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VSG/VSSG • Installation, Operation and Maintenance Manual •Vilter/Emerson • 35391SSG
Section 3 • Installation
The equation used to calculate the leg height in Figure
3-11 is as follows:
Leg Height = (Total Airfl ow/Intake velocity)/Intake Perimeter
Leg Height = (247,000CFM/500FPM)/82ft
Leg Height = 6ft
In this particular case the calculated minimum height is
6 feet to maintain an intake velocity of 500FPM or less
based on having the coolers place 1 fan diameter away
from the nearest obstruction. Let’s look at an instal-
lation where the coolers need to be placed next to the
building as in Figure 3-12.
Based on the information above, we are going to solve
for the leg height that will provide an intake velocity of
500FPM. We know the following:
• The total airfl ow of the installation is 247,000CFM
• We have an intake perimeter of 3 sides 16ft, 16ft, and
25ft which totals 57’
• Our intake velocity guideline is 500FPM
The equation used to calculate the leg height in Figure
3-11 is as follows:
Leg Height = (Total Airfl ow/Intake velocity)/Intake Perimeter
Leg Height = (247,000CFM/500FPM)/57ft
Leg Height = 8.667ft
We would round the leg height up to 9ft for this particu-
lar situation.
Figure 3-12. Installation of Coolers - Next to Buildling
TOTAL INTAKE PERIMETER = 57 FEET
Figure 3-11. Leg Height
NOT PREFERRED
Intake Velocity
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