Special Control - Midea V8 Series Service Manual

V8/V8i PRO VRF 50Hz

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 Operation, the digital display on outdoor main PCB will display "d0".
7.1.1 Cooling Mode Oil Return Control
Timing of oil return operation:
▪
Calculated oil discharge has reached to specified level. The higher the compressor frequency step is, the more oil
discharge.
▪
Initial cumulative compressor operating time reaches 2 hours.
▪
Cumulative compressor operating time reaches 8 hours.
Tables 3-7.1 and Tables 3-7.2 show component control during oil return operation in cooling mode.
Table 3-7.1: Outdoor unit control during oil return operation in cooling mode
Wiring diagram
Component
Inverter
INV1
compressor A
Inverter
INV2
compressor B[1]
ODU
Inverter fan 1 FANA
Inverter fan 2[1] FANB
Four way valve ST1
EEVA
Electronic
expansion valve
EEVC
SV5
SV6[2]
Solenoid valve
SV8A/SV8B[1]
SV7
Ending conditions
Notes:
1. The Inverter compressor B.
2. The SV6 is only available for 26-32HP.
54
STEP1
label
PI control
PI control
OFF
PI control
OFF , then 17 pls 17 pls
ON
ON
compressor ON:ON
otherwise: OFF
Turn ON/OFF based on the low pressure and the high pressure etc.
End if startup
time arrives
180S.
Inverter fan 2 and SV8B are only available for 18-32HP.
Cooling oil return control
STEP2 STEP3
PI control, the
minimum step is as
follows:
8HP 27Hz
10HP 39Hz
12-14HP 52Hz
16-24HP 69Hz
PI control, initial ODU
26HP 99Hz
number is decided
28-34HP 108Hz
36-54HP 133Hz
56-66HP 158Hz
68-82HP 226Hz
84-96HP 262Hz
96HP and above
394Hz
2880pls PI control
17 pls
End if startup time
arrives 6 min or
the compressor
After 20S.
discharge volume
≥ Target value for
4min.
STEP5
PI control
PI control
After 2 min.