
PROBLEM
PROBABLE CAUSE
SOLUTION
TROUBLE SHOOTING GUIDES
FANS
material moving through flow passage
Housing
a. Foreign material in housing
b. Cutoff or other part loose (rattling during operation)
Electrical
a. AC hum in motor or relay
b. Starting relay chatter
c. Noisy motor bearings
d. Single phasing a 3 phase motor
High Air Velocity
a. Duct work too small for application.
b. Fan selection too small for application.
c. Registers or grilles too small for
application.
d. Heating or cooling coil with insufficient
face area for application.
Pulsation or Surge
a. Restricted system causes fan to operate at poor
point of rating.
b. Fan too large for application
c. Ducts vibrate at same frequency as fan pulsations.
Rattles and/or Rumbles
a. Vibrating duct work
b. Vibrating cabinet parts
c. Vibrating parts not isolated from building.
CFM Low - Insufficient
Fan
a. Mecanical volume control device is improperly set.
Air Flow
b. Fan running backwards
c. Cutoff missing or improperly installed.
d. Dirty fan blades.
e. Loose or slipping belts
f. Fan speed too slow
Duct System
a. Actual system is more restrictive (more resistant to flow)
b. Dampers closed
c. Registers closed
d. Leaks in supply ducts
e. Insulating duct liner loose.
CFM Low - Insufficient
Filters
a. Dirty or clogged
Air Flow (continued)