Positive safety device for the gas supply in a burner

The burner admission valve (25) is initially opened by a boost-type control circuit (27), having 1W output, via a self-resetting bi-metal (SRC), guarding against flue obstruction. A second boost circuit (24), with 30 mW output, keeps the valve open. Both circuits give higher output voltages than the battery which provides power supplies, and the latter is insufficient to operate the valve. The burner is lit by a spark generator (20), based on an oscillator (21) and a discharge circuit (22) giving a 15 kV output for 5 microseconds; this is associated with a flame detector (11) using the diode effect of ionisation. These devices are directed at an igniter gas nozzle near the burner. The equipment is further described in European Patent 0 821 198 (q.v.).