Mitsubishi Electric PKH18FK1 Technical & Service Manual page 39

(5) Detecting abnormalities in the outdoor unit
When the outdoor unit is determined to be abnormal by the following causes, the compressor will stop and the check code
" P8 " will appear on the remote controller display.
( i ) During compressor ON while hot adjustment is set.
1 If the difference between the indoor coil temperature and room temperature is in the RANGE B, the indoor fan will
stop.
2 Within 20 minutes after entering RANGE B (except for the first 10 seconds),
a) If the temperature difference enters RANGE A, the hot adjustment starts,
b) If the temperature difference is still in RANGE B, the outdoor unit is deemed abnormal.
c) If the temperature difference enters RANGE C, defrosting starts.
3 Within 20 minutes after entering RANGE C, if the temperature difference does not return to RANGE B,the outdoor unit
is deemed abnormal.
4 If the temperature difference returns to RANGE B, the next 20 minutes is an allowance period. If the difference enter
RANGE A during the allowance, defrosting ends and the hot adjustment starts. If the difference does not enter
RANGE A during the allowance, the outdoor unit is deemed abnormal.
( ii ) During compressor ON in defrosting
After 30 minutes of defrosting in hot adjustment, if the temperature difference is still in RANGE C, the outdoor unit is
determined to be abnormal.
When RANGE B does not change to RANGE A after 20 minutes have passed since RANGE C had outdoor unit is
determined to be abnormal.
( iii ) During compressor OFF
Not detecting abnormalities.
(6) Indoor coil temperature abnormality detection
An abnormality can be detected during compressor ON, except for the following.
For the first 30 minutes after the temperature difference between the indoor coil temperature and room temperature enters
the RANGE C.
When the temperature difference enters the RANGE C until it moves to the RANGE B.
(7) Defrosting operation
After the outdoor unit starts the defrosting operation, when the temperature difference between the indoor coil temperature
and room temperature gets out of RANGE A and into RANGE B, the indoor unit starts the defrosting mode. After the out-
door unit stops the defrosting operation, when the temperature difference returns to the RANGE A, the indoor unit stops
the defrosting mode. While the indoor unit is in the defrosting mode, the indoor fan and the booster heater stop.
RANGE A : Indoor coil temperature is more than 9 degrees above room temperature.
RANGE B : Indoor coil temperature is within 9 degrees either way of room temperature.
RANGE C : Indoor coil temperature is more than 9 degrees below room temperature
Indoor coil temperature
minus room temperature
(degree)
RANGE A
+9
0 RANGE B
-9
RANGE C
OC193-37