ECN Forum Forums Code Related Discussion NEC & other Code issues Is the interior of a conduit a wet location?

A difference of opinion has come up in my local area as to whether NM cable can be installed in a conduit sleeve on the outside of a building - or must it be UF?

Assuming that the conduit system is installed to be raintight what are the opinions on this situation?

Bill, my OPINION is that the conductors should be rated for wet location. (Frank) cinkerf

Frank,

Is UF (sleeved in conduit) used in your area to run from a panel up the side of a House to the attic? If NM cable has, by construction, an overall jacket (unbroken) that is moisture resistant and the conduit as run is arranged to drain would you think this was an acceptable practice?

i don't believe the conduit is considered a wet location. Maybe damp,but, not wet. We run thhn in conduit every day out side. You might call your local inspector if there is an inspection, however I believe it to be o.k.

Bill,
UF cable in conduit run up the side of house to attic is a common and acceptable practice. I have no problem with regular NM cable (romex) either. As you mentioned, the overall jacket is moisture resistant. Obviously, the UF cable would be my first choice. However, I couldn't imagine an Inspector rejecting the regular NM cable.

pip,
THHN conductors are usually "dual" rated THHN / THWN. THWN is rated for wet locations per section 310.8(c)(2). As you pointed out, it's always best to check with your local Inspector.


(Frank) cinkerf

Frank,

In our Area there are a number of Agencies approved for Electrical Inspection Services. Is this common elsewhere?

It seems that one of the Agencies is requiring that UF be used when sleeved inside any conduit in outside locations. I do not have any details if it is without exception. Obviously someone that wishes to use NM could always go to one of the other Agencies for Approval. I was just wondering if UF was required in any other Locations around the Country?

Bill,

We have one AHJ within our major City. Beyond the City limits there are several other Electrical Inspection Agencies that I'm aware of.

TECHNICALLY, UF cable, not regular NM cable is required within conduit in outside locations. The justification is that the outside location is considered a wet location. (At least in my area) However, as I mentioned in my previous post, the use of NM cable in this application is commonly accepted and approved.

(Frank) cinkerf

You may have a topic that has a difference between it's "code" and "practical" applications here...it happens......I am told there are instances were I will not be compliant no matter what....

Sparky,
There is always the possibility that a group of Inspectors will have a difference of opinion on a particular code item even if they all work for the same Electrical Inspection Agency. Unless the Agency, as a whole, requires a certain code rule to be enforced 100% the Electrical Inspector has the authority to exercise section 90.4 providing "effective safety is maintained".
I'm personally grateful our Industry has such a professional, well respected document as the NEC. Taking time to study the code and ask questions is time well spent.

(Frank) cinkerf

No flames here, many times i'm glad to have the AHJ make the call! Here's a good example pertinent to this thread
I do many underground services, no matter how well i clean & glue the pvc, it'll take on water, i've never seen an underground run stay dry, even though it could technically be called "dry"
So i simply install URD direct burial in pipe, assuming that, given frost, expansion etc., that it will be wet.
Another good one is a gas station job, in which there were many runs of rigid. One of the larger runs which came up out of the ground and ran along the building , had to have a special "wick" fitting. This wrench tight assembly, which could have been submerged for all of me, needed to have a way to rid itself of condensation accumulated within itself. I really never even knew of the latter gizmo, i'll just say it sure pays to do some asking