Electric water heater thermostat control circuit

Published:2011/5/3 9:16:00 Author:Christina | Keyword: Electric water heater, thermostat control | From:SeekIC

The electric water heaters always use the phase angle control method to control the temperature, that means the electric water heaters use the two-way SCR to control the heating element power's conduction angle of each half cycle. Greater the conduction angle is, longer the conduction time of each half cycle is, so the electric heating elements has the greater average power; otherwise the average power is smaller. This mode makes the load current's conduction and blocking more frequent to produce a large number of harmonics, these harmonics have great disturbance to other home appliances. Here I introduce the full cycle control method's water heater thermostat with automatic control circuit. 1 principle circuit Figure 1 is the electric water heater thermostat control circuit. Because the RL's conduction and blocking happen in the moment of the voltage is over-zero, and the number of conduction and blocking per second is less than the phase angle control method, so even in the use of high-power electric equipments, there will not have a great interference. Figure 1 Electric water heater thermostat self-control circuit 2 Selection of the main components In order to facilitate the adjustment, the electric water heater thermostat self-control circuit uses the potentiometer which has linear resistance characteristics. RT1 uses the PTC thermistor after the line treatment, RT2 uses the 60℃ step-type PTC thermistor. VS is determined by the RL's power, and this circuit's RL is 2KW, the SCR should be equipped with heat sink.



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