Can't find code re. Romex inside conduit

[HITCH-]

I need some help,
I can't find NC code on running romex inside conduit. I know that it is not typically done but it is not against code to do it. I already own the romex so in this instance it makes sense.
I would like to run (2) 14-2 circuits and (1)12-2 circuit. The first question is if all 3 circuits can be in the same conduit. In Maryland you were not allowed more than 2 circuits in any one conduit.
Second question is what size conduit is required.
Does anyone know where I can find the information on the correct conduit size?
Thanks for your help

 

[marinosr]

Your conduit would need to be 1" conduit.

NEC specifies that, for 3 or more conductors in a conduit, the maximum fill area must not exceed 40% of the total conduit cross-sectional area.

When running Romex in conduit, this is how you calculate the area: "(9) A multiconductor cable, optical fiber cable or flexible cord of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter"

14/2 has an approximate width of .6", 1/2 has approx width of .75" (slight margin of safety on both those measurements).

2* (.6/2)^2*pi + 1*(.75/2)^2*pi = 1.01" of fill

1^2*pi * 40% = 1.26 in^2 max fill in 1" conduit, so you're OK.

.75^2*pi * .4 = 0.71 in^2, so 0.75" conduit is too small.

My two cents, running NM in conduit is never worth the cost savings. It's such a pain in the ass.

In Maryland you were not allowed more than 2 circuits in any one conduit.

That's not correct. It's dependent on conduit size. Large commercial/industrial settings will have many branches running in one large conduit.

 

[HITCH-]

Thanks Richard,
I only have 2 right angles involved, and I can run the romex through the conduit before fastening it to the wall and ceiling.
It will run from the center of the back shop wall 3ft up to the ceiling, then 10 ft to the center of the ceiling to a junction box. From there it will be branch off 10ft in each direction to the center of the side walls of the shop, and then drop down each wall.

The situation in MD was that there was a conduit that ran from the breaker box in the basement through a bulkhead out of the house, under the deck and into the shop. That had a 12-2 circuit in it and a coax TV cable. I had an electrician run a line through there to put a 100amp panel in the shop. He said that there could be no more than 2 circuits in there so he had to remove the coax line.

 

[marinosr]

I'm sorry, the math above is wrong! Specifically in computing the areas of the conduit, I forgot to divide the diameter of the conduit in half to get the radius.

You would need to use 2" conduit in order to run three romex cables. (2/2)^2*pi * 40% = 1.26 in^2 max fill in 2" conduit

 

[Gofor]

Here in NC, you may get into a discussion with any permit inspector when running romex in conduit. Depends on the inspector, but you may have to prove your case to the next higher AHJ (Authority Having Jurisdiction), which would be the inspector's boss, then his boss, up to the Insurance Commissioner. As for NC Code, it basically is the NFPA code, although there may be a few exceptions.

 

[Oka]

Generally speaking romex is not allowed in any conduit. I usually cut the outer sheathing off then adapt into conduit. If it is a short run like 5 ft

or so you can use a connector with rubber compression to convert into a conduit directly. If it is a longer run then terminate at a box then cover to conduit and regular wire

 

[HITCH-]

Generally speaking romex is not allowed in any conduit. I usually cut the outer sheathing off then adapt into conduit. If it is a short run like 5 ft

Casey, I can't find anything in the code that says you can't run romex in conduit. I did find where it says that you are required to run romex in conduit in areas where it needs to be protected.
I belive that I also read that it is against code to remove the outer sheath from romex and use it in any kind of circuit. I belive that this is because there are no markings on the individual wires with their ratings.

If I didn't already have a couple hundred feet of romex on hand it would be a moot point and I would be using THHN.

I found another calculation online that said that the size of the conduit for 3 conductors would be 274% the diameter of the conductors. If the romex is 0.60" - 0 75"dia. then 2" conduit would be large enough at 40% fill, as Richard calculated.

 

[Oka]

Yeah, I know of those but most inspectors aren't willing to agree to it. Generally if you need to sleeve under a slab they will allow provided it is a 1.5"for one 12/2 or 12/3romex. But, the amount of friction you get from the AHJ (authorities having jurisdiction) , generally not worth the hassle.

BTW Most Romex is THHN rated wire. Conduit is also expensive now

 

[Gofor]

The reason for not running romex in conduit is heat build up.

 

[chris_goris]

At the risk of sounding snarky, you wont find it here either. Id start at my local codes enforcement office, theyre typically alot of help.

 

[HITCH-]

So Richard's calculation is correct and I would need 2" diameter conduit.
Casey is also correct that conduit is expensive.

It looks I can run THHN in EMT for less cost than the 2" conduit would be. I can strip the Romex and get the ground wire out of there to save some money.

 

[Gotcha6]

IIRC, the term used by the Inspectors is 'double raceway', since the Romex itself is considered a complete assembly when used in approved locations. Why not just set the Romex aside for a future use? I'm sure you'll find one. Also, I've pulled stripped Romex through 1/2" PVC conduit before, and the THW inner jacket on mine made it very difficult. THHN wire usually doesn't even require pulling soap because of the poly outer jacket.