| 摘要 |
PURPOSE:To prevent failure in heating or breakage of a piping system from occurring due to insufficient defrosting and enhance reliability, by providing a defrosting-maintaining timer for maintaining a defrosting condition for a period of several minutes after the start of a defrosting operation, even when the temperature of the piping system becomes equal to a predetermined reset temperature. CONSTITUTION:The moment defrosting is started, a defrosting output shown in diagram (a) becomes 'H'. Also, simultaneously when the defrosting is started as shown in diagram (e), charging of a capacitor 10 is started. An input terminal T1 of a defrosting-maintaining timer 8 is supplied with an 'L'-'H' signal having a divided period of 15/8min (slightly less than 2min), shown in diagram (b), from a timer 5 for forced finishing of defrosting, whereby the charged voltage of the capacitance 10 is increased, with rest periods of slightly less than 1min. The charged voltage of the capacitor 10 exceeds a reference voltage after about 2.5min from the start of defrosting. Thus, as shown in diagram (d), an output from a comparator 11 sent through a diode D3 to appear at an output terminal T2 as an output from the timer 8 is changed from 'L' to 'H', whereby a defrosting-finishing thermostat 3 is reset for returning to a normal operation.
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