Special Control - Midea MV5-X252W/V2GN1 Service Manual

V5 X VRF 50/60Hz

7 Special Control

7.1 Outdoor Unit Duty Cycling
In systems with multiple outdoor units, outdoor unit duty cycling is used to prevent compressor burn out due to
unbalanced oil levels between outdoor units.
Timing of outdoor unit duty cycling:
 After oil return operation.
 After defrosting operation.
 On restart following compressor stop after set temperatures achieved.
Figure 3-7.1 shows an example of duty cycling in a system with 4 outdoor units.
Figure 3-7.1: Duty cycling in a system with 4 outdoor units
Startup control
Normal operation
Master Slave 1 Slave 2 Slave 3
Outdoor unit Priority
duty cycling 1
Notes:
1. The address settings on the outdoor unit main PCBs for "master unit", "slave unit 1", "slave unit 2" and "slave unit 3" do not change.
7.2 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.
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 B
Four-way valve
Solenoid valve (liquid refrigerant injection)
Solenoid valve (oil balance)
Solenoid valve (fast defrosting)
Solenoid valve (EXV bypass)
Solenoid valve (indoor units bypass)
32
1
After oil return operation or
after defrosting operation or
on restart following compressor
stop after set temperatures
achieved
Priority Priority Priority
2 3 4
Wiring diagram label
COMP(INV)
COMP(INV1)
FANA
FAN2
EXVA
EXVB
ST1
SV2
SV4
SV5
SV6
SV7
Outdoor unit
duty cycling
8-12HP 14-22HP Control functions and states
● ●
Controlled according to load requirement
●
● ●
Controlled according to discharge pressure
●
● ●
Fully open
●
Off
● ●
Normal control
● ●
Normal control
● ●
Off
● ●
On
● ●
Normal control
● ●
Normal operation
Master Slave 1 Slave 2 Slave 3
Priority Priority Priority Priority
4 1 2 3
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