Special Control - Midea MV6-252WV2GN1 Service Manual

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 3 outdoor units.
Figure 3-7.1: Duty cycling in a system with 3 outdoor units
Startup control
Normal operation
Master Slave 1 Slave 2
Outdoor unit Priority
duty cycling
1
Notes:
1. The address settings on the outdoor unit main PCBs for "master unit", "slave unit 1", and "slave unit 2" 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. 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.
1
After oil return operation or
after defrosting operation or
on restart following compressor
stop after set temperatures
achieved
Priority Priority
2 3
V6 VRF 50/60Hz
Normal operation
Master Slave 1 Slave 2
Outdoor unit Priority Priority
duty cycling
3
Priority
1 2
45