Continuous flow gas fired hot water heater - thermostatic control with thermal inertia gives hysteresis effect

摘要

The heater has a gas fired burner (1) supplied from a towns gas network. The burnt gases pass up a vertical duct and discharge into the room containing the heater. The water pipe (4) is coiled round the outside of the flue duct and brazed to it for good heat transfer. After leaving this heat exchanger the water pipe passes through an enclosure (10) either before (A) or after (B) the main control valve. The enclosure (10) also contains the bulb (9) of a capillary thermostat connected by a capillary to a bellows operating the gas shut-off valve. The enclosure (10) is packed with poorly conducting material so that after the gas has been shut off a long period must elapse before the valve opens again.