Emerson VSG & VSSG Installation Manual download pdf (Page 33)

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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

Less

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Emerson VSG & VSSG Installation Manual Page 33