The document describes various arrangements and configurations for centrifugal fans, including: - 10 different drive arrangements that specify features like single or double width, single or double inlet, impeller placement, and bearing locations. - 8 discharge and rotation designations that specify airflow direction depending on features like top, bottom, horizontal or angular placement and clockwise or counterclockwise rotation. - 4 motor positions - W, X, Y, Z - to designate a motor's location relative to the drive side of a belt-driven centrifugal fan.

1. Fan Basics
Drive Arrangements for Centrifugal Fans†
SW - Single Width, SI - Single Inlet
DW - Double Width, DI - Double Inlet
Arr. 1 SWSI - For belt drive Arr. 2 SWSI - For belt drive
or direct drive connection. or direct drive connection.
Impeller over-hung. Two Impeller over-hung. Bearings
bearings on base. in bracket supported by fan
housing.
Arr. 3 SWSI - For belt drive Arr. 3 DWDI - For belt drive
or direct drive connection. or direct connection. One
One bearing on each side bearing on each side and
supported by fan housing. supported by fan housing.
†Adapted from AMCA Standard 99-2404-78
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2. Fan Basics
Drive Arrangements for Centrifugal Fans (cont.)
SW - Single Width, SI - Single Inlet
DW - Double Width, DI - Double Inlet
Arr. 4 SWSI - For direct Arr. 7 SWSI - For belt drive
drive. Impeller over-hung on or direct connection.
prime mover shaft. No bear- Arrangement 3 plus base for
ings on fan. Prime mover prime mover.
base mounted or integrally
directly connected.
Arr. 7 DWDI - For belt drive Arr. 8 SWSI - For belt drive
or direct connection. or direct connection.
Arrangement 3 plus base for Arrangement 1 plus
prime mover. extended base for prime
mover.
Arr. 9 SWSI - For belt drive. Arr. 10 SWSI - For belt
Impeller overhung, two drive. Impeller overhung,
bearings, with prime mover two bearings, with prime
outside base. mover inside base.
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3. Fan Basics
Rotation & Discharge Designations for
Centrifugal Fans*
Top Horizontal
Clockwise Counterclockwise
Top Angular Down
Clockwise Counterclockwise
Top Angular Up
Clockwise Counterclockwise
Down Blast
Clockwise Counterclockwise
* Rotation is always as viewed from drive side.
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4. Fan Basics
Rotation & Discharge Designations for
Centrifugal Fans* (cont.)
Up Blast
Clockwise Counterclockwise
Bottom Horizontal
Clockwise Counterclockwise
Bottom Angular Down
Clockwise Counterclockwise
Bottom Angular Up
Clockwise Counterclockwise
* Rotation is always as viewed from drive side.
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5. Fan Basics
Motor Positions for Belt Drive Centrifugal Fans†
To determine the location of the motor, face the drive side of the
fan and pick the proper motor position designated by the letters
W, X, Y or Z as shown in the drawing below.
†Adapted from AMCA Standard 99-2404-78
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