| 摘要 |
PURPOSE:To make it possible to obtain an optimum time point of start of defrosting and an optimum time for a defrosting operation without using a temperature sensor of an outdoor heat exchanger. CONSTITUTION:When a state that an operation is executed for 10 minutes or longer with an inverter frequency of 90Hz or above is assumed, a frequency switching means 17 switches over the inverter frequency in such a manner that the operation is executed for 3 minutes with 70Hz and then for 2 minutes with 85Hz. A deviation computing means 18 detects a Tc temperature Tc1. at the time point after the passage of 3 minutes and a Tc temperature Tc2 at the time point after the passage of 2 minutes in this case and determines a deviation dTc thereof. A discriminating means 19 discriminates that defrosting is necessary, when dTc<S. A defrosting operation time determining means 20 estimates the quantity of frost on the basis of the deviation dTc and determines the time for a defrosting operation on the basis of the quantity of the frost.
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