| 摘要 |
An electrical switch unit (1, 60, 61, 70) is provided for controlling the supply of electrical energy to an appliance (7, 65) that also has its own electrical control switch (38), in particular a water heater. The switch unit has a normally open load switch operatively closed by a electronic timer means, and a bypass detector circuit (25) is connected in parallel across the load switch so as to become energized when the electrical control switch of a connected appliance is closed. The timer means is operative to become activated consequent on the initiation of current flow through the detector circuit to effect closure of said load switch after a predetermined optionally adjustable time delay (that is independent of real-time), and to maintain the load switch in a closed condition for a time period after which the load switch is returned to its normally open condition. The invention extends to an electrical distribution box including such a switch and the switch may have a current sensor for association with otherwise independent electrical conductors serving other appliances to disable the timer if no other appliance is operative. |
