JPH02171547A - Gas hot water feeder - Google Patents

Abstract

PURPOSE:To prevent a boiling state from being generated even if a thermal load is low by a method wherein a mixing valve is arranged at a connecting part between a first thermal circuit hot water feeding pipe and a second thermal circuit hot water feeding pipe, and when a thermal load is high, the first and second hot water feeding pipes are fully opened and in turn when the thermal load is low, the first hot water feeding circuit is fully opened and the second hot water feeding circuit is metered to its minimum degree. CONSTITUTION:A mixing valve 12 is comprised of a fixed disk 14 and a movable disk 16. The fixed disk 14 is provided with a first inlet 17 communicating with a first thermal circuit hot water feeding pipe 6a, a second inlet 18 communicating with a second thermal circuit hot water feeding pipe 6b and an outlet 19 communicating with a downstream hot water feeding pipe 6. Each of through-holes 20, 21 and 22 of the movable disk 16 communicate with each other at a rear side of the movable disk 16. When the second through-hole 21 is coincided with a high flow rate part 18a, the mixing valve 12 shows that the first through- hole 20 is coincided with the first inlet 17 so as to fully open the hot water feeding pipes 6a and 6b of the first thermal circuit (a) and the second thermal circuit (b). When the second through-hole 21 is coincided with a low flow rate part 18b, the first through-hole 20 is coincided with the first inlet 17 to fully open the first thermal circuit hot water feeding pipe 6a and then the second thermal circuit hot water feeding pipe 6b is metered to a low flow rate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a gas water heater, particularly a gas proportional gas instantaneous water heater that controls the hot water temperature by the amount of gas. This invention relates to a gas water heater that has a capacity equivalent to the sum of the maximum capacities of two heat circuits.

[Prior Art] Conventionally, as this type of gas water heater, for example,
There is one published in No. 86642.

The device disclosed in Japanese Utility Model Application Publication No. 61-86642 has 112 gas heating units, that is, two heat circuits connected in parallel, and two water supply units.
The water is divided into two parts and supplied to two heat circuits, and the water is boiled in each heat circuit.

[Problem to be solved by the invention] In the conventional gas water heater described above, the minimum capacity as a water heater is a number corresponding to the sum of the minimum capacities of each heat circuit, and since the minimum number is large, a small heat load can be achieved. At times (for example, when supplying hot water to a low-temperature lagoon in the summer), the capacity may be too large to be used, making it inconvenient to use.

In addition, in order to avoid such problems, it is possible to take measures such as closing the heat source of one heat circuit when the heat load is small, but if such a method is adopted, the flow that flows into the two heat circuits will be reduced. Since the heat load required for the sum is handled by one heat circuit, boiling may occur in the heat circuit on the heating side.

The present invention was made in view of the above-mentioned problems of the conventional technology, and attempts to connect two thermal circuits in parallel to obtain a capability equivalent to the sum of the maximum capabilities of the circuits. In gas water heaters, when the required heat load is small, only one heat circuit can provide heat.
By reducing the minimum capacity to a capacity equivalent to the minimum capacity of one of the heat circuits and allowing most of the feed water to flow through the circuit that provides heat, boiling will not occur even when the heat load is small. The purpose is to

In addition, when the required heat load exceeds the sum of the maximum capacities of the two heat circuits, the water supply to the circuit is automatically throttled using the mixing valve described above to meet the required heat load within the capacity range of 11ll. The purpose is also to make it possible to keep it inside.

[Means for Achieving the Object] In order to achieve the first object, in the gas water heater of the present invention, the hot water supply pipe of the first heat circuit is connected to the hot water supply pipe of the second heat circuit. a mixing valve provided in the connecting portion to be connected; an inlet water temperature sensor provided in the water supply pipe on the upstream side of the part where the water supply pipe branches into the first heat circuit side and the second heat circuit side; and the branching water supply pipe. The first heat circuit is provided in the first heat circuit side water supply pipe and the second heat circuit side water supply pipe downstream from the first heat circuit. 2nd stream i) A sensor, a temperature setting device, a calculation means for calculating the required heat load based on the set temperature of the temperature setting device and the detection value of each of the above-mentioned sensors, and the calculation value of the calculation means is lower than a predetermined reference value. When the mixing valve is small, the passage area on the second heat circuit side of the mixing valve is minimized, and the passage area on the first heat circuit side is maximized,
When the value is larger than the predetermined reference value, the mixing valve control means controls the mixing valve so as to maximize the passage area on both the first heat circuit side and the second heat circuit side of the mixing valve, and the calculated value of the calculation means meets the predetermined reference value. When the value is smaller than the value, the heat source device of the first thermal circuit is
If it is larger than the reference value, the first. The second heat circuit is provided with combustion control means for burning the heat source devices of both the second heat circuits and controlling the combustion based on a predetermined combustion sequence.

In order to achieve the second object, the gas water heater of the present invention has, in addition to the above configuration, a calculated value of the itching means. Capacity overcut means is provided for υIII of the mixing valve so as to minimize the passage area of both the first heating circuit side and the second heating circuit side of the mixing valve, respectively, when the sum of the maximum capacities of the second heating circuits is exceeded. It is something.

[Function] According to the first configuration of the present invention, when the required heat load is smaller than the predetermined reference value, the passage area on the second heat circuit side of the mixing valve is minimized, and the passage area on the first heat circuit side is minimized. The passage area of is maximized, most of the feed water flows into the first heat circuit, and the amount of heat is provided only by this circuit, and the predetermined base temperature is increased. 1! When it is larger than the value, the passage area of both the first heat circuit side and the second heat circuit side of the mixing valve becomes maximum, and water is supplied from the first heat circuit side to the second heat circuit side. The heat flows approximately equally into the second heat circuit, and each heat amount is given in the reheat circuit.

Further, the required heat load is small, and even if the passage area on the second heat circuit side of the mixing valve is narrowed, some water flows to the second heat circuit side, and no stagnant water is generated.

Furthermore, according to the second configuration, when the required heat load exceeds the sum of the maximum capacities of the first and second circuits, that is, when it exceeds the hot water supply capacity, the first and second heat circuits of the mixing valve The area of each passage on the heat circuit side is reduced, and the water supply to the reheat circuit is restricted.

Therefore, the required heat load is automatically kept within the capability of the water heater.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

The drawings show an embodiment of the gas water heater according to claim 1 in FIGS. 1 to 11, and another embodiment of the gas water heater according to claim 2 in FIGS. 12 to 22, respectively.

First, the equation of feed <i shown in FIGS. 1 to 11 will be explained.

In Fig. 2, (A) is the body of the water heater, and inside there are two heat circuits (hereinafter referred to as the first heat circuit (a), the second heat circuit (b),
).

Above 1. The second heat circuits (a) and (b) each include heat exchangers (1) and (2), and heat source devices (3) and (4), and the heat source devices (3) and (4) are gas burners.

(5) is a water supply pipe, (6) is a hot water supply pipe, and the water supply pipe (5) branches in the middle, one of which is the inlet of the heat exchanger (1) of the first heat circuit (a). and the other is the second thermal circuit (
b) are respectively connected to the heat exchanger (2) inlet.

In addition, the hot water supply pipe (6) is connected to the heat exchanger (
1) a first heat circuit side hot water supply pipe (6a) extending from the outlet;
A second heat exchanger (2) extending from the heat exchanger (2) outlet of the second heat circuit (b)
It merges with the heat circuit side hot water supply pipe (6b) and extends outside the fuselage (A).

The water supply pipe (5) has a water supply temperature sensor (7) upstream from the branch and a first heat circuit (5a) downstream from the branch.
A first flow sensor (8) is provided on the first flow side, and a second flow rate sensor (9) is provided on the second heat circuit side (5b).

In addition, the hot water supply pipe (6) has a first hot water temperature sensor (10) on the first thermal circuit side (6a) and a second hot water temperature sensor (10) on the second thermal circuit side (6b).
A hot water supply temperature sensor (11) is provided respectively, and a mixing valve (12) is installed at the connecting portion of both hot water supply pipes (6a) (6b).
), and further a water flow valve (13) is provided downstream thereof.

The above-mentioned water supply temperature sensor (7>, first and second water supply temperature sensors (10) and (11) are composed of, for example, a thermistor,
The flow rate sensors (8) and (9) are conventionally well-known sensors that are installed in the flow rate and detect the rotation of the W wheel, which is prevented from rotating by running water, as an electrical signal using a magnet attached to each rotation and a Hall element that detects the magnetic field of the magnet. It has the following structural form.

Each of the above sensors (7), (8), (9) (101 (11) is later) is electrically connected to the control device (B), and the water supply temperature sensor (A) is connected to the water heater. The water temperature TO is set to 1. Second feed temperature sensor (10) (1
1) is the temperature TH1 of the water flowing out from the heat exchangers (1) and (2) of the first heat circuit (a) and the second heat circuit (b), respectively.
TH2 and 1st. Second flow sensor (8) (9')
are the water flows fiFs1., which are supplied to the first thermal circuit (a) and the second thermal circuit (b), respectively. FS2 is detected respectively.

The detected values of each of the above-mentioned sensors (7), (8), (9), and (10H11) are input to the control device (B).

As shown in FIGS. 3 and 4, the mixing valve (12) has a valve element mounted on a fixed disk (14), watertightly and slidably superimposed on the fixed disk (14), and a motor (15). a movable desk (16) that is rotationally driven by a
), the second population (18) connects to the second heat circuit side feed lagoon pipe (6b), and the exit (19).
) is drilled through and the outlet (19) communicates with the downstream hot water supply pipe (6).

The movable desk (16) also has a first through hole (20) corresponding to the first population (11) and a second through hole (20) corresponding to the second population (18).
The through hole (21), the third through hole (2) corresponding to the outlet (19)
2) are drilled, and each of these holes (20) (21)
(22) communicate with each other behind the movable desk (16).

Above 1st. Second population (17) (18) and exit (19)
are arranged at equal intervals on concentric circles, and are formed in the shape of an arc with the same length extending in the circumferential direction, but the second population (1
8) has a radial width of the first population (17) and the exit (19)
A large flow part (18a) equal to that of the large flow part (18a), and a large flow part (18a)
It has a small flow part (18b) with an extremely small radial width compared to 18a), and both parts (18a) (18b
) each occupy 1/2 of the circumferential length of the second population (18), and the small stream m section (18b) is provided on the side closer to the outlet (19).

The first to third through holes (20), (21, and 22) have the same shape and size as the large flow part (18a) of the second population (18), that is, the first population (17) and the outlet (19). It is formed in a size and shape that is divided into two equal parts in the circumferential direction, and when the second through hole (21) is aligned with the large flow part (18a) of the second population (18), the first through hole ( 20) are arranged concentrically so as to match the exit side half of the first port (17), and the third through hole (22) to match the second port side half of the exit (19), respectively.

Therefore, the mixing valve (12) is connected to the second valve as shown in FIG.
The through hole (21) is the large flow part (18a) of the second population (18)
A movable desk (1
6), the first through hole (20) is the first population (17
), both the first thermal circuit (a), the two measuring thermal circuits (b), and the individual hot water supply pipes (6a and 6b) are fully opened.

In addition, as shown in FIG.
Even when the movable desk (16) is in the position (referred to as the position), the first passage hole (20) matches the first population (17), and while the first heat circuit side hot water supply pipe (6a) is fully opened, The second heat circuit side supply 5tff path (6b) is narrowed down to a small flow M.

In addition, the movable desk (16) is A in the third through hole (22).

B Matches the exit (19) no matter which position it is in.

Further, the mixing valve (12) is equipped with a position sensor (not shown) for detecting the position of the movable desk, and the position sensor and motor (15) are electrically connected to the control device t(B). A sensor detects the position of the movable desk (16). The position sensor is, for example, a Hall IC, a microswitch, a potentiometer, a photocoupler, or a step number integration of a stepping motor, and its detection signal is input to the control device (B).

The position of the movable desk (16) in the mixing valve (12) is controlled by the control device (B) through the drive of the motor (15).

The water flow valve (13) is driven by a motor (23) to open and close, and even when the valve is closed, it does not completely close the flow path.
It has a structure that can ensure a certain amount of flow rate.

This water flow valve (13) is controlled by a control device @(B) so as to close only when the required heat load exceeds the capacity of the water heater.

The control device (B) consists of, for example, a microcomputer, mainly a microprocessor (24).

It consists of a memory (25), an interface (26), and each of the above sensors (7) (8) (9) (
10) The detected value of (11) and the set temperature set by the temperature setting device (C) are input to the interface (26).

The control device ff1 (B) is connected to the above interface (2).
Based on the external data input to the memory (2)
5), and generates an output to the motor (15) of the mixing valve (12) to control the position of the movable desk (16). Generating or extinguishing output to the gas supply valves (27) (2g) of the heat source devices (3) and (4) of the second heat circuits (a) and (b) to control opening and closing of the valves (27) and (28). .

Flowcharts of programs stored in the ROM for controlling the mixing valve (12) and heat source device (3H4) are shown in FIGS. 9 to 11.

Here, according to FIGS. 9 to 11, the operation of the present refilling machine will be described as an example. The case where the second thermal circuit (a Hb > has a minimum capacity of 2.5 and a maximum capacity of 16, respectively) will be described.

In the figure, ``■'' to ``■'' and 0 to 0.0 to 0 represent each step in the program.

When the program stars 1-, S=
Set a flag of 0. Next, set the temperature in step ■!
The set temperature TS set in (C) is read, and in step (2), a drive output is generated to the motor (15) of the mixing valve (12), and the movable desk (16) is set to the A position, and the first thermal circuit side and Hot water supply pipes (6a) (6b) on the second heat circuit side
) are fully opened.

Then, in step ■, the flow rate FSI on the first thermal circuit (a) side is
, the flow rate FS2 on the second thermal circuit (b) side, and the feed water temperature TC are read, and in step ■, FSL or FS2≧Q1
(for example, 1.254/min), and if FSi or FS2≧QiJ/min, then step
It is determined whether Sl +FS2≧QT (for example, 2.5 J/min).

On the other hand, if FSI or FS2<Ql in step (2), the heat source device is extinguished according to a separate extinguishing sequence in step (2), or the process returns to step (2) and waits. However, immediately after the start, the first and second thermal circuits (a) (b)
) are not burned, so we will return to step ■.

Also, when FSI +FS2 <QT in step (2), the fire is extinguished in the same manner according to the extinguishing sequence, or the process returns to step (2) and waits.

When H31+FS2≧Qr in step (2), the required heat load HQ is calculated by step (2). The calculation formula for calculating the above required heat load HQ is HQ= (Ts-Tc)
X (FSI + FS2).

Next, in step ■, it is determined whether S=0 or not, and when S-〇, HQ≦HQT (for example, 175
Kcaf/min). And HQ≦HQ
In the case of d/min, the subroutine 0 shown in FIG.
Process according to.

That is, the step is the movable desk (16) of the mixing valve (12).
) Determine whether the position is the B position, and if it is the B position, open the gas supply valve (27) of the first thermal circuit (a) in step 0 to burn only the first thermal circuit (a). Then, the combustion is controlled based on a predetermined combustion sequence, and the process returns to step (3) of the main routine.

At this time, the heat amount of combustion in the first heat circuit (a) is controlled so that hot water slightly higher than the set temperature TS is drawn out.

The above combustion sequence is based on the set temperature Ts, the detected value Tc of the feed water temperature sensor, and the detected values FS1 and FS of the flow m sensor, respectively.
The required heat load calculated from 2, the set temperature TS and the first
．． Detection value T)1 of the second hot water supply temperature sensor (10) (11)
1, T) consists of conventionally well-known feedforward+feedback control that controls the gas cycle based on the difference between T) and 12.

In addition, when the movable desk (16) of the mixing valve (12) is not at the B position in step 0, the mixing valve (16) is not in the B position in step 0.
A drive voltage is applied to the motor (15) of 12) to rotate the movable desk (16) to the 8th position, this is confirmed in step 0, and the first heat circuit (a) is rotated based on the combustion sequence in step 0. Combustion is controlled and the process returns to step (2) of the main routine.

On the other hand, when 5f-O in step ① described above, HQ≦HQi (for example, 125 caf/min)
When HQ≦HQi, the flag is set to S=0 in step 12, and the processing according to the subroutine described above is performed, and after HQ>HQt, the processing according to the subroutine ① shown in FIG. 11 is performed.

That is, in step 0, it is checked whether the movable disk (16) of the mixing valve (12) is in the A position, and when it is in the 8 position, in step 0, the 1st and 2nd heat circuits (a
) and (b), each heat circuit (a Hb
) of the mixing valve (12) is controlled according to a predetermined sequence. In step 0, the movable desk (
16) is not at the A position, apply a driving voltage to the motor (15) of the mixing valve (12) in step O to rotate the movable desk (16) to the A position, and confirm this in step 0. The process moves to step O, and at the same time returns to step (2) of the main routine.

Also, in step [stock], if 1-IQ>HQT, the flag is set to S=1 in step ■, and step ■
It is determined whether HQ≦HQi, and if HQ>HQT, processing according to subroutine 0 is performed. And HQ≦
In the case of HQi, the flag is set to S-o in step (2) and processing according to the subroutine (2) is performed.

After that, this operation is repeated until hot water supply is stopped.

Next, a water heater according to a second aspect of the present invention shown in FIGS. 12 to 22 will be explained.

It should be noted that the same reference numerals are given to the same parts in the drawings for parts that overlap with the description of the above-mentioned water heater according to claim 1, and the description thereof will be omitted.

This water heater differs from the water heater described above in that the amount of water supplied is reduced by the mixing valve (12) when the capacity is exceeded.

Therefore, this water heater is not equipped with a water flow valve (13).
Instead, the first of the fixed desks (14) of the mixing valve (12)
．． The second population (17) (18) and the exit (19), the first to third through holes (201 (21)) of the movable desk (16) (
22) is formed into the shape shown in FIGS. 14 and 15.

That is, 1st. Second population (17) (18) and exit (19
) are circular arc-shaped holes extending in the circumferential direction on concentric circles, and the first. The circumferential lengths of the second population (17) and (18) are the same, and the extension of the line connecting both circumferential ends of the exit (19) and the center of the desk is the same as the first population. It is formed to pass through the circumferential center of the second population (17) (18).

In addition, the first population (17) has a large flow rate part (17a) that occupies 2/3 of the circumferential length, and a radial width of the large flow rate part (11) that occupies 1/3 of the circumferential length. It has a small flow part (17b) formed to be extremely smaller than the width, and the small flow part (17b) is formed to be extremely smaller than the width.
7b) is provided on one side of the first population (11) on the exit (19) side.

The second population (18) occupies 1/3 of the circumferential length, and the large flow part (18a) occupies 2/3, and the first population (18) occupies 2/3 of the circumferential length.
1 small flow part (18b) similar to the small flow part (17b) in 7)
are formed respectively, and the small flow part (ISB) is formed as a large flow part (ISB).
8a) on both sides in the circumferential direction.

On the other hand, the first movable desk. The second through hole (20) (21) has the same shape as the large flow h1 part (18a) of the second population (18),
The third through hole (22) is formed to have the same dimensions as the outlet (19).
It is formed in a shape that is divided into two equal parts, and the second through hole (
21) is aligned with the large flow part (18a) of the second population (18), and the first through hole (20) is aligned with the first population (18).
Matches the small flow part side half of the large flow part (17a) of 7),
Further, the third through hole (22) is arranged in a positional relationship such that it matches the center of the outlet (19).

Therefore, the mixing valve (12) that is rejected is connected to the second through hole (18) and the second port (16) as shown in FIG.
21) where the large flow rate part (18a) matches (hereinafter referred to as A
position), the first through hole (20) is also in the first position.
The first one corresponds to the large flow area (17a) of the population (17).
The hot water supply pipes (6a) (6b) on each side of the second thermal circuit are both fully opened.

In addition, the position where the second through hole (21) matches the outlet side small flow rate part (18b) of the second port (18) as shown in FIG.
(hereinafter referred to as position B), the first through hole (20)
matches the large flow part (17a) of the first population (17),
While the first heat circuit side hot water supply pipe (6a) is fully opened, the second heat circuit side hot water supply pipe (6b) is narrowed down to a small flow rate.

Furthermore, when the second passage hole (21) is located at a position (hereinafter referred to as position C) that matches the first population side small flow part (18b) of the second inlet (18) as shown in FIG. hole (2
0) also matches the small flow rate part (17b) of the first population (17), and the first. Hot water supply pipes (6a) (6) on each side of the second heat circuit
b) Both are reduced to a small flow rate.

The 19th ROM in the memory (25) of the control device (B)
Programs as shown in the flowcharts in Figures to Figure 22 are stored, and according to this program the mixing valve (12)
control.

As can be seen from FIG. 19, the program for the water heater according to claim 1 described above determines whether or not the required heat load is within the capacity range of the water heater. A step of determining whether HQ≦800 kcal/min when the second thermal circuits (a) and (b) have a minimum capacity of 2°5 and a maximum capacity of 16, respectively;
>) A subroutine (2) is added that defines processing when lQmax (for example, 800 d/min).

Therefore, in this water heater, up to step ■ and when S≠0 in step ■, steps ■ and ■ are as claimed in claim 1 described above.
It works exactly the same as the water heater described, but there is no HQ in step ■.
≦l-I Q maX judgment is added, and HQ
> When HQ is max, processing according to subroutine (①) is performed.

That is, when HQ>)lQn+ax in step O, the movable plate (16) of the mixing valve (12)
, and if it is at position C, move to step O. Both of the second heat circuits (a) and (b) are combusted and the combustion is controlled based on a predetermined combustion sequence, and the process returns to step (2) of the main routine. ) to rotate the movable desk (16) to position C, confirm this in step O, and proceed to step O.

On the other hand, when HQ≦HQ max in the step (2), the process proceeds to the step (2), but from this point onward, the steps [stock] and the following of the supply la iso program according to claim 1 described above with reference to FIGS. 9 to 12 are performed. It proceeds exactly the same way.

[Effect j Since the present invention is configured as described above, it produces the effects described below.

(1) A U joint valve is provided at the connecting portion where the hot water supply pipe on the first heat circuit side is connected to the hot water supply pipe on the second heat circuit side, and when the required heat load is large by this mixing valve, the first. The hot water supply pipes of both second heat circuits are fully opened, and when the required heat load is small, the hot water supply circuit of the first heat circuit is fully opened, and the hot water supply circuit of the second hot water circuit is narrowed down to the minimum. Even though the heat circuits are connected in parallel, when the required heat load is small, boiling can be achieved using only one heat circuit, and the minimum capacity can be reduced to the minimum capacity of one heat circuit.

Moreover, in this case, most of the supplied water flows through the heat circuit that provides the heat, so there is no risk of boiling.

(2) In the hot water supply method according to claim 2, even when the required heat load exceeds the capacity of the water heater, the mixing valve is used to supply the first water. Since the water flow areas of the hot water supply pipes of the second heat circuit are respectively reduced, there is no need to separately provide a water volume pulp for overcutting the capacity, the structure is simple, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the gas water heater according to claim 1, FIG. 2 is a schematic configuration diagram schematically showing the overall configuration, and FIG. 3 is a functional block diagram showing the main components of the present invention. It is a front view showing an example of a certain mixing valve with main parts cut away. Fourth
The figure is a side view with main parts cut away. Fig. 5 is a bottom view of the fixed desk of the mixing valve, Fig. 6 is a bottom view of the movable desk, Figs. 7 and 8 are explanatory diagrams explaining the operating state of the mixing valve, and Figs. It is a flowchart showing a program. FIG. 12 is a functional block diagram showing the configuration of the gas water heater according to claim 2, FIG. 13 is a schematic configuration diagram schematically showing the overall configuration, and FIG. 14 is the bottom surface of the fixed desk of the mixing valve. Figure 15 is a bottom view of the movable desk, Figure 16 is a bottom view of the movable desk.
Figures 18 to 18 are explanatory diagrams illustrating the operating state of the mixing valve;
19 to 22 are flowcharts showing the operating program. a: First heat circuit b: Second heat circuit 5: Water supply pipe 5a: First heat circuit side water supply pipe 5b = Second heat circuit side water supply pipe 6: Hot water supply pipe 6a: First heat circuit side hot water supply Pipe 6b: Second heat circuit side supply/drain pipe 72 Inlet water temperature sensor 8: First flow sensor 9: Second flow Ji sensor B: Control device C: Temperature setting device

Claims (2)

[Claims] (1) In a gas water heater in which two heat circuits are connected in parallel, the hot water supply pipe on the first heat circuit side is provided at a connection part that connects to the hot water supply pipe on the second heat circuit side, and a mixing valve that changes the mixing ratio of the fluid from the heat circuit side and the fluid from the second heat circuit side; and a mixing valve that changes the mixing ratio of the fluid from the heat circuit side and the fluid from the second heat circuit side; An inlet water temperature sensor provided in the pipe, first and second flow rate sensors provided respectively in the first heat circuit side water supply pipe and the second heat circuit side water supply pipe downstream from the branch part, and a temperature setting device. and a calculation means for calculating the necessary heat load based on the set temperature of the temperature setting device and the detection values of the respective sensors, and a second heat circuit of the mixing valve when the calculation value of the calculation means is smaller than a predetermined reference value. The passage area on the side of the mixing valve is minimized, and the passage area on the first heat circuit side is maximized.
a mixing valve control means that controls the mixing valve so as to maximize the passage area on both the heat circuit side and the second heat circuit side; and a heat source of the first heat circuit when the calculated value of the calculation means is smaller than the predetermined reference value. A gas water heater characterized in that the gas water heater is equipped with a combustion control means that causes the heat source devices of both the first and second heat circuits to combust, respectively, when the heat source device is larger than a reference value, and controls the combustion based on a predetermined combustion sequence. . (2) In a gas water heater in which two heat circuits are connected in parallel, the hot water supply pipe on the first heat circuit side is provided at a connecting part that connects to the hot water supply pipe on the second heat circuit side, and a mixing valve that changes the mixing ratio of the fluid from the heat circuit side and the fluid from the second heat circuit side; and a mixing valve that changes the mixing ratio of the fluid from the heat circuit side and the fluid from the second heat circuit side; An inlet water temperature sensor provided in the pipe, first and second flow rate sensors provided respectively in the first heat circuit side water supply pipe and the second heat circuit side water supply pipe downstream from the branch part, and temperature setting. a calculation means for calculating the required heat load based on the set temperature of the temperature setting device and the detection value of each of the above-mentioned sensors; Minimize the passage area on the circuit side and maximize the passage area on the first heat circuit side, and when the area is larger than a predetermined reference value, maximize the passage area on both the first heat circuit side and the second heat circuit side of the mixing valve. A mixing valve control means that controls the mixing valve so that when the calculation value of the calculation means exceeds the sum of the maximum capacities of the first and second heating circuits, the passage area on both the first heating circuit sides of the mixing valve is capacity overcut means for controlling the mixing valve so as to reduce the heat source of the first heat circuit when the calculated value of the calculation means is smaller than the predetermined reference value; A gas water heater characterized by comprising combustion control means for combusting both heat source devices and controlling the combustion based on a predetermined combustion sequence.