Mitsubishi Electric Mr.Slim MSH24WN Service Manual page 21

4. Defrosting
Defrosting of outdoor heat exchanger is controlled by deicer P.C. board, with detection by the defrost thermistor RT61.
(1) Starting conditions of defrost
When all conditions of a) ~ c) 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 27°F or less.
c) After releasing the high pressure protection 4 minutes and 10 seconds have elapsed.
(2) Releasing conditions of defrost
When the condition d) or e) is satisfied, the defrosting operation stops.
d) The defrost thermistor RT61 reads 56°F or more.
e) The defrosting time exceeds 10 minutes.
(3) Defrosting time chart
Defrost thermistor RT61
56°F or more
27°F or less
Outdoor 52C
ON
contactor
(Compressor)
OFF
ON
X62
(R.V. coil)
OFF
ON
SR61
Outdoor fan
OFF
ON
Defrost
counter
OFF
ON
Very Low
Indoor fan
OFF
Horizontal
Indoor vane
Set position
NOTE1 • When the indoor coil thermistor RT12 reads above 64°F, indoor fan operates at Very Low for 30 seconds.
• When the indoor coil thermistor RT12 reads 64°F or less, the indoor fan stops.
15 sec.
30 sec.
Max 10 min.
NOTE1
30 sec.
21
5 sec.