Mitsubishi Electric LGH-50RSDC-E1 Handbook page 21

No. Symptom
6 After opera-
tion has been
stopped, the fan
continues to run
for a while.
7 The damper does
not operate.
When the bypass
condition selec-
tion signal (TM3
PB, V) is being
used,
8 Operation moni-
tor or malfunction
monitor is not cor-
rectly output.
9 LED 1 on the cir-
cuit board is not lit
in spite of power
supplying.
Cause
The function setting switch SW 1-2
(Operation monitor output with delay
function) is ON.
When OA temperature is 8°C or lower, ener-
gy recovery ventilation mode is turned on.
Trial operation switch SW 1-1 is ON.
Malfunction of the circuit board, or the
damper motor
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.
The function setting switch SW 1-4
(Ventilation priority mode during ventila-
tion setting input on) is ON.
• The connected terminal block is incorrect.
• Connection error
• The function setting switch SW 1-2 or
SW 1-5 is not set to ON.
Connection error of the power supply lead
wires
Connection error of the transformer
Transformer malfunction
Disconnection of the fuse
Malfunction of the small circuit board
When the switch SW 1-2 is ON, the fan
continues to operate for 3 minutes after
Lossnay operation has been stopped.
Refer to 7. (4) (page 13).
(This is not a failure.)
Check the OA temperature.
Turn off the trial operation switch SW 1-1.
See the "Checklist of LED failure dis-
plays" (page 17).
Check the connections of the external
signal wires and the terminal blocks
(TM2, TM3). (TM3 PB or V is for bypass
condition selection)
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.
When the switch SW 1-4 and TM3 V input
is ON, operation mode is fi xed in energy
recovery ventilation.
Refer to 7. (2)
• Check the connections of the terminal
blocks (TM4).
• Check the switch SW 1-2 (Operation
monitor output with delay function) or
SW 1-5 (Operation monitor output).
Check the wiring of the connector (CN1)
and the power supply terminal block
(TM1) on the circuit board.
Check the connection of the connectors
(CN2 and CN14) on the circuit board.
Check the transformer output. If it has a
defect, replace the transformer.
Replace the circuit board.
Replace the circuit board if none of above
related actions works.
─ 21 ─
Corrective action
(page 11).