High-Temperature Limit Control; Low-Temperature Limit Control; Defrost Operation - Toshiba RAS-07SKHP-E Service Manual

7-4. 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. 7-4-1.
Compressor Outdoor fan
OFF OFF
OFF
ON
ON
ON
Fig. 7-4-1

7-5. 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. 7-5-1 and 7-5-2.
RAS-07SKHP-E
RAS-10SKHP-E
Heat exchanger
temperature
(°C)
5
2
Fig. 7-5-1
Heat exchanger
temp.
(°C)
60
53
52
Compressor Outdoor fan
ON
Less than 2°C continues
for 5 minutes
OFF
− 20 −

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.
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.)
FILE NO. SVM-07023
Cumulative
compressor
C
operating time