JPH0510588A - Controlling method for temperature of output hot water of hot water supplying apparatus - Google Patents

Abstract

PURPOSE:To obtain excellent hot water reoutputting characteristic without influence of a magnitude of an undershooting amount of an outputting hot water temperature at the time of reoutputting hot water by alleviating an integrated amount by multiplying the integrated amount by a predetermined moderation ratio in response to lapse of a time from the time of stopping hot water outputting. CONSTITUTION:When hot water outputting is stopped, the stopping state is confirmed in a state that hot water is not reoutput, a drop of an outputting hot water temperature Th is detected, an integrated amount is alleviated in response to the dropping amount, an elapsing time from the time of stopping the hot water outputting is alleviated, and the integrated amount is alleviated in response to a predetermined elapsing time. For example, 2% is alleviated each time 10 seconds are elapsed. That is, a moderation ratio of 0.98 is multiplied, and stable hot water outputting characteristic is obtained even if an undershooting is large. Incidentally, a temperature dropping degree during a postpurging is different from that after the postpurging. That is, since the temperature dropping degree during the postpurging is large and that after the postpurging is small, the moderation ratios are altered before and after the postpurging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot water outlet temperature control method for hot water heaters, and more particularly to a hot water outlet temperature control method for hot water heaters which uses feedback control of gas amount with respect to hot water outlet temperature.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, a water inlet temperature sensor 4 and a water inlet amount sensor 5 are arranged in a water inlet passage 2 connected to an inlet side of a heat exchanger 1, and an outlet side of the heat exchanger 1 is arranged. The outlet temperature sensor 6 is arranged in the outlet passage 3 connected to
A gas proportional control valve 9 is provided in a gas passage 8 connected to the burner 7, and the detection data of the incoming water temperature sensor 4, the incoming water amount sensor 5, and the hot water temperature sensor 6 are input to the controller 10 and output from the controller 10. The control amount is output to the gas proportional control valve 9, and as the hot water outlet temperature control of the water heater whose gas amount is controlled, the burner using only the feedforward control based on the incoming water amount Qc, the incoming water temperature Tc, and the set temperature Ts. Control of combustion amount, or set temperature Ts and hot water temperature Th
It is generally known to control the combustion amount of the burner using only the feedback control based on the deviation between or and the control of the combustion amount of the burner by the control that combines the feedforward control and the feedback control.

Here, in the hot water outlet temperature control of the water heater using only the feedback control, the proportional (P) operation and the integral (I) operation are combined to secure stability by the P operation and gradually reduce the offset by the I operation. Control system,
Alternatively, a control method is known in which the P operation, the I operation, and the differential (D) operation are combined to improve the responsiveness by the D operation.

[0004]

However, in the hot water outlet temperature control of the water heater using only the above-mentioned conventional feedback control, the converged gas which is the value of the finally stabilized gas amount to obtain the desired hot water outlet temperature. The amount is calculated by I =
(Θ / K _I ) Σ (Ts −Th) is obtained by the I operation (where θ is the number of samplings, K _I is the integration time constant, Ts is the set temperature, and Th is the hot water temperature). It is known that when resuming hot water after it has been stopped, the integrated amount before the stop of hot water is remembered in order to improve the temperature characteristic of the hot water at the time of re-hot water. Although the tapping temperature does not drop so much when the time is short, that is, when the undershoot is small, good characteristics can be obtained (see FIG. 5a).
When the undershoot is large, that is, when the outlet hot water temperature is significantly lowered, a large temperature deviation occurs between the outlet hot water temperature and the set temperature, and when integrated as it is and added to the control amount, an overshoot occurs (see FIG. 5b). In order to solve this problem, for example, as shown in FIG. 4, a decrease in the hot water discharge temperature is detected between the time when the hot water discharge is stopped and the time when the hot water discharge is started again, and the integration amount is reduced according to the decrease in the hot water discharge temperature. There is proposed a method of performing the processing. However, in recent water heaters, the post-purge time is set to be long when hot water is stopped in order to accelerate the ignition operation when hot water is re-exposed, and this post-purge operation has the effect of actively cooling the heat exchanger. The temperature of the hot water in the heat exchanger is significantly lower than the hot water temperature of the hot water outlet detection unit, and a large undershoot occurs, but the amount of integration is reduced according to the drop in hot water temperature. However, it is not possible to cope with the difference between the hot water temperature in the heat exchanger and the hot water temperature of the hot water outlet temperature detection unit by simply performing the above procedure, and there is a problem of overshooting (see FIG. 5b).

An object of the present invention is to provide a hot water outlet temperature control method for a water heater, which can obtain good re-hot water characteristics without being influenced by the magnitude of the amount of undershoot of the hot water temperature at the time of hot water discharge again. is there.

[0006]

In order to achieve the above object, a method for controlling a hot water outlet temperature of a water heater according to the present invention detects a hot water outlet temperature, compares the hot water outlet temperature with a set temperature, and controls a gas amount according to the temperature deviation. In a hot water outlet temperature control method that uses only feedback control, the integral amount is multiplied by a predetermined reduction rate according to the time elapsed from the time when the hot water supply was stopped (for example, the reduction rate is 0.98 for the elapsed time of 10 seconds). The amount is reduced, and good re-melting characteristics can be obtained without being influenced by the magnitude of the amount of undershoot of the tapping temperature during re-melting.

[0007]

EXAMPLES Examples of the present invention will be described. When tapping hot water is stopped, it is in a state where it is not re-sprayed, that is, the stopped state is confirmed, a decrease in tapping temperature Th is detected, and an integrated amount is calculated according to the amount of decrease. And reduce the integrated amount according to a predetermined elapsed time by detecting the elapsed time from the time when the hot water is stopped, for example, reduce it by 2% every 10 seconds, that is, multiply by a reduction rate of 0.98. Therefore, as shown in FIG. 5c, stable hot water discharge characteristics can be obtained even if the undershoot is large.

It should be noted that the degree of temperature decrease during post-purge operation and the degree of temperature decrease after post-purging are different, that is, the degree of temperature decrease during post-purge is large and the degree of temperature decrease after completion of post-purge is small. It is good to change the reduction rate before and after post-purge.

[0009]

Since the present invention is configured as described above, the integrated amount is reduced by multiplying the integrated amount by a predetermined reduction rate according to the lapse of time after the tapping is stopped. It is possible to obtain good re-melting characteristics that are not affected by the magnitude of the undershoot amount of the hot water discharge temperature.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a water heater to which the present invention is applied.

FIG. 2 is a flowchart showing a control operation according to the present invention.

FIG. 3 is a characteristic diagram showing a change in an integral amount of a control operation according to the present invention.

FIG. 4 is a flowchart showing a conventional control operation.

[Fig. 5] Fig. 5 is a characteristic diagram of a change in tapping temperature, where "a" indicates a small undershoot, "b" indicates a large undershoot by the conventional control method, and "c" indicates a large undershoot by the control method of the present invention. Indicates.

[Explanation of symbols]

 1 Heat Exchanger 2 Inlet Channel 3 Outlet Channel 4 Inlet Temperature Sensor 5 Inlet Volume Sensor 6 Outlet Temperature Sensor 7 Burner 9 Gas Proportional Control Valve 10 Controller

Claims (1)

Claims: 1. A tapping temperature is detected and compared with a set temperature,
In the hot water outlet temperature control method using only feedback control for controlling the gas amount according to the temperature deviation,
A method for controlling a hot water supply temperature of a water heater, which is characterized in that an integrated amount is reduced according to a lapse of time after the hot water supply is stopped.