question on uf-b

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  #1  
Old 03-30-05, 10:36 AM
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question on uf-b

i ran two new lines out to my shed and exterioe pond outlets.followed all the direction and advice given here from you guys and everything worked out great,also read up on more things in wiring simplified....i just got a little confused reading a previous post on sub panel and running wire through conduit.....i ran the 12-2 uf-b cable through metal conduit,cause due to concrete was not able to bury it..is this ok,it is underground wire...i dont have it laying on the ground ,so it wont be laying in puddles of water,and have used all the proper conduit connectors,but im sure its not 100 percent water proof...just want to make sure i didnt do a mistake with the conduit....thanks guys and all your advice is greatly appreciated i was able to do a professional job thanks to you advice...
 
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  #2  
Old 03-30-05, 10:48 AM
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I would not run cable (uf-b, nm, etc.) in a conduit. Why not just pull individual conductors?

Juice
 
  #3  
Old 03-30-05, 10:55 AM
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Technically your installation is not up to code. Code allows cable in conduit for short runs for protection. When the entire run is in conduit then you are to use individual conductors. What constitutes short runs is ambiguous and up to interpretation.

And yes, your cable will be sitting in water. Condensation forms in conduit, and the cable will be sitting in this water.
 
  #4  
Old 03-30-05, 10:56 AM
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i already did run the uf-b...i was better running a black white and green 12 gauage individual wire.. do you think the uf-b will be ok for a month or two ,till i have time to run new seperate wires...
 
  #5  
Old 03-30-05, 11:00 AM
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A follow-up to Racraft's post - underground conduit will always have water in it. It is expected and is considered normal and nothing to worry about. So long as you do not damage any of the conductor insulation this will cause no problems. If you run your conduit downhill toward the house and enter through the basement wall, it will be a problem only because the water will travel down the conduit and enter your panel, causing corrosion and also unsafe working conditions when you have the panel face off.

Juice
 
  #6  
Old 03-30-05, 11:02 AM
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Will it catch on fire or blow up in "a little while"? Probably not. But if electrical work is in violation of the Code, it is technically not OK, even for a little while.

Juice
 
  #7  
Old 03-30-05, 11:49 AM
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I wouldn't lose sleep over it.

Originally Posted by racraft
Technically your installation is not up to code. Code allows cable in conduit for short runs for protection. When the entire run is in conduit then you are to use individual conductors. What constitutes short runs is ambiguous and up to interpretation.

And yes, your cable will be sitting in water. Condensation forms in conduit, and the cable will be sitting in this water.
What article in the NEC states this?

uf-b is rated for wet locations, per the NEC 2002 Article 340.10 Uses Permitted.

Physical protection (conduit) is required if the cable will be exposed to damage.


I'm not an inspector, but I don't see any hazard with your installation.
 

Last edited by thinman; 03-30-05 at 12:07 PM.
  #8  
Old 03-30-05, 12:14 PM
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Technically, running cable in conduit is a violation of the 2002 version of the NEC. However my understanding (not confirmed by direct reading, but by hear-say from an inspector on another forum) is that this particular restriction was not intentional, and that running cable in conduit is acceptable under the 2005 version of the NEC, as long as all other restrictions are met.

Depending upon what version of code has been adopted in your local, your installation may or may not be 'up to code'. If you are in an area under 1999 or 2005 code, you're probably in the clear; under 2002 you are in technical violation, but I'd bet the inspector would pass it.

In addition, even if you are under code that permits cable in conduit, you still have to meet the particular requirements for this installation. In particular, a conduit out of doors on or under the ground will be a wet location. The conductors or cable that you run in this conduit must be rated for wet locations. NM-B is rated for wet locations, so you are okay on this count.

Next, a conduit must be properly sized for the conductors or cables inside it. The general rule is that the total area of the conductors in a conduit must be no more that 40% of the area of the conduit. However there are two exceptions: for two conductors, the limit is 31%, and for 1 conductor the limit is 53% (these exceptions have to do with the ways that wires can snag). In addition, if you are running a cable that is not round, you have to calculate its area as though it were a round cable with a diameter of the _largest_ cable diameter....so a cable that is 5/8"x1/4" is treated as a circular cable 5/8" in diameter for the calculations.

Generally, it is better to run individual wires in conduit rather than cable, since the wires are smaller and easier to pull through the conduit. But I can see situations where the cable will be easier to work with, and other then design preference I don't see a problem with such an installation.

-Jon
 
  #9  
Old 03-30-05, 12:28 PM
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Originally Posted by winnie
Technically, running cable in conduit is a violation of the 2002 version of the NEC. However my understanding (not confirmed by direct reading, but by hear-say from an inspector on another forum) is that this particular restriction was not intentional, and that running cable in conduit is acceptable under the 2005 version of the NEC, as long as all other restrictions are met.-Jon
What article, or articles, in the 2002 NEC confirm this?

I know portable rated cords (SO, SOJ, etc.) are not allowed in conduit.
 
  #10  
Old 03-30-05, 12:30 PM
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Where's the code?

Could someone cite the code (NEC 2005 please) on disallowing UF or NM in conduit for some or all of the run, assuming that the size of the conduit is inceased to accomodate the extra fill of the cable sheath. I've heard this before, but I can't find the code that prohibits it.
 
  #11  
Old 03-30-05, 01:01 PM
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It's a very complicated subject. There is no direct statement one way or the other in the code. All inferences on this subject are indirect. People argue about this for months on end. Some articles seem to suggest that it is okay, and other articles seem to suggest that it is not. I abstain from the argument.

Whether or not you belive that it is allowed or disallowed by code, however, most people agree that it is ill-advised because running THWN is so much better.
 
  #12  
Old 03-30-05, 01:13 PM
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thanks for the replies guys..i have the conduit running down from 2 outdoor outlets,so im not worried about water running through the conduit into my basement...i made a mistake by not asking about the uf-b cable through conduit ...i just figured if it is good enough to be direct buried in the ground ,it would be ok to run it in conduit......the previous home owner just had regular romex running exposed behind the fence and the retaining wall,and non grounded outlets...so with the advice and help from here i redid the 2 whole lines,and just forgot to verify about the uf-b......i will change it to 3 single 12ga copper conductors black white green.....is there any special single conductor wire i should buy....is there different grades for outside or inside work....thanks again...
 
  #13  
Old 03-30-05, 01:30 PM
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You need wire that is rated THWN. But when you go to the store, you'll find that they only sell THHN. But then if you look closely and read all the fine print, you'll see that the THHN is dual rated both THHN and THWN, so then it's okay.
 
  #14  
Old 03-30-05, 01:31 PM
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Why is THWN so much better?

OK, so why is THWN so much better than say, UF for outdoors, or NM for indoors?

But consider this case. I'm currently designing a house to eventually build. I am planning for the future so that rewiring is made easy. My plan is to build into this house a multitude of RNC running vertically in most walls. Some will be used initially, and some left for future expansion. Those that are used initially can be re-pulled. Their purpose is to avoid fishing wires and cables (for power, signalling, data, radio transmitting, etc ... NM, fiber, cat-6, coax, etc) and make changing things relatively easy. It won't be that much different than an open channel in stud space; the idea is to create a smooth direct pull space that won't have any catches on it and can run from basement to 3rd floor.

So let's say you are adding a new circuit. The RNC runs vertical, but not horizontal. The panel to connect to is 30 feet horizontal from where the lower end. You could just run NM from the panel over to the conduit and straight up the conduit with no junction (just be sure the conduit end has protection on its edge). Or you could run NM to the conduit and put in a junction box to connect between NM and THWNs.

Personally, I want to avoid any unnecessary junctions. And I feel the transition from running along horizontal joists to running vertical in RNC is not sufficient to justify the junction.

At what point does a cavity space in a wall become conduit? If I were to construct the wall with wide (2 inch) smooth circular channels that run the full length with no catches, would it be called conduit? If I bored wide holes down the middle of non-load-bearing beams and stuck them in there to serve as wiring channels, would that now make things worse? So why can't some PVC conduit serve the same purpose?

If I were running conduit all the way from the panel to the load or receptacle, then single conductors would not bother me. But that's not going to be the case.
 
  #15  
Old 03-30-05, 01:54 PM
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On 3/10/05 I looked up the Code on this, and here's what I wrote:

"...notes to the Chapter 9 tables, which specify allowable conduit fill, state that (note 9) "A muliconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have eliptical cross sections (flat oval shape, as type NM is), the cross-sectional area calculation shall be based on the major diameter of the elipse as a circle diameter." It cacks up what Winnie said about calculating the fill, and it answers the question of where in the Code it allows or disallows cable in conduit.

But I still wouldn't do it. (My $0.02)

Juice
 
  #16  
Old 03-30-05, 03:03 PM
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Originally Posted by JuiceHead
...and it answers the question of where in the Code it allows or disallows cable in conduit.Juice

Not quite Juice. Note 9 to the tables only tells you how big a cable will be considered when sizing your conduit. It allows nothing but the ability to calculate.

Originally Posted by Skapare
Could someone cite the code (NEC 2005 please) on disallowing UF or NM in conduit for some or all of the run, assuming that the size of the conduit is inceased to accomodate the extra fill of the cable sheath. I've heard this before, but I can't find the code that prohibits it.
Can't cite an '05 code prohibiting it because there is none. The scenario that you described would be compliant.

Originally Posted by thinman
What article, or articles, in the 2002 NEC confirm this?
The '02 NEC, 3xx.22 section in all of the conduit articles added the following text:

Cables shall be permitted to be installed where such use is permitted by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

Looking in many of the cable articles (AC, NM, UF,) uses permitted section, you'll see that raceways is not mentioned, though in others (MC, TC, MV) it is.

When they updated that section, they unknowingly created the 'technical' violation that winnie spoke of. It wasn't their intention to prohibit these cables in conduit, and for the '05 they actually changed the text that they added in '02 to rectify the discrepancy, instead of changing the cable articles.

The '05 text now reads:

Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
 
  #17  
Old 03-30-05, 03:05 PM
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Originally Posted by lovmy4x4
thanks for the replies guys..i have the conduit running down from 2 outdoor outlets,so im not worried about water running through the conduit into my basement...i made a mistake by not asking about the uf-b cable through conduit ...i just figured if it is good enough to be direct buried in the ground ,it would be ok to run it in conduit......the previous home owner just had regular romex running exposed behind the fence and the retaining wall,and non grounded outlets...so with the advice and help from here i redid the 2 whole lines,and just forgot to verify about the uf-b......i will change it to 3 single 12ga copper conductors black white green.....is there any special single conductor wire i should buy....is there different grades for outside or inside work....thanks again...
Don't change anything and chalk it up to experience.

Per NEC, uf-b conductor insulation is moisture resistant, the same as THWN.

It says in the NEC article for uses permitted: "for use underground, including direct burial in the earth." That tells me you can use conduit.
 

Last edited by thinman; 03-30-05 at 03:19 PM.
  #18  
Old 03-30-05, 03:17 PM
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Nice Work, Bolted Fault!

I didn't think to look under raceways!
 
  #19  
Old 03-31-05, 12:09 AM
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Juice, you cheated. You appear to have quoted note 9 in Chapter 9, but you inserted words that are not in the code. If the words "(flat oval shape, as type NM is)" had actually be in the code as you quoted it, there would not be the debate there is. But those words are not there.

Bolted Fault's post is quite interesting and summarizes the code basis of the debate quite well. I'm glad to see that the 2005 code addresses the confusion (my copy of the 2005 is still on order).
 
  #20  
Old 03-31-05, 06:18 AM
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To John Nelson and to all,

It was not my intent to cheat when I added the words "(flat oval shape, as type NM is)" in parentheses. I hope I did not mislead anyone, But I can understand anyone assuming that this was included in the NEC wording, ver batim, as my supplemental wording was within the quotation marks and since the NEC uses parentheses routinely. I should have used [brackets] instead, which clearly identify the words within them as supplemental information not included in the quote but instead added by the writer using the quote to make his/her point.

In short, the NEC note I quoted did not say "(flat oval shape, as type NM is)".

Sorry for any confusion. John, thank you for keeping me on my toes.

Juice
 
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