29
NOTE: There should be a 3 to 6 mm gap between the
mating part hub and the bushing flange. If the gap is
closed, the bushing is probably the wrong size.
3. With taper-lock bushed hubs, be sure the bushing bolts
are tightened evenly to prevent side-to-side pulley wob-
ble. Check by rotating sheaves and rechecking sheave
alignment. When substituting field-supplied sheaves for
factory-supplied sheaves, only the motor sheave should
be changed.
Blower Fan Performance Adjustment — The
unit is supplied with variable sheave drive on the fan motor to
adjust for differing airflows at various ESP conditions. Select
an airflow requirement on the left side of the table, then move
horizontally to right under the required ESP for the sheave
turns open, rpm and horsepower for that condition. Fully
closed, the sheave will produce the highest static capability
(higher rpm).
To change fan speeds from factory settings:
1. Shut off unit power supply.
2. Remove belt from motor sheave.
3. Lift motor assembly.
4. Loosen the
5
/
16
-in. hex nuts on the grommet motor adjust-
ment bolts (2 per bolt). To increase the belt tension loosen
the top hex nut. To decrease the belt tension loosen the
bottom hex nut.
5. Turn the bolts by hand to the desired position then tighten
the
5
/
16
-in. hex nuts ( 2 per bolt).
6. Lower the motor assembly.
7. Install the belt.
8. Tension the belt per section below.
9. Restore power to the unit.
BELT TENSION ADJUSTMENT — Using a gage, apply
4 lb of force to the center of the belt and adjust the tension until
a deflection of
1
/
64
-in. is achieved for every inch of shaft center
distance. See Fig. 25.
Ideal belt tension is the lowest value under which belt slip
will not occur at peak load conditions.
Table 17 — Blower Sheave and Belt Specifications
*Airflow configurations J, K, N, and P.
†Airflow configurations Q, T, U, and V.
**Airflow configurations W, X, Z, and 1.
Fig. 24 — Sheave Alignment
a50-7135tf
BELT SPAN
LB FORCE
DEFLECTION
Fig. 25 — Fan Belt Tension
a50-7136ef
UNIT SIZE
50HQP
COMPONENT
DRIVE PACKAGE
A* B† C**
072
BLOWER SHEAVE BK67 X 1 BK85 X 1 BK67 X 1
MOTOR SHEAVE 1VP34 X 7/8 1VP34 X 7/8 1VP44 X 7/8
MOTOR HP 1 1 1
BELT B X 46 B X 50 B X 48
096
BLOWER SHEAVE BK67 X 1 BK77 X 1 BK62 X 1
MOTOR SHEAVE 1VP40 X 7/8 1VP34 X 7/8 1VP44 X 7/8
MOTOR HP 2 2 2
BELT B X 46 B X 48 B X 46
120
BLOWER SHEAVE BK67 X 1 BK67 X 1 BK67 X 1
MOTOR SHEAVE 1VP44 X 7/8 1VP34 X 7/8 1VP50 X 7/8
MOTOR HP 3 3 3
BELT B X 48 B X 46 B X 48
