet of the water supply pipe or a vicinity of a height of a lower end of the coil.

2. The hot water supply tank according to claim 1, wherein the heat insulation material covers at least a portion of the outer surface of the tank having a height equal to or greater than the height of the lower end of the coil.

3. The hot water supply tank according to claim 2, wherein the outlet of the water supply pipe is disposed below the lower end of the coil, and the heat insulation material has a lower end on the outer surface of the tank in a range equal to or greater than the height of the outlet of the water supply pipe and below the height of the lower end of the coil.

4. The hot water supply tank according to any one of claims 1 to 3, wherein: the tank is a cylindrical tank extending in an up-down direction and including an upper mirror plate disposed on an upper side, a lower mirror plate disposed on a lower side, and a cylindrical body portion connecting the upper mirror plate and the lower mirror plate; the outlet of the water supply pipe is disposed below an upper end of the lower mirror plate; and the heat insulation material covers all or a part of the body portion.

5. The hot water supply tank according to any one of claims 1 to 4, wherein an upper portion of the heat insulation material has higher heat insulation performance than a lower portion of the heat insulation material.

6. The hot water supply tank according to claim 5, wherein a material of the upper portion has higher heat insulation performance than a material of the lower portion, and a thickness of the heat insulation material is substantially a same in the upper and lower portions.

7. The hot water supply tank according to claim 5, wherein a thickness of the upper portion is thicker than a thickness of the lower portion, and a material of the heat insulation material is substantially a same in the upper and lower portions.

8. The hot water supply tank according to any one of claims 5 to 7, further comprising a temperature sensor that measures a representative value of a temperature of the hot water in the tank, wherein a height of a switching portion of the heat insulation performance of the heat insulation material is substantially a same as a height at which the temperature sensor is installed.

9. A hot water supply tank unit comprising the hot water supply tank according to any one of claims 1 to 8, and a water heat exchanger that heats the circulating water with a circulating refrigerant.

10. The hot water supply tank unit according to claim 9, further comprising: a housing that has a bottom plate and accommodates the hot water supply tank; a leg portion provided on a bottom surface of the tank; and a fixing member that fixes the leg portion to the bottom plate.

11. A hot water supply tank unit comprising: the hot water supply tank according to claim 4; a water heat exchanger that heats the circulating water with a circulating refrigerant; a housing that has a bottom plate and accommodates the hot water supply tank; a leg portion provided on a bottom surface of the lower mirror plate; and a fixing member that fixes the leg portion to the bottom plate.

12. A heat pump water heater comprising the hot water supply tank unit according to any one of claims 9 to 11, and a refrigeration circuit that circulates the refrigerant to the water heat exchanger.

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