romex inside conduit

[Jim Baird]

As I've mentioned before, I farm my services to more than one small AHJ in my area part time, so, some days I am the muni.

Local electrician called this AM to run by me his help's installation of a two-inch conduit to gather and contain a number of branch circuit wires that pass up and/or below ceiling/floor from panel. This instead of bundling and shoving thru a two inch or so hole in plates.

The only issue I know of with romex in conduit is fill limits on conductors in conduit, which he acknowledged, but reasoned that the romex sheathing offers some separation and noted that in residential many circuits go most of the time with virtually no load.

I told him his thinking makes sense to me, and that I would not flag the technical violation made by the use.

Opinions?

[Jim Port]

Sleeving cables into a conduit is allowed under certain conditions. The panel must be surface mounted and the sleeve must enter the top of the panel. I will look for the rest later.

from 312.5

© Cables. Where cable is used, each cable shall be secured

to the cabinet, cutout box, or meter socket enclosure.

Exception: Cables with entirely nonmetallic sheaths shall

be permitted to enter the top of a surface-mounted enclosure

through one or more nonflexible raceways not less

than 450 mm (18 in.) and not more than 3.0 m (10 ft) in

length, provided all of the following conditions are met:

(a) Each cable is fastened within 300 mm (12 in.),

measured along the sheath, of the outer end of the raceway.

(b) The raceway extends directly above the enclosure

and does not penetrate a structural ceiling.

© A fitting is provided on each end of the raceway to

protect the cable(s) from abrasion and the fittings remain

accessible after installation.

(d) The raceway is sealed or plugged at the outer end

using approved means so as to prevent access to the enclosure

through the raceway.

(e) The cable sheath is continuous through the raceway

and extends into the enclosure beyond the fitting not

less than 6 mm (1#8260;4 in.).

(f) The raceway is fastened at its outer end and at

other points in accordance with the applicable article.

(g) Where installed as conduit or tubing, the allowable

cable fill does not exceed that permitted for complete conduit

or tubing systems by Table 1 of Chapter 9 of this Code

and all applicable notes thereto.

[Jim Katen]

What Jim Port said.

Though there are two things about that section that I've never understood. One is that the conduit is required to be *at least* 18" long - why? Another is that you can run a conduit above the panel but not below it. Someday, I'd like to hear the logic behind those.

As for derating, it really doesn't matter whether or not the application is residential or not. There's 24" of grace. After that, you're supposed to derate per Table 310.15(B)(2)(a). With romex, you can usually get away with up to 9 current carrying conductors before the derating falls below the Romex's initial ampacity.

[Douglas Hansen]

The rule on protection where entering a panel was new to article 312 in 2002. It is a very specific case that is an exception to the basic rule that each cable be secured to the panel.

NM cable and other types of cable are allowed to be pulled through raceways as long as they meet the fill requirements. You could pull romex through EMT all through your house if you were so inclined. It isn't prohibited by the rules for NM or for EMT. Note 9 to Table 1 in chapter 9 tells us to count the multiconductor cable as a single conductor for fill purposes (not for derating) and to use the long dimension on elliptical cables.

[plummen]

Run an extra piece of pvc to split the home-runs up coming back into the panel

[jclint05]

What about section 300.17?

[Marc]

"Does not penetrate a structural ceiling". If you bundle cables thru a hole in the top plates of a wall which is supporting ceiling joists, that would be penetrating a structural ceiling, would it?

Marc

[Jim Katen]

What about section 300.17?

It says you can't overfill conduit. What about it?

[jclint05]

It says to limit number & size of conductors in raceways for what should be obvious reasons. As I understand, that includes nipples.

[Jim Katen]

It says to limit number & size of conductors in raceways for what should be obvious reasons. As I understand, that includes nipples.

Sorry, I'm missing your point. What aspect of conduit fill have we not addressed so far in this thread?