3
IMH IO&M
B51221-002
Duct Installation
Efficient fan performance relies on the proper installa
-
tion of inlet and discharge ducts. Be sure your fan con
-
forms to the guidelines below.
Non-Ducted Inlet Clearance
If your fan has an open inlet (no duct work), the fan must
be placed 1 fan wheel diameter away from walls and bulk-
heads. An inlet bell should be used in this case.
Non-Ducted Inlet Clearance
MIN 1 DIA
Free Discharge
Avoid a free discharge into the plenum. This will result in
lost efficiency because it doesn't allow for a static regain.
Correct
Incorrect
Free Discharge
Inlet Duct Turns
For ducted inlets, allow at least 3 fan wheel diameters
between duct turns or elbows and the fan inlet.
Correct
Incorrect
Inlet Duct Turns
MIN 3
DIA
Discharge Duct Turns
Make sure that duct turns located near the fan discharge
curve in the direction of the fan's rotation. Refer to the Dis
-
charge Duct Turns illustration.
Correct
Incorrect
Discharge Duct Turns
MIN 3
DIA
Wheel-to-Inlet Clearance
The correct wheel-to-inlet clearance is critical to proper
fan performance. This clearance should be verified before
initial start-up since rough handling during shipment could
cause a shift in fan components. Refer to wheel/inlet draw
-
ing below for correct clearance. Adjust the overlap by loos
-
ening the wheel hub and moving the wheel along the shaft
to obtain the correct value.
WHEEL TO INLET
CLEARANCE
MH, MHB, MHR
WHEEL TO INLET
OVERLAP
MHA
Wheel-to-Inlet Clearance and Overlap
Size
MH, MHBM, MHR
MHA
Wheel-to-Inlet
Ring Clearance
Wheel-to-Inlet
Ring Overlap
Min.
Max.
Min.
Max.
70
3/16
5/16
1/8
1/4
90
3/16
5/16
1/8
4/4
110
3/16
5/16
3/16
5/16
130
3/16
5/16
1/4
3/8
150
3/16
5/16
1/4
3/8
170
3/16
5/16
5/16
7/16
190
3/16
5/16
3/8
1/2
210
5/16
7/16
7/16
9/16
230
5/16
7/16
7/16
9/16
260
5/16
7/16
1/2
5/8
290
5/16
7/16
5/8
3/4
Wiring Installation
All wiring should be in accordance with local ordinanc-
es and the National Electrical Code, NFPA 70. Ensure the
power supply (voltage, frequency, and current carrying ca-
pacity of wires) is in accordance with the motor name-plate.
Lock off all power sources before unit is wired to
power source.
Leave enough slack in the wiring to allow for motor move-
ment when adjusting belt tension. Some fractional motors
have to be removed in order to make the connection with
the terminal box at the end of the motor. To remove motor,
remove bolts securing motor base to power assembly. Do
not remove motor mounting bolts.
Follow the wiring diagram in the disconnect switch
and the wiring diagram provided with the motor.
Correctly label the circuit on the main power box
and always identify a closed switch to promote
safety (i.e., red tape over a closed switch).
Wheel Rotation
Test the fan to ensure the rotation of the wheel is the
same as indicated by the arrow marked Rotation.
115 and 230 Single Phase Motors
Fan wheel rotation is set correctly at the factory. Chang
-
ing the rotation of this type of motor should only be at-
tempted by a qualified electrician.
208, 230, and 460, 3 Phase Motors
These motors are electrically reversible by switching two
of the supply leads. For this reason, the rotation of the fan
cannot be restricted to one direction at the factory.
See
Wiring Diagrams on page tk (4) for specific information on
reversing wheel direction.
Do not allow the fan to run in the wrong direction.
This will overheat the motor and cause serious
damage. For 3-phase motors, if the fan is running
in the wrong direction, check the control switch.
It is possible to interchange two leads at this lo-
cation so that the fan is operating in the correct
direction.
