JPH0668414B2 - Water heater controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater controller.

2. Description of the Related Art In recent years, there has been a demand for improved water quality in the field of water heaters, and in response, a gas proportional valve has been developed on the actuator side, while PID control has been applied to water heaters as a control system. Further, with the recent spread of microcomputers (hereinafter referred to as "microcomputers"), digital PID control by microcomputers has been applied to water heaters instead of the conventional analog PID control, and it is attempted to further improve the quality of hot water and reduce costs.

One example of improving the quality of hot water by digital PID control is setting change PID control when the hot water temperature rises (immediately after the start of use of the water heater), which will be described below with reference to the drawings. FIG. 3 shows an overall configuration diagram of the water heater. The control unit 1 ignites the ignition device 2, opens the gas proportional valve 3 to ignite the main burner 4, and detects the ignition by the ignition detection circuit 5. When the main burner 4 burns, water is converted into hot water by the heat exchanger 6, and the control unit 1 detects the current hot water temperature by the hot water thermistor 7 and adjusts the gas temperature to the hot water temperature set by the hot water temperature setting unit. Control the proportional valve 3.

FIG. 4 shows a flow chart of setting change PID control in one embodiment for improving the quality of hot water by digital PID control. With normal PID control However, Tc: Proportional valve output TERn: Current deviation of thermistor TERn _-1 : 〃 Last time 〃 Ti: Integral constant Td: Derivative constant is calculated by the control unit 1 and proportional valve 3 is controlled. As shown in B and B, when the water temperature setting unit is changed immediately after the water heater is started and when the water temperature setting unit is changed while the water heater is being used, the normal condition is satisfied.
Stop PID calculation and change the setting Move to PID calculation, stop integral calculation (stop addition of deviation), and set normal under appropriate conditions
Return to PID. As a result, it is possible to prevent overshoot from the set temperature as shown by A and B in FIG. 5, and obtain hot water temperature characteristics without overshoot as shown in FIG. This is quite effective in preventing boiling at high temperature settings and low incoming water temperatures.

Problems to be Solved by the Invention However, in the above method, since the deviation is not added when the integral calculation is stopped, the proportional valve output becomes small, and as shown in FIG. Hereinafter, the settling time) becomes long and the hot water temperature characteristic deteriorates.

The present invention is to solve the above problems, to prevent boiling by performing a setting change PID calculation in the case of high temperature setting, to shorten the settling time by executing the normal PID in other settings The present invention provides a control device for a water heater capable of performing the above.

Means for Solving the Problems In order to solve the above problems, the present invention judges whether the set temperature is high or low immediately after the start of use, and when changing the setting, it is possible to change from the high temperature setting to the low / medium temperature setting. It is to judge the change from the low / medium temperature setting to the high temperature setting.

Action From the above configuration, when the high temperature is set, the integral calculation is stopped in the setting change PID mode to prevent boiling, and when the low temperature is set, there is some overshoot in the normal PID mode, but the settling time is shortened. Will be done.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a flow chart of a control device according to an embodiment of the present invention. In FIG. 1, immediately after the start of use, the high temperature setting is judged by A, and if the high temperature setting is set, the process proceeds to the setting change PID and the integral calculation is stopped to prevent overshoot. Second
A in the figure shows the situation. On the contrary, if it is judged that the temperature is low, the PID is normally used for calculation, and the settling time is shortened. B of FIG. 2 shows such a state.

Thus, according to the control device of the present embodiment, when setting the high temperature, to prevent boiling by prohibiting the integral calculation with the setting change PID,
When setting a low temperature, the settling time can be shortened by the normal PID calculation.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to prevent boiling when a high temperature is set, shorten the settling time when a low temperature is set, and improve the hot water temperature characteristic.

[Brief description of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention, FIG. 2 is an example of hot water temperature characteristics of an embodiment of the present invention, FIG. 3 is an overall configuration diagram of a water heater, and FIG. 4 is a conventional setting change. FIG. 5, FIG. 5 is an example of hot water supply characteristics of normal PID, and FIG. 6 is an example of hot water temperature characteristics of conventional setting change PID. 1 ... Control device, 2 ... Ignition device, 3 ... Gas proportional valve,
4 ... Main burner, 5 ... Ignition detection circuit, 6 ... Heat exchanger, 7 ... Water discharge thermistor

Claims (1)

[Claims] 1. A proportional valve for supplying gas to a main burner,
An ignition device for igniting the main burner, an ignition detection circuit for detecting this ignition, a heat exchanger heated by the main burner, and a water discharge pipe for letting out water heated by the heat exchanger are provided. Has a water discharge thermistor, a water temperature setting unit and a controller for digital PID control of the proportional valve so that the water temperature detected by the water thermistor becomes the water temperature set by the water temperature setting unit, When changing from the low / medium temperature setting of the water temperature setting part to the high temperature setting and the high temperature setting at the start of use, the integral calculation of the digital PID control is prohibited, and when the high temperature setting is changed to the low / medium temperature setting. A water heater controller configured to perform normal digital PID control.