Haier SYJS-0308 Service Manual page 72

2. Compressor control
The compressor will start at 10Hz and running between 30Hz to 120Hz. In operation the compressor
running frequency is determined by three elements : the number of indoor units in operation , the
temperature difference of each indoor units between setting temperature and room temperature ,
the size of each indoor unit.
3. Outdoor fan motor speed control
(Ta : ambient temperature , T p : outdoor unit pipe temperature)
ITEM MODE
1 cooling
2 cooling
3 cooling
4 cooling
5 heating
6 heating
7 heating
4 Electronic expansion valve control
Each indoor unit has a electronic expansion valve to control refrigerant volume. For split type indoor
unit, the valve is designed in a electronic expansion valve box. Indoor unit PCB communicates with
the electronic valve box PCB. For other type , the valve is in the indoor unit itself. The electronic
expansion valve is controlled as follows:
Tin : stands for the liquid refrigerant temperature ; T o : stands for the gas refrigerant temperature
Tov : overheat temperature
Overheat temperature is preset in indoor unit PCB. In cooling mode operation ,indoor unit
PCB can detect the current overheat temperature by calculating To-Tin.If the To-Tin
temperature is higher than Tov, the valve volume will become larger until To-Tin= Tov. In heating
operating ,outdoor PCB will control outdoor electronic valve accordingly.
5 All indoor units must operate in the same mode. If the compressor is in heating mode, the indoor unit
is not allowed to be set in cooling mode, the outdoor unit will not accept different running mode from
indoor unit.
T a
T p
＞32 ℃
45℃
＜31 ℃ ＞
＜31 ℃ 40 ℃＜T
T
＜31 ℃ ＜39 ℃
p
＞15 ℃
10 ℃＜T ＜14 ℃
a
＜9℃
FAN SPEED
H
H
＜44 ℃
M
p
L
L
M
H
refrigerant flowing direction