Test circuit

A safety control system for actuating and deactuating a burner circuit for a boiler comprising, first and second electrical circuits and power supply means for said circuits;

• said first electrical circuit including a heat source, an initially closed switch, thermostat and aquastat means and switch in said first circuit responsive thereto, an electrode disposed in the boiler for completing said first circuit through a water path to the grounded wall of the boiler when the water level in the boiler is not below the electrode, and when the water level in the boiler falls below the electrode the heat source is deenergized and the consequent movement of the heat sensitive means causes reopening of an initially open switch of the second circuit and deactuation of said controlled circuit;
• said second electrical circuit including said initially open switch, means operative when said initially open switch of said second circuit is closed to actuate said control circuit, and heat sensitive means operative when both the switches of said first circuit are closed to close the initially open switch of said second circuit and, after a time interval, open the initially closed switch of the first circuit;
• and a test circuit comprising a test switch having normally open first and normally closed second contacts, said normally closed second contacts being in series with said water path, a voltage indicator, and means connecting said normally open first contacts and voltage indicator in series across said water path to indicate a potential drop thereacross.