Description Of Safety And Reliability Prevention Function; Defrost Operation - Toshiba RAS-13SKHP-E Service Manual

7-4. Drescription of Safety and Reliability Prevention Function
7-4-1. Low-Temperature Limit Control
The microcontroller detects the indoor heat exchanger
temperature to prevent the indoor heat exchanger from
freezing.
The compressor and outdoor fan motor are controlled
as shown in Fig. 7-4-1.
RAS-13SKHP-E
Heat exchanger
temperature
(°C)
6
2
Fig. 7-4-1
7-4-2 High-Temperature Limit Control
The microcontroller detects the indoor heat exchanger
temperature to prevent pressure of a refrigerating cycle
from increasing excessively.
The compressor and outdoor fan motor are controlled
as shown in Fig. 7-4-2.
Compressor Outdoor fan
OFF
OFF
OFF
ON
ON
ON
Fig. 7-4-2
Compressor Outdoor fan
ON
Less than 2°C continues
for 5 minutes
OFF
Heat exchanger
temp.
(°C)
60
53
52
-

7-4-3. 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.
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. 7-4-3. 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. 7-4-3 (Indoor fan speed : M)
17 -
FILE NO. SVM-07033-1
D
B
Cumulative
compressor
C
operating time