Re: USA-isian only
One prime reason for line voltage control on electric heat is that modern thermostats will use duty cycle control of the power to ramp the heat output to match demand.
I have a thermostat on an electric radiant panel that works this way. Four levels of active drive, 25%, 50%, 75%, 100%, and it uses PID control to determine the required output from the panel to achieve the set point. As a result, it rarely turns completely off, or completely on, once the room temperature stabilizes.
That would entail a lot of 'chatter' using relays. The thermostat is solid state, and uses zero-cross sensing to avoid high IR drop during activate/cut transitions.
Biting the hand that feeds IT
