Mitsubishi Electric PCA Series Service Manual page 22

Abnormal point and detection method
Check code
Freezing/overheating protection is oper-
ating
1 Freezing protection (Cooling mode)
The unit is in 6-minute resume preven-
tion mode if pipe <liquid or condenser/
evaporator> temperature stays under
−15°C for 3 minutes, 3 minutes after the
compressor started. Abnormal if it stays
under −15°C for 3 minutes again within
16 minutes after 6-minute resume pre-
vention mode.
2 Overheating protection (Heating mode)
P6
The units is in 6-minute resume
prevention mode if pipe <condenser/
evaporator> temperature is detected as
over 70°C after the compressor started.
Abnormal if the temperature of over
70°C is detected again within 30 minutes
after 6-minute resume prevention mode.
Pipe temperature
<Cool mode>
Detected as abnormal when the pipe tem-
perature is not in the cooling range 3 min-
utes after compressor start and 6 minutes
after the liquid or condenser/evaporator
pipe is out of cooling range.
Note 1: It takes at least 9 minutes to
detect.
Note 2: Abnormality P8 is not detected in
dry mode.
Cooling range: −3 °C ] (TH−TH1)
TH: Lower temperature between liquid pipe
temperature (TH2) and condenser/
evaporator temperature (TH5)
TH1: Intake temperature
P8
<Heat mode>
When 10 seconds have passed after the
compressor starts operation and the hot
adjustment mode has finished, the unit is
detected as abnormal when condenser/
evaporator pipe temperature is not in heat-
ing range within 20 minutes.
Note 3: It takes at least 27 minutes to
detect abnormality.
Note 4: It excludes the period of defrosting.
(Detection restarts when defrosting
mode is over.)
Heating range: 3 °C [ (TH5−TH1)
OCH725
Cause
(Cool or dry mode)
1 Clogged filter (reduced airflow)
2 Short cycle of air path
3 Low-load (low temperature)
operation out of the tolerance
range
4 Defective indoor fan motor
• Fan motor is defective.
• Indoor controller board is defec-
tive.
5 Defective outdoor fan control
6 Overcharge of refrigerant
7 Defective refrigerant circuit
(clogs)
(Heating mode)
1 Clogged filter (reduced airflow)
2 Short cycle of air path
3 Overload (high temperature)
operation out of the tolerance
range
4 Defective indoor fan motor
• Fan motor is defective.
• Indoor controller board is defec-
tive.
5 Defective outdoor fan control
6 Overcharge of refrigerant
7 Defective refrigerant circuit
(clogs)
8 Bypass circuit of outdoor unit
is defective.
1 Slight temperature difference
between indoor room
temperature and pipe <liquid
or condenser / evaporator>
temperature thermistor
• Shortage of refrigerant
• Disconnected holder of pipe
<liquid or condenser /
evaporator> thermistor
• Defective refrigerant circuit
2 Reversed connection of
extension pipe (on plural units
connection)
3 Reversed wiring of indoor/
outdoor unit connecting wire
(on plural units connection)
4 Defective detection of indoor
room temperature and pipe
<condenser / evaporator>
temperature thermistor
5 Stop valve is not opened
completely.
22
Countermeasure
(Cool or dry mode)
1 Check clogs of the filter.
2 Remove blockage.
4 Refer to "9-6. HOW TO CHECK THE
PARTS".
5 Check outdoor fan motor.
67 Check operating condition of refrigerant
circuit.
(Heating mode)
1 Check clogs of the filter.
2 Remove blockage.
4 Refer to "9-6. HOW TO CHECK THE
PARTS".
5 Check outdoor fan motor.
6–8Check operating condition of refrigerant
circuit.
1–4Check pipe <liquid or condenser/evapora-
tor> temperature with room temperature
display on remote controller and outdoor
controller circuit board.
Pipe <liquid or condenser/evaporator>
temperature display is indicated by set-
ting SW2 of outdoor controller circuit
board as follows.
(
Conduct temperature check with outdoor
controller circuit board after connecting
'A-Control Service Tool(PAC-SK52ST)'.
23Check reversed connection of extension
pipe or reversed wiring of indoor/outdoor
unit connecting wire.
)