MIL-HDBK-1012/3

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EXAMPLE TWO

ESTIMATING IN-FLOOR DUCT

A. Distribution Duct. In-floor distribution duct requirements

may be estimated by applying a guideline of 6.5 sq. cm

(1 sq. in.) of duct cross-sectional area for each 10 sq. m

(100 sq. ft.) of usable floor space served. Assuming that no

more than three cables will be pulled to each workstation and

each workstation occupies 10 sq. m (100 sq. ft.), the total

length of in-floor distribution duct may be estimated as follows:

1.

Calculate:

Length of distribution ducts = length of the area served by the

telecommunications closet (l) multiplied by the width of the same

area (w) divided by the duct separation 1.7 m (5 ft.), plus the

length of the area (l).

Note: An additional length of the service area is added in this

calculation to account for the cost of a duct being installed

within 24 in. of both outside edges of the service area.

Length of distribution ducts = (L

xW

/5) + L

=

= (l x w) + l

5

2. Example:

If the distribution zone is 100 ft. long and

100 ft. wide:

Length of distribution ducts = (100 x 100) + 100

5

= (10,000/5) + 100

= 2000 + 100

= 2100 ft.

Range of Cross-Sectional Area

Duct Size

Standard

21 to 25 sq. cm (3.3 to 3.9 sq. in.)

Large

49 to 57 sq. cm (7.6 to 8.9 sq. in.)

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