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Chip C Chip C is offline
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Default NEC question: low-voltage wiring crossing 120v wiring.

On Sep 29, 5:30*pm, wrote:
On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

wrote:
I am running network cables *-- shielded, if that makes a difference --
above suspended ceiling where there is already 120V Romex wiring in
places. This 120V wiring is stapled to the joists at intervals.


Is it OK for the network cables to lie on the ceiling support members,
and thus beneath the Romex? Or should the network cables be above the
Romex? Or should one or both be in conduit? -- more precisely, should
what is now Romex be redone with individual conductors in conduit?


Perce


*no issue even with cat5 or cat5e non sheilded - as long as your space
above the ceiling is not an air plenum - and then you just need plenum
rated cat5


If there is romex there already, then let's hope it isn't plenum
space.

Only in commercial buildings would I expect space above suspended
ceilings to be used as air plenum (return air is drawn through it on
its way back to the hvac system), and commercial building code
anywhere in N.America requires power conductors to be in conduit or
armored cable, and data cabling to be in either conduit (in which
case, it might not need to be plenum rated) or a cable tray, the
better to prevent it from collapsing into the space during a fire,
blocking egress and creating a hazard for firefighters. At least
that's how it was explained to me.

Single-family residential code doesn't say anything about low-voltage
cabling except that you can't put it in the same boxes as 120V.

Having said that, I think laying it onto the suspended ceiling, as I
understand the OP is proposing, is going to be a pain whenever someone
wants to lift a panel. I'd find some clips to tack it to the joists.

I wouldn't expect simple romex runs to be an interference problem for
data communications. Fluorescent ballasts, light dimmers, fan speed
controls and any kind of motor or switching power supply, maybe.

Chip C
Toronto