Mitsubishi Electric PKH18FK Technical & Service Manual page 48

3-5 Defrosting in HEAT mode
<Defrosting time chart>
Indoor unit
ON
Indoor fan
OFF
ON
Auto vane
OFF
Outdoor unit
ON
4-way valve
OFF
ON
Bypass valve
OFF
ON
Outdoor fan
OFF
ON
Compressor
OFF
(1) Start conditions
A. When all of the following conditions are satisfied, defrosting will start. However, when the bypass valve turns OFF,
defrosting starts 10 minutes later.
(a) More than seven minutes have passed since the compressor start-up.
(b) The outdoor coil thermistor reads 23˚F or below.
(c) The outdoor fan motor output step is 100%
(d) Total time of compressor operation exceeds 30 minutes, and the outdoor coil temperature has fallen by 14 degrees
or more in comparison with that of 10 minutes after the compressor start-up.
NOTE: The outdoor coil temperature 10 minutes after the compressor start-up is memorized until the defrosting
operation has ended.
B. When all of the following conditions are satisfied, defrosting will start.
(a) ~ (c) The same as above (a) ~ (c) in item A
(d) Total time of compressor operation exceeds "defrost interval".
Further information on the defrost interval is described in (3).
C. After the total time of compressor operation exceeds the defrost interval, the thermostat repeats ON/OFF three times.
Two minutes after the fourth "ON" of the thermostat, if the outdoor coil thermistor reads 23˚F or below and the fan out-
put output is 100%, defrosting will start.
NOTE: The count of the thermostat ON/OFF is cleared by the compressor-OFF command or defrosting start-up.
(2) During defrosting
Even if the thermostat turns OFF, defrosting continues.
The 4-way valve, bypass valve, outdoor fan, and indoor fan are OFF.
48
Defrosting
starts.
35degrees(SW5-3 OFF)or 20degrees(SW5-3:ON)discharge direction
Set direction
(Remote controller still displays set direction.)
Defrosting
stops.
Set direction