Mitsubishi Electric LGH-50RSDC-E1 Handbook page 20

When the unit does not operate or operates irregularly
No. Symptom
1 The fans do not
operate.
2 • The fans do not
stop.
• The fan speed
does not
change.
3 Air volume chang-
es by itself.
4 The SA fan pe-
riodically stops
operating.
5 The SA fan pe-
riodically stops
operating, and the
EA fan air volume
decreases.
Cause
Power is not supplied to the unit.
Power supply voltage is out of rated
range.
• Improper connection or wiring of the
external signals.
• The type of external signals does not
match the connected terminal block.
The type of external signals is incorrect.
(Uncharged a-contact)
The external device signals are not input. Check the external devices.
The signal cables from the external de-
vices are longer than specifi ed.
The external signal wires and the power
supply cable are too close.
Malfunction of the circuit board, or the fan
motor
The trial operation switch SW 1-1 is ON.
The external device signals are input.
The external signal wires and the power
supply cable are too close.
The signal cables from the external de-
vices are longer than specifi ed.
The function setting switch SW 1-7
(Automatic air volume increasing during
bypass setting) is ON.
• When -15°C < OA temperature
the SA fan regularly stops for 10 minutes
to prevent the Lossnay core from freez-
ing.
• When OA temperature is -15°C or lower,
The SA fan stops to prevent the Lossnay
core from freezing.
When OA temperature is -15°C or lower,
the SA fan stops operating to prevent the
Lossnay core from freezing.
Then, the EA fan runs at speed 5 if the
switch SW 1-3 is ON.
Check the power supply.
(220 to 240 V AC 50 Hz)
Check the power supply.
(220 to 240 V AC 50 Hz)
Check the connections of the external
signal wires and the terminal blocks (TM2,
TM3).
TM2 1-4 and TM3 5 are for fan speed selection.
TM3 PB is for bypass condition selection.
TM3 V is for ventilation priority mode.
Check the type of external signals.
Check the wiring length of the signal
cables. (Make sure the wiring length from
the external devices is within 20 m.)
Keep the wires for fan speed and bypass
condition selections more than 10 cm
away from the power supply cable.
See the "Checklist of LED failure dis-
plays" (page 17).
Check the trial operation switch SW 1-1.
Check the external devices.
Keep the wires for fan speed and bypass
condition selections more than 10 cm
away from the power supply cable.
Check the wiring length of the signal
cables. (Make sure the wiring length from
the external devices is within 20 m.)
If energy recovery ventilation mode is au-
tomatically switched to bypass ventilation
with the switch SW 1-7 is ON, fan speed
will increase 1 step higher than its pres-
ent speed (with a summer criteria).
If the operation mode is switched to en-
ergy recovery ventilation, fan speed will
return to its original speed.
Refer to 7. (1)
(This is not a failure.)
Refer to 7. (1)
-10°C,
(This is not a failure.)
Refer to 7. (1)
(This is not a failure.)
─ 20 ─
Corrective action
(page 10).
(page 11).
(page 11).