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Fig. 53 — Sealing Power Wires in Flexible Conduit
Motor Power Wiring
The fan section is provided with a decal indicating the recom-
mended location to drill or punch hole(s) to accommodate an elec-
trical conduit for the fan-motor wiring. The decal is located on the
motor side, approximately 4 in. in from the side and 4 in. down
from the top of the corner above where the motor will be installed.
Where possible, the conduit should be installed in a panel which
will not be removed, such as the discharge panel.
SINGLE POINT POWER WIRING
The SPP box is provided with labels indicating acceptable wiring
penetration locations. All motors are wired in the factory and are
provided with overload protection.
EC MOTOR FAN POWER BOX WIRING
The ECMFP box is provided with labels indicating acceptable
wiring penetration locations. All motors are wired in the factory
and are provided with overload protection.
MOTOR OVERLOAD PROTECTION
Fan-motor starters and overload protectors are field-supplied and
installed. A label on the fan motor indicates the correct size of the
overload protectors required to be installed in the motor starter.
Sheaves
Factory-supplied drives are pre-aligned and tensioned. However,
Carrier recommends checking the belt tension and alignment be-
fore starting the unit. Always check the drive alignment after ad-
justing belt tension.
To install sheaves on the fan or motor shaft, remove any rust-pre-
ventive coating on the shaft. Make sure the shaft is clean and free
of burrs. Add grease or lubricant to bore of sheave before install-
ing. Mount sheave on the shaft; to prevent bearing damage, do not
use excessive force (i.e., a hammer). Place sheaves for minimum
overhang (see Fig. 54).
Each factory-assembled fan, shaft, and drive sheave assembly is
precision aligned and balanced. If excessive unit vibration occurs
after field replacement of sheaves, the unit should be rebalanced.
To change the drive ratio, reselect and replace the motor sheave,
not the fan sheave.
After 24 hours of unit operation, the drive belts may stretch.
Check the belt tension after 24 hours of operation and adjust if
necessary. Periodically check belt tension throughout the run-in
period, which is normally the initial 72 hours of operation.
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Fig. 54 — Determining Sheave-Shaft Overhang
ALIGNMENT
Make sure that fan shafts and motor shafts are parallel and level.
The most common causes of misalignment are nonparallel shafts
and improperly located sheaves. Where shafts are not parallel,
belts on one side are drawn tighter and pull more than their share
of the load. As a result, these belts wear out faster, requiring the
entire set to be replaced before it has given maximum service. If
misalignment is in the sheave, belts enter and leave the grooves at
an angle, causing excessive belt and sheave wear.
1.
Shaft alignment can be checked by measuring the distance
between the shafts at 3 or more locations. If the distances are
equal, then the shafts are parallel.
2.
Sheave Alignment:
Fixed sheaves — To check the location of the fixed sheaves
on the shafts, a straightedge or a piece of string can be used. If
the sheaves are properly aligned, the string will touch them at
the points indicated by the arrows in Fig. 55.
Adjustable sheaves — To check the location of adjustable
sheave on shaft, make sure that the centerlines of both
sheaves are in line and parallel with the bearing support chan-
nel. See Fig. 55. Adjustable pitch drives are installed on the
motor shaft. Carrier recommends that adjustable sheaves
should only be used for initial balancing and should be
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