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(5) Defrosting
Defrosting of outdoor heat exchanger is controlled by deicer P.C. board, with detection by the defrost thermistor RT61.
1
Defrost starting conditions
When all conditions of a),b) are satisfied, the defrosting operation starts.
a) Under the heat operation, the compressor cumulative operation time exceeds 40 minutes without the defrosting opera-
tion working.
b) The defrost thermistor RT61 reads - 3°C or less.
2
Defrost terminating conditions
When the condition d) or e) is satisfied, the defrosting operation stops.
d) The defrost thermistor RT61 reads 3.1°C or more.
e) The defrosting time exceeds 10 minutes.
NOTE
w
When the indoor coil thermistor reads above 18°C, indoor fan operates at VLo for 30 seconds.
w
When the indoor coil thermistor reads 18°C or less, the indoor fan stops.
<Defrosting time chart>
Defrost thermistor
3.1
:
or more
-3
:
or less
Outdoor 52C relay
(Compressor)
X62
(Reversing valve)
SR61
Outdoor fan
Defrost
counter
Indoor fan
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Max 10 min.
30 sec.
15 sec.
30 sec.
15 sec.
VLo
w
RT61
OC281-B-3.qxp 04.2.10 2:23 PM Page 76