| 摘要 |
<p>PURPOSE:To prevent temperature within a hot water tank from being excessively lowered by a method wherein a signal from a hot water temperature sensor is compared with a boiling temperature set signal and a differential value of an energization of an electric heater is decreased when the boiling temperature set is low. CONSTITUTION:When a hot water temperature sensor 3a detects that temperature within a hot water tank is low, an output from a comparator 13 shows an 'L' voltage, transistors 18a and 15 are turned ON, a feed-back resistor 14 is inserted in parallel with a reference resistor 25. A differential value until the reference voltage is decreased and energization for an electric heater 2a is stopped is generated. A transistor 21a is also turned ON to drive a coil 22a, energization of a heater 2a is started and when a hot water temperature sensor 3a detects its boiling temperature, output from the comparator 13 shows 'H' voltage, a feed-back resistor 14 is turned off, the reference voltage becomes high and then energization of the heater 2a is terminated. When a set boiling temperature is low, the reference voltage is low, so that even if the feed-back resistor 14 is connected in parallel, the voltage is less decreased and the differential value is decreased.</p> |
