Lennox LCH036 Installation Instructions Manual page 67

INSTALLATIONS WITH DUCTWORK
ROOFTOP UNIT
SUPPLY
MAIN
DUCT RUN
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 22.
PULLEY ALIGNMENT
BELT
MOTOR PULLEY
NOT ALIGNED
FIGURE 22
1- Loosen four bolts securing motor base to mounting
frame. See figure 18.
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.
LOCATION OF STATIC PRESSURE READINGS
RETURN AIR
READING LOCATION
RE­
TURN
FIRST BRANCH
OFF OF MAIN RUN
SUPPLY AIR
READING
LOCATION
ALIGNED
BLOWER PULLEY
INSTALLATIONS WITH CEILING DIFFUSERS
SUPPLY AIR
READING
LOCATION
FIGURE 21
E-Check Belt Tension
Overtensioning belts shortens belt and bearing life.
Check belt tension as follows:
1- Measure span length X. See figure 23.
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
undertensioned belt. A force above these values
indicates an overtensioned belt.
MEASURE BELT TENSION
DEFLECTION 1/64" PER INCH OF SPAN
OR 1.5mm PER 100mm OF SPAN
F-Field-Furnished Blower Drives
For field-furnished blower drives, use pages 16 through
18 to determine the drive kit number and table 4 or 5 for
drive component manufacturer's numbers.
Page 17
ROOFTOP UNIT
RE­
SUPPLY
TURN
DIFFUSER
below these values
FORCE
FIGURE 23
RETURN AIR
READING
LOCATION
indicates an