Toshiba RAS-13UKHP-ES3 Service Manual page 30

7-6. Defrost Operation *
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.
A
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
Fig. 7-6-2
Heat pump model only
D
B
Cumulative
compressor
C
operating time
minutes minutes
40 40
10 minutes
1 cycle
<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.
DEFROST LAMP :
• During defrost operation, the PRE-DEF. lamp is
on and the indoor and outdoor fans are off.
• The compressor start protection timer is inter-
looked with the PRE-DEF. lamp. So the PRE-DEF.
Lamp is off (the fans stop) for about 3 minutes
after the START/STOP button is turned on. When
the compressor is turned on, the PRE-DEF. lamp
comes on. After the heat ex-changer is preheated
to about 24°C or higher, the PRE-DEF. Lamp
goes off, and the indoor fan starts.
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FILE NO. SVM-04001