| 摘要 |
<p>An electric hot water heater has a water storage vessel (1) with a cold water inlet (3) adjacent the bottom and a hot water outlet (4) adjacent the top. The heater includes an off-peak heating circuit which has a first heating element (5) disposed in a lower portion of said vessel (1) and an associated first thermostat switch (6) to control flow of current therethrough during the off-peak supply period. An auxiliary heating circuit is connected to a continuous mains supply and includes an ON/OFF switch (12) to control supply of current to the auxiliary heating circuit, an auxiliary heating element (7), and an associated second thermostat switch (8) to control flow of current through the auxiliary heating element (7) when the ON/OFF switch (12) is in the ON condition. Circuit means operable in response to the auxiliary thermostat switch (8) when the ON/OFF switch (12) is in the ON condition permit supply of current to the off-peak heating circuit only when the second thermostat switch (8) senses a temperature above a selected value and interrupts the supply of current to the auxiliary heating element (7). The circuit means further permits supply of current to the off-peak heating circuit irrespective of the water temperature sensed by the auxiliary thermostat switch (8) when the ON/OFF switch (12) is in the OFF condition.</p> |
