Defrost Operation; Condition To Start The Defrost Operation; Defrost Operation Time Control; Ending Condition At Defrost Operation - Toshiba RAS-10SKH-E Service Manual

7-11. 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.
7-11-1. Condition to Start the Defrost
Operation
The defrost operation starts whichever below
conditions are specified.
(1) When the cumulative compressor operation 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.
7-11-1. 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.
(˚C)
19
A
10
40
Fig. 7-11-1 (Indoor fan speed : M)

7-11-2. Defrost Operation Time Control

<In case of B>
(1) The heating operation is performed for at least 40
minutes.
(2) The maximum defrost operation time is 6 minutes.
The defrost operation time for the 4th cycle is 10
minutes. (When the outdoor temperature is very
low, however, the defrost operation time is 10
minutes.)
D
B
Cumulative
compressor
C
operation time
90 (min.)
minutes minutes
40
<In case of C>
(1) The heating operation is performed for at least 90
minutes.
(2) The defrost operation time is 10 minutes.
7-11-3. Ending Condition at Defrost
Operation
(1) When the compressor current becomes 7.5A or
more during defrost operation, the defrost opera-
tion stops and the heat 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-
locked with the PRE-DEF. lamp. So the PRE-
DEF. lamp is off (the fans stop) for about 3 min-
utes 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 30°C or higher,
the PRE-DEF. lamp goes off, and the indoor fan
starts.
– 18 –
minutes minutes
40 40 40
Max 6 minutes 10 minutes
1 cycle
Fig. 7-11-2