I have a situation where 2" PVC provides a conduit from basement to attic via outside of the house. As such if that classifies as a wet or damp location and NM-B wire cannot be used in that section of conduit, then what choice is there currently other than UF-B ?

Just one run needed for 240 volt 3-wire (red/black/neutral/ground) either 12 gauge or 10-gauge, currently on 20 amp breaker, do not foresee need to ever go above 30 amp need, this is for AC air handler in attic.

The conduit is 2", and wish to keep the ends of conduit open so runs of RG-6 coax or CAT-6 cabling can be done to reach attic then down to second floor rooms. Only the one run of 12/3 or 10/3 is needed from basement up to attic through exterior 2" conduit to reach AC air handler in attic. Only possible space issue is at one 2" LB conduit body.

From exit of top of load center to entrance of 2" conduit in basement ceiling the wire would not be in conduit. And in attic from conduit exit to Jbox on AC unit wire would not be in conduit

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    Things with 2 or more conductors in them are not wire. They are cables. Cable contains wires. UF and NM are cables. Running wire not in conduit is illegal. Commented Apr 5, 2018 at 15:14
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    You cannot run data wire down the same conduit as power. Commented Apr 6, 2018 at 8:39

2 Answers 2


You use individual wires in conduit, not a cable

Pulling cable through conduit is a miserable job -- NM and UF cables use solid wire, making them awful stiff, and the jacket just makes them stiffer and harder to pull still, especially around bends. Instead, you want to take some single wires rated for wet location service (you can get THHN/THWN-2 dual-rated single conductors basically anywhere building supplies are sold) and pull an appropriate bundle of those through your conduit instead of a cable.

This will make your pull easier then and there because said bundle's less stiff and snag-prone due to not having a jacket; furthermore, you can get stranded THHN/THWN-2 wire in most places, which will make your pull easier still as stranded wire beats solid wire of equal size on flexibility, every time. Just do not ever try to get away with shucking the jacket off a cable to get at the wires inside -- wires inside cables are not marked for use outside the cable jacket!

At the ends of the conduit, you'd put a box and transition to a cable wiring method there

With individual wires in conduit, the conduit run needs to be complete between boxes. So, this simply means you need a suitable box at each end of the run, mounted indoors, that you can make splices in to transition between NM and wires-in-conduit.

Run another conduit for the networking wires

You can't put network or coax cables in the same conduit as power wires -- this is governed by 800.133(A) and 820.133(A), not 300.3(C).

  • Good answer I would give you two pluses if I could. Commented Apr 5, 2018 at 13:01
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    Is there an issue with having 240v wiring and RF/Networking cable in the same conduit? Is that allowed?
    – JPhi1618
    Commented Apr 5, 2018 at 14:06
  • @JPhi1618 Major issue on about three counts: ELV cable cannot be run in the same conduit as LV cable (unless all cables are rated for the highest voltage present, and ethernet cable is usually good for 30V, plus I think it might need to be double insulated which conduit wire is not), interference from power can wreak havoc with data lines in close proximity, and you probably don't want to try and pull ethernet down the same conduit anyway. No code references; I'm not in the US. Commented Apr 6, 2018 at 8:45
  • @SomeoneSomewhere, thanks, that's what I thought, and the asker mentioned wanting to use the same 2" conduit.
    – JPhi1618
    Commented Apr 6, 2018 at 13:36

Conduit can be used two ways:

  • as raceway for individual wires like THWN that are required to run in some kind of raceway. This is the conduit wiring method. The conduit must be continuous throughout the use of this method. You can transition to another wiring method at a junction box. You are also allowed to pull cable through the conduit if you really, really want the exercise!
  • as a mere protective shield. In this case conduit is not a wiring method. You're actual!y using another wiring method such as UF cable. You can enter and exit conduit at will, gaps allowed, and you don't need a junction box at the end of conduit because you're not actually transitioning wiring methods, you are in UF wiring method (or whichever) the whole way and must comply with that method's rules.

"Wire", as you refer to it, is actually muticonductor cable containing several actual wires, such as NM, UF and the like. Generally pulling cable through conduit is an act of masochism. However #12 or #10 solid cable will pull easily through 2" conduit because it is wildly oversized for a single #10 circuit (oversize is good). Certainly easier than the #0000 aluminum THWN single-strand one typically puts in 2".

You cannot put low voltage or comms wires in the same conduit with mains power. Not even a question.


Sigh... OK... yeah, there's one exception, but it's completely useless to your goal, hence my hasty armwave. What you want to do is come out of the mains+data conduit to a cover plate with an ethernet, cable TV etc. socket, then onto your cable box or PC. That's the thing you can't do because it means the circuit is not entirely in Class 1 wiring methods. Run two conduits if you want that.

The exception is intended for industrial controls, 24V-based office lighting controls, that sort of thing.

There's one more exception, but it involves running entirely non-metallic fiber optic cable inside mains conduit.

If you have any more questions about this topic area, ask a new question.

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    question: 300.3c page 70-134; 1000v or less, conductors of ac or dc circuit shall be permitted to occupy the same wiring enclosure, cable, or raceway. all conductors shall have an insulation rating equal to at least max circuit voltage applied to any conductor within the enclosure, cable, or raceway.
    – ron
    Commented Apr 5, 2018 at 16:47
  • @ron not enough, keep reading. TLDR: there's an exception that allows low voltage wiring to mix with mains if and only if every inch of the LV circuit is contained within Class I wiring methods and class 1 rated chassis. That's for industrial controls, 24V relay controlled office lighting where the works is in conduit, jazz like that. Commented Apr 5, 2018 at 16:59
  • 7-646 for 80.133A in NEC 2017, not marked as new, exception 1: section 800.133(A)(2) shall not apply where either (1) all of the conductors... are in a raceway or in a metal-sheathed, metal-clad, non-metallic sheathed, type AC, or Type UF cables, or...
    – ron
    Commented Apr 16, 2018 at 4:10
  • @Ron no, you're just being argumentative and judgmental because you don't like my answer. That is lawyering; but it's driven by another type of behavior called "Justifying": decide in advance what you're gonna do, then search for Code which supports it. "What's the matter with that?" It requires selectively ignoring Code which does not support it. Commented Apr 16, 2018 at 14:47

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