Carrier 48TCA04---A12 appendix Supply FAN Blower Section, Supply Fan Belt-Drive

C07156

	Fig. 4 - Screens Installed on Outdoor-Air Hood
	(Sizes 7-1/2 to 12-1/2 Tons Shown)
48TC
	To remove the screen, loosen the screws in the top retainer
	and slip the retainer up until the filter can be removed.
	Re-install by placing the frame in its track, rotating the
	retainer back down and tighten all screws.
	SUPPLY FAN (BLOWER) SECTION

! WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could cause personal injury or death.

Before performing service or maintenance operations on the fan system, shut off all unit power and tag-out the unit disconnect switch. Do not reach into the fan section with power still applied to unit.

Supply Fan (Belt-Drive)

The supply fan system consists of a forward-curved centrifugal blower wheel on a solid shaft with two concentric type bearings, one on each side of the blower housing. A fixed-pitch driven pulley is attached to the fan shaft and an adjustable-pitch driver pulley is on the motor. The pulleys are connected using a “V” type belt. (See Fig. 5.)

C07087

Fig. 5 - Belt Drive Motor Mounting

Belt

Check the belt condition and tension quarterly. Inspect the belt for signs of cracking, fraying or glazing along the

inside surfaces. Check belt tension by using a spring-force tool (such as Browning’s Part Number “Belt Tension Checker” or equivalent tool); tension should be 6-lbs at a 5/8-in. deflection when measured at the centerline of the belt span. This point is at the center of the belt when measuring the distance between the motor shaft and the blower shaft.

NOTE: Without the spring-tension tool, place a straight edge across 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 plate front bolts and rear bolt and sliding the plate toward the fan (to reduce tension) or away from fan (to increase tension). Ensure the 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 not substitute a “FHP” type belt. When installing the new belt, do not use a tool (screwdriver or pry-bar) to force the belt over the pulley flanges, this will stress the belt and cause a reduction in belt life.

2.Loosen the motor mounting plate front bolts and rear bolts.

3.Push the motor and its mounting plate towards the blower housing as close as possible to reduce the cen- ter distance between fan shaft and motor shaft.

4.Remove the belt by gently lifting the old belt over one of the pulleys.

5.Install the new belt by gently sliding the belt over both pulleys and then sliding the motor and plate away from the fan housing until proper tension is achieved.

6.Check the alignment of the pulleys, adjust if neces- sary.

7.Tighten all bolts.

8.Check the tension after a few hours of runtime and re-adjust as required.

Adjustable-Pitch Pulley on Motor

The motor pulley is an adjustable-pitch type that allows a servicer to implement changes in the fan wheel speed to match as-installed ductwork systems. The pulley consists of a fixed flange side that faces the motor (secured to the motor shaft) and a movable flange side that can be rotated around the fixed flange side that increases or reduces the pitch diameter of this driver pulley. (See Fig. 6.)

As the pitch diameter is changed by adjusting the position of the movable flange, the centerline on this pulley shifts laterally (along the motor shaft). This creates a requirement for a realignment of the pulleys after any adjustment of the movable flange. 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 surfaces are signs of improper belt tension and/or belt slippage. Pulley replacement may be necessary.

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