CLIMATIC™50 – IOM – Rooftops/ Aircoolair CL50-ROOFTOPS-IOM-1107-E
22
DEFROST – Heat Pump
Function
Avoid the evaporator icing (external coil) in heat pump operation in winter time.
Description
To avoid the icing of the external air exchanger in winter operation, it is necessary to reverse the refrigerant cycle on a
regular basis to de-ice by heating the exchanger.
The defrost is activated when the air temperature is under a set point (3422)
When defrost is demanded, the sequence is as following:
1. Pre-heating of supplementary heating elements during 1 minute (Option)
2. Stop compressors and fans
3. Reverse 4 way valve
4. Start compressors.
5. When the fans are started several times (3625) or if compressors are in operation for more than 6 minutes, stop
the compressors.
6. Reverse 4 way valve
7. End of defrost
Two different type of Defrost demand are possible.
• Dynamic defrost (set point 3621 = Dynamic)
• Cycling defrost (set point 3621 = Cyclic)
Cycling defrost
The unit will start a cyclic defrost under a regular period of time (instruction 3624)
Dynamic defrost
This allows the unit to start the defrost cycle only when required. This is achieved through the measurement of the
temperature difference between the coil and the outdoor. The defrost will be initiated shortly after the Climatic50 has
located the largest gradient in the curve.
3621 ! Defrost mode.
3622 ! Outside air temperature under which the defrost cycle is activated.
3623 ! LP temperature under which the defrost cycle is activated for the cyclic mode and defrost cycle activation
sensibility for the dynamic mode (standard ratio between dry coil ∆T and iced coil ∆T) .
3624 ! Minimum compressors operating time between 2 defrosts
3625 ! Number of fans Restart operations according to the pressure.
Temperature difference
between coil and outdoor
Coil
clean
Coil freezing
Coil
frozen
Defrost cycle start
Highest gradient
Time
To Next Page
Loading...