Mitsubishi Heavy Industries SRK20ZIX-S Service Manual page 64

2.6.10 Outline of automatic operation
(1) Determination of operation mode
The unit checks the indoor temperature and the outdoor air temperature, determines the operation mode, and then begins in the
automatic operation.
Indoor air temperature (˚C)
(2) The unit checks the temperature every hour after the start of operation and, if the result of check is not same as the previous op-
eration mode, changes the operation mode.
(3) When the unit is started again within one hour after the stop of automatic operation or when the automatic operation is selected
during heating, cooling or dehumidifying operation, the unit is operated in the previous operation mode.
(4) Setting temperature can be adjusted within the following range. There is the relationship as shown below between the signals of
the wireless remote controller and the setting temperature.
Cooling
Setting
Dehumidifying
temperature
Heating
2.6.11 Protective control function
(1) Frost prevention control (During cooling or dehumidifying)
(a) Operating conditions
1) Indoor heat exchanger temperature (Th2) is lower than 5ºC.
2) 5 minutes after reaching the compressor command speed except 0 rps.
(b) Detail of anti-frost operation
Indoor heat exchanger
Item
Lower limit of compressor command speed
Indoor fan
Outdoor fan
4-way valve
Notes (1) When the indoor heat exchanger temperature is in the range of 2.5~5 ºC, the speed is reduced by 4 rps at each 20 seconds.
(2) When the temperature is lower than 2.5 ºC, the compressor is stopped.
(3) When the indoor heat exchanger temperature is in the range of 5~8 ºC, the compressor command speed is been maintained.
(c) Reset conditions: When either of the following condition is satisfied.
1) The indoor heat exchanger temperature (Th2) is 8ºC or higher.
2) The compressor command speed is 0 rps.
27.5
25.5
19.5
–6 –5 –4
18 19 20
19 20 21
20 21 22
temperature 5°C or lower
22 rps (model 50 : 25 rps)
Depends on operation mode
Depends on command speed
OFF
Dehumidifying
Heating
18
Outdoor air temperature (˚C)
Signals of wireless remote controller (Display)
–3 –2 –1 ±0
21 22 23 24
22 23 24 25
23 24 25 26
2.5°C or lower
0 rps
Protects the fan tap just before
frost prevention control
Depends on stop mode
63
- -
Cooling
30
+1 +2 +3 +4
25 26 27 28
26 27 28 29
27 28 29 30
compressor
command
speed
Lower
limit
speed
0 rps
2.5 5
Indoor heat exchanger
temperature (ºC)
Unit : ºC
+5 +6
29 30
30 31
31 32
8