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Technical Information
Service Manual
6. Function and Control
1.Function Control
1) Cooling mode
a. Turning on the unit for cooling operation, and if any one of the indoor units satisfy the cooling operation condition, the system will start
for cooling operation; and the electronic expansion valve, the outdoor fan and the compressor start operation.
b. When some of the indoor units satisfy the stop-condition while some indoor units does not satisfy the stop-condition, the compressor
does not stop, the compressor adjust the frequency according to demand. For the indoor unit with stop-condition satisfies, the
corresponding electronic expansion valve will be closed.
c. Change Cooling mode to heating mode
When change the unit to heating mode from cooling mode, the whole system will stop first. Then the system will restart in heating mode
after the compressor stops.
d. 4-way valve
In this mode, the 4-way valve is closed.
e. Outdoor fan control in cooling mode
The outdoor fan starts before 5s of the starting of compressor. The outdoor fan will run in high speed after starting and then it will run in
set speed.
2) Dry mode (dehumidification mode)
This mode is the same as cooling mode;
3) Heating mode
a. Turning on the unit for heating operation, If any one of the indoor unit satisfy the heating condition, the system will start to run in heating
mode
b. If all the indoor units satisfy the stop-condition, the compressor stops and the outdoor fan stops after 1min;
c. If only part of the indoor units satisfy the stop-condition, the compressor decrease the frequency immediately and operates according to
demand.
d. Change Heating mode to cooling mode or dehumidification mode, the whole system will stop first, then restart under the required mode.
e. Defrosting function
When the defrosting condition is satisfied, the 4-way valve reverses the direction, the outdoor fan stop. After the 4-way valve reverses the
direction, the frequency of compressor rises, and the unit will start defrosting under cooling cycle.
f. Oil-return control in heating mode
a)If the whole system runs in low frequency for a long time, the system will run a oil-return operation in high frequency, the oil-return
operation will runs for 60 second.
4) Fan mode
Only indoor fan run. Compressor, outdoor fan and 4-way valve are closed .
2.Protection Function
1) Mode conflict protection of indoor units
When the setting mode is different of different indoor unit, the unit runs in below status:
a. The system mode is determined by the first turning on indoor unit except indoor unit is in fan mode. Cooling mode (dry mode) is in
conflict with heating mode.
b. If the first turning on unit is fan mode, and the second turning on unit is cooling or heating mode, then the system will run in cooling or
heating mode.
2) Overload protection
If the tube temperature at the high pressure side is higher than normal, the compressor frequency is restricted or decreased to normal
operation frequency.
