Water heater

Abstract

 A water heater including: a hot water tank 3; a water supply pipe 12; an entering-water pipe 18; a heating device 10; an outgoing-hot water pipe 19; and a water quality adjusting portion 23, wherein the entering-water pipe 18 or the water supply pipe 12 includes a first closing valve 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. It is unnecessary to drain water in the entire system of the water heater, and it is possible to carry out maintenance of the water quality adjusting portion 23 which suppress deposition of scale.

Description

[TECHNICAL FIELD]

[0001] The present invention relates to a water heater.

[BACKGROUND TECHNIQUE]

[0002] 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).

[0003] Fig. 11 shows the conventional water heater described in patent document 1. As shown in Fig. 11, 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.

[0004] 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.

[0005] 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]

[0006] 

[Patent Document 1] Japanese Patent Application Laid-open No.2011-69572

[SUMMARY OF THE INVENTION]

[PROBLEM TO BE SOLVED BY THE INVENTION]

[0007] According to the conventional configuration, however, when the water quality adjusting portion is exchanged or maintenance thereof is carried out, if the water quality adjusting portion is detached, the water quality adjusting portion is detached by water pressure applied to interior of the water heater, and water in the water heater flows out from a portion which becomes atmospheric pressure. Hence, there is a problem that an operator must carry out the maintenance after water flowing through the water heater is drained, and this makes the maintenance of the water quality adjusting portion complicated.

[0008] 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]

[0009] 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 2a 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; 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; and a water quality adjusting portion which can be attached to and detached from the entering-water pipe or the water supply pipe, which reforms the inflow water into water having quality in which scale is less prone to be generated, and which flows the water out, wherein the entering-water pipe or the water supply pipe 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.

[0010] According to this, it is possible to close a water-in pipe by closing valves which are placed on an upstream side and a downstream side of the water quality adjusting portion. Hence, even if the water quality adjusting portion is detached, a water-draining operation at the time of maintenance can easily be carried out only by flowing out water which stays between the closed two closing valves.

[EFFECT OF THE INVENTION]

[0011] 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]

[0012] 

Fig. 1 is a schematic block diagram of a water heater according to a first embodiment of the present invention;

Fig. 2 is a schematic block diagram of a water quality adjusting unit of the water heater;

Fig. 3 is a schematic block diagram of a water heater according to a second embodiment of the invention;

Fig. 4 is a schematic block diagram of a water quality adjusting unit of the water heater;

Fig. 5 is a schematic block diagram of a water heater according to a third embodiment of the invention;

Fig. 6 is a schematic block diagram of a water quality adjusting unit of the water heater;

Fig. 7 is a schematic block diagram of an air-suction device of the water heater in the third embodiment of the invention;

Fig. 8(a) is a schematic block diagram of another air-suction device of the water heater in the third embodiment of the invention, and Fig. 8(b) is a plan view of essential portions of the air-suction device;

Fig. 9 is a schematic block diagram of a water heater according to a fourth embodiment of the invention;

Fig. 10 is a schematic block diagram of a water quality adjusting unit of the water heater; and

Fig. 11 is a schematic block diagram of a conventional water heater.

[MODE FOR CARRYING OUT THE INVENTION]

[0013] 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; 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; and a water quality adjusting portion which can be attached to and detached from the entering-water pipe or the water supply pipe, which reforms the inflow water into water having quality in which scale is less prone to be generated, and which flows the water out, wherein the entering-water pipe or the water supply pipe 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.

[0014] According to this aspect, since the water-in pipe or the water supply pipe can be closed by the closing valves located upstream and downstream of the water quality adjusting portion, it is possible to carry out the maintenance of the water quality adjusting portion without draining water in the entire system of the water heater. Hence, maintenance easiness of the water quality adjusting portion is enhanced.

[0015] According to a second aspect of the invention, in the first aspect, the water heater further includes a drainage passage having a drainage valve between the first closing valve and the second closing valve.

[0016] According to this aspect, water is drained from the dp 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.

[0017] According to a third aspect of the invention, in the second aspect, the drainage passage is placed on a vertically lower side of the water quality adjusting portion.

[0018] 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. Hence, maintenance easiness of the water quality adjusting portion is enhanced.

[0019] According to a fourth aspect of the invention, in the first aspect, the water heater further includes an air-suction device for making outside air flow into the entering-water pipe or the water supply pipe, and the air-suction device is placed between the first closing valve and the second closing valve.

[0020] According to this aspect, it is possible to close the water-in pipe or the water supply pipe by the closing valves, and to smoothly flow out water which stays between the two closing valves using the drainage valve and the air-suction device. Hence, maintenance easiness of the water quality adjusting portion is enhanced.

[0021] According to a fifth aspect of the invention, in the fourth aspect, the air-suction device is placed on a vertically upper side of the water quality adjusting portion.

[0022] According to this aspect, outside air easily flows in from the air-suction device, and it is possible to smoothly flow out water which stays between the two closing valves. Hence, maintenance easiness of the water quality adjusting portion is enhanced.

[0023] According to a sixth aspect of the invention, in the fourth or fifth aspect, the air-suction device includes an air-suction plug and a negative pressure air-suction valve, and the negative pressure air-suction valve is provided between the air-suction plug and the entering-water pipe or between the air-suction plug and the water supply pipe.

[0024] According to this aspect, if pressure in the water-in pipe or the water supply pipe becomes negative pressure, outside air is automatically sucked. Therefore, it is possible to smoothly flow out water which stays between the two closing valves. The negative pressure air-suction valve prevents hot water from flowing out from the air-suction device, and it is possible to more easily carry out the maintenance of the water quality adjusting portion.

[0025] Embodiments of the present invention will be described below with reference to the drawings. The invention is not limited to the embodiments.

(First Embodiment)

[0026] Fig. 1 is a schematic block diagram of a water heater according to a first embodiment of the present invention, and Fig. 2 is a schematic block diagram of a water quality adjusting unit of the water heater.

[0027] 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.

[0028] 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 as refrigerant. If carbon dioxide is used as refrigerant, high pressure side pressure in the heat pump unit becomes equal to or higher than critical pressure. Hence, in the heat exchanger 11, water is heated to high temperature (e.g., 85 degrees).

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033]  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.

[0034] The water quality adjusting unit 40 is placed around 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 entering-water pipe 18 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 entering-water pipe 18.

[0035] According to this, the connecting portion 47a and the connecting portion 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.

[0036] The water quality adjusting portion 23 is connected to the entering-water pipes 18 between the circulation pump 8 and the heat exchanger 11. 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 entering-water pipe 18.

[0037] The water quality adjusting portion 23 is connected to the entering-water pipes 18 through the inflow port 23a and the outflow port 23b. In this embodiment, the water quality adjusting portion 23 and the entering-water pipes 18 are connected to each other by inserting pipes configuring the entering-water pipes 18 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 entering-water pipes 18. In this case, seal members such as O-rings are placed between the entering-water pipes 18 and the inflow port 23a, and between the entering-water pipes 18 and the outflow port 23b. Union type or screw type joints can be used at the inflow port 23a and the outflow port 23b.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] A closing valve (first closing valve) 25a is placed in the entering-water pipe 18 upstream of the water quality adjusting portion 23. A closing valve (second closing valve) 25b is placed in the entering-water pipe 18 downstream of the water quality adjusting portion 23. In this embodiment, the closing valve 25a is placed in the entering-water pipe 18 upstream of the connecting portion 47a. The closing valve 25b is placed in the entering-water pipe 18 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 entering-water pipes 18. 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).

[0042] The drainage passage 26b having the drainage valve 26a is placed in the entering-water pipe 18 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).

[0043] Here, the drainage valve 26a is placed downstream of the water quality adjusting portion 23 in the vertical direction. According to this, when the closing valves 25a and 25b are closed and the drainage valve 26a is opened and water is drained, drainage performance is enhanced. 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.

[0044] Action and an effect of the water heater having the above-described configuration will be described below.

[0045] First, the heating operation for heating water in the hot water tank 3 to produce hot water will be described.

[0046] 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.

[0047] When the heating operation is carried out, the closing valves 25a and 25b are opened and the drainage valve 26a is closed.

[0048] 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.

[0049] 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.

[0050] 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).

[0051] 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.

[0052] Here, water sent from the lower portion of the hot water tank 3 by the circulation pump 8 flows through the water quality adjusting portion 23 connected to the entering-water pipes 18. At this time, the scale inhibitors 22 charged into the water quality adjusting portion 23 dissolve in water. Hence, water in which the scale inhibitors 22 dissolve flows into the heat exchanger 11.

[0053] 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.

[0054] 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.

[0055] 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 degree 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.

[0056] 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 entering-water pipe 18 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 entering-water pipe 18 which opens into atmosphere, and it becomes more difficult to carry out the maintenance.

[0057] 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 entering-water pipes 18. 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. Since the closing valves 25a and 25b are placed upstream and downstream of the water quality adjusting portion 23 in this manner, it is unnecessary for an operator to drain a large amount of hot water in the water heater, and it is possible to efficiently carry out the maintenance of the water quality adjusting portion 23 in a short time.

[0058] The water heater of the embodiment includes the drainage passage 26b having the drainage valve 26a in the entering-water pipe 18 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.

[0059] 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.

[0060] 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 entering-water pipes 18 without draining a large amount of water in the water heater.

[0061] 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.

[0062] Although the drainage passage 26b is provided in the entering-water pipe 18 between the closing valve 25a and the inflow port 23a, the drainage passage 26b may be provided in the entering-water pipe 18 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.

[0063] The example of the present invention is not limited to this. For example, the water quality adjusting unit 40 and the closing valves 25a and 25b may be placed in the water supply pipe 12. At this time, the water quality adjusting unit 40 and the closing valves 25a and 25b are placed downstream of the decompression valve 13. 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.

[0064] It is preferable that the water quality adjusting portion 23 and the closing valves 25a and 25b are 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.

[0065] 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.

(Second Embodiment)

[0066] Fig. 3 is a schematic block diagram of a water heater according to a second embodiment of the invention, and Fig. 4 is a schematic block diagram of a water quality adjusting unit of the water heater. In the second embodiment, the same symbols as those of the first embodiment are allocated to the same members, and detailed description thereof will be omitted.

[0067] As shown in Figs. 3 and 4, a water heater of the second embodiment is characterized in that the entering-water pipe 18 includes a main flow path 18a in which the water quality adjusting portion 23 is placed and an auxiliary flow path 18b which bypasses the water quality adjusting portion 23.

[0068] In the second embodiment, the drainage passage 26b having the drainage valve 26a is placed downstream of the closing valve 25a with respect to a flowing direction of water which flows through the entering-water pipe 18 and upstream of a branching location between the main flow path 18a and the auxiliary flow path 18b. The drainage passage 26b is placed downstream of the connecting portion 47a.

[0069] Action and an effect of the water heater having the above-described configuration will be described below.

[0070] In a heating operation, water which is sent by the circulation pump 8 under pressure and which flows through the entering-water pipe 18 separately flows into the main flow path 18a and the auxiliary flow path 18b as shown in Fig. 4. Water which flows through the main flow path 18a flows into the water quality adjusting portion 23. In the water quality adjusting portion 23, the scale inhibitors 22 dissolve in water and water in which scale is less prone to be generated is produced. Water which flows out from the water quality adjusting portion 23 merges with water which flowed through the auxiliary flow path 18b. Here, by adjusting a shunt flow rate (separately flowing rate) of water which separately flows into the main flow path 18a and the auxiliary flow path 18b, it is possible to adjust a dissolving degree of scale inhibitors 22 in water which flows into the heat exchanger 11. Hence, it is possible not only to enhance the maintenance easiness of the water quality adjusting portion 23, but also to appropriately adjust the dissolving degree of the scale inhibitors 22 and to prevent the scale inhibitors 22 from being used wastefully.

[0071] In the second embodiment, the water quality adjusting unit 40 and the closing valves 25a and 25b may be placed in the water supply pipe 12.

(Third Embodiment)

[0072] Fig. 5 is a schematic block diagram of a water heater according to a third embodiment of the invention, and Fig. 6 is a schematic block diagram of a water quality adjusting unit of the water heater. In the third embodiment, the same symbols as those of the first and the second embodiments are allocated to the same members, and detailed description thereof will be omitted.

[0073] An air-suction device 31 is placed in the entering-water pipe 18 between the closing valves 25a and 25b. In the third embodiment, an air-suction device 31 having an air-suction plug 31a and an air-suction passage 32 is placed on the water-in pipe 18 between the outflow port 23b and the closing valve 25b. That is, the air-suction device 31 is placed in the water quality adjusting unit 40. The air-suction plug 31a has a function to close and open the air-suction passage 32.

[0074] If the air-suction plug 31a opens the air-suction passage 32, the entering-water pipe 18 is opened into atmosphere. The opening and closing operations of the air-suction passage 32 carried out by the air-suction device 31 may be carried out by a manual operation of an operator, or may be carried out automatically by a control device (not shown). If the air-suction passage 32 is opened by the air-suction plug 31a and the drainage valve 26a is opened, drainage performance of water which stays in the entering-water pipe 18 is enhanced.

[0075] Here, a connected location between the air-suction passage 32 and the entering-water pipe 18 is located upstream of the water quality adjusting portion 23 in the vertical direction. According to this, outside air smoothly flows into the entering-water pipe 18 which is closed by the closing valves 25a and 25b. Hence, drainage performance is enhanced.

[0076] Fig. 7 is a sectional view showing a configuration of the air-suction plug 31a in this embodiment. The air-suction plug 31a is fitted into the air-suction passage 32, thereby closing the air-suction passage 32. An O-ring 43 is provided around the tip end of the air-suction plug 31a. The air-suction plug 31a is twisted with a hand and a sealed degree of the air-suction passage 32 by the O-ring 43 is loosened, thereby opening the entering-water pipe 18 into the atmosphere, and outside air is made to flow into the entering-water pipe 18.

[0077] According to the water heater of this embodiment, the entering-water pipe 18 between the outflow port 23b and the closing valve 25b includes the air-suction passage 32 having the air-suction plug 31a. Outside air flows into the entering-water pipe 18 by opening the air-suction plug 31a. Therefore, drainage performance of water which stays between the closing valves 25a and 25b is enhanced.

[0078] As shown in Figs. 8, the air-suction device 31 may include an air-suction plug 31a and a negative pressure air-suction valve (vacuum-operated inlet valve) 31b. Fig. 8(a) is a sectional view showing the air-suction device 31 in which the air-suction plug 31a and the negative pressure air-suction valve 31b are integrally provided together, and Fig. 8(b) is a plan view of essential portions of the check valve body 34 as viewed from communication ports 34a.

[0079] The negative pressure air-suction valve 31b includes a check valve 33 which receives pressure in the entering-water pipe 18 and atmospheric pressure. If a pressure difference is generated between the pressure in the entering-water pipe 18 and the atmospheric pressure, the check valve 33 accommodated in the negative pressure air-suction valve 31b is operated, and outside air is made to flow into the entering-water pipe 18.

[0080] More specifically, the negative pressure air-suction valve 31b includes two check valves 33a and 33b which are arranged in series so that fluid flows in the same direction (toward interior of entering-water pipe 18). The negative pressure air-suction valve 31b also includes a check valve body 34 provided with angular communication ports 34a in which the check valves 33a and 33b are accommodated and which is in communication with the entering-water pipe 18, and an air-suction valve body 35 which is connected to the check valve body 34 and which has an air-suction port 36 for guiding outside air into the check valve body 34. The check valve body 34 and the entering-water pipe 18 are fixed to each other through a bolt 41. The check valve body 34 and the air-suction valve body 35 are fixed to each other through a bolt 42.

[0081] The plurality of communication ports 34a are provided such that they are deviated from each other in position in the vertical direction and/or the horizontal direction. In this embodiment, two communication ports 34a are provided as shown in Fig. 8(b). According to this, even if one of the communication ports 34a is closed for some reason, outside air can be guided into the entering-water pipe 18 by the other communication port 34a.

[0082] The air-suction valve body 35 has a plug hole 35a into which the air-suction plug 31a is fitted. The air-suction port 36 is closed by fitting the air-suction plug 31a into the plug hole 35a. The air-suction plug 31a can open the air-suction port 36. A hose 38 is connected to the air-suction port 36. Fig. 8 shows a state where the air-suction port 36 is opened by the air-suction plug 31a. At this time, a stopper 39 which can be attached to and detached from the air-suction plug 31a maintains a state where the air-suction port 36 is opened by the air-suction plug 31a.

[0083] When maintenance of the water quality adjusting portion 23 is carried out by the air-suction device 31, the entering-water pipe 18 is closed by the closing valves 25a and 25b and then, the air-suction port 36 is opened by the air-suction plug 31a. The drainage passage 26b is opened by the drainage valve 26a.

[0084] If the drainage passage 26b is opened, water which stays between the closing valves 25a and 25b is drained into outside through the drainage passage 26b. If the draining operation proceeds, negative pressure is generated in the entering-water pipe 18 between the closing valves 25a and 25b, and a pressure difference is generated with respect to the atmospheric pressure. If a pressure difference of a given level is generated, the check valve 33 which is configured such that fluid flows into the entering-water pipe 18 is opened, and outside air flows into the entering-water pipe 18 through the air-suction port 36.

[0085] This prevents water from issuing from the air-suction plug 31a and the air-suction port 36. If outside air flows into the entering-water pipe 18 between the closing valves 25a and 25b, it is possible to more reliably drain water which stays in the entering-water pipe 18 between the closing valves 25a and 25b.

[0086] 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, the flow path is first closed by the closing valves 25a and 25b. Next, the drainage valve 26a of the drainage passage 26b is opened, and water which stays between the closing valves 25a and 25b is drained. At this time, the entering-water pipe 18 may be opened into the atmosphere by the air-suction device 31, and outside air may be made to flow into the entering-water pipe 18. Next, the water quality adjusting portion 23 which can be attached to and detached from the entering-water pipe 18 is removed. According to this, only water which stays between the closing valves 25a and 25b is drained, and it is unnecessary to drain water in the entire water heater. Hence, maintenance of the water quality adjusting portion 23 can efficiently be carried out.

(Fourth Embodiment)

[0087] Fig. 9 is a schematic block diagram of a water heater according to a fourth embodiment of the invention, and Fig. 10 is a schematic block diagram of a water quality adjusting unit of the water heater. In the fourth embodiment, the same symbols as those of the first to third embodiments are allocated to the same members, and detailed description thereof will be omitted.

[0088] In the fourth embodiment, the air-suction device 31 is placed downstream of a branching location between the main flow path 18a and the auxiliary flow path 18b with respect to a flowing direction of water which flows through the entering-water pipe 18 and upstream of the connecting portion 47b. A connected location between the air-suction passage 32 and the entering-water pipe 18 is higher in the vertical direction than the water quality adjusting portion 23. The connected location between the air-suction passage 32 and the entering-water pipe 18 may be located on any of the main flow path 18a and the auxiliary flow path 18b. The air-suction device 31 may have the air-suction plug 31a as shown in Fig. 7 or may have the air-suction plug 31a and the negative pressure air-suction valve 31b as shown in Fig. 8.

[INDUSTRIAL APPLICABILITY]

[0089] 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]

[0090] 

3

hot water tank

8

circulation pump

10

heating device

12

water supply pipe

18

entering-water pipe

19

outgoing-hot water pipe

23

water quality adjusting portion

25a, 25b

closing valve

26a

drainage valve

26b

drainage passage

31

air-suction device

31a

air-suction plug

31b

negative pressure air-suction valve

Claims

1. 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;

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; and

a water quality adjusting portion which can be attached to and detached from the entering-water pipe or the water supply pipe, which reforms the inflow water into water having quality in which scale is less prone to be generated, and which flows the water out, wherein

the entering-water pipe or the water supply pipe 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.

2. The water heater according to claim 1, further comprising a drainage passage having a drainage valve between the first closing valve and the second closing valve.

3. The water heater according to claim 2, wherein the drainage passage is placed on a vertically lower side of the water quality adjusting portion.

4. The water heater according to claim 1, further comprising an air-suction device for making outside air flow into the entering-water pipe or the water supply pipe, wherein the air-suction device is placed between the first closing valve and the second closing valve.

5. The water heater according to claim 4, wherein the air-suction device is placed on a vertically upper side of the water quality adjusting portion.

6. The water heater according to claim 4 or 5, wherein the air-suction device includes an air-suction plug and a negative pressure air-suction valve, and the negative pressure air-suction valve is provided between the air-suction plug and the entering-water pipe or between the air-suction plug and the water supply pipe.

Drawing