Midea ATOM B Series Service Manual page 23

Atom B Series VRF 50/60Hz
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
Inverter compressor
DC fan motor
Electronic expansion valve
Four-way valve
Table 3‐6.6: Indoor unit component control during defrosting operation
Component
Electronic expansion valve
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.
22
Wiring diagram
label
COMP
FAN
EEV1
ST1
Unit state
Thermo on
Fan Standby
Thermo off
Thermo on
Standby
Thermo off
28‐60 model Control functions and states
Fixed frequency
●
Fan speed controlled according to outdoor ambient
●
temperature (T4) before
Position 480 (steps)
●
● Off
Control functions and states
Operate on setting fan speed (Prevent cold wind priority)
Operate on setting fan speed (Prevent cold wind priority)
Off
480 (steps)
480 (steps)
480 (steps)
running in defrosting