Instantaneous hot water circulation unit with scale cleaning function

Provided is an instantaneous hot water circulation unit with a scale cleaning function which can easily perform pipe cleaning for removing scale. The instantaneous hot water circulation unit which includes a hot water supply inlet portion connected to a hot water discharge unit of a hot water supply device, a hot water supply outlet portion connected to an external hot water supply unit, a hot water returning unit, a hot water outgoing unit, a hot water supply pipe, a hot water pipe, and a circulation pump, and a bypass pipe, which drives the circulation pump to perform an instantaneous hot water circulation operation when stoping hot water supply, wherein a storage tank configured to store a cleaning agent used in a cleaning operation of cleaning an inside of the pipe of the hot water supply device is provided at the bypass pipe.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of Japan patent application serial no. 2017-030113, filed on Feb. 21, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to an instantaneous hot water circulation unit which is connected to a hot water supply device and forms an instantaneous hot water system, particularly, to an instantaneous hot-water circulation unit having a function of removing scale adhering inside a pipe forming an internal passage of the hot water supply device.

Description of Related Art

Conventionally, a hot water supply device which is configured to heat service water using combustion heat of fuel and to supply hot water from a hot water supply faucet have been widely used. Generally, in such a hot-water supply device, low temperature water comes out immediately after the hot water supply faucet is opened. Thereafter, it takes time according to a route between the hot water supply device and the hot water supply faucet until hot water at a hot water supply temperature comes out. To allow warm water to be supplied immediately after the hot water supply faucet is opened, for example, as disclosed in Patent Document 1, an instantaneous hot water supply system in which a circulation passage is formed between a hot water supply device and a hot water supply faucet, and hot water heated by the hot water supply device is circulated by a circulation pump provided in the circulation passage is known.

In an area in which hard water containing large amounts of minerals such as calcium is used as service water, precipitated minerals become scale and adhere inside a pipe of the hot water supply device, particularly inside a pipe of a heat exchanger for heating the service water. In an instantaneous hot water supply system, since a frequency of heating water is high, adhesion of the scale proceeds quickly. Since the adhered scale disturbs heat exchange, heating capacity of the hot water supply device is lowered, and the pipe may reach an abnormally high temperature or may be clogged, and thus the hot water supply device may be broken. Therefore, it is necessary to remove the scale periodically.

Meanwhile, as disclosed in Patent Document 2, a technique for detecting adhesion of scale to promote pipe cleaning and a technique for preventing breakage by prohibiting combustion in the hot water supply device when the adhesion of the scale is detected are known. An operator connects equipment for pipe cleaning to the hot water supply device and then performs the pipe cleaning for removing scale. For example, one ends of two hoses are connected to each of a water supply portion and a hot water discharge portion of the hot water supply device, the other end of each hose is placed in a water tank containing a cleaning agent, and a cleaning pump is driven to circulate the cleaning agent between the hot water supply device and the water tank to perform the pipe cleaning. At this time, isolation valves disposed in the water supply portion and the hot water discharge portion are operated so that the cleaning agent is not introduced into in an upstream side of the water supply portion in the hot water supply device or a downstream side of the hot water discharge portion therein. Such pipe cleaning is performed similarly in the hot water supply system.

However, since the pipe cleaning for removing scale requires many working processes and it is necessary to prepare equipment for pipe cleaning, a user of the hot water supply device cannot easily perform the pipe cleaning. Therefore, a professional worker is arranged to perform the pipe cleaning. Further, in the hot water supply device, since it is necessary to provide the isolation valve in each of the water supply portion and the hot water discharge portion for pipe cleaning, there is a problem that installation cost of the hot water supply device increases.

SUMMARY

An aspect of the disclosure is to provide an instantaneous hot water circulation unit with a scale cleaning function which can easily perform pipe cleaning for removing scale.

According to a first embodiment, there is provided an instantaneous hot water circulation unit which includes a hot water supply inlet portion connected to a hot water discharge unit of a hot water supply device, a hot water supply outlet portion connected to an external hot water supply unit, a hot water returning unit configured to introduce returning hot water from the hot water supply unit, a hot water outgoing unit connected to a water supply unit of the hot water supply device, a hot water supply pipe configured to connect the hot water supply inlet portion with the hot water supply outlet portion, a hot water pipe configured to connect the hot water returning unit with the hot water outgoing unit, and a circulation pump provided in the hot water supply pipe or the hot water pipe, and which drives the circulation pump to perform an instantaneous hot water circulation operation in which hot water heated by the hot water supply unit is circulated when the hot water supply unit stops hot water supply, and includes a bypass pipe configured to connect the hot water supply pipe and the hot water pipe, wherein a storage tank configured to store a cleaning agent used in a cleaning operation of cleaning an inside of the pipe of the hot water supply device is provided at the bypass pipe.

According to a second embodiment, in the first embodiment, a blocking unit configured to prevent the hot water from flowing through the bypass pipe in the instantaneous hot water circulation operation and to prevent the hot water from flowing through the hot water supply outlet portion and the hot water returning unit in the cleaning operation unit may be provided.

According to a third embodiment, in the first or second embodiment, a drain portion may be provided in the storage tank or the bypass pipe, and when the cleaning operation is completed, the hot water containing the cleaning agent may be discharged from the drain portion.

According to a fourth embodiment, in any one of the first to third embodiments, a controller configured to control the cleaning operation and a water amount detection unit configured to detect a hot water supply usage amount may be included, and the controller may automatically start the cleaning operation when a period during which the cleaning operation is not performed exceeds a preset period or when an accumulated amount of the hot water supply usage amount detected by the water amount detection unit exceeds a preset accumulated amount.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, configurations for performing the disclosure will be described on the basis of embodiments.

Embodiments

First, an instantaneous hot water supply system1will be described.

As illustrated inFIG. 1, in the instantaneous hot water supply system1, a hot water supply device2, an instantaneous hot water circulation unit3, a hot water supply outgoing pipe7and a hot water supply returning pipe8are connected to each other to form a hot water circulation passage. One or more external hot water supply units are provided in the circulation passage, for example, a first hot water supply unit4is disposed as a shower in a bathroom, and a second hot water supply unit5is disposed as a hot water supply faucet of a washstand. Further, a water supply pipe10for supplying service water is connected to the hot water supply returning pipe8. Also, an arrow WS indicates water supply, and an arrow D indicates drainage.

Next, the hot water supply device2will be described.

As illustrated inFIG. 2, the hot water supply device2includes a combustion unit11, a heat exchanger12, a heating pipe13connected from a water supply unit9to a hot water discharge unit6via the heat exchanger12, and a hot water supply controller14which controls combustion of the combustion unit11. The combustion unit11mixes air guided from a blower fan15with a fuel gas and burns it to generate a high-temperature combustion gas. The heat exchanger12heats water by exchanging heat between the combustion gas and the hot water flowing through the heating pipe13.

A heated water amount sensor16awhich detects an amount of hot water flowing through the heat exchanger12, an incoming water temperature sensor16b,a hot water discharge temperature sensor16c,a hot water discharge control valve17which adjusts a hot water discharge amount, and a hot water supply bypass pipe18which bypasses the heat exchanger12are disposed in heating pipe13. A hot water supply bypass control valve19which adjusts the amount of hot water flowing through the hot water supply bypass pipe18is disposed in the hot water supply bypass pipe18. The hot water supply bypass control valve19may adjust a discharge temperature of the hot water by adjusting a mixing ratio of the heated hot water flowing through the heating pipe13and the hot water flowing through the hot water supply bypass pipe18. Also, the heating pipe13may not include the hot water supply bypass pipe18and the hot water supply bypass control valve19. In this case, the discharge temperature of the hot water may be adjusted by controlling a combusting state of the combustion unit11.

The hot water supply controller14controls the discharge temperature of the hot water by driving the hot water supply bypass control valve19or the blower fan15on the basis of an output of the hot water discharge temperature sensor16cor the like provided in the hot water supply device2. Although not illustrated, the hot water supply device2has an operation unit connected to the hot water supply controller14to receive an operation of a user. The operation unit includes an input unit having an input switch or the like, an information display unit, an audio output unit, and so on.

Next, the instantaneous hot water circulation unit3will be described

As illustrated inFIG. 1, the instantaneous hot water circulation unit3includes a hot water supply inlet portion30, a hot water supply outlet portion31, a hot water supply pipe32which connects the hot water supply inlet portion30with the hot water supply outlet portion31, a hot water returning unit33, a hot water outgoing unit34, and a hot water pipe35connecting the hot water returning unit33with the hot water outgoing unit34, and also is accommodated in an exterior case36.

A circulation pump37and a water amount sensor38are disposed as a water amount detection unit for detecting the amount of hot water flowing through the hot water pipe35in the hot water pipe35. Further, a hot water bypass pipe39bypassing the circulation pump37is provided in the hot water pipe35. A check valve40is disposed in the hot water bypass pipe39.

A bypass pipe41branching from the hot water supply pipe32and connected to the hot water pipe35is provided in the hot water supply pipe32, and a storage tank42is disposed in the middle of the bypass pipe41. A first three-way valve43forming a blocking unit is disposed at a branching portion between the hot water supply pipe32and the bypass pipe41. A merging portion for connecting the bypass pipe41with the hot water pipe35is located upstream of the branching portion of the hot water bypass pipe39, and a second three-way valve44forming a blocking unit is disposed at the merging portion.

The first three-way valve43is switched to the hot water supply pipe32side or the bypass pipe41side so that a fluid introduced from the hot water supply inlet portion30flows through the hot water supply outlet portion31or the storage tank42. The second three-way valve44is switched to the hot water pipe35side or the bypass pipe41side so that the hot water introduced from the hot water returning unit33or the fluid in the storage tank42flows through the hot water outgoing unit34.

An upstream pipe portion41aof the bypass pipe41branching from the hot water supply pipe32is connected to an upper portion of the storage tank42. A downstream pipe portion41bof the bypass pipe41connected to the hot water pipe35is connected to a lower portion of the storage tank42. A drain pipe46having a drain valve45is disposed as a drain portion at a bottom of the storage tank42. An overflow pipe48connected to a portion of the drain pipe46on a downstream side of the drain valve45from an upper limit position of a stored water level is disposed to discharge the hot water overflowing from the storage tank42.

An injection port42aof a cleaning agent used in a cleaning operation for performing pipe cleaning and a plurality of electrodes for detecting the stored water level are disposed in a top surface portion of the storage tank42. In the exterior case36, an opening is provided at a position corresponding to the injection port42a. Although not illustrated, the exterior case36may have a lid member capable of closing the opening.

The instantaneous hot water circulation unit3includes a circulation controller49as a controller and controls the cleaning operation or the like by driving the circulation pump37, the first three-way valve43, the second three-way valves44or the like in cooperation with the hot water supply controller14of the hot water supply device2. Also, the circulation controller49has a timer function and accumulates hot water supply usage amounts detected by the water amount sensor38when the circulation pump is not being driven. Further, the hot water supply controller14may have the timer function and the hot water supply usage amount accumulating function and may constitute the controller together with the circulation controller49. Furthermore, the hot water supply controller14may have the timer function and the hot water supply usage amount accumulating function and may be formed to control the cleaning operation or the like by driving the circulation pump37or the like, and thus the circulation controller49may be omitted. The hot water supply usage amounts detected by the heated water amount sensor16amay be accumulated.

Next, the operation and effects of the instantaneous hot water circulation unit3of the disclosure will be described.

As illustrated inFIG. 3, when the hot water supply is stopped and thus the hot water is not supplied from the hot water supply unit, the controller performs an instantaneous hot water circulation operation. In the instantaneous hot water circulation operation, the first three-way valve43is switched to the hot water supply pipe32side and the second three-way valve44is switched to the hot water pipe35side so that a flow of the hot water in the bypass pipe41is blocked. Further, the circulation pump37is driven to circulate the warm water heated by the hot water supply device2.

By the circulation pump37and the first and second three-way valves43and44, the warm water discharged from the hot water supply device2can be caused to flow through the hot water supply outgoing pipe7, and the returning hot water flowing through the hot water supply returning pipe8can flow into the hot water supply device2. A wax thermo valve (not illustrated) is disposed at a connecting portion47between the hot water supply outgoing pipe7and the hot water supply returning pipe8. The wax thermo valve is closed to stop the circulation of the hot water when the circulating warm water is equal to or higher than a predetermined temperature.

When the water amount sensor38detects a water amount less than a predetermined minimum working water amount due to the closing of the wax thermo valve, energy consumption during an instantaneous hot water circulation operation is minimized by stopping the circulation pump37and the combustion of the combustion unit11. While the circulation is stopped, the circulation pump37is intermittently driven to check whether or not the wax thereto valve is open due to a decrease in a temperature of the hot water. When the wax thermo valve opens and the water amount sensor38detects an amount of water equal to or larger than the minimum working water amount due to the driving of the circulation pump37, the combustion of the combustion unit11starts, and the instantaneous hot water circulation operation restarts.

As illustrated inFIG. 4, for example, when the hot water supply starts from the first hot water supply unit4, the warm water in the hot water supply outgoing pipe7is supplied. Further, the service water supplied from the water supply pipe10flows through the hot water pipe35and flows into the hot water supply device2. The service water is heated by the hot water supply device2and becomes the warm water, and this warm water flows through the hot water supply pipe32and is supplied to the hot water supply outgoing pipe7. Therefore, instantaneous hot water supply in which the warm water is discharged immediately after the start of the hot water supply is realized.

During the hot water supply, since the hot water flows due to a supply pressure of the service water, the circulation pump37is stopped. At this time, by allowing the service water to flow through the hot water bypass pipe39, the stopped circulation pump37is prevented from becoming water flow resistance and thus preventing the hot water from easily flowing and reducing the discharge amount of the hot water. Incidentally, the circulation pump37may be operated to correspond to the hot water supply of a large flow rate.

The controller measures a period from the start of the operation of the instantaneous hot water circulation system or a period from the previous cleaning operation. When a period during which the cleaning operation is not performed exceeds a preset period, or when the accumulated amount of the hot water detected by the water amount detection unit exceeds a preset accumulated amount, the controller starts the cleaning operation. The set period is appropriately set according to hardness (use area) or the like of the service water and is set to a period of, for example, a half year or a year. The set accumulated amount is likewise set appropriately according to the use area or the like. At the start of the cleaning operation, for example, the user is informed to insert the cleaning agent into the storage tank42by display or voice from the operation unit.

After the cleaning agent is inserted into the storage tank42, the user inputs completion of an injection of the cleaning agent, for example, by operating the operation unit. After the injection of the cleaning agent, as illustrated inFIG. 5, the controller switches the first three-way valve43to the bypass pipe41side to block the flow of the hot water at the hot water supply outlet portion31and introduces the hot water, for example, to the upper limit of the stored water level of the storage tank42. The cleaning agent is an acidic agent which dissolves scale and contains citric acid, acetic acid, and so on. Further, the cleaning agent to be injected may be in the form of a tablet or granules, or a liquid may be injected.

As illustrated inFIG. 6, when the hot water containing the cleaning agent is circulated, the second three-way valve44is switched to the bypass pipe41side to block the flow of the hot water in the hot water returning unit33. Also, the first three-way valve43maintains a flow blocking state of the hot water supply outlet portion31. By driving the circulation pump37in this state, the cleaning agent in the storage tank42flows into the hot water supply device2, flows through the heating pipe13and returns to the storage tank42. At this time, the hot water supply bypass control valve19of the hot water supply device2is closed.

When a predetermined time (for example, one hour) elapses after the start of the circulation of the cleaning agent, the circulation pump37is stopped, the drain valve45is opened, and the cleaning agent is discharged from the drain pipe46. When discharge of the cleaning agent is completed, the drain valve45is closed, and the second three-way valve44is switched to the hot water pipe35side as illustrated inFIG. 5to introduce the service water, for example, to the upper limit of the stored water level of the storage tank42. After that, the second three-way valve44is switched to the bypass pipe41side, and the drain valve45is opened to discharge the introduced service water from the drain pipe46. The cleaning agent is reliably discharged from an inside of the cleaned pipe by repeating such flushing due to introduction and discharge of the service water a plurality of times (for example, three times).

After completion of the flushing, the second three-way valve44is switched to the hot water pipe35side to introduce the service water and thus to discharge air in the cleaned pipe to the storage tank42, the first three-way valve43is switched to the hot water supply pipe32side to terminate the cleaning operation, and the instantaneous hot water circulation operation starts as illustrated inFIG. 3. Further, it is preferable that the service water stored in the storage tank42by the introduction of the service water be discharged from the drain pipe46.

The instantaneous hot water circulation unit3with the cleaning function according to the disclosure circulates the warm water between the hot water supply device2and the hot water supply unit during the instantaneous hot water circulation operation and circulates the cleaning agent between the hot water supply device2and the instantaneous hot water circulation unit3during the cleaning operation. Therefore, it is unnecessary to prepare pipe cleaning equipment for the cleaning operation and to connect the equipment with the hot water supply device2, and it is possible to easily perform the pipe cleaning by injecting the cleaning agent.

Further, since the blocking unit is provided in the instantaneous hot water circulation unit3, mixing of the cleaning agent into the hot water for hot water supply during the cleaning operation can be prevented. Therefore, the isolation valve normally disposed in the water supply unit9and the hot water discharge unit6of the hot water supply device2can be omitted.

In addition, since the drain pipe46for discharging the cleaning agent is provided, it is possible to reliably discharge the cleaning agent and to prevent the cleaning agent from entering the hot water for hot water supply. Also, since the controller automatically starts the cleaning operation with the elapse of the set period or exceeding of the set accumulated amount, the cleaning operation can start periodically or at a timing when the scale adheres to some extent, and thus breakage due to the scale can be prevented.

Next, a modified example in which the above-described embodiment is partially modified will be described with reference toFIG. 7.

[1] The circulation pump37of the instantaneous hot water circulation unit3may be disposed at a portion of the hot water supply pipe32on the upstream side of the branching portion of the bypass pipe41.

[2] The drain pipe46may be disposed in the downstream pipe portion41bof the bypass pipe41.

[3] The blocking unit may include servo valves53aand53bdisposed instead of the first three-way valve43, and a servo valve54aand a check valve54bdisposed instead of the second three-way valve44.

[4] In addition, those skilled in the art can implement the disclosure in such a manner that various modifications are added to the above embodiments without departing from the spirit of the disclosure, and the disclosure includes such modifications.

Due to the above-described first embodiment configuration, since the equipment for pipe cleaning which removes scale is provided in the instantaneous hot water circulation unit which constitutes a hot water supply system, pipe cleaning of the hot water supply device can be easily preformed.

Due to the above-described second embodiment configuration, since it is possible to prevent mixing of the cleaning agent into the hot water for hot water supply, an isolation valve disposed in the water supply unit and the hot water discharge unit of the hot water supply device can be omitted.

Due to the above-described third embodiment configuration, it is possible to reliably discharge the cleaning agent and to prevent the mixing of the cleaning agent into the hot water for hot water supply.

Due to the above-described fourth embodiment configuration, the cleaning operation can start periodically or at a timing when the scale adheres to some extent, and thus breakage due to the scale can be prevented.

According to the disclosure, it is possible to provide an instantaneous hot water circulation unit with a scale cleaning function which can easily perform pipe cleaning for removing scale.