Defrost Operation - Toshiba RAS-13UKHP-E Service Manual

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 speci-
fied value. (This value is decided by the micropro-
cessor.) (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 tempera-
ture 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
Fig. 7-6-2
Cumulative
compressor
operating time
C
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 opera-
tion 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.
– 27 –
FILE NO. SVM-02001