Control circuit for electric room heaters - has two heater coils interconnected by relay with winding in series with thermostats

摘要

The room heating system with heaters (H1,H2) using firebrick has the power supply connection (2) for a heater (H1) at one end connected by a relay contact (a) to the mains supply (P). A second heater (H2) has a connection (3) similarly joined by another contact (r) of the relay (R) to the power supply. The control winding of the relay is connected between the mains supply and a room thermostat (RT) in series with a further thermostat (HT) on the first heater. The latter thermostat has a switching hysteresis of more than 5 degrees. The coil of the second room heater is in series with a further room thermostat (RT2). One of the two room thermostats has a clock to control switching to suit lower night temperatures.