Kruger ADA Series General Instructions Manual page 4

Fan is vibrating excessively
Impeller
 Impeller unbalanced due to deposits (dirt or grease)

Impeller unbalanced due to wear
Drive 
Unbalanced pulleys

Belts may vibrate excessively
Required air volume not achieved
Impeller 
Impeller not centered with inlet collar(s)

Impeller/inlet dirty or clogged

Improper running clearance

Improper inlet cone to wheel fit

Impeller installed or running wrong direction

Incorrect speed of impeller because of:
i)
ii) Belt drive ratio not correct
iii) Too high slip of V-belt
iv) Wrong calibration of inverter
Duct System 
Shutters or dampers of the system are closed

Object obstructs fan or duct

Inlet guide vanes are partly close

Dampers closed

Registers closed

Leaks in supply duct

Obstructions near fan outlet or inlet

Sharp elbows near fan outlet or inlet

Improper designed turning vanes

Insulating duct liner loose

Pressure resistance offered by the system higher than
the design value

Fluid density higher than the design value

Improper set inlet vane or damper

Actual system is more restrictive (more resistance to
flow) than expected

Obstructed fan outlet inlets
Elbows, cabinet walls or other obstructions restrict air
flow. Inlet obstructions cause more restrictive
systems but do not cause increased negative
pressure readings near the fan inlet(s)
Fan speed may be increased to counteract the effect
of restricted fan inlet(s). Caution! Do not increase
speed beyond the fan manufacturers
recommendations

No straight duct at fan outlet
(Fans which are normally used in duct system are
tested with a length of straight duct at fan outlet. If
there is no straight duct at the fan outlet, decreased
performance may result.
If it is not practical to install a straight section of duct
at the fan outlet, the fan speed may be increased to
overcome this pressure loss. Caution! Do not increase
fan speed beyond the fan manufacturers
recommendations.)

Projections, dampers or other obstruction in a part of
the system where air velocity is high
 Obstructions in high velocity air stream
Possible cause
Possible cause
Wrong motor speed
Remedy
 Clean impeller, rebalance the system

Replace impeller

Balance the pulley or the system

Proper sheave alignment and adjust to correct belt
tension
Remedy

Adjust the impeller to the center of inlet collar(s)

Clean the impeller or inlet

Change to correct clearance

Adjust to correct fit

Change to correct rotation by changing poles of
electrical feed line to motor
i) Change motor or belt drive
ii) Change belt drive
iii) Increase tension of belts
iv) Adjust inverter calibration

Open damper or IVC

Clear obstructed ducts

Open grill/diffuser damper

Open Damper

Open Register

Seal the Leakage

Clear obstruction

Redesign and change elbow

Redesign and change vanes