Haier 1U71S2SG1FA Service Manual page 224

Multi:
D: Entering condition
When the compressor running frequency is lower than 58Hz (E) continuously for 4 hrs, the system will enter oil
return operation. In the course of mode changeover, manual unit stop or protective unit stop, the time will be
accumulative. After the compressor restarts up, the time will be counted continuously. In a continuous 4 hrs, if the
compressor running frequency is not less than 72Hz for over 10 minutes continuously, the accumulative time will be
cleared. Also after the heating defrosting, the time will be cleared.
E: Procedure
Cooling mode: refer to "the oil return procedure in cooling mode"
Heating mode: refer to "the oil return procedure in heating mode"
F: The protection treatment in oil return operation
In the course of oil return, because of protection or abnormal unit stop, after the unit restarts up, the time will not be
cleared, the system will need another oil return operation. In the refrigerant flow course in the oil return of cooling
mode or after the oil return, and within 5 minutes after the refrigerant being eliminated is over, the anti-freezed
protection is invalid, and also the low voltage protection is invalid. But the other protection is valid.
In the course of oil return from heating mode to cooling mode, if abnormal condition occurs or the unit stops for
protection, then the system needs not another oil return within 3 minutes after the unit stops and it will start up
directly, then to heating mode.
In the course of oil return from heating mode to cooling mode, the anti-freezed protection is null and void, and the
low voltage protection is null either. The other protection is valid.
Oil return procedure in cooling mode:
Send oil return signal
Inverter compressor
running indoor PMV
stopped indoor PMV
Outdoor motor
running indoor motor AUTO
stopped indoor motor STOP
4-way valve
oil return begins
60s
Oil return frequency
auto frequency
auto angle
OFF angle 5(E)
AUTO
AUTO (TC or ambient temp. control)
AUTO (set fan speed)
OFF
oil return over
ref. eliminated
Low frequency
350pulse(E)
120pulse(E)
80(E)
OFF angle 5(E)
STOP
OFF
221
30s
auto frequency
auto angle
AUTO
AUTO
STOP
OFF