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Determine the Required Fan/Blower Size (Volume Airflow)

Step 1. Select the product family which best fits your application:
• Compact Cooling Fans (economical fan with no filter)
• Cooling Fan Packages (economical fan package with low-density filter)
• Type 12 Cooling Fan Package
• Filter Fan Packages (high-tech fan package with high-density filter, for IP54 rating)
• Blower Package (centrifugal blower package with filter for densely packed enclosures)

Step 2. Determine the internal heat load in Watts (W).
1 W = 3.413 BTU/Hr.

Step 3. Determine desired temperature difference in degrees F.
Determine the ΔT (F), the temperature difference between the maximum temperature outside the enclosure (To) and the maximum desired temperature inside the enclosure (Ti).
To - Ti = ΔT for heat exchangers and fans
NOTE: 1 C ΔT = 1.8 F ΔT

Step 4. Plot your application using the selection graph to the right.
• Find Watts (internal heat load) on the vertical scale
• Draw a horizontal line across to the intersection point with the diagonal line representing your ΔT
• Extend a vertical line down to the horizontal scale to determine your CFM requirement
• Continue the vertical line to identify applicable fan or blower
A sample line is shown in red for a 400 W heat load and a ΔT of 20 F, which indicates a 63 CFM airflow requirement.

Step 5. Make sure the line intersects the bar which includes the exhaust grille kit(s) from the product family chosen in Step 1.
Remember, actual airflow going through your enclosure may be less depending on how densely packed your enclosure is.
Fan output (CFM) is reduced by 10-15% when operated at 50 Hz.

Or calculate using the formula:
CFM = (3.16 x W) / ΔT (°F)
Where:
Watts = Internal Heat Load in Watts
ΔT = Internal Temperature minus Ambient Temperature in °F
CFM = Required airflow in ft.3/min.
Example:
An internal heat load of 400 W requires airflow of about 63 CFM to maintain the enclosure at a ΔT of 20 F above the ambient temperature.

CFM = (3.16 x W) / ΔT (°F) ≈ 63 CFM    


 
Heat Load Graph and Fan Package Bar Chart