Page 42
BLOWER ASSEMBLY
TO INCREASE BELT TENSION
1−Loosen four screws securing blower motor to
sliding base.
2−Turn adjusting screw to the left, or counter-
clockwise, to move the motor downward and
tighten the belt.
3−Tighten four screws.
TO INCREASE CFM
LOOSEN ALLEN SCREW &
TURN PULLEY CLOCKWISE
TO DECREASE CFM
TURN PULLEY
COUNTERCLOCKWISE
FIGURE 12
LOOSEN SCREWS
TO ADJUST BELT
TENSION
BLOWER
MOTOR
REMOVE SCREWS TO SLIDE
BLOWER ASSEMBLY OUT OF UNIT
LOOSEN SCREWS TO
ADJUST BELT TENSION
PULLEY
ALLEN
SCREW
BELT TENSION
ADJUSTING SCREWS
BLOWER
ASSEMBLY
SLIDING BASE
PULLEY
MOTOR
ALLEN
SCREW
SIDE VIEW
D−Blower Belt Adjustment
Maximum life and wear can be obtained from belts only if
proper pulley alignment and belt tension are maintained.
Tension new belts after a 24−48 hour period of operation.
This will allow belt to stretch and seat grooves. Make sure
blower and motor pulley are aligned as shown in figure 13.
FIGURE 13
PULLEY ALIGNMENT
BELT
BLOWER
PULLEY
MOTOR
PULLEY
NOT ALIGNED
ALIGNED
1− Loosen four screws securing blower motor to sliding
base. See figure 12.
2− To increase belt tension −
Turn belt tension adjusting screw to the left, or counter-
clockwise, to tighten the belt. This increases the dis-
tance between the blower motor and the blower hous-
ing.
To loosen belt tension −
Turn the adjusting screw to the right, or clockwise to
loosen belt tension.
3− Tighten four screws securing blower motor to sliding
base once adjustments have been made.
E−Check Belt Tension
Overtensioning belts shortens belt and bearing life. Check
belt tension as follows:
1− Measure span length X. See figure 14.
MEASURE BELT TENSION
FIGURE 14
DEFLECTION 1/64" PER INCH OF SPAN
OR 1.5mm PER 100mm OF SPAN
FORCE
2− Apply perpendicular force to center of span (X) with
enough pressure to deflect belt 1/64" for every inch of
span length or 1.5mm per 100mm of span length.
Example: Deflection distance of a 40" span would be
40/64" or 5/8".
Example: Deflection distance of a 400mm span would
be 6mm.
3− Measure belt deflection force. For a used belt, the
deflection force should be 5 lbs. (35kPa). A new belt
deflection force should be 7 lbs. (48kPa).
F−Furnished Blower Drives
For field furnished blower drives, see BLOWER DATA
(table of contents) for CFM and PRM. The BLOWER DATA
section also has tables for CAV and VAV drive numbers and
manufacturer’s model numbers.
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