Carrier WeatherExpert 48LC Series - Step 14 - Check Belt Tension; Belt Force - Deflection Method; Belt Tension Method

72
Step 14 — Check Belt Tension
Measure the belt span length as shown in Fig. 77. Calculate the re-
quired deflection by multiplying the belt span length by
1
/
64
. For
example, if the belt span length is 32 inches:
32 x
1
/
64
=
1
/
2
-in. deflection.
BELT FORCE — DEFLECTION METHOD
Check the belt tension with a spring-force belt force deflection
gage (available from drive belt manufacturer).
1. Place a straightedge along the belt between the two pul-
leys. Measure the distance between the motor shaft and the
blower shaft.
2. Set the tension gage to the desired tension (see Table 1 in
Fig. 77). Place the large O-ring at that point.
3. Press the tension checker downward on the belt until the
large O-ring is at the bottom of the straightedge.
4. Adjust the belt tension as needed.
Adjust belt tension by loosing the motor mounting plate front bolts
and rear bolt (see Fig. 78) and slide the plate towards the fan (to
reduce tension) or away from the fan (to increase tension). Ensure
the blower shaft and motor shaft are parallel to each other (pulleys
aligned). Tighten all bolts securely when finished.
Fig. 77 — V-Belt Force Label
BELT TENSION METHOD
Requires belt tension gage that measures tension in belt in units of
lbs force.
Fig. 78 — Belt Drive Motor Mounting
Table 1
Table 2
BELT
CROSS
SECTION
SMALLEST
SHEAVE
DIAMETER
BELT DEFLECTION FORCE (LBS)
UNNOTCHED
BELTS
NOTCHED BELTS
USED NEW USED NEW
A, AX
3.0-3.6 3.7 5.5 4.1 6.1
3.8-4.8 4.5 6.8 5.0 7.4
5.0-7.0 5.4 8.0 5.7 8.4
B, BX
3.4-4.2 — — 4.9 7.2
4.4-5.6 5.3 7.9 7.1 10.5
5.8-8.6 6.3 9.4 8.5 12.6
BELT CONDITION TENSION FORCE IN BELT (LBS)
New 100
Used 80
BLOWER PULLEY
V-BELT
MOTOR
PULLEY
MOTOR
MOTOR MOUNTING
PLATE
MOUNTING
BOLTS (4)