Electric water heater for keeping water at or near boiling point

摘要

A vessel (1) contains water (2) and has a supply inlet (6) and hot water outlet (7). An electric heater element (3) has its own temperature sensor (4). This and the water temperature sensor (5) are connected to the controller (8) with its temperature selector (9). There is a main supply (10). When the water boils, the energy supply is reduced either by switching it on and off or by modulating it. Temperature is maintained at or just below boiling point. Lack of water is detected by an increased rate of rise of heater element temperature. The energy supply is then switched off.