Fume Exhaust Fans
10
Wheel Rotation
Rotation direction of the wheel is critical and incorrect
rotation will result in reduced air performance, increased
motor loading and possible motor burnout.
Check wheel rotation by momentarily energizing the
unit and noting if rotation is in the same direction as the
airflow at the outlet and conforms to the rotation decal
affixed to the unit.
Wheels as viewed from the drive side:
NOTE
Model VJC and VJI units should be operated only
when attached to the system for which they were
designed. Without proper system static pressure, the
motor could be overloaded.
Ro
ta
ti
o
n
Ro
ta
ti
o
n
Backward Inclined
Airfoil
Wheels must rotate freely and not rub on the inlet cone.
Model VJC and VJI wheels overlap the inlet cone. Refer
to the table for the proper dimension.
Radial Gap and Alignment
Efficient fan performance can be maintained by having
the correct radial gap, overlap and wheel alignment.
These items should be checked after the fan has been
in operation for 24 hours and before start-up when the
unit has been disassembled.
Radial Gap:
Adjust inlet cone
position such that the radial gap
between the wheel cone and inlet
cone is evenly distributed around
the wheel.
Radial gap is adjusted by
loosening the inlet cone/ring bolts
and centering the cone/ring on the
wheel. If additional adjustment is
required to maintain a constant
radial gap, loosening the bearing
bolts and centering the wheel is
acceptable as a secondary option.
Overlap:
Overlap is adjusted by loosening the wheel
hub from the shaft and moving the wheel to the desired
position along the shaft.
The transition between the inlet cone and wheel should
be as shown; there is a smooth feel to the profile when
moving from one component to the other.
Method for Centering Wheel:
On belt drive units,
centering can be accomplished by (a) loosening the inlet
cone bolts to move the inlet cone or by (b) loosening
the bearings in order to move the shaft. Wheel and inlet
cone overlap can be adjusted by loosening the wheel
hub set screws and moving the wheel to the desired
position. Tighten all fasteners and set screws securely
and realign drive pulleys after adjustment.
Wheel
Cone
Radial
Gap
Radial
Gap
Overlap
A
Straight
Edge
Straight
Edge
Inlet
Cone
Inlet
Cone
Radial Gap, Overlap and Wheel Alignment
Radial Gap and Overlap Dimensions
VJC-200 VJC-300
VJI
A
Overlap
Overlap
Tolerance
inches
(mm)
206
306
4
15
⁄
16
(125)
3
⁄
8
(10)
1
⁄
8
(3)
207
307
4
15
⁄
16
(125)
3
⁄
8
(10)
1
⁄
8
(3)
208
308
4
15
⁄
16
(125)
3
⁄
8
(10)
1
⁄
8
(3)
7
1
7
⁄
16
(37)
2
15
⁄
32
(63)
1
⁄
8
(3)
8
2
11
⁄
16
(68)
1
7
⁄
32
(31)
1
⁄
8
(3)
9
3
11
⁄
16
(94)
7
⁄
32
(6)
1
⁄
8
(3)
10
3
11
⁄
16
(94)
7
⁄
32
(6)
1
⁄
8
(3)
212
312
12
4
1
⁄
4
(108)
11
⁄
32
(9)
1
⁄
8
(3)
215
315
15
5
3
⁄
16
(132)
7
⁄
16
(11)
1
⁄
8
(3)
18
6
3
⁄
8
(162)
15
⁄
32
(12)
1
⁄
8
(3)
20
7
(178)
1
⁄
2
(13)
3
⁄
16
(5)
24
8
5
⁄
8
(219)
9
⁄
15
(14)
1
⁄
4
(6)
