Mitsubishi Electric PRH-P8MYA Technical & Service Manual page 68

<Abnormality detected during unit operation: Indoor-side unit>
Abnormal- Meaning of abnormality display and
ity display abnormality troubleshooting
Drain overflow protection opera-
tion
1) When the drain sensor thermistor
overheats and the temperature
rise is small, the compressor en-
ters the check mode and is turned
off and the indoor-side fan is
turned off.
P5
2) If the state above is detected again
in the check mode, drain pump
abnormality is recognized.
3) Always detected during drain
pump operation.
Freezing/excessive rise protection
operation
1) Freezing protection
When the piping temperature re-
mains at –15 °C or lower for 3 min-
utes after 3 minutes have elapsed
since the compressor started, the
compressor enters the 6 minutes
restart prohibit mode and if the
piping temperature again remains
at –15 °C for 3 minutes within 16
minutes after 6 minutes restarting,
P6
an abnormality is recognized.
2) Excessive rise protection
When a piping temperature rise
to 70 °C or higher is detected af-
ter the compressor starts, the
compressor enters the 6 minutes
restart prohibit mode. If a piping
temperature rise up to 70 °C or
higher is detected again within 10
minutes after 6 minutes restarting,
an abnormality is recognized.
Cause
(1) Drain pump trouble.
(2) Drain faulty.
Drain pump clogged.
Drain pipe clogged.
(3) Water droplets on drain sensor.
Drain water waves created by trans-
mission of drain water from lead wire,
clogged filter, etc.
(4) Indoor-side controller board faulty.
<Cool and dry>
(1) Filter is clogged (insufficient air flow).
(2) Air duct short cycle.
(3) Low load operation (low temperature)
exceeding allowable range.
(4) Indoor-side fan motor faulty.
(5) Outdoor-side fan control faulty
(intermediate period, winter).
(6) Refrigerant overcharged.
(7) Refrigerant circuit faulty (clogged).
<Heat>
(1) Filter clogged (insufficient air flow)
(2) Air duct short cycle.
(3) Overload operation (high tempera-
ture) exceeding allowable range.
(4) Indoor-side fan motor faulty.
(5) Outdoor-side fan control faulty
(intermediate period)
(6) Refrigerant overcharged.
(7) Refrigerant circuit faulty (clogged)
(8) Unit bypass circuit faulty.
- 65 -
Judgment method and remedy
(1) Check drain up mechanism.
(2) Check drain characteristic.
(3) Check drain sensor lead wire arrange-
ment and check for filter clogging.
(4) If abnormality reproduced by shorting
between drain sensor connector CN31
pins 1 and 2 and operating air condi-
tioner, replace indoor-side controller
board.
If there are no problems above, there
are no abnormalities.
Turn on the power and operate.
<Cool and dry>
(1) Check filter for clogging.
(2) Remove obstruction.
(4) Check indoor-side fan motor
operation and winding resistance.
(5) Check outdoor-side fan motor
operation.
(6)(7)
Check refrigerant circuit operation.
<Heat>
(1) Check filter for clogging.
(2) Remove obstruction.
(4) Check indoor-side fan motor
operation and winding resistance.
(5) Check outdoor-side fan motor
operation.
(6)-(8)
Check refrigerant circuit operation.