ECN Forum
Posted By: leland wet location - 12/27/09 05:29 AM
Brain block and too lazy to look right now (sorry).
Now I know NM is not rated for 'WET' location,but ok for Damp.
I also understand anything in conduit under ground is 'wet'.

So to the point: IF I run NM across an open ceiling (not allowed above a drop ceiling),poke thru the out side wall with PVC,LB down into a bell box with a WR GFCI and an 'in use' cover.

Is that cool? Commercial application.
Posted By: Jim M Re: wet location - 12/27/09 05:43 AM
Most seem to consider NM into the back of a disco or box ok. Running it thru a LB is not ok. You would need to switch wiring methods at the plane of the wall.
Posted By: leland Re: wet location - 12/27/09 05:45 AM
So if I install a change over connector,is that good?
Posted By: gfretwell Re: wet location - 12/27/09 06:11 AM
Why not just use UF?
Posted By: leland Re: wet location - 12/27/09 07:03 AM
mechanical protection Greg.

Install-
Straight from panel to outside wall location.With NM, all interior.
Now I drill a 1" hole from out side in,sleeve a piece of 1/2 pvc,inside out/mount an LB and drop down to the WP box.
The NM just slides in the conduit,thru the LB and terminates on the WR GFCI rec.

IMO,the conduit is a sleeve. BUT... Is it a wet location?
Posted By: gfretwell Re: wet location - 12/27/09 08:01 AM
It is certainly a wet location but UF will go anywhere NM will go plus being OK "wet". (run in in your RNC sleeve) If PP is important, pipe it all the way and use THWN.
Posted By: Niko Re: wet location - 12/29/09 06:36 AM
334.10(A)(1) states that the NM cable can be installed in NORMALLY DRY location. woudn't you agree that the interior of LB is NORMALLY DRY location? depending on the location, i can't think of any immediate time that i have opened a LB cover and it was wet inside.

Besides i think sometimes it is O.K. to not follow the code verbatim, and make some exception, because I know from experience that it will be a safe installation. just like leland's installation.
Of course it all depends on the AHJ.
Posted By: gfretwell Re: wet location - 12/29/09 08:33 AM
I suppose the AHJ makes the rules but article 100 says wet locations are "... unprotected locations exposed to weather".
In 2008 they also removed the confusion about above grade wet location raceways
Quote
300.9 Raceways in Wet Locations Above Grade.
Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall comply with 310.8(C).


Posted By: HotLine1 Re: wet location - 12/29/09 02:28 PM
Le:
Your proposed install would get another 'nay' from me.
Posted By: renosteinke Re: wet location - 12/29/09 03:59 PM
Please note that the latest code edition goes so far as to ban the use of ordinary NM in even damp locations. On another forum, home inspectors are even being urged to call out crawl space NM runs as being contrary to the NEC.

I don't say I agree with this - but that's the way the code reads. First they tell you that NM allowed in damp locations ... then a few paragraphs later tell you that NM-B, the stuff we actually use, can't go into even damp areas.

The law has a principle of not entertaining petty claims. It frowns upon $1 lawsuits and 1mph speeding tickets, for example. There's even a fancy latin name for this principle.
What I'm getting at is that I would not fault an installation that had a transition to a 'proper' wiring method as soon as possible, after entering a different environment.

NM ("Romex") is an amazing material. First they expand its' use, pointing to 70+ years of use as proof that it is safe. Then they tell us we can't put it in the one place where most of it goes (crawl spaces) and require us to use AFCI's to protect it. They tell manufacturers they have to use 'wet location' conductors (Thhn/Thwn) then tell us it can't even be in damp locations.

I can't speak for anyone else, but I'm confused!
Posted By: Jim M Re: wet location - 12/29/09 07:37 PM
Originally Posted by gfretwell
I suppose the AHJ makes the rules but article 100 says wet locations are "... unprotected locations exposed to weather".
In 2008 they also removed the confusion about above grade wet location raceways


I can think of one place near here that interpreted NM outside as ok in a conduit sleeve. Seems that changed the "unprotected" into "protected" and made everything OK. Sure that wasn't the intent but I can see how they came up with that.
Posted By: gfretwell Re: wet location - 12/29/09 09:37 PM
From what I read the problem is the paper packing in the NM. It can wick water. I am not sure why they still have the paper in there in the first place. I suppose it is just so they can sell UF for more money and make you carry two products. That is really 3 products if you include "damp" rated NM-c but I have never seen that. When you look for NM-c on the web sites for the manufacturers you get routed to UF
Posted By: Niko Re: wet location - 12/30/09 09:53 AM
Does anyone know what type of insulation the individual conductors have?
I will contact southwire tomorrow.
Posted By: HotLine1 Re: wet location - 12/30/09 02:20 PM
Can't say that I ever seen an insulation ID on the conductors within NM cable. IMHO, appears to be THHN, without the outer clear nylon.

Posted By: Niko Re: wet location - 12/30/09 05:31 PM
From Southwire application engineer

"The conductors inside of our Romex products are listed as THHN only. You are correct in the statement that most conductors are multi rated. Romex is listed as a complete product and the conductors SHALL NOT be used with out the outer jacket. It can only be used as Romex and where Romex is approved for use by the NEC."
Posted By: gfretwell Re: wet location - 12/30/09 07:08 PM
I do think the practice is incongruous in the way it applies "wet" and "dry" at the face of an exterior wall. It is OK to terminate RX in the canopy of an exterior light if the box is recessed in the wall but if you extend this wire through a short sleeve on the exterior wall it is "wet/damp".
I have seen differing opinions about a surface mounted box fed directly through the wall.
It doesn't really matter if this is an insulation issue or a "paper in the jacket" issue, it will still be present in the canopy of that outside light but everyone says the RX is OK there.
I don't understand it but that is the accepted interpretation.
Posted By: George Little Re: wet location - 12/30/09 08:56 PM
Contrary to the statement by the Southwire Engineer, there is nothing in the files that says that the conductors inside NM cable are THHN. It only says that the conductors are rated for 90°
Greg I agree with you on your attitude on wet locations and feeding the fixtures etc. that have the stub out directly into the boxes.
Posted By: Jim M Re: wet location - 12/31/09 03:20 AM
George, are you saying that you believe that UF should be run from the switch to the fixture box or just that there seems to be a potential conflict with the Code when using NM into the back of the box?
Posted By: watersparkfalls Re: wet location - 12/31/09 07:03 AM
I agree Reno, romex also has seen a wider privilege of use. So which is it good enough or hazardous? Here in my jurisdiction most inspectors will allow minimal footage of romex in damp/wet locations (just don't push the limit i.e. half the distance of total run).
Posted By: gfretwell Re: wet location - 12/31/09 08:39 AM
From what see, the criteria is you can't have the RX jacket on the wet side of the wall. IE you can have a pancake on the wall with the conductors sticking out and it is OK. Just don't come out the wall with RX and go somewhere.
Posted By: leland Re: wet location - 12/31/09 04:01 PM
Interesting dialog.
Many angles appear when you get to "Interpret".
Almost becomes fun!

As far as the 'wip to the fixture/rec- I can see them (CMP) requireing UF or LT some day.


Thanx!
Any way: i just boxed it inside and changed to PVC down.
That should make all pleased. smile
Posted By: HotLine1 Re: wet location - 12/31/09 07:00 PM
NM in sealtite for AC Cu units shows up on occasion; the re-inspect on occasion is the 'skinned' NM in the sealtite; the re-re-inspect usually is THHN/THWN.

NM in PVC shows up on occasion also with similar results as above.

Posted By: gfretwell Re: wet location - 12/31/09 08:09 PM
I was lucky that 99% of the inspecting I did was commercial so I didn't see much Romex. I failed the first RX job I saw (physical protection problems < 1.25" from framing) They ended up sleeving in in EMT after some protesting about "how they do it up north".
Posted By: renosteinke Re: wet location - 12/31/09 09:10 PM
Sticking to the point: I don't have an issue with 'de minimus' use of romex in what are nominally wet locations; entering the base of the light next to your front door being a good example.

That's my problem with those who take the code as far as they can. We've all seen wires that were spliced using a twist, solder, and tape; can anyone document just what exactly makes this an 'approved' means? Or, for that matter, where placing a wire nut over twisted wires is officially endorsed?

Drifitng off point ... ever notice that most folks on the road treat the speed limit as though it were a requirement to drive at that speed? That there is something 'wrong' about doint 35 in a 40 zone?

Well, the same psychology applies to electric work as well. Romex had, until recently, been regarded as a very limited wiring method, to be used only in certain circumstances. It was clear to all that it was intended only for stick-framed single family homes.
I'm not making this up, either. Metal studs didn't exist until the 70's, and the code limited romex to buildings three stories or less. For those unaware, three stories is as high as you can go using wood ballon-framing as the structural supports. (Trivia: Cement blocks can only go 5 stories). That code restriction was a major hint as to the intended uses of romex.

A few cycles back (was it 99?) we re-worded this part of the NEC, substituting fire-rated construction classes in place of the previous restriction. Voila! Suddenly romex was allowed for use in commercial buildings.

So, now we are faced with an attitude that romex is the 'default' wiring method, with other methods used only as a last resort - and all manner of methods used to remain with romex, to 'push the envelope.' We're also seeing romex used more with steel studs, a circumstance for which it was never intended - and, IMO, for which bushings are a poor adaptation. (Ever try to mount a plastic nail-on box to a steel stud?)

IMO, the use of romex has drifted far from its' intended course, in part because of changes in the way we make things. Sad to say, there are many electricians who have not worked with any other wiring method. (Scary, but true!) What was meant as a way to make tract homes has crabbed into every corner of construction. I think the entire NEC article needs a substantial review.
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