JPH04116341A - Automated hot water filling device for bathtub - Google Patents

Abstract

PURPOSE:To protect a back-flow prevention device from tap water supply pressure by closing a water solenoid valve when the open state of an opening/closing valve is detected or after the opening/closing valve is opened. CONSTITUTION:A hot water output pipe 13 is branched into two pipes, one getting a connection pipe 18 to a bath circulation circuit 30, on which pipe 18 a hot water supply solenoid valve (water solenoid valve) 19 opened and closed in response to an instruction of hot water supply is provided, and further downstream thereof a back-flow prevention device 20 is provided. Downstream the back-flow prevention device 20 there are disposed a hot water supply opening/closing valve for performing the opening/ closing operation associated with the opening/closing operation of the hot water supply valve 19 and an opening/closing valve 28, and downstream of the opening/closing valve 28 the connection pipe 18 is connected with the bath circulation circuit 30. Upon the hot water supply, the opening/closing valve 28 is opened prior to the hot water supply valve 19, and the hot water supply valve 19 is opened in the state where a flow rate is limited by a hot water amount servo 16. Hereby, in a hot water supply circuit 10 water supply from a water supply pipe 11 passes through a main heat exchanger 12 and is heated, and hot water passes through the hot water supply valve 19, back-flow prevention device 20, and opening/closing valve 28 and flows into the bath circulation circuit 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic hot water filling device in which a backflow prevention device is disposed in piping to a bath circulation circuit that separates a bathtub.

1-Prior art-1 An automatic hot water filling device that uses water supply pressure to supply hot water to a bathtub installed at a high place (J, since the bathtub and water supply need to be separated, A backflow prevention device formed between two check valves with an atmosphere open I'' is placed in the piping, and the popular open 1+ is 1'.

When the valve element on the downstream side is opened by the supplied hot water, it is reversibly closed, and conversely, when the supply of hot water is stopped, the atmosphere opening port opens when the valve element on the downstream side is closed.

Zunawaji, the atmosphere opening TIML is closed only when hot water is supplied, and the bathtub is communicated with the water supply.

Therefore, when hot water starts or stops passing through the backflow preventer, a small amount of hot water will flow out of the open opening.

This sluice is open to the atmosphere [A hopper is provided outside of 1 to collect any hot water that flows out, and the hot water in the hopper is placed in the bath circulation circuit after the hot water is filled] 2 Pumps are used to pump the water into the bathtub. pumped out.

On the other hand, the wind F-N ring circuit is equipped with a heat exchanger for reheating, and in order to heat efficiently when reheating,
It is circulated by hot water in the bath circulation circuit or by a pump. At this time, in order to separate the bath circulation circuit from the hot water filling pipe in which the backflow prevention device 1 is installed, the backflow prevention device 1. An on-off valve is provided to cut off communication with the tensioned pipeline.

[Problem to be solved by the invention - 1 As described above, a hot water filling device with one bath circulation circuit is not only capable of filling hot water, but also has the ability to reheat the bath circulation circuit. The actions of , and are not necessarily performed as a series of actions, but can be seen as two actions each, so the filling action may start after the reheating action.

Therefore, when performing hot water filling operation after reheating (-), if the first flow on-off valve of the backflow d device is closed, the supplied hot water will be stopped by the on-off valve, and the water supply will be turned off. There is a problem in that the supply pressure is temporarily applied to the backflow prevention 11 device.

The object of the present invention is to protect a backflow prevention device 6' disposed in a hot water filling pipe from water supply pressure.

1 Means for Solving the Problem 1 The present invention includes a water solenoid valve connected in series to a hot water filling pipe of a bath circulation circuit formed by connecting a heat exchanger equipped with 11 heating means, a bathtub, and a pump. A backflow prevention device and an on-off valve formed in connection with the opening/closing operation of the valve body of the check valve [7 to open and close reversibly to atmosphere 1] are arranged in order between the two reverse II valves arranged. , in an automatic hot water filling device that performs predetermined hot water filling control for the bath 19, when the opening operation of the water solenoid valve is detected as the open state of the opening/closing valve, or when the opening operation of the opening/closing valve is detected. What you do after doing something is called technique I/i means.

Further, the on-off valve may be closed after the water solenoid valve is closed.

1 Effect] In the present invention, when the water solenoid valve is opened, it is determined whether the on-off valve is open or not, and if the on-off valve is open, the water solenoid valve is opened as is, and the on-off valve is not open. If the on-off valve is opened, then the on-off valve is opened.

Therefore, the hot water that has passed through the water electromagnetic valve passes through the backflow prevention device and the on-off valve and is supplied to the bath circulation circuit.

In the second aspect of the invention, since the on-off valve is closed after the water solenoid valve is closed, no supply pressure remains in the backflow prevention device.

[Effects of the Invention] In the present invention, in a hot water filling pipeline, when the water solenoid valve on the 10th flow side of the backflow prevention device opens, the water is supplied because the opening/closing valve on the downstream side of the backflow prevention device is open. Whether it's the pressure of hot water or the backflow prevention device, it won't cause any eye contact.

Further, in the invention of claim 2, since the on-off valve is not closed before the water solenoid valve is closed, no supply pressure is applied to the backflow prevention device.

Therefore, the backflow prevention device 61 can be protected from the water supply pressure.

[Example 1 Next, the present invention will be explained based on examples.

FIG. 2 shows a waste hot water supply bath system 1- as an automatic hot water filling device of the present invention.

Is the Kasu hot water supply bath system 1 a water supply pipe 1 connected to a water supply source calculated backwards? , a hot water supply circuit 10 which also includes a main heat exchanger 12 for heating supplied water, and a bath circulation circuit 30 for reheating the bathtub B.

The water supply pipe 11 is connected to a bypass pipe 14 whose other end is connected to a hot water outlet pipe 3 downstream of the main heat exchanger 12, or as a side path of the heat exchanger 12, and the bypass pipe 14 is connected to Bypass electricity (water valve 1) for mixing hot water flowing out from the upper heat exchanger 12 and water supplied from the water supply pipe 1
5 are provided.

The hot water outlet pipe 13 has a hot water section servo 16 for adjusting the flow rate of water supplied from the water supply pipe 11 (1'+n, the hot water outlet pipe 13 is a hot water flow rate servo) 6, which is branched into two downstream. T-
A hot water supply pipe 17 is connected to several water supply ports (not shown), and the other is a connection pipe 18 to a bath circulation circuit 30.

The connecting pipe 18 is equipped with a solenoid valve 19 (hereinafter referred to as "water filling valve 1") 19 that opens and closes in response to instructions for filling water.
・A backflow prevention device 20 is provided on the flow of the bath to prevent backflow of water from the bath circulation circuit 30.

As shown in FIG. 3, the backflow prevention device 20 includes a first back check valve 2] and a second check valve 22 arranged in series, and the first back check valve 2
], an atmosphere opening IM 123 is formed in the valve chamber 21a of the first check valve 21, and an atmosphere opening/closing valve 23.3 that operates reversibly is provided in the valve body 2lb of the first check valve 21. In response to the opening operation of the body 2lb as the hot water flows in, the atmosphere opening 23 is closed by the atmosphere opening/closing valve 23.a. The valve chamber 21a is provided with a hopper 2-1 (j1) for temporarily storing hot water flowing out from the atmosphere opening 1] 23 on the outside of the atmosphere opening 23, and the hopper 24 is connected to the valve chamber 21a through the atmosphere opening 1] An external communication pipe 25 is provided for communicating with the outside, and a discharge pipe 26 is provided at the bottom of the hopper 24 for discharging the water inside the hopper 24.

The discharge pipe 26 is connected to the downstream side of the second check valve 22.
A solenoid valve (hereinafter referred to as ``drain fl'') 27 is provided.

Connecting pipes 1 and 3 downstream of the backflow prevention device 20 are provided with a hot water filling on/off valve (hereinafter referred to as 1-on/off valve-1) 28 as a way valve that opens and closes in conjunction with the opening/closing operation of one hot water filling valve. A connecting pipe 181 is connected to the bath circulation circuit 30 downstream of the on-off valve 28.

The bath circulation circuit 301j, the forward direction pipe 30a connected to the bath mB via the pump 31 and the bath heat exchanger 32 from the connection part 30A with the connection pipe 18, and the communication between the bathtub)-3 and the connection pipe 18 are established. A reverse pipe line 3 connected to the bathtub B via a conveyance switching valve (hereinafter referred to as F "switching valve 1") 33 for cutting off the transport.
01) are connected in a closed manner via the bathtub 1yB, and the forward direction pipe 30a゛ζ is such that hot water always moves from the connection part 30A to the bathtub B during each operating operation. , in the reverse direction pipe 30b, hot water moves from the connection part 30A toward the bathtub B in the meat transfer operation to be described later, and conversely, in the single transfer operation and the reheating operation, the hot water moves toward the bathtub B.
Hot water moves from the fIB toward the connecting portion 30A.

The pump 31 connects the connecting portion 3 in the forward conduit 30a.
The 0A side is the suction part 3]a, and the bathtub Bl! ! lI from the discharge section 31. b) Move the hot water.

The forward pipe 30a is equipped with a water flow switch 34 for detecting the flow of hot water in the bath circulation circuit 30, and the reverse pipe 3011 is equipped with a slanted water level sensor 35 for detecting the water level in the bathtub B. or are provided.

The water level sensor 35 utilizes a semi-hemispherical diffusion resistance type pressure sensing element that utilizes the Vieso resistance effect in which electrical resistance changes in response to strain in a semiconductor single crystal.

In addition, the hot water amount servo 16, the on-off valves', 28, and the switching valve 33 are controlled by I'il'il CAD motors, respectively.
i! water flow servo 1G, on/off valve 28, switching valve 33
There is a state detection element for detecting each open state or open state.

In addition, in FIG. 2, 36, 37, and 38 are thermisters, and 39, 40 are flow sensors.

In addition, each heat exchanger] 2.32 is provided with a 1,000 burner 4] and a bath burner 42, and in the fuel supply pipe 43 to each burner 41.42, 44 is a former solenoid valve, 45.4
6 is a gas solenoid valve, 47 is a governor proportional valve, 48 is a waste governor, and 4 is a gas solenoid valve.

4]a, 4.2a is a blower that supplies combustion air to each burner 41.42;
1.4.2 is also equipped with an ignition electrode (not shown) and a flame lock for flame detection.

The waste water supply bath system 1 having the above configuration is controlled by a control device 50.

The control device 50 is composed of a microcomputer, several drive circuits, etc., and includes, for example, a bath remote control 51 installed in the bathroom and a main remote control 52 installed in the kitchen. Combustion control and water control are performed according to the operating state of the and the detection state of each thermistor, etc., and hot water supply operation, automatic hot water filling operation, reheating operation, and heat retention operation are performed.

Each remote control is equipped with a setting switch to set the hot water temperature for hot water supply operation, and to set the hot water temperature and water level for hot water filling, as well as a liquid crystal display to display the setting status and operating status. When you operate the fully automatic switch (iii) on the remote control, fully automatic operation is performed with automatic hot water filling operation, reheating operation, and warming operation as a series of operation operations.

Regarding fully automatic operation, there is an operation switch that can be used to set the temperature a predetermined temperature higher or lower than the set temperature, or to set the water level to a predetermined water level (゛) higher than the set water level. If these switches are operated instead of the switch, full automatic operation will be performed according to the changed conditions.

For hot water supply operation, open the hot water tap (not shown) installed at the downstream end of the hot water pipe 17, and when the flow rate sensor 39 detects that water is flowing, heating is performed by the main burner 41, and each The combustion amount of the main burner 41 is adjusted according to the set temperature of the remote controller, and the hot water supply (C) 11 is adjusted by the hot water thermostat 16 and the bypass solenoid valve 15.

The automatic hot water filling operation is performed only when the hot water supply operation is not in progress by operating the hot water filling switch and the fully automatic switch provided on each remote control.
Regardless of whether or not there is hot water in B, filling the hot water is completed under the set conditions.

The hot water filling operation in the automatic hot water filling operation and 17 refer to the one-way conveyance operation in which hot water is filled from only the forward pipe line 30a of the bath circulation interval E@30 to the bathtub B, and the forward pipe i? There are two ways to perform the reconveying operation of filling hot water into the bathtub B via the two pipes 830a and the reverse pipe 301), and each filling operation is performed according to a predetermined sequence as described later. It will be held in

The automatic hot water filling control will be explained below based on FIG. 4.

In the automatic hot water filling control, 59 is first used to prime the operation of the pump 31 to determine whether there is hot water in the bathtub B or to detect the water level when there is hot water in the bathtub B. (Step 1)
), supplying hot water to each pipe.

After that, the hot water 41 in the bath circulation circuit 30 is set as the water supply.
In order to determine if there is no water, the pump 31 is driven 2, and if a water flow is detected by the water flow switch 34, it is determined that hot water remains in the bathtub B.

If it is determined that there is hot water based on the water rate setting (YES in step 2), it is determined whether the water level in the bathtub B is at a water level set in advance using the remote control (step 3).

In step 3, if it is determined that the set water level has been reached (YES), it is considered that a considerable amount of water remains in bathtub B, so the temperature of the water in bathtub B should be adjusted.
In order to increase the temperature, proceed to step 10, which will be described later.

If it is determined in step 3 that the set water level has not been reached (No), the process moves to step 9, which will be described later, to further fill the water.

If it is determined that there is no hot water in bathtub B as a result of the water rate determination in step 2 (2) (No), the water level calculated in advance corresponding to the water level in bathtub ■3 is determined as follows. The Kechi hot water filling up to this point is performed by re-conveying operation (Step 4).

After the water filling is completed, the pump 31 is operated again to adjust the water supply (step 5).

Normally, this water rate setting "ζ" indicates that hot water is being supplied close to the set water level in the bathtub I3, so it is determined that there is hot water in the bathtub B. (No in step 5)
, it is thought that the user forgot to close the drain plug of the bathtub B, so the error stop occurs [Step 6], and then a hopper drain request is set to drain the hopper 24 (Step 7).

If there is hot water in the bathtub 3 (YES), it is determined whether the hot water in the bathtub B has reached the set water level or has reached the set water level.

If the set water level has not been reached (NO in step 8), the water level sensor 3 biased toward the reverse pipe 30b
One-sided conveyance operation is performed based on the detected water level in step 5 (step 9).
).

If it is determined that the hot water in bathtub B is up to the set water level (Y+ES in step 8), the one-way conveyance operation in step 9 is omitted and the process moves to step 10.

In step 10, the hot water in the bathtub B, which has reached the set water level, is circulated by driving the pump 3 and heated by the bath burner 42. This heating is performed by thermistor 38
The temperature of the hot water detected by the temperature changes to the set temperature set on the remote control.

As a result of this heating, the water temperature is heated up to the set temperature set on the remote control (YES in step 111).
), the water filling operation has been completed, and a hopper drain request is set to drain the water in the hopper 24 (step 12).

Next, the reconveying operation of Jr. will be explained with reference to FIG.

In the reconveying operation C, it is necessary to close the switching valve 33 in order to protect the water level sensor 35, so it is determined whether the switching valve 33 is closed or not. In the case (No in step 21), Ki.~l
<The motor is operated at a fixed time 111 times to close the switching valve 33 (step 22).

If the switching valve 33 is closed (YES in step 21), then it is determined whether the on-off valve 28 is open to protect the backflow prevention device 20, and if it is closed. (No in step 23), the motor is driven to gear 1 for a fixed period of time to open the on-off valve 28 (
Step 24).

If the on-off valve 28 is open (yEs in step 23), close the hot water flow servo 16 to prevent water hammer 11 (step 25), limit the flow rate when one hot water filling valve is open. The water flow servo is 1G or the minimum opening is C.
When the closed state is detected, the hot water filling valve 19 is opened (step 26).

When the water filling valve I9 is opened to start filling the water, the water flow servo 6 is opened (step 27) in order to prevent the low-cut operation described later from being performed.
Make sure you can get the hot water filling flow rate for 1 minute.

Up to this point, hot water has been filled only from the forward pipe line 30a of the bath circulation circuit 30, so the switching valve 33 is opened (step 28), and hot water is also supplied to the bathtub B from the reverse pipe line 30b. Then, retransport operation is performed.

After opening the hot water filling valve] 9, open the bathtub B/＼If the supplied water reaches the calculated water level with respect to the water level of the bathtub B (YES in step 2), the eddy electric servo ] 6 to restrict the flow rate Step 30
), and then closes the 4f-r switching valve 33 (step 3).
), then close the hot water filling valve 9 (step 32).

Furthermore, after that, the hot water amount-servo 16 is opened (step 33), and the on-off valve 28 is closed (step 3).
4).

Next, the single conveyance operation will be explained based on FIG. 5.

Since hot water is not supplied from the reverse direction pipe 301-) in the one-way conveyance operation "ζ", it is determined whether the switching valve 33 is closed or not, and if it is not closed (step 4
]-, NO), the cathode motor is driven and the switching valve 3 is
3 (step 42).

If the switching valve 33 is closed (YES in step 41), it is determined whether the on-off valve 28 is open or not. ), the motor is driven to gear 1 to open the on-off valve (step 44).

After that, in order to prevent water hammer, the opening operation of the hot water supply valve 19 is performed (step 7'15), the flow rate is restricted when the hot water filling valve 19 is opened, and the hot water flow rate servo J6 is closed. When detected, one hot water filling valve is opened (step-'1
6).

When the hot water filling valve 19 is opened and hot water filling is started, the hot water filling valve 16 is then opened (step 47) to obtain a sufficient hot water filling flow rate.

In the one-sided conveyance operation, the water level in the bathtub B is detected by the water level sensor 35, but the one-sided conveyance operation is performed after the water level in the bath circulation circuit 30 is determined by driving the pump 31. Since the inside of the directional pipe 30b is filled with hot water, the water level can be detected by the water level sensor 35.

If the water level in the bathtub B has reached the detected water level or the water level set by the remote controller (YES in step 48), the water volume sensor 16 is closed to limit the meteor (step 4). , close one hot water filling valve (step 50).

After that, the opening operation of the hot water amount servo 16 is performed (step 51).
-), and further closes the on-off valve 28 (step 52).

Next, the hopper drainage operation will be explained.

The hopper drains from the atmosphere opening port 23 when the hot water filling valve]9 is opened and closed.
The hot water that flows out from the hopper 24 and is stored in the hopper 24 is prevented from flowing out from the external communication [I25], and
This is to prevent problems caused by freezing during cold weather.

In this embodiment, hopper drainage is performed after the automatic hot water filling operation is completed, and when the hot water filling operation is stopped due to an error.
+ Performed when there is a flag indicating water request.

Hereinafter, hopper drainage control will be explained based on FIG. 6.

Hopper drainage control ``ζζ'' determines whether or not the above-mentioned hopper drainage request flag is present, and if there is a hopper drainage request (yEs in step 61), determines whether the switching valve 33 is closed or not. However, if the switching valve 33 is open (NO in step 62), the switching valve 33 is closed (step 63).
YES in step 62), it is determined whether the on-off valve 28 is open or not, and the on-off valve 28 closes "if it is" (NO in step 6/), the on-off valve 28 is opened (step 65). ).

If the on-off valve 28 is open (YES in Sudeb 64)
S), the pump is started to be driven, and in step 66), it is determined whether or not the low cut operation has been performed.

Here, the low cut 1~operation means that the hot water filling valve 19 is opened,
If the flow detected by the raw paper sensor 40 does not reach a sufficient value even though the hot water servo 16 is opened,
- The automatic water filling operation is interrupted and the water filling valve 1-9 is closed.

This low-temperature operation is performed when hot water supply operation is performed during hot water filling operation, when the water pressure of the water supply is extremely low, or when there is a blockage in the pipes in the bath circulation circuit 30, etc. is possible.

When such a low cut operation occurs, the first check valve 21 of the backflow prevention device 20 does not open smoothly, and as a result, the atmosphere opening/closing valve 23a or the atmosphere opening 112 does not open smoothly.
3 is not closed promptly, more hot water than normal flows out from the atmosphere opening I2, and a lot of hot water accumulates in the hopper 24.

Therefore, it is necessary to increase the operating time of the pump "31" for draining the hopper.

Therefore, regarding the operating time of the drain timer that determines the operating time of hopper draining, if the low-cut operation is not performed (NO in step 67), the hopper 2
Since the amount of hot water in the tank 4 is small, the operation time of the drain timer is shortened to 5 seconds.
If the operation is f4-)l-, (YES in step 67), the amount of hot water in the hopper 24 is large, so the operation time of the drain timer is set to a long time of 15 seconds (six steps).

After 2 seconds have elapsed since the pump 31 was activated (YES in step 70), the first reverse valve 2]-
Since the hot water in the valve chamber 21a is pumped out, the drain valve 27 is opened after 2 seconds (step 71).

When the time set in the drain timer has elapsed since the pump 31 started operating (YES, S in step 72),
The on-off valve 28 is closed (step 73), separating the bath circulation circuit 30 and the backflow prevention device 20 to prevent hot water in the bathtub B from flowing back into the hopper 24. When the water is stopped (step 74), the drain valve 27 is also closed (step 75).

Thereafter, the switching valve 33 is opened (step 76), and the hopper drainage control is completed.

Note that if the automatic hot water filling operation is interrupted due to a caulking operation (due to the hot water supply operation), the hot water filling operation will be resumed as soon as the hot water supply operation is completed.

Next, the hot water filling operation of the double conveyance operation or the single conveyance operation in the waste hot water supply bath system of the present embodiment having the following configuration F- will be briefly explained.

When it is confirmed that the switching valve 33 is closed, the opening/closing valve 28 is opened prior to the hot water filling valve 9, and one hot water filling valve is opened with the hot water amount being limited by the hot water flow rate sensor 16.

Then, in the hot water supply circuit 10, the water supplied from the water supply pipe 11 passes through the main heat exchanger 12 and is heated, and the hot water passes through one hot water filling valve, a backflow prevention device 20, and an on-off valve 28 to be used in the bath. It flows into the circulation circuit 30.

At this time, the switching valve 33 is closed, and hot water is supplied to the bathtub B only from the forward pipe 30a.

Thereafter, the water supply port 16 is opened, the flow rate is increased, and the water filling operation is determined.

In the case of hot water filling operation or meat delivery, select switch valve 3 at this point.
3 is opened, and hot water is filled into the bathtub B from the reverse pipe line 30b as well.

At this time, the hot water supplied from the connecting pipe 8 is already supplied to the bathtub +3/\ by the forward pipe 302), and the inflow pressure to the reverse pipe 30 +-) is Since the water filling valve] 9 is much smaller than the initial state when it is open, the influence on the water level sensor 35 is small.

In the case of double-transfer operation, the amount of water corresponding to the water level set on the remote control is supplied to the bathtub), and in the case of single-transfer operation, when the set water level is reached, the fidget water flow servo After 16 is closed, one of the hot water filling valves is closed to complete hot water filling, and then the hot water volume servo 16 is opened and the on-off valve 28 is closed.

After that, when the predetermined boiling and pumping operations are completed and a request is made to drain the hopper, the hot water in the hopper 24 or the bath a? It is collected into B.

At this time, when the drain valve 27 is closed, the valve chamber 2 l
The water in the hopper 24 is collected through the second reverse valve 22, and after a predetermined time (2 seconds), when the drain valve 27 is opened, the water in the hopper 24 is collected and sent to the bathtub B. It will be done.

Once the water in the backflow prevention device 20 has been collected, the heat retention control is then activated for full automatic operation.

As described above, in the present invention, when the hot water filling valve is opened, the on-off valve is also opened, and the on-off valve is closed after the hot water filling valve is closed. Jj, t, l- Because the pressure of the two water pipes is not applied to the device, the backflow prevention device can be protected.

In this embodiment, the discharge pipe of the hopper is equipped with a discharge solenoid valve, but a check valve may be used instead of the discharge solenoid valve.

[Brief explanation of the drawing]

Fig. 1 is a flowchart for explaining both conveyance operations in an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of a waste hot water supply bath system showing an embodiment, and Fig. 3 is a reverse flow in a gas hot water supply bath system of an embodiment. 1 and 4 are flowcharts for explaining the automatic hot water bath control in the embodiment, and FIG. 5 is a flowchart for explaining the single conveyance operation in the embodiment. Figure 6 shows the hopper drainage side t in the embodiment.
It is a flowchart for explaining all. In the diagram, 1 Kasu hot water supply bath system (automatic hot water filling device),
10...Hot water supply times! 1'8 (water filling pipe), 19・Solenoid valve for hot water filling (water solenoid valve), 20・Backflow prevention device, 28
... On-off valve for filling hot water (on-off valve), 30. Bath circulation circuit, 31 Pump, 42. Bath burner heating means), ■
-3...Bathtub.

Claims (1)

[Claims] 1) A water solenoid valve and two check valves arranged in series in a water filling pipe to a bath circulation circuit formed by connecting a heat exchanger equipped with a heating means, a bathtub, and a pump. A backflow prevention device having an atmosphere opening port that is reversibly opened and closed in conjunction with the opening and closing operation of the valve body of the check valve, and an opening/closing valve are arranged in this order, and a predetermined hot water filling control is performed for the bathtub. An automatic hot water filling device that performs the following: The opening operation of the water electromagnetic valve is performed when the open state of the on-off valve is detected or after the opening operation of the on-off valve is performed. 2) The automatic hot water filling device according to claim 1, wherein the on-off valve is closed after the water solenoid valve is closed.