Defrost Operation (Nkhd Series Only) - Toshiba RAS-13NKHD-E Service Manual

7-6. Defrost Operation (NKHD Series only)

During the heating operation, the outdoor heat
exchanger temperature goes down and sometimes it is
frozen.
In this case, the air conditioner stops the heating
operation and starts the defrost operation to melt ice.
7-6-1. Condition to start the defrost operation
The defrost operation starts whichever below
conditions are satisfied.
(1) When the cumulative compressor operating time is
longer than 40 or 90 minutes and difference
between the indoor heat exchanger temperature
and the room temperature is less than the
specified value. (This value is decided by the
microprocessor.) (Control example is shown in
Fig. 7-6-1. In case of B or C, the defrost operation
starts.)
(2) When the current limit control or the high
temperature limit control is performed for total of
90 minutes.
D
A
B
Fig. 7-6-1 (Indoor fan speed : M)
7-6-2. Defrost operation time control
<In case of B>
(1) The heating operation is performed for at least
40 minutes.
(2) The maximum defrost operating time is 6 minutes.
The defrost operating time for the 4th cycle is
10 minutes. (When the outdoor temperature is
very low, however, the defrost operating time is
10 minutes.)
minutes minutes
40 40
Max 6 minutes
1 cycle
Fig. 7-6-2
Cumulative
compressor
C
operating time
minutes minutes
40 40
10 minutes
<In case of C>
(1) The heating operation is performed for at least 90
minutes.
(2) The defrost operating time is 10 minutes.
7-6-3. Ending condition at defrost operation
(1) When the compressor current becomes 7.5A or
more during defrost operation, the defrost
operation stops and the heating operation restarts.
(The current sensor detects the compressor
current.)
(2) The defrost operation continues for at most
6 minutes or 10 minutes.
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FILE NO. SVM-04022