Step 13 - Check Belt Tension; Belt Force - Deflection Method; Belt Tension Method; Pre-Start And Start-Up - Bryant Legacy 549J 12 Series Installation Instructions Manual

Step 13 — Check Belt Tension
Measure the belt span length as shown in Fig. 54. Calculate the
required deflection by multiplying the belt span length by
For example, if the belt span length is 32 inches:
32 x / =
1 1
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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. 54). 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. 55) and slide the plate towards the
fan (to reduce tension) or away from the fan (to increase ten-
sion). Ensure the blower shaft and motor shaft are parallel to
each other (pulleys aligned). Tighten all bolts securely when
finished.

BELT TENSION METHOD

Requires belt tension gage that measures tension in belt in units
of lbs force.
BELT DEFLECTION FORCE - SEE TABLE 1
SET
SCREW
TORQUE ALL SHEAVE SET SCREWS TO 110-130 in. lbs
BELT SMALLEST
CROSS SHEAVE
SECTION DIAMETER
USED
3.0-3.6
A, AX 3.8-4.8
5.0-7.0
3.4-4.2
B, BX 4.4-5.6
5.8-8.6
BELT CONDITION
New
Used
Fig. 54 — V-Belt Force Label
/ -in. deflection.
2
DEFLECTION = BELT SPAN
64
STRAIGHT
EDGE
SET
SCREW
BELT DEFLECTION FORCE (LBS)
UNNOTCHED
NOTCHED BELTS
BELTS
NEW USED
3.7 5.5 4.1
4.5 6.8 5.0
5.4 8.0 5.7
— — 4.9
5.3 7.9 7.1
6.3 9.4 8.5
Table 1
TENSION FORCE IN BELT (LBS)
100
80
Table 2
/ .
1
64
MOUNTING
BOLTS (4)
Fig. 55 — Belt Drive Motor Mounting

Pre-Start and Start-Up

This completes the mechanical installation of the unit. Refer to
the unit's Service Manual for detailed Pre-Start and Start-Up
instructions. Download the latest versions from HVAC Part-
ners (www.hvacpartners.com).
NEW
6.1
7.4
8.4
7.2
10.5
12.6
41
BLOWER PULLEY
V-BELT
MOTOR
PULLEY
MOTOR
MOTOR MOUNTING
PLATE