NEC and Telecomm


Old 12-15-01, 03:42 PM
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NEC and Telecomm

What does the NEC have to say about telephone lines?

My projects would entail:

A. Installing telephone junction oxes and Cat-5 cable
(My understanding is that NEC says to keep the low voltage stuff out of the boxes and raceways which have 120V stuff, and otherwise it doesn't regulate.)

B. Moving an existing old style entry point/demarc from the utility room to the attic. (Outside wire enters the attic through the wall of the dormer, and then traverses to the utility room through its ceiling. the demarc is rounded by a wire that snakes over to a cold water pipe. I'd like to fetch a ground from the nearby subpanel, though I understand it might be preferred to fetch ground from the distantand exterior main panel.)

C. Eventually having a Standard Network Interface (SNI) installed. Here I'm thinking that I'll want the SNI in the attic; wanting the aerial telecomm service drop to attach to the existing electrical riser and have the telcomm cable tuck into the attic at the eave.

Old 12-15-01, 03:57 PM
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I believe that you are correct about those minimal requirements for telephone wire.

I think your telephone company would need to be involved in any move of the demarc. They own everything on their side, and they are not in the habit of letting homeowners mess with it. If you screw up, it could screw up their service to your neighbors. They're not going to risk that.
Old 12-15-01, 07:00 PM
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Really don't understand what you're describing.

You need no ground for your cat 5 cable. You may want a ground for any shield you may have, but typically shields are used exterior only. The variations in the twist of each pair in cable inhibits spurious noise from surroundings and other pairs. If you have a shielded cable and want to ground it, can be done anywhere using and ground (i.e.) from your Wire Center or even an outlet.

Your only ground for the system is from the box on the outside of your house which is the demarc for the phone company. That ground is for the lightning suppressor carbon (600V typically) and some of the lightning suppressors don't even use a ground since one half of your circuit is typically Phoneco grounded. (-48VDC and Grd) The suppressor separates/melts at an over voltage condition. Older houses typically use no ground at all at the demarc.

From what I understand, the phoneco uses no demarcs inside homes...... The homeowner is responsible for the wires from the demark to the interior. For example, if the trouble is inside the house from the demarc point, its yours.
Old 12-16-01, 04:35 PM
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I'd never heard of grounding Cat-5. The ground in question is for the telephone company demarc, which is the guts of an old Western Electric unit. That demarc is inside of my house. I've replaced the interior wiring with Cat-5, for now using only the blue pair. As near as I can tell, the wire fromthe existing demarc to ground is solely to support the overvoltage protection of the leads coming to the house, like from induced voltage from a lightning strike. As I understand it, this grounding function and purpose is the same in principle as the grounding of a modern SNI (though the components may differ).

[For what its worth, it seems the contraption would also protect the external system from an overvoltage generated within my house.]

It's this old demarc that I want to move pending its modernization (and its the ground wire to it that I don't really want coming from the water heater's cold water inlet).


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