Fedders R407C Service Manual page 63

When the indoor coil temperature reaches 10ºC or higher for 2 minutes de-icing will be
terminated and normal cool mode operation resumes. However, if the coil temperature is still
below 10ºC after 10 minutes, de-icing operation will still be terminated to resume normal
cool mode operation.
40 minutes after the completion of one de-icing cycle, another detection of the indoor coil
temperature is made. If the indoor coil temperature detected is less than 2ºC, then another de-
icing cycle is executed. Similarly, if it is found that the indoor coil does not require de-icing
after sensing its temperature, another indoor coil temperature detection is carried out 40
minutes later to see if de-icing is required by then. The de-icing temperature checking
repeats in this fashion as long as the system resides in cool mode operation.
10 C
Indoor coil
Temperature
2 C
Compressor
& O/Fan
I/Fan
5. Outdoor Coil Protection Against Icing in Heat Mode (applicable on Heat Pump Unit
only)
After switching on the compressor in heat mode, the electronic air-con controller will monitor
the outdoor coil temperature, after 30 minutes later the unit will perform outdoor coil de-icing
if necessary. While the outdoor coil is being de-iced, the green LED on the LED board will
blink at approximately 95 times per minute.
Outdoor coil temperature checking algorithm for protection against icing progresses as
follows:
The controller will monitor and read the outdoor coil temperature as soon as the compressor
is turned on in heat mode for 30 mins. If the temperature is found to be lower than -4 C, for2
mins and meet the defrost starting condition. It will perform De-ice according to the
algorithm, if not, the controller will continue monitoring the outdoor coil temperature.
2 min.
ON
Indoor Coil De-icing in cool mode
2 min.
10 min.
OFF
Change according to the indoor coil temp.
OFF
ON OFF
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