4
Fig. 3 — Filter Installation
MANUAL OUTSIDE AIR HOOD SCREEN
This inlet screen is secured by a retainer angle across the top edge
of the hood. (See Fig. 4.)
To remove the screen, loosen the screws in the top retainer and slip
the retainer up until the filter can be removed. Re-install by plac-
ing the frame in its track, rotating the retainer back down and
tighten all screws.
Fig. 4 — Screens Installed on Outdoor-Air Hood
SUPPLY FAN (BLOWER) SECTION
Supply Fan (Belt-Drive)
The supply fan system consists of a forward-curved centrifugal
blower wheel on a solid shaft with two concentric type bearings,
one on each side of the blower housing. A fixed-pitch driven pul-
ley is attached to the fan shaft and an adjustable-pitch driver pulley
is on the motor. The pulleys are connected using a “V” type belt.
(See Fig. 5.)
Fig. 5 — Belt Drive Motor Mounting
BELT
Check the belt condition and tension quarterly. Inspect the belt for
signs of cracking, fraying or glazing along the inside surfaces.
Check belt tension by using a spring-force tool (such as Brown-
ing’s Part Number “Belt Tension Checker” or equivalent tool);
tension should be 6 lb at a
5
/
8
-in. deflection when measured at the
centerline of the belt span. This point is at the center of the belt
when measuring the distance between the motor shaft and the
blower shaft.
NOTE: Without the spring-tension tool, place a straight edge
across the belt surface at the pulleys, then deflect the belt at mid-
span using one finger to a
1
/
2
-in. deflection.
Adjust belt tension by loosening the motor mounting plate front
bolts and rear bolt and sliding the plate toward the fan (to reduce
tension) or away from fan (to increase tension). Ensure the blower
shaft and the motor shaft are parallel to each other (pulleys
aligned). Tighten all bolts when finished.
To replace the belt:
1. Use a belt with same section type or similar size. Do not sub-
stitute a “FHP” type belt. When installing the new belt, do not
use a tool (screwdriver or pry-bar) to force the belt over the
pulley flanges, this will stress the belt and cause a reduction
in belt life.
2. Loosen the motor mounting plate front bolts and rear bolts.
3. Push the motor and its mounting plate towards the blower
housing as close as possible to reduce the center distance
between fan shaft and motor shaft.
4. Remove the belt by gently lifting the old belt over one of the
pulleys.
5. Install the new belt by gently sliding the belt over both pul-
leys and then sliding the motor and plate away from the fan
housing until proper tension is achieved.
6. Check the alignment of the pulleys, adjust if necessary.
7. Tighten all bolts.
8. Check the tension after a few hours of runtime and re-adjust
as required.
ADJUSTABLE-PITCH PULLEY ON MOTOR
The motor pulley is an adjustable-pitch type that allows a servicer
to implement changes in the fan wheel speed to match as-installed
ductwork systems. The pulley consists of a fixed flange side that
faces the motor (secured to the motor shaft) and a movable flange
side that can be rotated around the fixed flange side that increases
or reduces the pitch diameter of this driver pulley. (See Fig. 6.)
As the pitch diameter is changed by adjusting the position of the
movable flange, the centerline on this pulley shifts laterally (along
the motor shaft). This creates a requirement for a realignment of
the pulleys after any adjustment of the movable flange. Also reset
the belt tension after each realignment.
CAUTION
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could cause personal injury or
death.
Before performing service or maintenance operations on the
fan system, shut off all unit power and lockout/tag-out the unit
disconnect switch. DO NOT reach into the fan section with
power still applied to unit.
DIVIDER
BAROMETRIC
RELIEF
CLEANABLE
ALUMINUM
FILTER
FILTER
HOOD
FILTER
CLIP
OUTSIDE
AIR
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