Safety valve for continuous flow electric water heater - is operated by thermostat on cold feed to heater

摘要

A continuous type electric water heater for domestic use has a heater body with a cold water feed and a tap controlled hot water discharge. The heater element is controlled by a flow switch in the water flow. A safety cut off is worked by a pressure switch since a non-return valve in the cold feed ensures that the pressure must rise if the heating element is on without flow through the heater. In case the non-return valve lets by, a further cut is provided by a thermostat clamped to the cold feed near the inlet to the heater and this operates a relay which opens a contactor in the electric supply to the heater element.