Page 17
FIGURE 22
LOCATION OF STATIC PRESSURE READINGS
SUPPLY AIR
READING
LOCATION
SUPPLY
RE
TURN
INSTALLATIONS WITH DUCTWORK
SUPPLY
RE
TURN
INSTALLATIONS WITH CEILING DIFFUSERS
MAIN
DUCT RUN
FIRST BRANCH
OFF OF MAIN RUN
DIFFUSER
ROOFTOP UNIT
ROOFTOP UNIT
SUPPLY AIR
READING
LOCATION
RETURN AIR
READING LOCATION
RETURN AIR
READING
LOCATION
D-Blower Belt Adjustment - No Tensioner
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 in the pulley grooves. Make sure blower and motor
pulleys are aligned as shown in figure 23.
FIGURE 23
PULLEY ALIGNMENT
BELT
BLOWER PULLEY
MOTOR PULLEY
NOT ALIGNED
ALIGNED
1- Loosen four bolts securing motor base to mounting
2-
To increase belt tension -
Turn both adjusting bolts to the right, or clockwise, to
move the motor outward and tighten the belt. This
increases the distance between the blower motor and
the blower housing.
To loosen belt tension -
Turn the adjusting bolt to the left, or counterclockwise
to loosen belt tension.
IMPORTANT - Align edges of blower motor base and
mounting frame base parallel before tightening four bolts
on the side of base. Motor shaft and blower shaft must be
parallel.
3- Tighten bolts on side of base.
E-Check Belt Tension
Overtensioning belts shortens belt and bearing life.
Check belt tension as follows:
1- Measure span length X. See figure 24.
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 new 2 and 3hp
belt, the deflection force should be 5.0-7.0 lbs.
(35-48kPa). For a new 5hp belt, the deflection force
should be 7-10lbs. (48-69kPa).
A force below these values indicates an
undertensioned belt. A force above these values
indicates an overtensioned belt.
MEASURE BELT TENSION
FIGURE 24
DEFLECTION 1/64” PER INCH OF SPAN
OR 1.5mm PER 100mm OF SPAN
FORCE
F-Field-Furnished Blower Drives
For field-furnished blower drives, use pages 18 through
20 to determine the drive kit number and table 5 or 6 for
drive component manufacturer's numbers.
