Gas-fired water heater safety device - automatically shuts off gas burner when down draught or flue blockage is detected

摘要

The gas-fired water heater has a flow safety device (3) between the heater (1) and the flue (10) with further outlets (12) at the sides leading to a trap chamber. Two temp. sensors (14,17) at the outlet (9) leading to the flue (10) and at one of the side outlets are coupled to an evaluation circuit (16) comprising the difference between their outputs with a reference value to selectively disconnect the gas supply to the water heater. A third temp. sensor may be positioned at the inlet (8) to the safety flow control (3) from the heater (1). Pref. the evaluation circuit (16) uses a multi-stage binary counter coupled to a comparator providing the difference between the temp. sensor outputs. The heater may comprise a through-flow water heater or a boiler.