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

366. Check fan speed with a strobe-type tachometer or use thefollowing formula: Obtain the motor rpm from the fanmotor nameplate and read sheave pitch diameters markedon the fan and motor pulleys, or estimate the pitch diame-ters by using the pulley outside diameters.Then:Example:Actual ApproximateNameplate MotorRpm = 1760 1760Mtr Sheave PitchDiameter = 8.9 in. 9.0 (OD)Fan Sheave PitchDiameter = 12.4 in. 12.5 (OD)Fan Rpm = 1760 x 8.9 1760 x 9= 12.4 12.5= 1263 Rpm 1267 RpmRefer to Table 1, Physical Data for maximum allowablefan speeds for standard wheels. Excessive fan speed mayresult in condensate carryover from cooling coil or fanmotor overload and wheel failure.7. Check direction of rotation (see Fig. 45). Arrow on driveside of fan housing indicates correct direction of rotation.8. Check vibration. If excessive vibration occurs, check forthe following:a. Variable sheave (if air balance of system has beenaccomplished: replace sheave with fixed sheavefor continuous application).b. Drive misalignment.c. Mismatched, worn or loose belts.d. Wheel or sheaves loose on shaft.e. Loose bearings.f. Loose mounting bolts.g. Motor out of balance.h. Sheaves eccentric or out of balance.i. Vibration isolators improperly adjusted.j. Out-of-balance or corroded wheel (rebalance orreplace if necessary).k. Accumulation of material on wheel (removeexcess material).COILSChilled Water Coil — Typical coil vents, drains, and liftingpoints are shown in Fig. 25.DX Coil — Charge refrigerant. Also refer to condensing unitservice and installation instructions. Refrigerant operatingcharge for unit coil is shown in Table 2.SERVICEGeneral1. Place a suitable walkway to protect floor insulationwhenever entering the fan section.2. Review Safety Considerations at beginning of these in-structions. Good safety habits are important tools whenperforming service procedures.3. To make speed measurements, use a strobe-style tachom-eter or calculate per Step 6 of Start-Up, Check List onpage 35.Fan Motor Replacement1. Shut off motor power.2. Disconnect and tag power wires at motor terminals.3. Loosen motor brace-to-mounting-rail attaching bolts.Loosen belt tensioning bolts to adjust the motor positionso V-belts can be removed without stretching overgrooves.4. Mark belt as to position. Remove and set aside belts.5. Remove motor to motor bracket holddown bolts.6. Remove motor pulley and set aside.7. Remove motor.8. Install new motor. Reassemble by reversing Steps 1-6. Besure to reinstall multiple belts in their original position.Use a complete new set if required. Do not stretch beltsover sheaves. Review the sections on motor and sheaveinstallation, sheave alignment and belt tensioning dis-cussed previously (Fig. 21-23).9. Reconnect motor leads and restore power. Check fan forproper rotation as described in Start-Up, Check List onpage 35.Coil CleaningDETERGENT — Spray mild detergent solution on coils withgarden-type sprayer. Rinse with fresh water. Check to ensurecondensate line is free. Excess water from cleaning may floodunit if condensate line is plugged.STEAM — Remove coil to facilitate cleaning and preventdamage to unit insulation. See Coil Removal section onpage 37.Winter Shutdown (Chilled Water Coil Only) —It is recommended that auxiliary drain piping be added tocoil piping if yearly winterizing of coils is anticipated. Thisauxiliary piping should be located at the highest and lowestpoint on the respective header connection for each coil.ANTIFREEZE METHODS OF COIL PROTECTION1. Close coil water supply and return valves.2. Drain coil as follows:Method I — ‘Break’ flange of coupling at each headerlocation. Separate flange or coupling connection to facili-tate coil draining.Method II — Open both valves to auxiliary drain piping.3. After coil is drained, Method I, connect line with a servicevalve and union from upper nozzle to an antifreeze reser-voir. Connect a self-priming reversible pump between thelow header connection and the reservoir. Method II, makeconnection to auxiliary drain valves.4. Fill reservoir with any inhibited antifreeze acceptable tocode and underwriter authority.Fan Rpm =Motor Rpm x Motor SheavePitch Diameter (in.)Fan Sheave Pitch Diameter (in.)Fig. 45 — Fan Wheel Rotation