Step 11 - Check Fan Sheave And Belt Alignment - Carrier Omnizone 50XCW06 Installation Start-Up And Operatig Instructions

UNIT
MODEL
SIZE
50XCW900-200A00 06 51.3
50XCW900-201A00 08 51.3
50XCW900-202A00 12 66.0
50XCW900-203A00 14 66.0
50XCW900-204A00 16 86.0
50XCW900-205A00 24 86.0
NOTE: Dimensions are in inches.
Fig. 24 — 50XCW Plenum Unit
Step 11 — Check Fan Sheave and Belt Align-
ment
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. 25).
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.
A B C D E
14 26.8 30 10
14 26.8 45 10
14 28.9 60 10
19 28.9 48 15
19 28.9 60 15
19 28.9 80 15
WGT
(lb)
65
65
80
80
115
115
Fig. 25 — 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.
25