Carrier 50TC*17 Series Service And Maintenance Instructions

6surfaces are signs of improper belt tension and/or beltslippage. Pulley replacement may be necessary.Changing Fan Speed1. Shut off the main unit power supply, and use the ap-proved Lockout/Tagout procedures.2. Loosen the belt by loosening the motor adjustmentbolts as described in the Belt Adjustment sectionabove.3. Loosen the movable pulley flange setscrew. (See Fig.6.)4. Screw the movable flange toward fixed flange to in-crease speed and away from fixed flange to decreasespeed. Increasing fan speed increases load on the mo-tor. Do not exceed maximum speed specified in theProduct Data or motor amperage listed on the unit rat-ing plate..5. Set the movable flange at the nearest keyway or flatof the pulley hub and tighten the setscrew to torque of72 ± 5 in−lbs (8.14 ± 0.56 Nm).Aligning the Fan and Motor Pulleys1. Loosen the fan pulley setscrews.2. Slide the fan pulley along the fan shaft. Make angularalignment by loosening the motor from its mounting.See Fig. 7.3. Tighten the fan pulley setscrews and motor mountingbolts to torque specifications.4. Recheck the belt tension. See Fig. 6.C07075Fig. 7 − Supply−Fan Pulley AdjustmentBearingsThis fan system uses bearings featuring concentric splitlocking collars. The collars are tightened through a capscrew bridging the split portion of the collar. The capscrew has a Torx T25 socket head. To tighten the lockingcollar: Hold the locking collar tightly against the innerrace of the bearing and torque the cap screw to 65−70in−lb (7.4−7.9 Nm). See Fig. 8.LOCKING COLLART-25 TORX SOCKETHEAD CAP SCREWC11505Fig. 8 − Tightening Locking CollarSTAGED AIR VOLUME (SAV) CONTROL:2−SPEED FAN WITH VARIABLEFREQUENCY DRIVE (VFD)Staged Air Volume (SAV) Indoor Fan SpeedSystemNOTE: The SAV option is not available on units withHumidi−MiZer adaptive humidification system.The SAV system utilizes a Fan Speed control board andVariable Frequency Drive (VFD) to automatically adjustthe indoor fan motor speed in sequence with the unit’sventilation, cooling and heating operation. Conforming toASHRAE 90.1 2010 Standard Section 6.4.3.10.b, duringthe first stage of cooling operation the SAV system willadjust the fan motor to provide two- thirds (2/3) of thedesign airflow rate for the unit. When the call for thesecond stage of cooling is required, the SAV system willallow the design airflow rate for the unit established(100%). During the heating mode, the SAV system willallow total design airflow rate (100%) operation. Duringventilation mode, the SAV system will operate the fanmotor at 2/3 speed.Identifying Factory OptionThis supplement only applies to units that meet thecriteria detailed in Table 1. If the unit does not meet thatcriteria, discard this document.Table 1 – Model−Size / VFD Option IndicatorModel / Sizes Position inModel NumberVDPFIOP Indicator50TC 17 − 30 17 G, JSee Appendix I for the Model Number Nomenclaturebreakdown.Unit Installation with SAV Option50HC Rooftop—Refer to the base unit installationinstructions for standard required operating and serviceclearances.