| 摘要 |
An electrical control circuit for a hot water furnace is disclosed. The control circuit comprises at least one main heating element (A; B) adapted for connection to a power source for heating water when circulated through the furnace, an additional heating element (C), also adapted for connection to the power source, and switch means (R3, R4, R5) for disconnecting the main heating element (A; B) when burnt out and connecting the additional heating element (C).
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