Electric continuous flow water heater - has safety relay between heaters and 3-phase supply, triggered by voltage monitoring unit and water flow monitor

摘要

The water heater has resistance heaters in a tank with water inlet and outlet. There is a device for reducing the power when the water flow is small and the heater circuitry has both control switches and a safety switch. Each of the cables to the heaters (H1..H4) has a connection to a voltage monitoring unit (7), from which one output goes directly to one end of the coil (8) of the safety relay. The other output goes to the other end of the coil via a switch (9), controlled according to the input water flow. The electrical supply is three-phase. ADVANTAGE - Rapid reduction of heating power if water supply reduced.