Midea MV6-R252WV2RN1 - 7.2 Defrosting Operation

V6R VRF 50Hz
43
Part 3
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Control
7.2 Defrosting Operation
In order to recover heating capacity, the defrosting operation is conducted when the outdoor unit heat exchanger is
performing as an evaporator. The defrosting operation is controlled according to outdoor ambient temperature, outdoor
heat exchanger temperature, indoor heat exchanger temperature and outdoor units running time. When the outdoor unit
is running in defrosting, the digital display on outdoor main PCB will display “df”.
Reverse Cycle Defrosting Operation
Timing of reverse cycle defrosting operation:
 Te<-2°C and T4<20°C, meeting either of the points below:
1) When there is an obviously drop in the temperature of outdoor unit heat exchanger outlet
2) When cumulative operating time after the latest defrosting control arrives an hour
 Compulsive defrosting or oil return set manually after PI control 1min. (Set n17 by “SW5” in main board or spot check
board)
Table 3-7.3: Outdoor unit and MS component control during defrosting operation
Component
Wiring
diagram
label
Defrosting operation control
Control before Defrosting
Defrosting control
Control after Defrosting
ODU
Inverter
compressor A
INV1
Reduce frequency step
One ODU unit system: 28Hz,
upper limit 88Hz
Two ODU units system: 56Hz,
upper limit 176Hz
Three ODU units system: 84Hz,
upper limit 264Hz
Current frequency
enters PI control
PI control
Inverter fan 1
FANA
PI control
Initial OFF
But 10 Step or higher if the high
pressure is larger than 2.2MPa.
Initial step then PI control
Inverter fan 2
FANB
Four way valve
ST1
ON
Initial step according to ambient
temperature and indoor load
Electronic
expansion valve
EEVA
Compressor operation, 2880pls
Compressor not operation, initial 135pls, then adjusted according to the module temperature
EEVC
0pls
Compressor operation, 17pls→ +8pls per 20S based on high pressure
or discharge temperature.
Compressor not operation, 0pls.
Solenoid valve
SV5
ON
SV8A
Compressor operation, ON
Compressor not operation, OFF
SV7
Turn ON/OFF based on the low pressure and the high pressure etc.
MS01
Electric ball
valve
EVBA
Normal Operation Control
2950pls
Normal Operation Control
EVBB
Normal Operation Control
0pls
Normal Operation Control
EVBC
Normal Operation Control
2950pls
Normal Operation Control
Electronic
expansion valve
EEVA
Normal Operation Control
0pls
Normal Operation Control
MS04-12
Solenoid valve
SV(n)A
Normal Operation Control
ON
Normal Operation Control
SV(n)B
Normal Operation Control
OFF
Normal Operation Control
SVP
Normal Operation Control
OFF
Normal Operation Control
Electronic
expansion valve
EEVA
Normal Operation Control
0pls
Normal Operation Control
Ending conditions
End if Pc-Pe<0.4MPa,
Maximum 120S
Defrost completion condition
judgment, maximum time is
9min
90S or
Pc-Pe<0.4MPa
for 20S
After 30S
Defrosting control time is no less than 135S and fulfill one of the conditions below:
 Pc-max ≥ 3.0MPa.
 Total defrosting control time has reached 9 minutes.
 T3_min >Target value for a certain time.