Lennox ZGB Series Unit Information page 30

1 - The following measurements must be made with air
filters in place and no cooling demand.
2 - With all access panels in place, measure static
pressure external to unit (from supply to return).
Blower performance data is based on static pressure
readings taken in locations shown in figure 6.
Note - Static pressure readings can vary if not taken
where shown.
3 - Referring to the blower tables starting on Page 6,
use static pressure and RPM readings to determine
unit CFM. Use air resistance table when installing
units with any of the options or accessories listed
INSTALLATIONS WITH DUCTWORK
ROOFTOP UNIT
SUPPLY
TURN
MAIN
DUCT RUN
TO INCREASE BELT TENSION
1-Loosen four bolts securing motor base to mounting frame.
2-Slide the motor downward to tighten the belt.
3-Tighten four bolts on motor base.
SIDE VIEW
MOTOR
TO INCREASE CFM
LOOSEN ALLEN SCREW &
TURN PULLEY CLOCKWISE
LOCATION OF STATIC PRESSURE READINGS
RETURN AIR
READING LOCATION
FIRST BRANCH
OFF OF MAIN RUN
SUPPLY AIR
READING
LOCATION
BLOWER ASSEMBLY
LOOSEN FOUR BOLTS
AND SLIDE BLOWER
MOTOR DOWNWARD
TO TIGHTEN BELT
ALLEN
SCREW
PULLEY
TO DECREASE CFM
TURN PULLEY
COUNTERCLOCKWISE
4 - The blower RPM can be adjusted at the motor pulley.
Loosen Allen screw and turn adjustable pulley
clockwise to increase CFM. Turn counterclockwise
to decrease CFM. See figure 7. Do not exceed
minimum and maximum number of pulley turns as
shown in table 5.
5 - ZGB074S4T Unit Only -
If low speed during ventilation is desired, replace J351
connector with J350.
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt
A Section
INSTALLATIONS WITH CEILING DIFFUSERS
ROOFTOP UNIT
SUPPLY AIR
READING
LOCATION
FIGURE 6
FIGURE 7
Page 30
TABLE 5
Min. Turns Open Max Turns Open
No Minimum
RETURN AIR
READING
LOCATION
SUPPLY
TURN
DIFFUSER
5