28
Air Handling Unit
Installation, Operation, and Maintenance Manual
April 2021
Symptom
Source
Condition
Solution
CFM too low
Filters
Clogged, filter selection
• Verify filter is correct for application.
• Replace clogged filters.
Coil
Dirt clogged
Clean coil
Fan
Fan running backward
• Reverse fan rotation.
• Swap two leads of a three phase motor.
Fan speed too low
Adjust pulley pitch diameter.
Cut-off missing or not properly
installed
Inspect cut-off installation and install per vendor instructions.
Fan inlet obstruction
• Re-sheave fan/motor to increase fan speed.
• Correct obstructions.
Impeller not centered on inlet
collar
Adjust as required.
Duct System
Closed dampers
Open dampers and inspect operators.
Closed registers
Open registers, check adequacy of lining material. Correct as required.
Leaks in supply
Repair as needed.
System more flow restricted than
expected
Re-sheave fan/motor to increase fan speed.
Unit
Leaks in fan airseal
Inspect for leaks around fan outlet through cabinet bulkhead and repair as
required.
Continued from previous page.