When the compressor running frequency is lower than 58Hz (E) continuously for 8 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 8 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.
Cooling mode: refer to “the oil return procedure in cooling mode”
Heating mode: refer to “the oil return procedure in heating mode”
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
oil return begins
oil return over
60s
ref. eliminated
30s
Oil return frequency
auto frequency
Low frequency
Inverter compressor
auto frequency
350pulse(E)
running indoor PMV
auto angle
auto angle
120pulse(E)
80(E)
stopped indoor PMV
OFF angle 5(E)
OFF angle 5(E)
Outdoor motor AUTO
AUTO (TC or ambient temp. control)
AUTO
running indoor motor AUTO
AUTO (set fan speed)
AUTO
stopped indoor motor STOP
STOP
STOP
4-way valve
OFF
OFF
OFF
-85-
3.11 Oil return operation control
3.11.1 Entering condition
3.11.2 Procedure
3.11.3 The protection treatment in oil return operation
___________________________________________________________________________________
___________________________________________________________________________________
