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Installation, Operation & Maintenance Manual

IM-995

Troubleshooting Guidelines

Use current safety practices when investigating fan or system
performance problems. General safe practices and performance
troubleshooting guidelines can be found in AMCA Publications
410 and 202, respectively. Fan application and field measurement
procedures can be found in AMCA Publications 201 and 203.

Below is a list of possible areas to check when air or sound values
do not match expectations. Most fan problems can be pinpointed
to one of these common causes.

Air Capacity Problems

1. Resistance of the system is not at design rating. If resistance

is lower than expected, both airflow and horsepower may be
up. If resistance is higher than anticipated, air volume will be
down.

2. Fan speed is not at design speed.
3. Air density is not at the design value. Also check air performance

measurement techniques/procedures.

4. Devices for air modulation are closed or plugged. Also check

filters.

5. Wheel mounted improperly or is rotating in reverse.
6. Parts of the system or fan have been damaged or need

cleaning.

Noise Problems

1. Air performance is incorrect and the fan is not at design point

of operation. Fan is being forced to operate in an unstable
flow region near peak or to the left of the peak of the curve.

2. Bearing failure. Check bearings (lubrication).
3. Supply voltage high or inconsistent supply frequency.

Adjustable frequency controllers can generate motor noise.

4. Objects which are installed in a high velocity airstream can

generate noise. This includes flow sensors, turning vanes, etc.

5. Poor fan inlet conditions.
6. Acoustics or sound measurement procedure incorrect.

Vibration Problems

1.   Misalignment of drive components. Check belt or coupling.
2.   Poor foundation or mounting structure (resonances).
3.   Foreign material attached to rotating components.
4.   Damaged  rotating  components  (bearings,  shaft,  fan,  wheel,

sheaves).

5.  Broken, loose or missing setscrews.
6.   Loose bolts.
7.   Vibration transmitted by another source.
8.   Water accumulating in airfoil blades.
9.   Fan is operating in stall or unstable flow region.

Motor Problems

1.   Incorrect wiring.
2.   Speed of fan too high.
3.   Parts improperly installed; binding.
4.   Bearings improperly lubricated.
5.   WR

capability of motor too low for application.

6.   Protection devices may be improperly sized.
7.  VFD compatible electrically? Effective shaft grounding?
8.   Is cabling and grounding correct?

Drive Problems

1.  Belts improperly tensioned.
2.  Drive alignment is poor. Check belt or coupling.
3.  Coupling lubrication.

Vibration Guidelines

Condition

Fan

Application

Category

Rigidly Mounted

mm/s (in./s)

Flexibly Mounted

mm/s (in./s)

Start-up

BV-3

6.4 (0.25)

8.8 (0.35)

Alarm

BV-3

10.2 (0.40)

16.5 (0.65)

Shutdown

BV-3

12.7 (0.50)

17.8 (0.70)

Values shown are peak velocity, mm/s (inches/s), filter out.

Most fans manufactured by Twin City Fan & Blower are factory
balanced  prior  to  shipment.  Certain  high  horsepower,  large  or
unusual  voltage  fans,  may  not  be  run  as  an  assembly  due  to
power  constraints,  however  the  rotors  have  been  dynamically
balanced. Installation variables, handling and movement of the
fan  during  shipment  may  cause  the  rotating  assembly  to  shift.
Balance should be checked once the fan is installed. If a final trim
balance is required, it is the end user's responsibility to bring the
fan back to factory specifications. Final trim balancing is not the
responsibility of Twin City Fan & Blower. Refer to the Vibration
Guidelines table below.

NOTICE

Twin City Fan