York YHKMXH009BARR-FX Service Manual page 86

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3.11 Oil return operation control
3.11.1 Entering condition
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.
3.11.2 Procedure
Cooling mode: refer to "the oil return procedure in cooling mode"
Heating mode: refer to "the oil return procedure in heating mode"
3.11.3 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
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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
350pulse(E)
80(E)
STOP
OFF
-85-
oil return over
ref. eliminated 30s
auto frequency
Low frequency
auto angle
120pulse(E)
OFF angle 5(E)
AUTO
AUTO
STOP
OFF