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Can cable tray cable run in cable tray systems be left unsupported between sections of tray?
2

Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

(OP)
We're in the process of designing some cable tray/conduit system in a highly congested basement space of an industrial plant. There are approximately 200 cables of various sizes on the project. An all conduit design would be considerably more expensive and is not being considered.

The proposed cable tray routes show long straight pieces of tray. But to get around the obstacles the design the cables simply swung into the next long straight piece unsupported.
All the tray is bonded together with a #4/0 ground cable. All of the cable is tray rated but is not armored.

I don't think it looks particularly good...but with all the constaints in space it seems like a reasonable design and is definitely the cheapest way to do it.

But can you do this? ...leave all tray cable unsupported for 2'-3'? What I would like to see is cable tray fittings to make these elevation changes...but again they cost extra $$ that they don't want to spend if they don't have to.

Thanks.

RE: Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

(OP)
To answer my own question.... I read in the NEC:

392.18 Cable Tray Installation.
(A) Complete System. Cable trays shall be installed as a
complete system. Field bends or modifications shall be so
made that the electrical continuity of the cable tray system
and support for the cables is maintained. Cable tray systems
shall be permitted to have mechanically discontinuous segments
between cable runs.

So per the NEC....it's to be installed as a complete system (in other words continuous)...except it can be discontinuous.
Still confused.

RE: Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

Does this help any? From the handbook:

Runs of cable tray are not required by 392.18(A) to be totally
mechanically continuous from the equipment source to
the equipment termination. Breaks in the mechanical continuity
of cable tray systems are permitted and often occur at
tees, crossovers, elevation changes, or firestops, or for thermal
contraction and expansion. Also, cable tray systems are
not required to be mechanically connected to the equipment
they serve.

RE: Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

See 392.30(B)(3) - distance shall not exceed 6'.

RE: Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

392.30(A) isn't a bad choice, either.

392.30 Securing and Supporting.
(A) Cable Trays. Cable trays shall be supported at inter-
vals in accordance with the installation instructions.

RE: Can cable tray cable run in cable tray systems be left unsupported between sections of tray?

Heavy duty tray (sometimes known as high voltage tray) is approved for 6 Meter spans between supports. (20') Cantilevered overhangs are much less.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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