PURPOSE: To enable to defrost without imparing comfortability by a method wherein the power supply to a preheater is controlled in proportion to the result of comparison of the integrated power supply time to the preheater and the set power supply time with the intention to operate the preheater in order to prevent the lowering of blowing off air temperature at the start of defrosting.
CONSTITUTION: When the heating operation is started, the signal of a frosting signal generator 1 and the signal of a starting timer 2, which starts to operate after the elapse of 45min, and inputted to an AND gate 3, resulting in preventing the frosting signal from sending to a discriminator 8b. When the frosting signal is inputted to the discriminator 8b after the elapse of 45min, the integrated power supply time ta, which is the sum of the continuous power supply time of an indoor motor 7 stored in a memory 6 and of the continuous power supply time of the preheater stored in a discriminator 8a, is compared with the set heater power supply time (about 6min) tb. When the time ta is larger than or equal to the time tb, a defrosting controlling circuit 4 is put into operation in order to start defrosting. On the contrary, when the time ta is smaller than the time tb, a preheater energizing circuit 5 is put into operation for the duration of time that the time ta becomes zero value and, after the finish of preheating, the defrosting is started.
WATANABE ISAMU
HASHIMOTO TAKESHI
MATSUMOTO KAZUNORI
TAKADA JIROU
YAMAGATA MASATAKA
TOKYO SANYO ELECTRIC CO