| 摘要 |
PROBLEM TO BE SOLVED: To detect possible 'dry fire' in an electric water heater with simple algorithm and also with high accuracy by enabling faithful detection of the temperature of a pot thereof, when the same pot containing only a small quantity of remaining water is boiled dry. SOLUTION: This electric water heater comprises the pot 2 for containing a liquid, a heating means 3 for heating the liquid filled in the pot 2, a temperature-sensing means 4 being attached to the bottom of the pot, a flow path 5 for releasing the liquid from inside pot to outside pot, or for circulating the liquid onto pot, a motor 6 for releasing or circulating the liquid inside pot and a means 7 for detecting possible 'dry fire' in the pot 2, then for thereby allowing the heating means 3 to be suspended. The means 7 for detecting possible 'dry fire' drives the motor 6 at a lower voltage than at the liquid- circulation so as to draw remaining water inside the pot into the flow path 5 at the start of heating. This can pull such remaining water, which means an extremely small quantity, into the flow path 5 and can prevent the same pulled water from being returned to the pot through a circulation outlet.
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