| 摘要 |
<p>An electric heater for circulating water is constructed as a unit from several tubes. The water circulated through these and the electric heating elements dip into them. The elements can be raised or lowered by an automatic control system so that the depth of immersion and therefore rate of heating is varied to suit the demand. The tubes are extruded and soldered into headers to form the heating unit. The heating elements are raised and lowered by electromagnets supplied by direct current obtained from rectification of an AC supply. The electro-magnets are controlled by room thermostats, safety thermostats and an outdoor thermostat.</p> |
