Defrost Operation; Condition To Start The Defrost Operation; Defrost Operation Time Control; Ending Condition At Defrost Operation - Toshiba RAS-10YKH-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 condi-
tions 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 opera-
tion starts.)
(2) When the current limit control or the high tem-
perature limit control is performed for total of 90
minutes.
(˚C)
D
19
A
B
10
40
Fig. 7-11-1 (Indoor fan speed : M)
Cumulative
compressor
C
operation time
90 (min.)
– 23 –

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 min-
utes. 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.)
minutes minutes
40 40
Max 6 minutes
1 cycle
Fig. 7-11-2
<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
interlocked 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
exchanger is preheated to about 30°C or
higher, the PRE-DEF. lamp goes off, and the
indoor fan starts.
minutes minutes
40 40
10 minutes