| 摘要 |
<p>PURPOSE:To obtain a waterless burning preventer for a water heater, which is capable of providing hysteresis between a detecting water level and a non-detecting water level, by a method wherein a water level detecting electrode, being hung down to a predetermined height in a water tank and formed by a shape-memory alloy becoming low resistance state when it is submerged into water, and a heating unit, detecting the signal of the water level detecting electrode and heating water in the water tank only when the water level detecting electrode shows a low resistance, are controlled. CONSTITUTION:Temperature in the water tank 1 is low before increasing the temperature of water in the water tank 1, therefore, the electrode 15b of a water level detecting electrode 15, which is consisting of a shape-memory alloy, is provided with the state of L-shape. In this case, a temperature control circuit can not be operated unless the level of the water is elevated to a height higher than a predetermined water level (L1). When the water level is elevated to a height higher than the predetermined water level (L1), the temperature control circuit is operated to increase the temperature in the water tank 1. Accordingly, the temperature of the water level detecting electrode is increased gradually and the electrode 15b, consisting of the shape-memory alloy, approaches linear state, therefore, said electrode 15b is dipped into the water deeply and the water level may be detected under a stabilized state.</p> |
