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-   -   Is conduit over fill really bad? (http://www.diychatroom.com/f18/conduit-over-fill-really-bad-163281/)

RancherRob 11-13-2012 11:24 PM

Is conduit over fill really bad?
 
According NEC 310.15(B) we can't have more than 3 conductors in a conduit without de-rating. Well the inspector pointed it out at breaker panels but didn't notice that we have another 8 or so places where we have upto 8 cables of 12/2 romex in 2" pvc conduits. The electrician doesn't think we should bother fixing it and says it isn't a problem. If we did fix it, it would probably cost me another few grand and a weeks lost progress on the house so I'm ok leaving it as is as long as there is really NO danger. Can anyone shed some light on whether it is something to really be concerned about or not? The fact the government says 3 or more in any conduit seems ridiculous as many of their codes do but I also don't want to risk a fire or my family being hurt so am looking to your experience and expert advice. Thanks for any help you can provide.

joed 11-13-2012 11:46 PM

You can actually have up to nine wires(not cables) before derating has an effect on the wire size. And only the current carrying wires count.

frenchelectrican 11-14-2012 01:29 AM

Quote:

Originally Posted by RancherRob (Post 1051740)
According NEC 310.15(B) we can't have more than 3 conductors in a conduit without de-rating. Well the inspector pointed it out at breaker panels but didn't notice that we have another 8 or so places where we have upto 8 cables of 12/2 romex in 2" pvc conduits. The electrician doesn't think we should bother fixing it and says it isn't a problem. If we did fix it, it would probably cost me another few grand and a weeks lost progress on the house so I'm ok leaving it as is as long as there is really NO danger. Can anyone shed some light on whether it is something to really be concerned about or not? The fact the government says 3 or more in any conduit seems ridiculous as many of their codes do but I also don't want to risk a fire or my family being hurt so am looking to your experience and expert advice. Thanks for any help you can provide.

The other sticky issue is the length of the 2" conduit if you are more than 24 inches on conduit the derating do count as well so that is the other kicker it will get ya.

For the detating on numbers of conductors ( note : not cable , conductors only ) in the conduit usealy a magic number always 9 current carry conductors not the ground ( green or green/yellow stripe conductors ) and by the way netural if there that DO count as well.

Merci,
Marc

Speedy Petey 11-14-2012 06:56 AM

WHY do you have 8 cables of 12/2 romex in 2" pvc???

RancherRob 11-14-2012 11:37 AM

Quote:

Originally Posted by Speedy Petey (Post 1051813)
WHY do you have 8 cables of 12/2 romex in 2" pvc???

We had some difficult and problematic chases from attic to basement in a 2 story house so thought it would be easier to put in a conduit for the electrician as well as thinking that after sheetrock we could pull another wire in case we forgot something. So it is definitely more than 24"; More like 24'. With 8 cables, given the hot and neutrals it has 16 conductors. I know it is against code. But from a practical side, is there anything dangerous about it? What problems could it cause? What are the chances the heat would build up and cause a fire or something else really bad? I'm looking for real world opinions vs. government code opinions. I don't always do what the government tells me to unless it makes sense :)

Julius793 11-14-2012 12:06 PM

If you don't understand the nec that may be due to the fact that your not an electrician but to think its just the gov trying to dictate how you live your life your an idiot. Now as to derating conductor you can have as many conductors as you like (until it reaches the conduit fill limitation) the thing is you will need to treat these conductors as if they are of a lower ampacity.

J. V. 11-14-2012 12:34 PM

NEC 310.15(b) has absolutely nothing to with conduit fill. That is the wire ampacity chart.

joed 11-14-2012 01:21 PM

Now you are starting to mix two different issues, conduit fill and derating. One has to do with how many wires/cables can fit in a conduit. The other has to do with how many amps a conductor can carry when you bundle it with other conductors.

RancherRob 11-14-2012 01:44 PM

No, I am not an electrician just a lowly HomeOwner. So I don't pretend to understand this stuff. That is why I am asking for help and an explanation. I have the electrical inspector telling me we have too many cables in a conduit and have to de-rate them and the electrician telling me that they are fine and won't be a problem on the conduits the inspector didn't notice. That is why I was inquiring because I have two "experts" telling me different things. I was just looking to confirm or deny what the electrician is telling me from a real world/practical stand point vs. what the code says.
Julias, if my thinking that the government isn't always 100% accurate and correct or doesn't always make laws/code that is in my best interest, makes me an idiot, fine, call me one. Especially if it makes you feel better about yourself. :)
However I've been around long enough and dealt with government laws and codes enough to know that they aren't always right (if not outright wrong) and so that is why I was asking the question. I'm just hoping to get a little practical help from those that know a lot more than me.

r_marcinko 11-14-2012 02:21 PM

Quote:

Originally Posted by Julius793 (Post 1051998)
If you don't understand the nec that may be due to the fact that your not an electrician but to think its just the gov trying to dictate how you live your life your an idiot.

I know I'm new, and I'm sorry, but I 'm gonna say something here: You're the idiot AND a jerk. I'm sure the irony of calling someone else an idiot, while doing it with a gross grammatical error, is completely lost on you. A shame a regular won't call you out for being such an ass.

Julius793 11-14-2012 02:59 PM

Quote:

Originally Posted by RancherRob
The fact the government says 3 or more in any conduit seems ridiculous as many of their codes do.

This was the primary reason for my comment just because you have different people telling you different thing that doesn't make things ridiculous!!

Quote:

Originally Posted by RancherRob
I have the electrical inspector telling me we have too many cables in a conduit and have to de-rate them and the electrician telling me that they are fine and won't be a problem on the conduits the inspector didn't notice. .

What does it mean "on the conduits the inspector didn't notice" ???

tylernt 11-14-2012 03:00 PM

Code aside, from a practical standpoint such an installation would "probably" be safe "most" of the time. It's when you have many high-current devices all running at the same time that heat will build up in the conduit, possibly to the point where things catch on fire.

The heat occurs because even copper, which has excellent conductivity, has measurable resistance. Resistance creates heat in proportion to current. If you're only running a few alarm clocks and compact fluorescent light bulbs on all those bundled wires, the effect is negligible. Fire up the whirlpool tub, window A/C, space heater, blow dryer etc and it's a whole different story. Maybe you'll never use window A/C, space heaters, or a whirlpool tub, but the next owners might, and they have the right to safe, adequate, and code-compliant wiring in their new-to-them home. That's why we have building codes and inspections: to protect the next poor slob in line.

So. Since this is all 12/2 Romex, can you just change out all your 20A breakers to 15A and meet code by de-rating those 20A circuits by 75%? The electrician shouldn't even bill you for new breakers because he can use the 20A ones on another job.

Note, in addition to ampacity de-rating, I think you also need to treat Romex as a round cable with a diameter equal to the Romex's widest point. So though you may meet the ampacity requirements by de-rating, you may still be overstuffed physically. If that is the case, especially if drywall is not up yet, just drill holes adjacent to the existing conduits and run a second conduit alongside each. Now you only have 8 conductors per conduit and don't need to de-rate. And your physical fill is cut in half also. You'll have to pull and refish half of the cables, but they'll hopefully be long enough to avoid splicing (maybe a short pigtail in the breaker panel).

jbfan 11-14-2012 03:09 PM

If the inspector can cite a code violation, and the electrician chooses to ignore it, you are the one to suffer.
The inspector will not pass the inspection, therefore no electricity.

Your electrician should fix any and all code violations (that are valid violations) free.

tylernt 11-14-2012 03:13 PM

Quote:

Originally Posted by jbfan (Post 1052089)
Your electrician should fix any and all code violations (that are valid violations) free.

Indeed, that should be in your written contract (you do have one, right)?

Julius793 11-14-2012 03:21 PM

Quote:

Originally Posted by tylernt
Since this is all 12/2 Romex, can you just change out all your 20A breakers to 15A and meet code by de-rating those 20A circuits by 75%? The electrician shouldn't even bill you for new breakers because he can use the 20A ones on another job.

If he has 8 set of Romex that would be 16 CCC and the derating would be at 50%. And the electrician shouldn't charge because he can use the breakers somewhere else?


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