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Air Handling Unit
Installation, Operation, and Maintenance Manual
April 2021
13.0 Troubleshooting Guide
Symptom
Source
Condition
Solution
Vibration
Drive Assembly
Fan and motor pulleys not
aligned
Align pulleys per Section 12.4 of this manual.
Fan and motor shafts not parallel Align motor shaft with fan shaft by adjusting the motor position and/or
installing shims.
Belt slippage
• Replace worn or stretched belts or pulleys.
• Clean dirty belts with soap and water.
• Do not use a belt dressing of any kind. If belts are usable, check tension and
adjust as required.
• Inspect the belts to determine if belt wear is uniform and if the belt lengths
are equal. If not, replace the belts.
• Check the motor and fan to determine if all hold down bolts are secure.
• Check the belt model number to ensure proper size.
System not balanced
• Check alignment of shaft, motor and pulleys.
• Adjustable pitch pulleys with motors over 15 hp motors are especially prone
to unbalance. Check wheel balance, rebalance if necessary.
Belts loose
Adjust belt tightness. Replacement belts should be matched set.
Pulley wobble
• Check the integrity and tightness of the bushing. Tighten or replace as
needed.
• On pulleys without bushings, make sure set screws are properly tightened.
Worn pulley
Replace pulleys.
Bearings
Lack of lubrication
• Lubricate as required.
• Increase the lubrication frequency and inspect the seals for excessive
leaking.
• Make sure the lubricant is appropriate for application.
• Inspect the lubricant for contaminant-induced friction causing excessive
lubricant evaporation. Purge system per this manual and replace with fresh
lubricant. (Cleaning bearings may be necessary).
• Make sure bearings are securely on shaft.
Bearing wear
Frequently inspect the bearings for degree of wear and replace bearings as
required.
Imbalance
Improper belt tension
• Check belt condition.
• Replace worn or cracked belts.
• Adjust the belt tension per this manual to achieve proper deflection.
Dirt on impeller
• Clean dirt from impeller and shaft.
• Inspect impeller for pit corrosion.
• Make sure shaft is properly aligned.
Noise
Vibration
See previously identified
conditions
Refer to Vibration symptoms above.
Inlet Ring
Impeller hitting inlet ring
• Center impeller on inlet ring.
• Repair or replace damaged impeller.
Housing
Debris in housing
• Remove debris.
• Tighten loose parts.
Motor
Hum
• Check motor bearings and correct as required.
• Verify lead-in cable is secure.
• Verify correct motor phasing.
Air Velocity
Duct leaks, damaged fins, coil
leaks
Repair or replace as required.
Registers or grills too small for
application
Enlarge registers/grills as required.
Compressed air leak
Repair or replace pneumatic lines, fittings, actuators, controls or gauges as
needed.
Coil has insufficient face area for
application
Restrict application or select a new coil as required.
Duct too small for application
Correct as required.
Obstruction
Dampers
Verify proper damper adjustment and operation.
Duct expansion
Eliminate sudden expansion/contraction of duct.
Pulsation/surge
Restricted system
Eliminate restrictions.
Fan pulsations and ducts
vibrating at same frequency
• Verify fan speed.
• Reorient duct work to change operating frequency.
Continued on next page.
