PROBLEM
PROBABLE CAUSE
SOLUTION
TROUBLE SHOOTING GUIDES
FANS
useful indicators in defining system characteristics
Field static pressure measurements rarely correspond
with laboratory static pressure measurements unless
the fan inlet and fan outlet conditions of the installation
are exactly the same as the inlet and outlet conditions
in the laboratory
Static Pressure Low,
System
System has less resistance to flow than expected
CFM High
This is a common occurrence. Fan speed may be
reduced to obtain desired flow rate. This will reduce
HP (operating cost).
Fan
a. Backward inclined impeller installed backwards. HP
will be high
b. Fan speed too high
Static Pressure Low,
System
a. Fan inlet and/or outlet conditions not same as tested.
CFM Low
Static Pressure High
System
a. Obstruction in system
CFM Low
b. Dirty filters
c. Dirty coils
d. System too restricted
HP High
Fan
a. Backward inclined impeller installed backwards
b. Fan speed too high
c. Too low system resistance for forward curved fan
System
a. Oversized duct work
b. Face and by-pass dampers oriented so coil dampers
are open at same time by-pass dampers are open
c. Filter(s) - left out
d. Access door open
Fan Selection
a. Fan not operating at efficient point of rating. Fan size
or type may not be best for application
Fan Does Not Operate
Electrical or Mechanical
a. Blown fuses
b. Broken belts
c. Loose pulleys
d. Electricity turned off