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1. Choose a Tray Design
Design depends on many factors, including the nature of the cables
to be installed, site conditions, and aesthetics. Tray options include:
* Ladder — used in applications with intermediate to
long support spans.
* Trough — features a ventilated bottom. Used in applications that generate moderate heat.
* Solid Bottom — typically used in applications that
generate minimal heat, such as electrical and telecommunication
projects.
* Channel — features a one-piece ventilated or solid
bottom. Used for installations featuring small amounts of cable
supported on short to medium spans.
* Single Rail aluminum — for light-duty applications
where quick installation is desired.
* Wire Mesh — for low voltage, telecommunication, and
fiber optic cables supported on short spans.
Article 392 of the National Electrical Code (NEC) provides
guidelines that can help determine the proper tray type.
2. Choose a metal and finish
Your choice depends on the environment in which the tray will be
used. Not all finishes available for all tray types.
* Aluminum: copper-free and corrosion resistant. Lightweight.
Used indoor or outdoors.
* Steel - Hot Dip Galvanized after Fabrication: primarily
for outdoor applications, as it provides excellent weather protection.
* Steel - Mill Galvanized: indoor applications only.
* Steel - Stainless: inherently corrosion resistant, but
expensive.
* Fiberglass: for highly corrosive areas.
* PVC Coating: for use with either aluminum or steel tray.
* Other Finishes: epoxy, primer, or standard
paint.
Consult PW for more information.
3. Determine Load/Span Class
Referred to as the "NEMA Class," this designation defines
the load carrying capability and the support span distances in
a cable tray system.
Just as a civil engineer must know the load and support span of
a bridge, one must know the load and support span of the cable tray.
A NEMA class consists of two parts: a number and a letter. The number
identifies the support span while the letter corresponds to a working
load. A=50 lbs/ft, B=75 lbs/ft, and C=100 lbs/ft.
4. Determine Rung Spacing
Applicable only to ladder tray, the rung spacing should correspond
to the nature of the cables to be installed. Standard spacings are
6", 9", 12", and 18", with 9” the most
commonly specified spacing.
5. Specify Load Depth
Signifies the distance from the top of the cable supporting member
(rungs or bottom ribs) to the top of the side rail; normally 3",
4", 5", or 6".
6. Choose Tray Widths
Standard cable tray widths are 6", 9", 12", 18",
24", 30", and 36". This is the nominal inside width
of the tray that is available for cable fill. Other widths available
upon request.
Article 392 of the National Electrical Code (NEC) provides guidelines
that can help calculate the proper tray width.
7. Choose Fitting Radius
Standard radii for cable tray fittings are 12", 24", and
36", representing the bend radius of the fitting’s inner
corner, and governed by the minimum allowable bend radius of the
cables to be installed in the tray.
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he best way to choose cable or data tray is through a
no-obligation discussion with a PW sales representative.
Follow these steps prior to ordering: