Replacing old ungrounded Romex on lighting circuit


Old 03-31-15, 11:39 AM
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Replacing old ungrounded Romex on lighting circuit

Would like to know if this is compliant. I want to run a new MC cable circuit from the panel through a crawl space up to a wall switch to a bedroom ceiling light. Currently the circuit powering the bedroom light and switch is ungrounded romex which is going from the panel to the attic where it powers a couple of other room's lights before it powers the bedroom light I want to change wire to. From the light I want to change the cable to, the Romex powers the lights in an adjacent bathroom and closet. In effect, the wiring to be changed is roughly in the middle of the circuit - the downstream bathroom and closet part of the circuit are all fed from the junction box that houses the light fixture I want to run MC cable to. The light fixture junction box isn't large enough for the MC cable and the old Romex.

I would like to disconnect the old panel side of the Romex at the nearest junction box to the bedroom light - it would still power the upstream lights - and add a junction box where the new MC cable and the old Romex which is feeding the downstream bathroom and closet lights can be connected. So, i'd end up with the old Romex still feeding the rooms before the bedroom but terminated at the closest junction box and new MC cable from the panel powering the bedroom light, with the old Romex downstream from the bedroom now powered by the MC cable, tied in by a new junction box.
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Old 03-31-15, 03:00 PM
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Generally speaking the only ungrounded wiring you're allowed to work on is for "repair" purpose only. For example, a mouse has chewed the wire between points A and B and you run a new piece of romex from A to B to replace the damaged piece.

It sounds like what you want to do is more of a remodelling situation, which in most areas would require that new work meet modern code. All of this is somewhat a grey area which is up to the local building department how extensively they enforce it in the jurisdiction. The code book leaves a lot of discretion to the inspector in this case.
Old 03-31-15, 03:11 PM
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I just had the pole to house wiring and main panel replaced and the electrician did something similar, in that he didn't have enough of the old romex coming from the attic to reach the new box so he put in a bunch of junction boxes in the attic and used grounded romex to tie into the old ungrounded romex which allowed enough length to reach the new box. The inspector passed it without a problem.
I did read somewhere that if you go back to the panel and start there you can do it, but like you said, it appears to be a grey area.
Old 04-01-15, 06:35 AM
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You may upgrade a circuit piecemeal in any order.

I would interpret that to include decommissioning the "first half" of an old circuit and running new wiring up from the panel, exactly, approximately, or vaguely following the route of said "first half" and thus re-energizing the "second half" of the old circuit.

But you may not extend wiring from old non-compliant wire, including where you have a new "part 1" from the panel connecting to an old "part 2" where, further downstream you want to add a "part 3."

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