EP2778562B1

EP2778562B1 - Water heater

Info

Publication number: EP2778562B1
Application number: EP14158078.7A
Authority: EP
Inventors: Keitarou Tahara; Tadashi Yanagisawa; Dai Miyoshi
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2013-03-13
Filing date: 2014-03-06
Publication date: 2018-10-24
Anticipated expiration: 2034-03-06
Also published as: JP2014173825A; CN104048404A; CN104048404B; EP2778562A1

Description

[TECHNICAL FIELD]

The present invention relates to a water heater.

[BACKGROUND TECHNIQUE]

As conventional water heaters of this kind, there is one in which high temperature hot water heated by a heating device is stored in a hot water tank, and the stored hot water is used (see patent document 1 for example).
Fig. 3 shows the conventional water heater described in patent document 1. As shown in Fig. 3, the water heater includes a heat pump unit 102 having a gas cooler (hot water-supply heat exchanger) 101, and a hot water storing unit 104 having a hot water tank 103 in which water and produced hot water are stored.
The heat pump unit 102 is configured by annularly connecting a compressor 105, a gas cooler 101, an expansion valve (decompressor) 106 and an evaporator 107 to one another through refrigerant pipes. A lower portion of the hot water tank 103 and upper portions of the circulation pump 108, the gas cooler 101 and the hot water tank 103 are connected to each other through pipes, thereby forming a water circuit.
The water heater described in patent document 1 includes a water quality adjusting portion (adding device) 109 which supplies inhibitors which suppress generation of scale to the water circuit between the lower portion of the hot water tank 103 and the gas cooler 101.

[PRIOR ART DOCUMENT]

[PATENT DOCUMENT]

[Patent Document 1] Japanese Patent Application Laid-open No. 2011-69572
EP2159505A1 discloses a heat pump type hot water supply device which is provided with a heat source side heat pump unit having a heat radiating heat exchanger that condenses refrigerant to radiate heat from the refrigerant. The hot water supply device is provided with a water tank that stores water, a water supply pipe that supplies water to the water tank from the outside, a water circulation pipe that is extended in a bypassing manner and circulates the water in the water tank from a bottom section to an upper section, a heat absorbing heat exchanger that is arranged on the water circulation pipe and connected to the heat radiating heat exchanger of the heat source side heat pump unit so as to absorb heat, and a hot water supply unit that comprises a hot water supply pipe that supplies warm water in the upper section of the water tank to the outside. The water supply pipe is branched into a plurality of water supply paths including a first water supply path and a second water supply path. The first water supply path supplies water supplied from the outside directly to the water tank. The second water supply path supplies water to the water tank after the water quality of the water from the outside is improved by the water quality adjusting unit so as to hardly generate scale. Accordingly, one of or both of the water supply paths are selectively used according to the water quality of the supplied water. This suppresses the deposition of scale.
JP2010091122 discloses a water heater including a hot water storage tank, a water heating means, and a water softening means. The water softening means is composed of a bipolar charged membrane having at least a pair of two layers of a cation exchanging layer and an anion exchanging layer disposed in Opposition to each other through a flow Channel, and a pair of electrodes disposed through the bipolar charged membrane. A hard component is removed by the bipolar charged membrane by introducing water softened by the water softening means to the water heating means, and the attachment of a scale in equipment can be prevented. Furthermore, since an area of an interface between the cation exchanging layer and the anion exchanging layer is large and the disassociation of water can be efficiently performed at a low voltage by applying voltages from both sides of the bipolar charged membrane, regeneration can be performed with low power consumption.

[SUMMARY OF THE INVENTION]

[PROBLEM TO BE SOLVED BY THE INVENTION]

According to the conventional configuration, however, when maintenance such as exchange of a water quality adjusting portion is required, an operator must stop the operation of the water heater, and there is a problem that this makes the maintenance of the water quality adjusting portion complicated.
The present invention has been accomplished to solve the above problem, and it is an object of the invention to provide a water heater in which maintenance easiness of the water quality adjusting portion is enhanced.

[MEANS FOR SOLVING THE PROBLEM]

To solve the above conventional problem, the present invention provides a water heater comprising: a hot water tank in which hot water is stored; a water supply pipe through which water is supplied to a lower portion of the hot water tank; an entering-water pipe through which the water is made to flow out from the lower portion of the hot water tank; a heating device for heating the water sent from the entering-water pipe; and an outgoing-hot water pipe through which the water heated by the heating device is supplied to an upper portion of the hot water tank, wherein the entering-water pipe or the water supply pipe includes a main flow path and an auxiliary flow path which bypasses the main flow path, wherein the main flow path includes a water quality adjusting portion placed around the main flow path and comprising a water quality adjusting portion and a drainage passage. The main flow path further includes a first closing valve which is placed upstream of the water quality adjusting portion and which closes a flow path and a second closing valve which is placed downstream of the water quality adjusting portion and which closes a flow path, wherein the water quality adjusting portion comprises a casing charged with scale inhibitors, an inflow port located at a vertically lower portion of the casing and an outflow port located at a vertically upper portion of the casing, such that water flowing into the water quality adjusting portion from the inflow port and out from the outflow port passes the entire casing with the scale inhibitors. The water quality adjusting portion can be attached to and detached from the main flow path and the drainage passage is arranged between the first closing valve and the inflow port; and comprises a drainage valve between the first closing valve and the second closing valve;
wherein the drainage valve is placed on a vertically lower side of the water quality adjusting portion for closing and opening a flow path of the drainage passage.
According to this, it is possible to carry out the maintenance of the water quality adjusting portion in a state where the main flow path is closed by the first closing valve and the second closing valve and water flows through the auxiliary flow path, i.e., in a state where the water heater is operated.

[EFFECT OF THE INVENTION]

According to the present invention, it is possible to provide a water heater in which maintenance easiness of the water quality adjusting portion is enhanced.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Fig. 1 is a schematic block diagram of a water heater according to an embodiment of the present invention;
Fig. 2 is a schematic block diagram of a water quality adjusting unit of the water heater; and
Fig. 3 is a block diagram of a conventional water heater.

[MODE FOR CARRYING OUT THE INVENTION]

A first aspect of the present invention provides a water heater comprising: a hot water tank in which hot water is stored; a water supply pipe through which water is supplied to a lower portion of the hot water tank; an entering-water pipe through which the water is made to flow out from the lower portion of the hot water tank; a heating device for heating the water sent from the entering-water pipe; and an outgoing-hot water pipe through which the water heated by the heating device is supplied to an upper portion of the hot water tank, wherein the entering-water pipe or the water supply pipe includes a main flow path and an auxiliary flow path which bypasses the main flow path, the main flow path includes a water quality adjusting portion which can be attached to and detached from the main flow path, which reforms the inflow water into water having quality in which scale is less prone to be generated, and which flows the water out, a first closing valve which is placed upstream of the water quality adjusting portion and which closes a flow path, and a second closing valve which is placed downstream of the water quality adjusting portion and which closes a flow path.
According to this aspect, it is possible to carry out the maintenance of the water quality adjusting portion in a state where the main flow path is closed by the first closing valve and the second closing valve and water flows through the auxiliary flow path. Therefore, it is possible to carry out the maintenance of the water quality adjusting portion without stopping the operation of the water heater.
According to a second aspect of the invention, in the first aspect, the main flow path further includes a drainage passage having a drainage valve between the first closing valve and the second closing valve.
According to this aspect, water is drained from the drainage passage after the closing valves are closed. Hence, the maintenance of the water quality adjusting portion can be carried out after pressure between the first closing valve and the second closing valve is reduced to atmospheric pressure. Hence, maintenance easiness of the water quality adjusting portion is enhanced. When the water quality adjusting portion is not used for a long term, if water is drained from the drainage passage, it is possible to prevent the water quality adjusting portion from being damaged by freezing of water which stays in the water quality adjusting portion.
According to a third aspect of the invention, in the first or second aspect, the drainage valve is placed on a vertically lower side of the water quality adjusting portion.
According to this aspect, it is possible to efficiently drain water which stays in the water quality adjusting portion. Even if water issues from the drainage valve during the draining operation, it is possible to restrain water from being poured over an operator, and it is possible to more efficiently carry out the maintenance of the water quality adjusting portion and exchange the water quality adjusting portion.
Embodiments of the present invention will be described below with reference to the drawings. The invention is not limited to the embodiments.

(First Embodiment)

Fig. 1 is a block diagram of a water heater according to an embodiment of the present invention.
As shown in Fig. 1, the water heater of the first embodiment includes a heating device 10, a hot water storing unit 4 and a water quality adjusting unit 40.
The heating device 10 is a heat pump unit configured by annularly connecting, through refrigerant pipes, a compressor 5 which compresses refrigerant, a heat exchanger 11 which exchanges heat between refrigerant and water, a decompressor (expansion valve) 6 which decompresses refrigerant, and an evaporator 7 which exchanges heat between air and refrigerant to one another. Carbon dioxide circulates through the refrigerant pipe. If carbon dioxide is used as refrigerant, high pressure side pressure in the heat pump unit becomes equal to or higher than critical pressure.
The hot water storing unit 4 includes a hot water tank 3 in which water is stored. A water supply pipe 12 is connected to a lower portion of the hot water tank 3. A decompression valve 13 is placed in the water supply pipe 12. Water supplied from a water pipe is decompressed by the decompression valve 13 and then, the water flows in from a lower portion of the hot water tank 3. The water supply pipe 12 supplies water to a lower portion of the hot water tank 3. A hot water-supply pipe 14 is connected to an upper portion of the hot water tank 3. Hot water stored in the hot water tank 3 is supplied from the hot water-supply pipe 14 to a hot water-supplying terminal 17 such as a tap, a shower head and a bathtub.
The hot water storing unit 4 includes a bypass pipe 16 which branches off from the water supply pipe 12 located downstream of the decompression valve 13 and which is connected to the hot water-supply pipe 14. A mixing valve 15 is placed between the hot water-supply pipe 14 and the bypass pipe 16. High temperature hot water which flows out from the upper portion of the hot water tank 3 into the hot water-supply pipe 14 is mixed with water which flows through the bypass pipe 16 in the mixing valve 15, temperature thereof is adjusted, and the hot water is supplied to the hot water-supplying terminal 17 through the hot water-supply pipe 14.
A lower portion of the hot water tank 3 and the heat exchanger 11 are connected to each other through water-in pipes 18. Water flows out from a lower portion of the hot water tank 3 through the water-in pipe 18. The heating device 10 heats water sent from the water-in pipe 18. The heat exchanger 11 and the upper portion of the hot water tank 3 are connected to each other through an outgoing-hot water pipe 19. The outgoing-hot water pipe 19 supplies water heated by the heating device 10 to the upper portion of the hot water tank 3. According to this, the lower portion of the hot water tank 3, the heat exchanger 11 and the upper portion of the hot water tank 3 are annularly connected one another in this order through the water-in pipe 18 and the outgoing-hot water pipe 19, and a water circuit is formed. A circulation pump 8 which sends water in the lower portion of the hot water tank 3 to the heat exchanger 11 under pressure is placed in the water-in pipe 18 in the hot water storing unit 4.
The entering-water pipe 18 includes main flow paths 18a and an auxiliary flow path 18b which bypasses the main flow path 18a. A later described water quality adjusting unit 40 is placed in the main flow path 18a.
When a heating operation for heating water in the hot water tank 3 is carried out, water stored in the lower portion of the hot water tank 3 flows through the water-in pipe 18 and flows into the heat exchanger 11. Water which flowed into the heat exchanger 11 exchanges heat with refrigerant and the water is heated. The heated high temperature hot water flows through the outgoing-hot water pipe 19 and flows into the upper portion of the hot water tank 3.
A water temperature sensor 20a which detects temperature of water heated by the heating device 10 is placed in the outgoing-hot water pipe 19 located in the heating device 10. A refrigerant temperature sensor 20b is placed in the refrigerant pipe which extends from the compressor 5 to the heat exchanger 11. An outside air temperature sensor 21 which measures outside air temperature is placed in the heating device 10. It is preferable that the outside air temperature sensor 21 is placed in the vicinity of and on the windward of the evaporator 7.
The water quality adjusting unit 40 is placed around a main flow path 18a of the entering-water pipe 18. The water quality adjusting unit 40 includes a water quality adjusting portion 23 and a drainage passage 26b having a drainage valve 26a. The water quality adjusting portion 23 reforms inflow water into water having quality in which scale is less prone to be generated, and the water quality adjusting portion 23 flows the reformed water out. The water quality adjusting unit 40 is connected to the main flow path 18a through connecting portions 47a and 47b. Union type or screw type joints can be used as the connecting portions 47a and 47b. By connecting the connecting portions 47a and 47b and the entering-water pipe 18 to each other, the water quality adjusting unit 40 can be attached to and detached from the main flow path 18a.
According to this, the connecting portions 47a and 47b can be connected to each other through another pipe instead of the water quality adjusting unit 40. Hence, the water quality adjusting unit 40 can be connected or not be connected between the heating device 10 and the hot water storing unit 4.
The water quality adjusting portion 23 is connected to the main flow paths 18a. As shown in Fig. 2, scale inhibitors 22 are charged into a casing of the water quality adjusting portion 23. The water quality adjusting portion 23 has a function to dissolve scale inhibitors 22 into inflow water, reforms the water into water in which scale is less prone to be generated, and flows the water out. The water quality adjusting portion 23 of the embodiment includes an inflow port 23a located at a vertically lower portion of the casing and an outflow port 23b located at a vertically upper portion of the casing. Water flows into the water quality adjusting portion 23 from the inflow port 23a and flows out from the outflow port 23b. That is, the water quality adjusting portion 23 itself configures the main flow path 18a.
The water quality adjusting portion 23 is connected to the main flow paths 18a through the inflow port 23a and the outflow port 23b. In this embodiment, the water quality adjusting portion 23 and the main flow paths 18a are connected to each other by inserting pipes configuring the main flow paths 18a into the inflow port 23a and the outflow port 23b. That is, the water quality adjusting portion 23 can be attached to and detached from the main flow paths 18a. In this case, seal members such as O-rings are placed between the main flow path 18a and the inflow port 23a, and between the main flow path 18a and the outflow port 23b. Union type or screw type joints can be used at the inflow port 23a and the outflow port 23b.
The water quality adjusting portion 23 in this embodiment is configured by charging the scale inhibitors 22 into the casing made of polyphenylene sulfide (PPS) resin. If the casing is made of PPS resin, pressure resistance can be enhanced.
If scale inhibitors 22 dissolve in water, the water suppresses growth of crystal of calcium carbonate (scale ingredient) included in the water, and this restrains scale from depositing. As the scale inhibitors 22, it is possible to use particles having polyphosphate salt as main ingredient. Typical examples of the polyphosphate salt are sodium tripolyphosphate and sodium hexametaphosphoric acid, but other polyphosphate salt may be used. Low molecular polymer such as phosphonic acid-based or carboxylic acid-based polymer electrolyte may be used as the main ingredient.
The inflow port 23a is placed at the vertically lower portion of the casing of the water quality adjusting portion 23 of this embodiment, and the outflow port 23b is placed at the vertically upper portion of the casing. According to this, water flows upward from a lower side through the casing of the water quality adjusting portion 23 into which the scale inhibitors 22 are charged. According to this, water flowing through the water quality adjusting portion 23 runs through the entire water quality adjusting portion 23. Hence, a dissolved degree (concentration of scale inhibitors 22 included in water per unit flow rate) of the scale inhibitors 22 which dissolve in water can be stabilized.
A closing valve (first closing valve) 25a is placed in the main flow path 18a upstream of the water quality adjusting portion 23. A closing valve (second closing valve) 25b is placed in the main flow path 18a downstream of the water quality adjusting portion 23. In this embodiment, the closing valve 25a is placed in the main flow path 18a upstream of the connecting portion 47a. The closing valve 25b is placed in the main flow path 18a downstream of the connecting portion 47b. The closing valve 25a and the closing valve 25b have functions to close and open a flow path of the main flow paths 18a. The closing valves 25a and 25b may be closed and opened by a manual operation of an operator, or may be automatically closed and opened by a control device (not shown).
The drainage passage 26b having the drainage valve 26a is placed in the main flow path 18a between the closing valve 25a and the inflow port 23a. That is, the drainage passage 26b is placed in the water quality adjusting unit 40. The drainage valve 26a has a function to close and open a flow path of the drainage passage 26b. The drainage valve 26a may be closed and opened by a manual operation of an operator, or may be automatically closed and opened by a control device (not shown).
Here, the drainage valve 26a is placed downstream of the water quality adjusting portion 23 in the vertical direction. A tip end of the drainage passage 26b is directed vertically downward rather than a horizontal direction. According to this, when water is drained from the drainage passage 26b, it is possible to restrain water from being poured over an operator.
Action and an effect of the water heater having the above-described configuration will be described below.
First, the heating operation for heating water in the hot water tank 3 to produce hot water will be described.
In the heating operation, a control device (not shown) controls operations of the compressor 5, the decompressor 6 and the circulation pump 8 to produce hot water.
When the heating operation is carried out, the closing valves 25a and 25b are opened and the drainage valve 26a is closed.
In the heating device 10, refrigerant flows into the compressor 5, the refrigerant is compressed to critical pressure or higher, and the refrigerant is discharged from the compressor 5. High temperature and high pressure refrigerant discharged from the compressor 5 flows into the heat exchanger 11. In the hot water storing unit 4, the circulation pump 8 is operated, water in the lower portion of the hot water tank 3 flows through the entering-water pipe 18 and flows into the heat exchanger 11.
The refrigerant which flowed into the heat exchanger 11 dissipates heat to water which flows from the entering-water pipe 18 into the heat exchanger 11 and then, the refrigerant flows out from the heat exchanger 11. The refrigerant which flowed out from the heat exchanger 11 is decompressed by the decompressor 6, the refrigerant is partially or entirely liquefied and then, the refrigerant flows into the evaporator 7. The refrigerant which flowed into the evaporator 7 absorbs heat from air and evaporates, and again flows into the compressor 5.
Water which flowed into the heat exchanger 11 absorbs heat from high temperature and high pressure refrigerant and becomes hot water. The hot water flows out from the heat exchanger 11, flows through the outgoing-hot water pipe 19 and flows from the upper portion of the hot water tank 3 and flows into the hot water tank 3. The refrigerant and water exchange heat in the heat exchanger 11 in this manner, high temperature hot water is produced. Here, since carbon dioxide is used as the refrigerant, it is possible to heat water to high temperature (e.g., 85 degrees for example).
When the heating operation is carried out, the control device controls the number of rotations of the circulation pump 8 such that temperature (heating temperature) of hot water detected by the water temperature sensor 20a becomes equal to predetermined temperature. The control device controls the compressor 5 and the decompressor 6 based on temperature of refrigerant detected by the refrigerant temperature sensor 20b and temperature of outside air detected by the outside air temperature sensor 21.
Here, water sent from the lower portion of the hot water tank 3 by the circulation pump 8 flows through the entering-water pipe 18 and diverges into the main flow path 18a and the auxiliary flow path 18b. Water which flows into the main flow path 18a passes through the water quality adjusting portion 23. At this time, scale inhibitors 22 charged into the water quality adjusting portion 23 dissolves in water. Hence, water in which scale inhibitors 22 dissolves flows out from the water quality adjusting portion 23, the water is mixed with water which flowed through the auxiliary flow path 18b, and the water flows into the heat exchanger 11.
Ingredients such as calcium carbonate included in water have such properties that if water is heated to high temperature, the ingredients are prone to be crystallized and deposited. Therefore, if the scale inhibitors 22 are made to dissolve in water which flows into the heat exchanger 11, it is possible to suppress growth of crystal such as calcium carbonate and to restrain scale from depositing especially in the heat exchanger 11 and the outgoing-hot water pipe 19 through which high temperature hot water flows.
The water quality adjusting portion 23 in this embodiment is configured such that water upwardly flows in one direction from a lower side in the casing into which the scale inhibitors 22 are charged. According to this, water runs through the entire water quality adjusting portion 23. Hence, a dissolving degree of the scale inhibitors 22 which flow out from the water quality adjusting portion 23 is stabilized.
Since the scale inhibitors 22 dissolve in water, an interior content of the scale inhibitors 22 charged into the water quality adjusting portion 23 is gradually reduced. If the interior content is reduced, the dissolving amount of scale inhibitors 22 in water is also gradually reduced, and the effect for suppressing deposition of scale is deteriorated. Hence, before the effect for suppressing deposition of scale is lost, it is necessary to exchange the water quality adjusting portion 23 or perform maintenance such as a replenishing operation of scale inhibitors 22. It is preferable that the maintenance is performed after the water quality adjusting portion 23 is detached from the entering-water pipe 18 from a standpoint of operability.
Water pressure corresponding to a pressure difference between the hot water tank 3 and the water quality adjusting portion 23 is applied to the water quality adjusting portion 23 after the heating operation is carried out. Hence, if the water quality adjusting portion 23 is detached in a state where the water pressure is applied, hot water stored in the hot water tank 3 flows toward the main flow path 18a which opens into atmosphere, and hot water flows out. Especially when hot water is stored in the entire hot water tank 3, high temperature hot water which flowed out from the lower portion of the hot water tank 3 flows out from the main flow path 18a which opens into atmosphere, and it becomes more difficult to carry out the maintenance.
Hence, in the water heater of the embodiment, the closing valves 25a and 25b are respectively placed upstream and downstream of the water quality adjusting portion 23. The closing valves 25a and 25b can close the flow paths of the main flow paths 18a. Hence, if the closing valves 25a and 25b close the entering-water pipes 18 and the water quality adjusting portion 23 is detached, only water which stays in the entering-water pipes 18 between the closing valves 25a and 25b flows out. That is, water which circulates through the water heater, e.g., hot water in the hot water tank 3 does not flow out at the time of maintenance. According to this, it is possible to efficiently carry out the maintenance of the water quality adjusting portion 23 in a short time.
Even if the closing valves 25a and 25b close the main flow path 18a, water which flows from the lower portion of the hot water tank 3 toward the entering-water pipe 18 flows through the auxiliary flow path 18b and flows into the heat exchanger 11. Hence, it is possible to carry out the maintenance of the water quality adjusting portion 23 while carrying out a heating operation of the water heater.
Further, the water heater of the embodiment includes the drainage passage 26b having the drainage valve 26a in the main flow path 18a between the closing valve 25a and the inflow port 23a. After the closing valves 25a and 25b are closed, the drainage valve 26a is opened. Hence, water which stays between the closing valves 25a and 25b is drained from the drainage passage 26b. Water pressure corresponding to the pressure difference between the hot water tank 3 and the water quality adjusting portion 23 is applied to the water quality adjusting portion 23 as described above. Hence, an operator opens the drainage valve 26a to drain water before the water quality adjusting portion 23 is detached. Therefore, pressure in the entering-water pipes 18 between the closing valves 25a and 25b can be reduced to the atmospheric pressure.
According to this, when the water quality adjusting portion 23 is detached, it is possible to prevent water from issuing out by the water pressure, and to efficiently carry out the maintenance of the water quality adjusting portion 23 in a short time. Since the drainage passage 26b is located at the vertically lower portion of the water quality adjusting portion 23, drainage performance is enhanced, and when water is drained, it is possible to restrain water from being poured over an operator. Hence, maintenance easiness is enhanced.
When the water quality adjusting portion 23 is not used for a long term, the closing valves 25a and 25b are closed and the drainage valve 26a is opened. Hence, water staying between the closing valves 25a and 25b is drained from the drainage passage 26b. According to this, it is possible to prevent the water quality adjusting portion 23 and the main flow path 18a from being damaged by freezing of water which stays in the water quality adjusting portion 23 and the main flow path 18a when outside air temperature is lowered.
In the embodiment, the water quality adjusting unit 40 is easily detached by closing the closing valves 25a and 25b and detaching the connecting portions 47a and 47b from the main flow paths 18a without draining a large amount of water in the water heater.
Although the heat pump unit is used as the heating device 10, other heating device 10 such as a combustor using gas and an electric heater may be used instead of the heat pump unit.
Although the drainage passage 26b is provided in the main flow path 18a between the closing valve 25a and the inflow port 23a, the drainage passage 26b may be provided in the main flow path 18a between the outflow port 23b and the closing valve 25b at a location vertically lower than the water quality adjusting portion 23. According to this, it is possible to smoothly drain water which stays between the outflow port 23b and the closing valve 25b.
The example of the present invention is not limited to this. For example, the main flow paths 18a and the auxiliary flow path 18b may be connected to the water supply pipe 12. In this case, the water quality adjusting unit 40 and the closing valves 25a and 25b are placed in the main flow path 18a which is formed in the water supply pipe 12. The main flow path 18a is placed downstream of the decompression valve 13 with respect to a direction of water which flows through the water supply pipe 12. According to this, water which is decompressed by the decompression valve 13 flows into the water quality adjusting portion 23. Hence, it is unnecessary to excessively increase the pressure resistance of the casing of the water quality adjusting portion 23, and it is possible to reduce the costs. Since the water quality adjusting portion 23 is placed in the water supply pipe 12, the scale inhibitors 22 can be made to dissolve in water which flows into the hot water tank 3. Hence, since water which flows into the heat exchanger 11 includes the scale inhibitors 22, it is possible to restrain scale from depositing as described above. Further, since water flows through the auxiliary flow path 18b and is supplied into the hot water tank 3, it is possible to carry out the maintenance of the water quality adjusting portion 23 without stopping the operation of the water heater.
It is preferable that the main flow path 18a is placed upstream of a branching location between the water supply pipe 12 and the bypass pipe 16 with respect to an inflow direction of water which flows through the water supply pipe 12. According to this, since water in which the scale inhibitors 22 dissolve flows also through the bypass pipe 16, a dissolving degree of the scale inhibitors 22 in hot water which is supplied to the hot water-supplying terminal 17 is maintained constant or higher.
When it is necessary to exchange the water quality adjusting portion 23 or carry out the maintenance such as a replenishing operation of scale inhibitors 22, an operator first close the flow path by the closing valves 25a and 25b. Next, the operator opens the drainage valve 26a of the drainage passage 26b to drain water which stays between the closing valves 25a and 25b. Then, the water quality adjusting portion 23 which can be attached to and detached from the entering-water pipe 18 is detached. According to this, it is only necessary to drain water which stays between the closing valves 25a and 25b and it is unnecessary to drain water in the entire water heater. Hence, it is possible to efficiently carry out the maintenance of the water quality adjusting portion 23.

[INDUSTRIAL APPLICABILITY]

The water heater of the present invention suppresses deposition of scale by the water quality adjusting portion, and maintenance easiness of the water quality adjusting portion is enhanced. Therefore, the invention can be applied to domestic and professional-use water heaters.

[EXPLANATION OF SYMBOLS]

3: hot water tank
8: circulation pump
10: heating device
12: water supply pipe
18: entering-water pipe
18a: main flow path
18b: auxiliary flow path
19: outgoing-hot water pipe
23: water quality adjusting portion
25a, 25b: closing valve
26a: drainage valve

[Fig. 1]

3: Hot water tank
4: Hot water storing unit
5: Compressor
6: Decompressor
7: Evaporator
8: Circulation pump
10: Heating device
11: Heat exchanger
12: Water supply pipe
13: Decompression valve
14: Hot water-supply pipe
15: Mixing valve
16: Bypass pipe
17: Hot water-supplying terminal
18: Entering-water pipe
19: Outgoing-hot water pipe
20a: water temperature sensor
20b: refrigerant temperature sensor
21: Outside air temperature sensor
22: Scale inhibitors
23: Water quality adjusting portion
25a, 25b: Closing valve
26a: Drainage valve
26b: Drainage passage
40: Water quality adjusting unit
47a, 47b: Connecting portion

[Fig. 2]

23: Water quality adjusting portion
23a: Inflow port
23b: Outflow port

Claims

A water heater comprising:
a hot water tank (3) in which hot water is stored;

a water supply pipe (12) through which water is supplied to a lower portion of the hot water tank (3);

an entering-water pipe (18) through which the water is made to flow out from the lower portion of the hot water tank (3);

a heating device (10) for heating the water sent from the entering-water pipe (18); and

an outgoing-hot water pipe (19) through which the water heated by the heating device (10) is supplied to an upper portion of the hot water tank (3),

wherein

the entering-water pipe (18) or the water supply pipe (12) includes a main flow path (18a) and an auxiliary flow path (18b) which bypasses the main flow path (18a),

wherein the main flow path (18a) includes
a water quality adjusting unit (40) placed around the main flow path (18a) and comprising a water quality adjusting portion; wherein

the main flow path (18a) further includes

a first closing valve (25a) which is placed upstream of the water quality adjusting portion (23) and which closes a flow path, and

a second closing valve (25b) which is placed downstream of the water quality adjusting portion (23) and which closes a flow path;

wherein the water quality adjusting portion (23) is attached to the main flow path (18a) for reforming the inflow water into water having a a quality in which scale is less prone to be generated, and to flow the water out;

characterized in that

the water quality adjusting portion (23) comprises a casing charged with scale inhibitors (22), an inflow port (23a) located at a vertically lower portion of the casing and an outflow port (23b) located at a vertically upper portion of the casing, such that water flowing into the water quality adjusting portion (23) from the inflow port (23a) and out from the outflow port (23b) passes the entire casing with the scale inhibitors (22),

wherein the water quality adjusting portion (23) can be attached to and detached from the main flow path (18a),

and in that the water quality adjusting unit (40) comprises a drainage passage (26b), wherein said drainage passage (26b) is arranged between the first closing valve (25a) and the inflow port (23a) in the water quality adjusting unit (40); and comprises a drainage valve (26a) between the first closing valve (25a) and the second closing valve (25b);

wherein the drainage valve (26a) is placed on a vertically lower side of the water quality adjusting portion (23) for closing and opening a flow path of the drainage passage (26b).