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6.2 Oil Return Operation
In order to prevent compressors from running out of oil, the oil return operation is conducted to recover oil that has
flowed out of the compressor(s) and into the piping system. This operation is performed for all units including units that
are in standby. When the outdoor unit is running in oil return, the digital display on outdoor main PCB will display “d0”.
Timing of oil return operation:
When the initial cumulative operating time reaches 140 minutes and then every 8 hours.
Tables 3-6.1 and 3-6.2 show component control during oil return operation in cooling mode.
Table 3-6.1: Outdoor unit component control during oil return operation in cooling mode
Control functions and states
● ● ● ●
Fixed frequency
● ●
● ● ● ●
Controlled according to
discharge pressure
DC fan motor B FAN2 ● ●
Electronic expansion valve A
● ● ● ●
Solenoid valve (Liquid injection)
● ● ● ●
Solenoid valve (oil balance)
● ● ● ●
Solenoid valve (refrigerant bypass)
● ● ● ●
Table 3-6.2: Indoor unit component control during oil return operation in cooling mode
Component Unit state Control functions and states
Fan
Thermo on Remote controller setting
Standby Off
Thermo off Off
Electronic expansion valve
Thermo on Normal control
Standby 300 (steps)
Thermo off 300 (steps)
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