Carrier 50KC04-06 Service And Maintenance Instructions

4SUPPLY FAN (BLOWER) SECTIONSupply Fan (Belt-Drive)The supply fan system consists of a forward-curved centrifugalblower wheel on a solid shaft with two concentric type bear-ings, one on each side of the blower housing. A fixed-pitchdriven pulley is attached to the fan shaft and an adjustable-pitch driver pulley is on the motor. The pulleys are connectedusing a “V” type belt. (See Fig. 5.)Fig. 5 — Belt Drive Motor MountingBELTCheck the belt condition and tension quarterly. Inspect the beltfor signs of cracking, fraying or glazing along the inside sur-faces. Check belt tension by using a spring-force tool (such asBrowning’s Part Number “Belt Tension Checker” or equivalenttool); tension should be 6-lbs at a 5 /8-in. deflection when mea-sured at the centerline of the belt span. This point is at the cen-ter of the belt when measuring the distance between the motorshaft and the blower shaft.NOTE: Without the spring-tension tool, place a straight edgeacross the belt surface at the pulleys, then deflect the belt at mid-span using one finger to a 1/2-in. deflection.Adjust belt tension by loosening the motor mounting platefront bolts and rear bolt and sliding the plate toward the fan (toreduce tension) or away from fan (to increase tension). Ensurethe blower shaft and the motor shaft are parallel to each other(pulleys aligned). Tighten all bolts when finished.To replace the belt:1. Use a belt with same section type or similar size. Do notsubstitute a “FHP” type belt. When installing the new belt,do not use a tool (screwdriver or pry-bar) to force the beltover the pulley flanges, this will stress the belt and cause areduction in belt life.2. Loosen the motor mounting plate front bolts and rearbolts.3. Push the motor and its mounting plate towards the blowerhousing as close as possible to reduce the center distancebetween fan shaft and motor shaft.4. Remove the belt by gently lifting the old belt over one ofthe pulleys.5. Install the new belt by gently sliding the belt over bothpulleys and then sliding the motor and plate away from thefan housing until proper tension is achieved.6. Check the alignment of the pulleys, adjust if necessary.7. Tighten all bolts.8. Check the tension after a few hours of runtime and re-adjust as required.ADJUSTABLE-PITCH PULLEY ON MOTORThe motor pulley is an adjustable-pitch type that allows a ser-vicer to implement changes in the fan wheel speed to match as-installed ductwork systems. The pulley consists of a fixedflange side that faces the motor (secured to the motor shaft)and a movable flange side that can be rotated around the fixedflange side that increases or reduces the pitch diameter of thisdriver pulley. (See Fig. 6.)Fig. 6 — Supply-Fan Pulley AdjustmentAs the pitch diameter is changed by adjusting the position ofthe movable flange, the centerline on this pulley shifts laterally(along the motor shaft). This creates a requirement for a re-alignment of the pulleys after any adjustment of the movableflange. Also, reset the belt tension after each realignment.Check the condition of the motor pulley for signs of wear.Glazing of the belt contact surfaces and erosion on these sur-faces are signs of improper belt tension and/or belt slippage.Pulley replacement may be necessary.To change fan speed:1. Shut off unit power supply.2. Loosen belt by loosening fan motor mounting nuts. (SeeFig. 5.)3. Loosen movable pulley flange setscrew. (See Fig. 6.)4. Screw movable flange toward fixed flange to increasespeed and away from fixed flange to decrease speed.Increasing fan speed increases load on motor. Do notexceed maximum speed specified.5. Set movable flange at nearest keyway of pulley hub andtighten setscrew to torque specifications.To align fan and motor pulleys:1. Loosen fan pulley setscrews.2. Slide fan pulley along fan shaft. Make angular alignmentby loosening motor from mounting.3. Tighten fan pulley setscrews and motor mounting bolts totorque specifications.4. Recheck belt tension.WARNINGELECTRICAL SHOCK HAZARDFailure to follow this warning could result in personal injuryor death.Before performing service or maintenance operations on thefan system, shut off all unit power and tag-out the unitdisconnect switch. Do not reach into the fan section withpower still applied to the unit.STRAIGHT EDGEMUST BE PARALLELWITH BELTSETSCREWSMOTOR ANDFANSHAFTSMUST BEPARALLELFIXED FLANGEMOVABLEFLANGESINGLE - GROOVEFAN PULLEYMOTOR PULLEY