Lennox ZHA Series, Unit Information

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Page 23
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
FIGURE 9
Blower Belt Adjustment
Maximum life and wear can be obtained from belts only if
proper pulley alignment and belt tension are main­
tained. Tension new belts after a 24-48 hour period of op­
eration. This will allow belt to stretch and seat grooves.
Make sure blower and motor pulley are aligned as shown in
figure 10.
FIGURE 10
PULLEY ALIGNMENT
BELT
BLOWER
PULLEY
MOTOR
PULLEY
NOT ALIGNED
ALIGNED
1- Loosen four bolts securing motor base to mounting
frame. See figure 8.
2- To increase belt tension -
Turn adjusting bolt 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 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 bolts on side of base.
Check Belt Tension
Overtensioning belts shortens belt and bearing life. Check
belt tension as follows:
1- Measure span length X. See figure 11.
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 these values indicates an underten­
sioned belt. A force above these values indicates an
overtensioned belt.
MEASURE BELT TENSION
FIGURE 11
DEFLECTION 1/64” PER INCH OF SPAN
OR 1.5mm PER 100mm OF SPAN
FORCE
Field-Furnished Blower Drives
For field-furnished blower drives, use the blower tables in
this manual to determine BHP and RPM required. Referen­
ce table 3 for drive component manufacturer's numbers.