I am working on a project, In my own home, Permanently installing a Faux Fireplace, Shiplap, and some iron pipe shelves. The shelves are going to have built in lighting in the form of Edision Bulbs at the end of the pipe elbows as shown in Fuchsia circles. However, I am having a dilemma of how to attach the AC lines to the dimmer in the fireplace side to meet code.

There is not a lot of room in the iron piping so i don't want to use solid wire there. My proposal is to use Stranded THHN 14 awg in the pipe and then transition to NM-B Wire at a junction box just to the side of the pipe flange to the wall. Since the box is a couple inches away the THHN would be "free" in the wall for a few inches, however, I would put braiding or heatshrink over this portion. My question is this, is this up to code? If not, what can I do to connect this that will meet code?

In this renovation I will be removing some portions of the Sheetrock from the wall to add other additional outlets and conduit for HDMI cable in the walls. Then replacing the Sheetrock and putting the Shiplap boards in on top of that. All of this to say, I will have access to the interior of the wall if you have an idea that requires that.

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  • can't put romex in that pipe?
    – Jasen
    Dec 4 '18 at 8:58

The problem with a project like this is that the code doesn't really want you to get creative with line voltage power. That's for good reasons: there are a lot of potential hazards if you go afoul of the code.

The unprotected splice from THHN stranded to NM in the wall is a no-go. You might be able to work something out with a box and cover that work with the pipe floor flange but you probably won't like the way it looks.

If the piping is seen as a home made non-listed light fixture, that's frowned upon. If you look at the piping as a protective sleeve for NM cable - and run NM with jacket in the piping - it might fly, but it would still be in a gray area at best. Then again considering the piping as part of the home's structure - that might fly, but you'll still probably need a box at the fixture.

If an inspector doesn't see it the way you do, you have a headache.

Grounding / bonding the piping is a real issue and screwing that up could create some pretty scary hazards.

There is a simple alternative. If you're going to get creative, get creative with low voltage lighting, the hazards are drastically reduced, and the code requirements reflect this. It goes from fuzzy gray area pain in the butt hurt somebody / start a fire worries, to do just about whatever you want and nobody cares.

  • The splice from THHN to NM is going to be in a junction box as stated above, only a few inches of THHN from the pipe to the box would be in the wall.
    – robogeek78
    Dec 4 '18 at 16:03
  • As far as the pipe, i see that as a conduit for the THHN wire.
    – robogeek78
    Dec 4 '18 at 16:04
  • @robogeek78 - OK so the splice is in the box, that's good; the THHN free passing through the wall finish and a few inches in the wall is non compliant. Dec 4 '18 at 16:17
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    @robogeek78 - I think you need to concentrate on the last paragraph. At your red rectangle/wall box, transition to low voltage (install a 2-gang box with the transformer on the LV side of the box), then go to town lighting up your shelving unit.
    – FreeMan
    Dec 4 '18 at 17:10
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    @FreeMan Yes the problem was finding a LV Edison bulb, But in the end i found one source. I am going with amzn.com/B00AH2OXFE and amzn.com/B077JWFZYQ. These are a Medium base 12V bulb, and a dimmable LED Driver. This should allow me to use CL2 rated Speaker wire to power the LV 12V to the bases. I will put a tag somewhere that tells other people that regular bulbs won't work, but there will be no dangerous voltage anywhere. Believe me I design and build Military 15kW solar power systems, I have a healthy respect for voltage and current, which is why I am asking these questions.
    – robogeek78
    Dec 4 '18 at 17:54

Going with low-voltage wiring is absolutely the way to do this thing. A bunch of nasty complicated code requirements diminisg, and now, useful amounts of lighting are now feasible inside the 55W limit, due to LED. I simply would not pursue a mains voltage solution here.

All use of mains on THHN, every inch, must be in a conduit or raceway wiring method. These are called out on chapter 3 of the Code. Iron pipe bears a close enough resemblance to Rigid conduit that it will match aesthetically and at the fittings. However pipe elbows will not do, you need Rigid curves. And pipe tees won't work either, you'd need conduit bodies so you can access the wire. That's a different look.

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