| 摘要 |
<p>A control unit for a gas-fired water heater comprises a resiliently-loaded main valve for controlling gas flow to a gas burner of the heater, the main gas valve being opened and closed by a flexible diaphragm exposed to pressure of water flowing through the water heater. A subsidiary gas valve located upstream in the gas supply of the main gas valve has a permanently open by-pass and is actuable by a user operated control which also adjusts the resilient loading of the main gas valve in such manner as to adjust the rate of water flow and the rate of gas flow to provide hot water of a required temperature and at a required rate of flow.</p> |
