Boiler control

Posted on Dec 5, 2012

The purpose of this circuit is to control the water temperature in a hot-water heating system. What it does is to lower the boiler temperature as the outside air temperature increases. The op amp is used as a comparator. Thermistor TH2 and R2 form a voltage divider that supplies a reference voltage to the op-amp`s inverting input. Thermistor TH2 is placed outdoors, and the values of TH2 and R2 should be chosen so that when the outside temperature is 25 °F, the resistance of the thermistor and resistor are equal. Resistor Rl and thermistor TH1 make up a voltage divider that supplies a voltage to the op amp`s noninverting input

Boiler control
Click here to download the full size of the above Circuit.

Thermistor THl is placed inside the boiler and the values of THl and Rl should be chosen so that when the boiler"s temperature is 160 °F, their resistances are equal. The output of the op amp controls Ql, which is configured as a transistor switch. When the logic output of the op amp is high, Ql is turned on, energizing relay RYl. The relay"s contacts should be wired so that the boiler"s heat supply is turned off (relay energized).

Leave Comment

characters left:

New Circuits



Popular Circuits

Biomedical Monitoring circuit AT89C2051
Capacitor internal resistor meter
Electronic lock using the 4022 octal counter
am transmitter circuits
sound activated lamp relay switch
Square Wave Generator
Schematic for voltage regulation via lm317
PWM - Pulse Width Modulation for DC Motor Speed and LED Brightness 2
Voice music outlet circuit diagram SK- made
FGDF-3 three-phase low-temperature iron plating power commutation control switch and electronic circuit