Carrier NP034-074 Installation, Start-up And Service Instructions Manual

Contents

Carrier NP034-074 Installation, Start-up And Service Instructions Manual Manual pdf 46 page image

AdjustmentsEVAPORATOR FAN AND POWER EXHAUST MOTORPLATE — Adjust using a 15⁄ 16-in. wrench on the adjustingbolts:1. Loosen holddown bolts. (See Fig. 44.)2. Turn the adjusting bolts to move the motor mounting platetoward or away from the fan to loosen or tighten the belts.Make the same number of turns to each bolt.3. Retighten holddown bolts.MODULATING POWER EXHAUST DIFFERENTIALPRESSURE SWITCH — On 034,044 units, the differentialpressure switch is located in the auxiliary control box. Theauxiliary control box is mounted in the corner next to thepower exhaust motor door. To gain access to the auxiliarycontrol box, remove the auxiliary control box cover. Whenreplacing the auxiliary control box cover, be sure to securethe cover properly in order to prevent water from being drawninto the auxiliary control box.On 054-074 units, the differential pressure switch is mountedbelow the auxiliary control box next to the access door la-beled FILTER SECTION.INLET GUIDE VANE DIFFERENTIAL PRESSURESWITCH (Units With Optional Inlet Guide Vanes and StaticPressure Control) — On 034,044 units, the inlet guide vanedifferential pressure switch is located in the auxiliary controlbox. The auxiliary control box is mounted in the corner ofthe unit under the side air hood that is next to the accessdoor marked FILTER SECTION. To gain access to the aux-iliary box, remove the auxiliary control box cover. When re-placing the auxiliary control box cover, be sure to secure thecover properly in order to prevent water from being drawninto the auxiliary control box.On 054-074 units, the inlet guide vane differential pressureswitch is mounted on an upright located behind the evaporator-fan motor. See Fig. 43.BELT INSTALLATION AND TENSIONINGIMPORTANT: When installing or replacing belts, al-ways use a complete set of new, matched belts to pre-vent potential vibration problems. Mixing belts oftenresults in premature breakage of the new belts.1. Turn off unit power.2. Adjust motor plate so belts can be installed without stretch-ing over the grooves of the pulley. (Forcing the belts canresult in uneven belt stretching and a mismatched set ofbelts.)3. Before tensioning the belts, equalize belt slack so that itis on the same side of the belt for all belts. Failure to doso may result in uneven belt stretching.4. Tighten belts using the motor plate adjusting bolts.5. Adjust until proper belt tension (1/2-in. deflection withone finger) is obtained. Be sure to adjust both adjustingbolts the same number of turns.NOTE: Check the tension at least twice during the firstday of operation, as there is normally a rapid decrease intension until the belts have run in. Check tensionperiodically thereafter and keep it at the recommendedtension.With the correct belt tension, belts may slip and squealmomentarily on start-up. This slippage is normal and dis-appears after wheel reaches operating speed. Excessive belttension shortens belt life and may cause bearing and shaftdamage.PULLEY ALIGNMENT — For proper belt life, the motorand fan pulleys must be properly aligned. To check, first turnoff unit power. Place a straightedge against the motor andfan pulleys. See Fig. 45. If the pulleys are properly aligned,the straightedge should be parallel to the belts.If they are not parallel, check that the motor shaft and fanshaft are parallel. If they are not, adjust the motor plate ad-justing bolts until they are.After verifying that the shafts are parallel, loosen the set-screws on the motor pulley. Move pulley on the shaft untilthe pulleys are parallel. To move the sheave on the shaft,loosen the belts. If necessary, blower sheave can also be movedon the shaft.INSTALLING ALTERNATE MOTOR PULLEY (Evapora-tor Fan Only) — On all units, the alternate motor pulley isfield-supplied. To install the alternate pulley:1. Turn off unit power.2. Loosen belts using motor adjusting bolts until belts canbe removed without stretching them over the grooves ofthe pulley.3. Remove belts.4. Loosen setscrews on motor pulley.5. Slide pulley off motor shaft. Make sure setscrews on newpulley are loose.6. Slide new pulley onto fan shaft and align it with the fanpulley as described in Pulley Alignment section above.7. Tighten setscrews.8. Install belts and tension properly as described in PulleyAlignment section above.CONDENSER FAN ADJUSTMENT1. Turn off unit power.2. Remove fan guard and loosen fan hub setscrew.3. See Fig. 32 and adjust fan height using a straight edgelaid across the fan deck.4. Tighten setscrew and replace rubber hubcap to preventhub from rusting to the motor shaft. Fill hub recess withPermagum if hub has no rubber hubcap.5. Replace fan guard.Fig. 44 — Motor Plate Adjustment46