Lennox LDT Series Information page 24

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 into pulley grooves.
Make sure blower and motor pulley are aligned. See figure
13 for blowers not equipped with a tensioner and figure 14
for units equipped with an optional belt tensioner.
Blowers Without Belt Tensioner
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
counterclockwise, to tighten the belt. This increases
the distance between the blower motor and the blower
housing.
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.
PULLEY ALIGNMENT - NO TENSIONER
ALIGNED
MOTOR
BELT
PULLEY
NOT ALIGNED
FIGURE 13
PULLEY ALIGNMENT - WITH TENSIONER
ALIGNED
MOTOR
PULLEY
NOT ALIGNED
FIGURE 14
BLOWER
PULLEY
TENSIONER
BELT
BLOWER
PULLEY
E-Check Belt Tension
Overtensioning belts shortens belt and bearing life. Check
belt tension as follows:
1- Measure span length X. See figure 15.
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).
A force below
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
See BLOWER DATA tables for blower drives.
Page 24
these values indicates
FORCE
FIGURE 15
and