Box and Raceway Sizing
Box and Raceway Sizing
Pull
boxes are
often utilized in conjunction with conduit. They can draw conductors across great distances without putting undue pressure on
the wire's surface or insulating because they are composed of metal sheeting, cast metallic material, or a not a metal substance. Pull boxes,
which can handle straight and slanted pulls, enable long wire runs to put at
closer intervals.
Pull boxes don't
contain connections of wires inside, despite looking similar to junction boxes.
They serve only as entry points for bringing conductor into a racetrack network
and feeding them as well.
Minimum size specifications: At least eight times the trading area of the biggest raceway between the
point where conductors enter and the opposite wall.
Straight
Pulls occurs
when the tube enters the box on one
end and exits the enclosure on the
other. Straight pulls require a diameter
eight times larger than the large conduit or raceway.
The
smallest length for the enclosure by
simply multiplying your biggest
raceway size by 8.
Least Box Length = Largest Raceway Size divided by 8. Assuming your racetrack is 3.
Least Box
Length=24
An angle pull
Regarding angle pulls, the
total of the following measurements must be used to determine the length
between every raceway entry within the box and the outermost opposing wall.
The trade volume is six
times that of the biggest race course. The total of every other raceway
entry's diameters in the row.
Suppose a pull box includes three
raceways with sizes of 4", 2",
and 2" and a 90° turn. The following calculation process would be
used: The diameter of the raceway is six times larger (6 x 4" = 24").
Total
of every other raceway diameters is equal to 2" + 2" = 4".Total = 24" +
4" = 28"
The straight distance
from each circuit's points of entry and exit also has to be six times the
diameter of the corresponding conduit.
Separations
Circuit separation for 4"
conduit: 6 x 4" = 24"
Circuit separation in a 2"
conduit is equal to 6 x 2" = 12"
Several
Raceways
Choose the distance
that is the greatest among any rows of raceways if there are several.
Use the largest computed
size if there are several rows of raceways.
Calculating
several raceways
For instance, if one row has raceways that are 3-3'' apart and another row has
raceways that are 3-1'' apart:
Determine Row 1:
(3" x 6) + 3" x 3) = 24"
Determine Row 2:
(1" x 6) + 1" x 1" = 8"
Select the bigger of
the two sizes, 24".
Separating
the raceways
In addition, the gap
between raceways which encircle the identical conductor can be at least six times the size of the
greatest raceway, as measured from the
closest edge to the closest edge of the raceways.
Computation
of the distance between raceways
The minimum distance
among raceways = Largest Raceway the size x 6.
For instance, suppose your raceway is 3" from top to bottom=18.
Multiple
Pull Types
The same box can accommodate several different pull types, such
as straight and angle pull. If you have many
pull kinds, you must determine all of them using the appropriate methods,
then pick the largest of the computed
sizes.
Calculating
Several Raceways
If you've got a box having a straight pull on a 3" raceway and an angled pull on a
3" raceway, for instance. The straight
pull measurement from left to right is 3" x 8" = 24".The angle pull from left to right be
calculated as 21"). The greater of
the two sizes, 24", should be used for your left-to-right calculation.
3 x 6 = 18 inches is the angle
pull calculation from top to bottom. Your box needs to be a minimum of 18" tall and 24"
broad.
Design Procedure
You should figure out the racetrack
distance, horizontal directions & vertical (top to bottom and bottom to
high) dimensions. Draw out the
arrangement since this can be unclear. A pull
box using a 1-3" raceway to the left, 1-2" raceway to the left, a
1-2" raceway on the opposite side, and a 1-3" raceway to the bottom
is an example of this. Thus, you have a 3" angled pull as well as a
2" straight draw.
§ Determine the dimensions of each raceway you'll be
using in step one.
§ Determine whether a Linear or Splice/Angle/U Pull is
required since various formulas must be used.
§ Determine the horizontal dimension.
§ Computation of the
horizontal size
Straight Pull: 8" x 2" = 16" from
Left to Right
8
x 2 = 16 from right to left
The width of your draw box needs to be a
minimum of 16".
Left to
right angle pull: (3 x 6) + 2 x (20)
§ Compute the vertical dimension.
§ Determination of the
vertical size (Only for Angle, Splice,
and U Pulls)
3
X 6 = 18 inches from bottom to top.
§ Measure the Length Between Raceways (Only for
Angle, Splice, and U Pulls)
Raceway
separation: 3" x 6" = 18"
§ Choose the greater of the
two distances when comparing raceways
to vertical and horizontal distances. (Only Angle, Splice, and U Pulls)
(Distance
between Raceways: 18") = (Vertical Distance: 18")
(18 inches
separate the raceways). (120% Horizontal Distance)
§ The minimum dimensions
for your pull box are 20" wide by 18" tall.
If there are multiple rows of raceways, determine their sizes (skip this step if
there is one raceway), then select the
largest one.
For
instance, if one row has raceways that are 3-3'' apart and row has are 3-1''
Determine Row
1: (3" x 6) + 3" x 3) = 24"
Determine
Row 2: (1" x 6) + 1" x 1" = 8"
Select the
bigger of the two sizes, 24".
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