Carrier 39LH Installation, Start-up And Service Instructions Manual

174. With sheaves aligned, tighten cap screws evenly andprogressively.NOTE: There should be a 1/8-in. to 1/4-in. gap betweenthe mating part hub and the bushing flange. If gap isclosed, the bushing is probably the wrong size.5. With taper-lock bushed hubs, be sure the bushing boltsare tightened evenly to prevent side-to-side pulley wob-ble. Check by rotating sheaves and rechecking sheavealignment. When substituting field-supplied sheaves forfactory-supplied sheaves, consider that the fan shaftsheave has been factory balanced with fan and shaft as anassembly. For this reason, substitution of motor sheave ispreferable for final speed adjustment.Install V-Belts — When installing or replacing belts, al-ways use a complete set of new belts. Mixing old and new beltswill result in the premature wear or breakage of the newerbelts.Refer to label on inside of fan access door for informationon factory-supplied drive.1. Always adjust the motor position so that V-belts can beinstalled without stretching over grooves. Forcing beltscan result in uneven stretching and a mismatched set ofbelts.2. Do not allow belt to bottom out in sheave.3. Tighten belts by turning motor-adjusting jackscrews.Turn each jackscrew an equal number of turns.4. Equalize belt slack so that it is on the same side of belt forall belts. Failure to do so may result in uneven beltstretching.5. Tension new drives at the maximum deflection forcerecommended (Table 5).On current production, the correct tension information islisted on the fan drive label. For older equipment or unitswith field-modified drives, use the deflection formula inthe following example and the tension data from Table 5.EXAMPLE:GivenBelt Span 16 in.Belt Cross-Section A, Super BeltSmall Sheave PD 5 in.Solutiona. From Table 5 find that deflection force for a newtype A, super belt with 5-in. small sheave PD is8 lb.b.Fig. 21 — Determining Sheave-Shaft OverhangFig. 22 — Sheave AlignmentDeflection = (Belt Span)64Deflection = 1664