Special Control; Oil Return Operation; Timing Of Oil Return Operation - Midea V6-i Series Service Manual

7 Special Control

7.1 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 3-7.1 and 3-7.2 show component control during oil return operation in cooling mode.
Table 3-7.1: Outdoor unit component control during oil return operation in cooling mode
Component
Inverter compressor A
Inverter compressor B
DC fan motor A
DC fan motor B
Electronic expansion valve A
Electronic expansion valve C
Four-way valve
Solenoid valve (oil balance)
Solenoid valve (fast defrosting)
Solenoid valve (EXV bypass)
Solenoid valve (indoor units
bypass)
Solenoid valve (inverter
compressor A vapor injection)
Solenoid valve (inverter
compressor B vapor injection)
Solenoid valve (inverter
compressor B pressure balance)
Table 3-7.2: Indoor unit component control during oil return operation in cooling mode
Fan
Electronic expansion valve
Wiring
8-12HP 14-18HP
diagram label
COMP(A)
●
COMP(B)
FANA
●
FANB
EXVA
●
EXVC
●
ST1
●
SV4
●
SV5
●
SV6
●
SV7
SV8A
●
SV8B
SV9
Component Unit state
Thermo on
Standby
Thermo off
Thermo on
Standby
Thermo off
20-24HP 26-28HP
● ● ●
● ●
● ● ●
● ●
● ● ●
● ● ●
● ● ●
● ● ●
● ● ●
● ● ●
●
● ●
●
● ●
Control functions and states
Remote controller setting
Off
Off
Normal control
300 (steps)
300 (steps)
V6-i VRF 50/60Hz
30-32HP Control functions and states
●
Fixed frequency
●
Fan speed controlled according
●
to discharge pressure
●
Position 480 (steps) or 3000
●
(steps)
Position 96 (steps)
●
Off
●
Normal control
●
On
●
On
●
Normal control
●
Controlled according to inverter
●
compressor A
Controlled according to inverter
●
compressor B
Open before compressor
●
startup
B
45