JP3386575B2 - Water heater and combustion control method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention stabilizes the hot water temperature at the time of re-opening hot water from a water heater having a bypass flow path that bypasses the heat exchanger by connecting the water supply pipe and the hot water discharge pipe of the heat exchanger. The present invention relates to a water heater and a combustion control method using the same.

[0002]

2. Description of the Related Art FIG. 4 illustrates a conventional water heater having a bypass passage and a combustion control method using the same.

FIG. 4 (a) shows a burner 2 in an instrument case 1, a combustion fan (not shown) for supplying combustion air of the burner 2, and heat which is heated by the flame of the burner 2. And a heat exchanger 3 from the water supply pipe 4 to the heat exchanger 3.
The entering water is heated by the combustion heat of the burner 2 to form hot water, and this hot water is guided to a desired place such as a kitchen through the hot water discharge pipe 5.

In the water heater and the combustion control method using the same shown in FIG. 4 (a), in order to suppress the overshoot due to the after-boiling, a bypass flow connecting the water supply pipe 4 side and the hot water discharge pipe 5 side is established. An electromagnetic valve 7 is provided in the passage 6, and at the time of hot water re-opening, the electromagnetic valve 7 is opened and a part of water entering from the water supply pipe 4 is used as post-boiled water that is discharged from the heat exchanger 3 through the bypass flow passage 6. The hot water temperature was lowered by mixing to suppress the overshoot of the hot water temperature.

Further, in the water heater and the combustion control method using the same shown in FIG. 4 (b), parallel flow paths 8a and 8b having different flow rates are provided in the section of the bypass flow path 3 and the respective flow paths are provided. Solenoid valves 7a and 7b are provided in the passages 8a and 8b, and the passage 8a
When the solenoid valve 7a is opened, the solenoid valve 7b on the flow path 8b side
Opening and opening both flow paths 8a, 8b solenoid valves 7a, 7b switch the amount of water passing through the bypass flow path 6 to three levels, and after tap water is again tapped, the tapping temperature by post boiling The amount of water to be mixed is variably controlled according to the size of the overshoot to suppress the overshoot of the tap water temperature.

[0006]

However, as shown in FIG.
In the water heater of (a) and the combustion control method using the same,
When the hot water tap (not shown) is opened again and hot water is again tapped after the combustion of the hot water supply is stopped, hot water of the set temperature in the hot water pipe 5 first comes out from the faucet, and then, While combustion is stopped,
There is an overshoot of the hot water outlet temperature due to the boiling after being heated to a temperature higher than the set temperature by propagating the heat from the can body of the heat exchanger 3 that retains the amount of heat due to the previous combustion to the hot water that is retained inside. The hot water comes out, and then the delay time from when the tap is opened until it is ignited and after the ignition, the heat of burner combustion is transferred to the heat exchanger 3, and the water passing through the heat exchanger 3 passes through the inside. Undershoot water below the set temperature due to delay of heat transfer transmitted to the
There is a problem that when the burner 2 burns, hot water having a set temperature controlled by temperature is discharged, a large fluctuation in hot water temperature occurs when the hot water is discharged again.

Further, in the water heater and the combustion control method using the same shown in FIG. 4 (a), the amount of water passing through the bypass passage 6 cannot be variably controlled. It is said that it is not possible to precisely control the hot water temperature at the time of re-hot water, since the water is overfilled and the hot water becomes lower than the set temperature when the overshoot of the hot water temperature is small. There was a problem.

Since the water heater and the combustion control method using the same shown in FIG. 4 (b) use two solenoid valves 7a and 7b, the amount of water passing through the bypass passage 6 can be switched to only three levels. Therefore, there is a problem that the control of the bypass water amount in detail according to the magnitude of the overshoot of the tapping temperature is not sufficient, and the tapping temperature at the time of tapping again cannot be precisely controlled.

The present invention has been made by paying attention to such a conventional problem, and precisely controls the overshoot and undershoot of the tapping temperature at the time of tapping again to precisely control the tapping temperature at tapping again. An object of the present invention is to provide a hot water heater that can be controlled and a combustion control method using the same.

[0010]

[Means for Solving the Problems] The gist of achieving the above object lies in the following two items.

[0011]

[0012]

[1] Water supply pipe (1) of the heat exchanger (11)
3) and the hot water pipe (14) are connected to each other and have a bypass flow path (15) that bypasses the heat exchanger (11), and do not pass water every time a predetermined waiting time elapses after the combustion is stopped. In a water heater for performing backup combustion by igniting and supplementing the backup heat amount to control the hot water temperature in the heat exchanger (11) within a predetermined allowable temperature range, the hot water heater is provided in the bypass flow path (15), and the bypass is provided. A bypass valve (19) for controlling the amount of bypass water flowing through the flow path (15), a hot water outlet temperature detecting means (28) interposed in the hot water outlet pipe (19) for detecting the water temperature at the location, and a heat exchanger. A bypass ratio, which is a ratio between the bypass water amount and the heat exchanger water amount flowing through the heat exchanger (11), based on the deviation between the inner hot water temperature and the hot water outlet set temperature, is defined as the heat exchanger inner hot water temperature and the hot water outlet temperature detecting means ( 28) Time lag and temperature with the water temperature detected A bypass ratio varying means (22) for controlling and adjusting the opening of the bypass valve based on the difference,
A water heater (10) comprising:

[2] Item When hot water is again discharged after the hot water supply is stopped,
The bypass ratio varying means (22) controls the opening degree of the bypass valve (19) to fill the hot water immediately after re-leaving hot water to stabilize the hot water temperature of the water heater (10). Hot water temperature control method.

[0015]

The hot water supply device (10) performs a hot water supply operation in which the hot water supply burner is ignited and hot water is supplied in response to the opening. In addition to the hot water supply operation, after the hot water supply combustion is stopped, every time a predetermined standby time elapses, ignition is performed without passing water to supplement the backup heat amount and the hot water temperature in the heat exchanger (11) is predetermined. It is also possible to perform the backup combustion controlled within the allowable temperature range.

A bypass flow path (1) provided so as to connect the water supply pipe (13) and the hot water discharge pipe (14) of the heat exchanger (11).
The water flowing in 5) bypasses the heat exchanger (11).

A bypass valve (19) provided in the bypass flow passage (15) controls the amount of bypass water flowing through the bypass flow passage (15).

A hot water outlet temperature detecting means (28) provided in the hot water outlet pipe (14) detects the water temperature at the location.

The bypass ratio calculation unit (24) provided in the bypass ratio varying means (22) determines the bypass water amount and the heat exchanger (11) based on the deviation between the hot water temperature in the heat exchanger and the hot water outlet set temperature. The bypass ratio, which is the ratio to the amount of water in the heat exchanger that flows, is obtained by correcting the time lag and the temperature difference between the water temperature detected by the hot water temperature detection means (28) and the hot water temperature in the heat exchanger.

The bypass valve drive section (26) provided in the bypass ratio varying means (22) uses the bypass valve (26) based on the bypass ratio generated by the bypass ratio calculation section (24) at the time of re-leaving hot water after the hot water supply is stopped. The opening degree control of 19) is executed to control the amount of bypass water mixed with the hot water of the hot water outlet pipe (14) of the heat exchanger (11), and the hot water immediately after re-leaving is filled to stabilize the hot water temperature.

Further, in the water heater (10) for performing the backup combustion, ignition is performed without passing water every time a predetermined waiting time elapses (every predetermined interval time) after the combustion is stopped, and the backup heat quantity is set. Heat exchanger (1
Add to 1).

In the combustion control method using the backup combustion, the hot water temperature in the heat exchanger (11) based on the backup heat quantity supplied at predetermined intervals is set to a lower limit value (lower limit temperature) and an upper limit value. It is compared with the value (upper limit temperature). The operation will be described below in (a) to (d).

(B) When the calculated value of the backup heat quantity deviates above or below the allowable range,
Combustion operation by a burner (12) or combustion fan (1
The cooling operation by 7) is performed, and the temperature of the hot water in the heat exchanger (11) is kept within the allowable range.

(B) When it is determined that the hot water temperature in the heat exchanger (11) is higher than the upper limit temperature, it is necessary for the hot water temperature in the heat exchanger (11) to fall within a predetermined allowable range. , The time (cooling time) of the cooling operation by the combustion fan (17) is calculated. Furthermore, the combustion fan (17) is rotated at high speed for the cooling time to cool the heat exchanger (11),
The hot water temperature in the heat exchanger (11) based on the backup heat quantity is kept within an allowable range. The cooling time is calculated, for example, in consideration of the outside air temperature.

After the cooling time has elapsed, the combustion fan (17)
Is transferred to a low speed constant rotation operation called post fan rotation. Further, the fan rotation is stopped when the set time of the post fan rotation is reached.

(C) On the other hand, when it is determined that the hot water temperature in the heat exchanger (11) based on the backup heat amount is lower than the lower limit temperature, the burner (11) is not allowed to pass water. The point ignition of 12) (called a little ignition) is performed, and the burner (12) is operated for a predetermined short time (for example, 2 seconds).
Are burned to heat the hot water in the heat exchanger (11) to raise the hot water temperature in the heat exchanger (11) within an allowable range. The point ignition of the burner (12) is called the backup combustion.

(D) When it is determined that the hot water temperature based on the backup combustion is within the range between the upper limit temperature and the lower limit temperature, the combustion fan (17) executes post fan rotation.

The rotation of the post fan means that the combustion fan (17) is previously rotated at a low speed (so-called combustion fan (17) is idling operation) in order to accelerate ignition. By adopting the post fan rotation, it is possible to shorten the time required to start the combustion fan (17) prior to ignition of the burner (12). Further, the heat exchanger (1
It is possible to prevent the hot water temperature in 1) from being overheated.

As a result, a bypass valve (19) is provided in the bypass passage (15) which connects the water supply pipe (13) of the heat exchanger (11) with the hot water discharge pipe (14), and when the hot water is again discharged, the bypass valve (19) is provided. Since the opening amount of the bypass valve (19) is controlled and the amount of water in the bypass flow passage (15) can be filled with the hot water discharged from the heat exchanger (11), an overshoot caused by post boiling water or the like at the time of re-hot water discharge It is possible to effectively suppress the occurrence of hot water, and it is possible to realize hot water with a small deviation from the set temperature without overshoot of the hot water temperature.

Further, by detecting the hot water temperature in the heat exchanger, the opening degree of the bypass valve (19) can be controlled according to the fluctuation of the hot water temperature in the heat exchanger during backup combustion. It is possible to precisely control the hot water temperature at the time of re-spouting hot water by accurately controlling the undershoot and undershoot.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a water heater according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a combustion control method of the water heater according to an embodiment of the present invention.

The hot water supply device (10) performs a hot water supply operation in which the hot water supply burner is ignited and hot water is supplied in response to the opening.

Further, as shown in FIG. 1, the water heater 10 that performs backup combustion in addition to the hot water supply operation does not pass water every time a predetermined interval time (standby time) elapses after combustion is stopped. It is arranged to perform backup combustion by igniting and supplementing the backup heat amount 22a to control the hot water temperature in the heat exchanger 11 within a predetermined allowable temperature range.

The water heater 10 is provided with a heat exchanger 11 and a burner 12, and a gas passage communicating with the burner 12 is provided with a gas valve 16 for controlling the flow rate of gas.

A water supply pipe 13 for supplying water is connected to the inlet side of the heat exchanger 11. In the water supply pipe 13,
An incoming water temperature sensor 18c for detecting the water supply temperature and a flow sensor 18e for detecting the incoming water flow rate are provided. In this embodiment, a temperature measuring element such as a hot water outlet thermistor or a thermocouple is used as the incoming water temperature sensor 18c.

A controller (not shown) for performing the hot water supply operation of the water heater 10 may be provided. A remote controller (not shown) may be connected to the control device, and the remote controller (not shown) may be provided with a button for setting a hot water outlet set temperature of hot water and a display portion of the hot water outlet set temperature.

The heat exchanger 11 is provided with a bypass flow passage 15 in parallel for controlling the outlet heated water temperature.

Further, the heat exchanger 11 is equipped with a combustion fan 17 so that combustion air is supplied from the combustion fan 17.

The combustion fan 17 has a fan rotation sensor 18
a is provided. Further, around the combustion fan 17, an outside air temperature sensor 18b for detecting the supply temperature of the combustion air is provided. In this embodiment, a hot water thermistor is used as the outside air temperature sensor 18b.

As shown in FIG. 1, the water heater 10 is provided with a bypass flow passage 15 that connects the water supply pipe 13 and the hot water outlet pipe 14 of the heat exchanger 11 and bypasses the heat exchanger 11.

The bypass valve 19 controls the bypass passage 1 so as to control the amount of bypass water flowing through the bypass passage 15.
5 is installed. The bypass valve 19 of the present embodiment is configured as a bypass valve drive unit 26 so that the opening degree can be controlled by a gear motor.

A heat exchanger internal hot water temperature sensor 18d as the heat exchanger internal hot water temperature detecting means 20 is provided in the hot water outlet pipe 14 so as to detect the hot water in the heat exchanger. As the hot water temperature detecting means 20 in the heat exchanger (heat exchanger hot water temperature sensor 18d), a temperature measuring element such as a hot water discharge thermistor or a thermocouple is arranged near the heat exchanger outlet.

In the present embodiment, the temperature of the hot water in the heat exchanger is measured using the temperature measuring element, but the present invention is not limited to this, and the deviation between the set temperature and the hot water in the heat exchanger is measured. The hot water temperature detecting means 20 in the heat exchanger is placed at any position where measurement is possible.
A plurality of (hot water temperature sensor 18d in the heat exchanger) may be provided.

The bypass ratio calculator 24 calculates a bypass ratio, which is a ratio between the bypass water amount and the heat exchanger 11 water amount flowing through the heat exchanger 11, based on the deviation between the hot water temperature in the heat exchanger and the set hot water temperature. In order to do so, the bypass ratio varying means 22 is provided.

The bypass valve drive unit 26 is provided in the bypass ratio varying means 22 so as to control the opening degree of the bypass valve 19 based on the bypass ratio. In this embodiment, a gear motor is used as the bypass valve drive unit 26.

Next, the operation will be described. As shown in FIG.
The flow sensor 18e detects the flow of water flowing into the heat exchanger 11 by opening a water faucet (not shown) and generates a flow sensor signal (not shown).

The burner 12 has a combustion gas 12 a supplied from a combustion fan 17 and air 12 b via a gas valve 16.
Premix with.

The controller (not shown) receives the flow sensor signal (not shown) to instruct the gas supply and the igniter (not shown) to perform an ignition operation, and gives the burner 12 a combustion command. Further, hot water boiling control and backup combustion control in the heat exchanger 11 are performed.

The hot water passes through the hot water discharge pipe 14 and is discharged from a water faucet (not shown). Further, the control device (not shown) closes the faucet (not shown) and the flow sensor 18e.
When the flow of water is no longer detected by the flow sensor 1
The combustion stop control of the burner 12 can be performed by receiving the OFF signal from 8e.

In the water heater 10 for performing the backup combustion of the present embodiment, water is not supplied at every predetermined interval time every time a predetermined waiting time elapses from the time when combustion is stopped, that is, a water flow signal from the flow sensor. Regardless, the safety circuit of the control device is released and ignition is performed to supplement the heat exchanger 11 with the backup heat amount.

Further, in the combustion control method using the backup combustion of the present embodiment, the hot water temperature in the heat exchanger 11 based on the backup heat quantity supplied at every predetermined interval time is the lower limit set value lower limit temperature and the lower limit set value lower limit temperature. Upper limit set value Compared to upper limit temperature. The operation will be described below in (a) to (d).

(A) When the calculated value of the backup heat quantity deviates from the upper or lower side of the allowable range, each time,
The combustion operation by the burner 12 or the cooling operation by the combustion fan 17 is performed, and the hot water temperature in the heat exchanger 11 is kept within the allowable range.

(B) When it is determined that the hot water temperature in the heat exchanger 11 is higher than the upper limit temperature, the combustion fan 17 required for the hot water temperature in the heat exchanger 11 to fall within a predetermined allowable range. Calculate the cooling time of the cooling operation.
Further, the combustion fan 17 is rotated at a high speed for the cooling time to cool the heat exchanger 11, and the hot water temperature in the heat exchanger 11 based on the backup heat quantity is kept within the allowable range. The cooling time is calculated, for example, in consideration of the outside air temperature.

After the elapse of the cooling time, the combustion fan 17 shifts to a low speed constant rotation operation called post fan rotation. Further, the fan rotation is stopped when the set time of the post fan rotation is reached.

(C) On the other hand, when it is determined that the hot water temperature in the heat exchanger 11 based on the backup heat amount is lower than the lower limit temperature, the burner 12 is not ignited without passing water to the heat exchanger 11. Ignition is performed, and the burner 12 is burned for a predetermined short time, for example, 2 seconds to heat the hot and cold water in the heat exchanger 11 to raise the hot water temperature in the heat exchanger 11 within an allowable range. The point ignition of the burner 12 is called the backup combustion.

(D) When it is determined that the hot water temperature based on the backup combustion is within the range between the upper limit temperature and the lower limit temperature, the combustion fan 17 executes post fan rotation.

The rotation of the post fan means that the combustion fan 17 is rotated at a low speed in advance in order to accelerate ignition, that is, the so-called combustion fan 17 is idling operation. By adopting the post fan rotation, the time required to start the combustion fan 17 prior to ignition of the burner 12 can be shortened. Further, it is possible to prevent the hot water temperature in the heat exchanger 11 from being overheated during the backup combustion.

The post-boiling amount (post-boiling temperature) of the hot water in the heat exchanger 11 can be obtained by calculating the hot water supply control result before the combustion is stopped every time the hot water supply device 10 stops combustion. The combustion fan 17 supplies air for combustion. The fan rotation sensor 18a provided in the combustion fan 17 detects the rotation state of the combustion fan 17 and gives the air flow rate to a control device (not shown).

The operation of the combustion control method for the water heater according to this embodiment will be described with reference to FIG. The bypass valve 19 provided in the bypass passage 15 controls the amount of bypass water flowing through the bypass passage 15.

The hot water temperature detector 20 (heat exchanger internal hot water temperature sensor 18d) provided in the hot water outlet pipe 14 detects the temperature of the heat exchanger 11 and changes the bypass ratio.

The hot water temperature in the heat exchanger is detected by the hot water outlet thermistor 28. The data on the hot water temperature in the heat exchanger is used to control the hot water temperature.

The bypass ratio calculator 24 installed in the bypass ratio varying means 22 determines the amount of bypass water and the amount of water in the heat exchanger 11 flowing through the heat exchanger 11 based on the deviation between the hot water in the heat exchanger and the set hot water temperature. The bypass ratio, which is the ratio of

The bypass valve drive unit 26 provided in the bypass ratio varying unit 22 executes the opening degree control of the bypass valve 19 based on the bypass ratio generated by the bypass ratio calculation unit 24 at the time of re-leaving hot water after the hot water supply is stopped. By controlling the amount of bypass water mixed with the hot water of the hot water outlet pipe 14 of the heat exchanger 11, the hot water immediately after the re-hot water is filled to stabilize the hot water temperature.

Thus, the bypass valve 19 is provided in the bypass passage 15 which connects the water supply pipe 13 and the hot water discharge pipe 14 of the heat exchanger 11, and when the hot water is again discharged, the bypass valve 19 is controlled to open the bypass. Since the amount of water in the flow path 15 can be filled with the hot water discharged from the heat exchanger 11, it is possible to effectively suppress the overshoot caused by the after-boiled hot water at the time of re-leaving hot water, and to prevent the overshoot of the hot water temperature. It is possible to realize hot water with little deviation from the set temperature.

Further, by detecting the hot water temperature in the heat exchanger, the opening degree of the bypass valve 19 can be controlled in accordance with the fluctuation of the hot water temperature in the heat exchanger, so that the overshoot or undershoot of the hot water temperature at the time of re-hot water can be accurately measured. It is possible to control well and precisely control the hot water temperature at the time of re-hot water.

The operation of the hot water heater combustion control method will be described in more detail.

In the conventional general bypass type water heater, the ratio (bypass ratio) of the amount of water passing from the water supply pipe 13 through the heat exchanger 11 to the amount of water passing through the bypass passage 15 is 5: 5.
It is fixed to.

On the other hand, in the water heater of the present embodiment and the combustion control method using the same, the bypass valve drive is performed on the basis of the bypass ratio generated by the bypass ratio calculation unit 24 at the time of re-leaving hot water after the stop of hot water combustion. The part 26 is the bypass valve 19
Is executed to control the amount of bypass water mixed with the hot water in the hot water outlet pipe 14 of the heat exchanger 11.

As a result, the amount of water passing through the bypass passage 15 can be freely changed and controlled. In this embodiment, the amount of water passing through the heat exchanger 11 is set larger than the amount of water passing through the bypass flow passage 15, and the bypass ratio is set to be 8: 2 at the center.

In the hot water supply apparatus and the combustion control method using the same according to the present embodiment, the hot water supply pipe 14 on the outlet side of the bypass passage 15 is provided.
A gear motor type control valve is provided at a position in the vicinity of the hot water supply connection port on the downstream side of the confluence point with and to perform variable control of the amount of hot water discharged.

Further, by interlocking the control valve 27 and the bypass valve 19, it is possible to collectively and optimally control the overshoot or undershoot of the hot water discharge temperature and the overshoot or undershoot of the hot water discharge amount.

Thus, the bypass valve 19 is provided in the bypass passage 15 which connects the water supply pipe 13 and the hot water discharge pipe 14 of the heat exchanger 11, and when the hot water is discharged again, the bypass valve 19 is controlled to open the bypass. Since the amount of water in the flow path 15 can be filled with the hot water discharged from the heat exchanger 11, it is possible to effectively suppress the overshoot caused by the after-boiled hot water at the time of re-leaving hot water, and to prevent the overshoot of the hot water temperature. It is possible to realize hot water with little deviation from the set temperature.

Further, the temperature of the heat exchange 11 is detected using the hot water temperature sensor 18d in the heat exchanger, and the hot water temperature in the heat exchanger is detected using the hot water outlet thermistor 28, so that the hot water temperature in the heat exchanger can be changed. Since it is possible to control the opening degree of the bypass valve 19, it is possible to precisely suppress the overshoot or undershoot of the hot water discharge temperature at the time of re-hot water discharge and precisely control the hot water temperature at the time of hot water discharge again.

Further, by increasing the amount of water passing through the heat exchanger 11, the temperature of the hot water produced by the heat exchanger 11 can be made lower than that of the conventional example.

In the case of the conventional example, since the ratio of the amount of water passing through the heat exchanger to the amount of water passing through the bypass passage is approximately 5: 5, for example, when using hot water at 50 degrees Celsius, the heat exchanger is On the 11th side, it is necessary to create hot water of 90 degrees Celsius or higher.

However, such high temperature hot water is used in the heat exchanger 1.
In the case of the production of No. 1, the calcium component contained in water is deposited, which becomes a deposit and becomes entangled with the control valve 27 of the gear motor or the like. Since the amount of water on the side of the exchanger is larger than the amount of water on the bypass flow path, when using hot water at 50 degrees Celsius, it is sufficient to create hot water at 60 degrees Celsius on the side of the heat exchanger (supply water temperature at this time). Is 10 degrees Celsius), and the temperature of the hot water produced by the heat exchanger 11 can be lowered as compared with the conventional example.

This eliminates the problem of precipitation of calcium components in water, which is very convenient.

Since the water supply amount varies depending on the water pressure, the water pressure of each area is stored in the memory, and when the destination is determined, the water pressure of the area is designated and the bypass water amount is calculated based on this designated water pressure. Alternatively, the appliance itself may be provided with a learning function, and the water pressure used at the destination may be detected by itself to calculate the bypass water amount that matches the water pressure used.

Further, as shown in FIG. 3, it has been experimentally confirmed that there is a slight time lag and temperature difference between the hot water temperature in the heat exchanger and the output value of the hot water outlet thermistor 28. Therefore, in the present embodiment, the hot water outlet thermistor 28 is provided near the outlet of the heat exchanger in order to detect the hot water temperature in the heat exchanger. By controlling the bypass valve 19 to correct the time lag and the temperature difference, the hot water outlet temperature can be controlled with higher accuracy.

In this embodiment, the water heater using gas is shown, but the invention is not particularly limited to this and can be applied to a water heater using fuel such as petroleum.

[0081]

According to the water heater and the combustion control method using the same according to the present invention, a bypass valve is provided in the bypass flow path which connects the water supply pipe and the hot water discharge pipe of the heat exchanger, and when hot water is again discharged. Since the opening amount of the bypass valve can be controlled to fill the amount of water in the bypass passage with the hot water discharged from the heat exchanger,
It is possible to effectively suppress overshoot caused by post-boiled hot water at the time of re-hot water, and to realize hot water with little deviation from the set temperature without overshoot of hot water temperature. Further, by controlling the bypass valve, the time lag between the hot water temperature in the heat exchanger and the water temperature detected by the hot water temperature detecting means and the temperature difference are corrected, so that the hot water temperature control can be performed with higher accuracy.

Furthermore, by detecting the hot water temperature in the heat exchanger, the opening degree of the bypass valve can be controlled according to the fluctuation of the hot water temperature in the heat exchanger, so that the overshoot or undershoot of the hot water temperature at the time of re-hot water can be accurately performed. It is possible to suppress and control the hot water temperature at the time of re-hot water precisely.

[Brief description of drawings]

FIG. 1 is a block diagram showing a water heater according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a combustion control method for a water heater according to an embodiment of the present invention.

FIG. 3 is a chart showing a time lag between the hot water temperature in the heat exchanger of the water heater and the output value of the hot water thermistor according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional water heater having a bypass passage and a combustion control method using the same.

[Explanation of symbols]

3 ... Heat exchanger 4 ... Water supply pipe 6, 6a, 6b ... Bypass channel 7, 7a, 7b ... Solenoid valve 10 ... Water heater 11 ... Heat exchanger 12 ... Burner 12a ... Combustion gas 12b ... air 13 ... Water pipe 14… Swimming pipe 15 ... Bypass channel 16 ... Gas valve 17 ... Combustion fan 18a ... Fan rotation sensor 18b ... outside air temperature sensor 18c ... Inlet temperature sensor 18d ... Hot water temperature sensor in heat exchanger 18e ... Flow sensor 19 ... Bypass valve 20 ... Means for detecting hot water temperature in heat exchanger 22 ... Bypass ratio varying means 24 ... Bypass ratio calculation unit 26 ... Bypass valve drive unit 27 ... Control valve 28 ... Dew hot water thermistor

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F24H 1/10 302

Claims (2)

(57) [Claims] 1. A bypass flow path is provided to connect a water supply pipe and a hot water discharge pipe of a heat exchanger to bypass the heat exchanger, and water is not passed every time a predetermined waiting time elapses after combustion is stopped. In a water heater that performs backup combustion by igniting and supplementing the backup heat amount to control the hot water temperature in the heat exchanger within a predetermined allowable temperature range, the bypass water amount that is provided in the bypass flow passage and flows through the bypass flow passage. A bypass valve for controlling the hot water temperature, a hot water outlet temperature detecting means for detecting the water temperature at the location, which is interposed in the hot water outlet pipe, and the bypass water amount and the heat amount based on the deviation between the hot water temperature in the heat exchanger and the hot water outlet set temperature. The bypass ratio, which is the ratio of the amount of water in the heat exchanger flowing through the exchanger, is adjusted by adjusting the opening of the bypass valve based on the time lag and the temperature difference between the hot water temperature in the heat exchanger and the water temperature detected by the outlet temperature detecting means. Controlled bypass ratio Water heater and characterized in that it comprises a varying means. 2. The opening ratio of the bypass valve is controlled by the bypass ratio varying means when the hot water is re-exposed after the hot water supply is stopped.
The hot water temperature control method according to claim 1, wherein the hot water temperature is stabilized by filling hot water immediately after re-leaving hot water.