Page 12
FIGURE 14
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
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 bolts to the left, or
counterclockwise to loosen belt tension.
IMPORTANT - Align top edges of blower motor base and
mounting frame base parallel before tightening two bolts
on the other side of base. Motor shaft and blower shaft
must be parallel.
3- Tighten two bolts on each side of the motor mounting
base. This secures the mounting base to the frame.
FIGURE 15
PULLEY ALIGNMENT
BELT
BLOWER
PULLEY
MOTOR
PULLEY
NOT ALIGNED
ALIGNED
F-Check Belt Tension
Overtensioning belts shortens belt and bearing life.
Check belt tension as follows:
1- Measure span length X. See figure 16.
MEASURE BELT TENSION
FIGURE 16
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 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.
G-Field-Furnished Blower Drives
For field-furnished blower drives, use pages 13 through
17 to determine BHP and RPM required. Reference table
3 for drive component manufacturer's numbers.
