Adding wires inside conduit

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Danny Daniels

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I understand code requirements for the question I am about to ask, but in "real world" applications I also know that sometimes the envelope can be slightly pushed without any negative ramifications whatsoever. I also agree safety comes first. With all this in mind, I have a quick question.

Over ten years ago an electrician added a 20 amp circuit to the panel to power new receptacles that I added. It's an exterior panel box located near the soffit and under a 27" wide roof eave. I wasn't present during the installation, but when I had to access the panel recently I noticed that he ran 12-2 Romex from the top of the box via 3/4 inch PVC conduit into the soffit. The actual length of exposed conduit is maybe 10 inches or so. Technically this would be a code violation, but it was installed a decade ago, it is well protected from the elements under the eave, and there has never been an issue with the installation or actual wiring, or anything else. Granted, a future inspection may tag it, but until then I am not going to worry about it.

I am now having another 20 amp circuit installed, but to ensure I meet code I am plannning to use solid core 12 ga THHN from the panel, thru conduit, then into the unfinished attic. From there I will splice into 12-2 Romex for the run across the attic. So here's the question: Since 3/4" conduit is already in place to accomodate the previously installed 12-2 Romex, would there be an issue running the new THHN thru the same conduit, rather than going thru the hassle of punching out holes to add a new piece of PVC? I know there is a limit to the number of wires that can be run thru specifically sized conduit, but since the THHN is basically 3 separate wires, and not sheathed Romex, would it be permissable to run them alongside 12-2 Romex inside the same conduit, without potential negative consequences? Other than suffering the wrath of a future inspector.
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Just wanted to get real world advice before the project gets underway. Tks.
 

Stuff

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3/4" you would have plenty of room. Note THHN is normally also rated THWN (wet) but no guarantee.

If you are already up there why not fix the problem? Pull out the NM (Romex®) and replace with THWN.
 

WorthFlorida

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NM is not allowed in conduit for the prevention of the wires from overheating.
 

hj

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HOW are you going to "splice" the THHN to the Romex? It would normally require a junction box, which would require cutting the existing Romex and "splicing" it also.
 

Reach4

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I am now having another 20 amp circuit installed, but to ensure I meet code I am plannning to use solid core 12 ga THHN from the panel, thru conduit, then into the unfinished attic.
Are you intending to run the THHN/THWN thru conduit to a box, or are you intending to treat the wood and drywall soffit as a conduit/raceway to contain the new wires?
 

WorthFlorida

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I’ve done this in my homes when adding outlets and switches in the garage. Usually the Romex will run through the attic and I need to go down the inside wall of the garage. The walls are cement block. At the ceiling I’ll put one of these connectors on the end of the conduit and continue with romex to the box, maybe 5 ft. Or at the connector strip back the outer sheathing and run just the conductors to the box. Much easier to anchor conduit to a cement block wall and for protection.



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