Midea ATOM MDV-V56WDHN1(AtB)

AtomBSeriesVRF50/60Hz  
22  
MideaAtomBSeriesServiceManual
6.2 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unitrunningtime.Whentheoutdoorunitis
runningindefrosting,thedigitaldisplayonoutdoormainPCBwilldisplay“df”.
Table3‐6.5:Outdoorunitcomponentcontrolduringdefrostingoperation
Component
Wiringdiagram
label
28‐60model Controlfunctionsandstates
Invertercompressor  COMP ● Fixedfrequency
DCfanmotor  FAN
●
Fanspeedcontrolledaccordingtooutdoorambient
temperature(T4)beforerunningindefrosting
Electronicexpansionvalve  EEV1
●
Position480(steps)
Four-wayvalve ST1
●
Off

Table3‐6.6:Indoorunitcomponentcontrolduringdefrostingoperation
Component Unitstate Controlfunctionsandstates
Fan
Thermoon Operateonsettingfanspeed(Preventcoldwindpriority)
Standby Operateonsettingfanspeed(Preventcoldwindpriority)
Thermooff Off
Electronicexpansionvalve
Thermoon 480(steps)
Standby 480(steps)
Thermooff 480(steps)
Note：Preventcoldwind：It’sonlyvalidinheatingoperation,andthiscontrolisprioritytoothercontrols(includingheatingoilreturnanddefrost),
Whichdeterminetheconversionbetweensettingfanspeedwithlowfanspeedandturnoffthefanaccordingtotheevaporatorcoiltemperature
T2.