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Radial Gap, Overlap and Wheel Alignment
Wheels must rotate freely and not rub on the inlet
cone. Model USF and CSW 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:
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.
Radial Gap and Overlap Dimensions
A
USFD-100
(145)
110
5
23
⁄
32
(148)
113
5
27
⁄
32
(177)
115
6
31
⁄
32
(191)
116
7
1
⁄
2
9 (229)
118
14
Utility and Centrifugal Fans
Overlap
A
Radial
Gap
Radial
Gap
Straight
Straight
Edge
Edge
Inlet
Inlet
Wheel
Cone
Cone
Cone
On belt drive
Overlap
Overlap
Tolerance
inches (mm)
(4)
(3)
5
⁄
1
⁄
32
8
(6)
(3)
7
⁄
1
⁄
32
8
(4)
(3)
5
⁄
1
⁄
32
8
(3)
(3)
1
⁄
1
⁄
8
8
(5)
(3)
3
⁄
1
⁄
16
8
Radial Gap and Overlap Dimensions
USF-200 USF-300 USF-400 CSW
206
306
207
307
208
308
210
310
407
7
408
8
409
9
410
10
212
312
412
12
213
313
413
13
215
315
415
15
216
316
416
16
218
318
418
18
220
320
420
20
222
322
422
22
324
424
24
327
427
27
330
430
30
333
433
33
336
436
36
340
440
40
344
444
44
349
449
49
54 18
60 20
66
73
Wheel Rotation
Rotation direction of the wheel is critical. 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:
Airflow
Backward Inclined
NOTE
Model USF and CSW 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.
Overlap
A
Overlap
Tolerance
inches (mm)
-
-
-
-
-
-
-
-
-
(125)
(10)
(3)
4
15
⁄
3
⁄
1
⁄
16
8
8
(37)
(63)
(3)
1
7
⁄
2
15
⁄
1
⁄
16
32
8
(68)
(31)
(3)
2
11
⁄
1
7
⁄
1
⁄
16
32
8
(94)
(6)
(3)
3
11
⁄
7
⁄
1
⁄
16
32
8
(94)
(6)
(3)
3
11
⁄
7
⁄
1
⁄
16
32
8
(108)
(3)
4
1
⁄
11
⁄
(9)
1
⁄
4
32
8
(119)
(10)
(3)
4
11
⁄
3
⁄
1
⁄
16
8
8
(132)
(11)
(3)
5
3
⁄
7
⁄
1
⁄
16
16
8
(146)
(11)
(3)
5
3
⁄
7
⁄
1
⁄
4
16
8
(162)
(12)
(3)
6
3
⁄
15
⁄
1
⁄
8
32
8
7 (178)
(13)
(5)
1
⁄
3
⁄
2
16
(198)
(13)
(5)
7
13
⁄
17
⁄
3
⁄
16
32
16
(219)
(14)
(6)
8
5
⁄
9
⁄
1
⁄
8
16
4
(240)
(17)
(6)
9
7
⁄
11
⁄
1
⁄
16
16
4
(268)
(17)
(10)
10
9
⁄
11
⁄
3
⁄
16
16
8
(291)
(24)
(10)
11
7
⁄
15
⁄
3
⁄
16
16
8
(324)
(24)
(10)
12
3
⁄
15
⁄
3
⁄
4
16
8
(360)
(23)
(10)
14
3
⁄
29
⁄
3
⁄
16
32
8
(395)
(29)
(10)
15
9
⁄
1
1
⁄
3
⁄
16
8
8
(435)
(32)
(13)
17
1
⁄
1
1
⁄
1
⁄
8
4
2
(478) 1
(39)
(13)
13
⁄
17
⁄
1
⁄
16
32
2
(532) 1
(40)
(13)
15
⁄
9
⁄
1
⁄
16
16
2
(581) 1
(48)
(13)
22
7
⁄
29
⁄
1
⁄
8
32
2
(648) 1
(48)
(13)
25
1
⁄
29
⁄
1
⁄
2
32
2
Airflow
Airfoil
®
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