| 摘要 |
The water supplied to an instantaneous electric water heater 7 is preheated by mixing cold water with hot water from a cylinder 1. The pre-heat apparatus 8 comprises a mixing valve 16 having separate inlets connected via respective non-return valves 19,20 to supplies of hot and cold water and an outlet connected via an on/ off solenoid valve 21 to a supply pipe 12 to the electric water heater 7. The pre-heat apparatus 8 further includes a cold water branch pipe 23 by-passing the mixing valve 16 and connected via an on/off solenoid valve 24 to the supply pipe 12. The on/off solenoid valves 21,24 are selectively operable by switching means for controlling flow through either the mixing valve 16 or the branch pipe 23 as required. <IMAGE>
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