Fan rotation is determined by looking at the fan from the drive end. The drive end is is the side of the fan housing through which the fan or motor shaft protrudes. For DWDI or Arrangement 3 SWSI fans, it is the side of the fan housing at which the belt drive sheave is mounted.
For centrifugal fans, discharge is the direction the fan outlet points.
Specification of the rotation and discharge when ordering a housed centrifugal fan is required so that the fan will fit in your system properly.
| Discharge Direction | Clockwise (CW) | Counterclockwise (CCW) |
| Top Horizontal (TH) |
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| Bottom Horizontal (BH) |
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| Up Blast (UB) |
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| Down Blast (DB) |
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| Top Angular Up (TAU) |
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| Top Angular Down (TAD) |
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| Bottom Angular Up (BAU) |
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| Bottom Angular Down (BAD) |
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