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
Defrosting operation control
Control before Defrosting
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
Initial OFF
But 10 Step or higher if the high
pressure is larger than 2.2MPa.
Initial step then PI control
Initial step according to ambient
temperature and indoor load
Electronic
expansion valve
Compressor operation, 2880pls
Compressor not operation, initial 135pls, then adjusted according to the module temperature
Compressor operation, 17pls→ +8pls per 20S based on high pressure
or discharge temperature.
Compressor not operation, 0pls.
Compressor operation, ON
Compressor not operation, OFF
Turn ON/OFF based on the low pressure and the high pressure etc.
Electronic
expansion valve
Electronic
expansion valve
End if Pc-Pe<0.4MPa,
Maximum 120S
Defrost completion condition
judgment, maximum time is
9min
90S or
Pc-Pe<0.4MPa
for 20S
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.
To Next Page
Loading...
Need help?
General
