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8
FAILURES AND REPAIRS
Failure
Possible cause
Solution
Fan does not
run (anymore)
No mains voltage
Failure of a phase
Under- over over voltage
Check line voltage
Ground fault
Check motor connection and line voltage
Short circuit winding
Replace fan
Motor thermal protection has
tripped (motor overheated)
−
Check free airways, if necessary.
remove foreign bodies
−
Check supply air temperature
−
Check voltage
Impeller is blocked or dirty
−
Disconnect the motor from the power
supply and secure it against being
switched on again
−
Check the voltage is disconnected
−
Remove the protective grille
−
Remove foreign bodies or dirt
−
Refit the protective grille
−
Further procedure as in chapter
"Commissioning"
Fan won’t start
Temperature too low for bearing
grease
Use bearing with cold grease
Airflow in wrong direction (motor
reverses at high speed)
Check airflow
(see airflow reverse rotation behavior)
See ‘Fan does not run’
Fan runs to
slow
Impeller / wing rubs
remove foreign objects / dirt in the fan
Active temperature management is
activated
(motor or electronics overheated)
Check whether the airways are free, if
necessary. remove foreign objects
See 'Impeller is blocked or dirty'
Check the temperature of the supply air
Check the installation space (air velocity over
the cooling elements)
Air flow to low
Fan runs too slowly
See ‘Fan runs to slow’
Airways blocked
Check whether airways are free (air supply /
exhaust valves, filters)
See 'Impeller is blocked or contaminated'
Pressure loss different than
projected
Check fan selection
Vibrations
unbalance
Check wings / shovels for damage,
contamination or icing
See "Impeller is blocked or contaminated"
No or wrong vibration dampers
(only with radial)
Fit correct vibration dampers
Unusual sound
Bearing damaged / worn
Replace bearing
For motor size 055 (“z” / “b” with cross flow) and
072 (o) replace fans
Impeller / wing rubs
Remove foreign objects / dirt in the fan
See 'Impeller is blocked or dirty'
Operation over the tear-off point
(for axial fans)
Check that airways are clear (air supply/exhaust
valves, filters)
Incorrect cover on nozzle (with
radial fans)
Observe assembly instructions
