Are ten wires always derated @ 50%?

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Re: Are ten wires always derated @ 50%?

Pierre,
Yet those conductors are taking space and keep the other conductors from being able to dissipate heat.
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If the space and heat dissipation from non current carrying conductors is an issue, then why does exception #1 permit an unlimited number(subject to raceway fill rules) of control conductors in the raceway with the power and lighting conductors? In this case only the power and lighting conductors are counted for derating purposes.
Don
 
Re: Are ten wires always derated @ 50%?

First off let me say that I believe this is a very good discussion that may even lead somewhere :cool:


Don
I hope you do not think that I am picking on you, I am making a general statement in my following part of this post.

"I don't think "

- what I tell the "guys" is that if you 'think' the answer is - you really may not know. What has to be said is a positive statement. Such as: control conductors are not counted as per "blah, blah, blah"

example:
"675.5 More Than Three Conductors in a Raceway or
Cable. The signal and control conductors of a raceway or cable shall not be counted for the purpose of derating the conductors as required in 310.15(B)(2)(a)."
 
Re: Are ten wires always derated @ 50%?

"Pierre,

quote:
--------------------------------------------------------------------------------
Yet those conductors are taking space and keep the other conductors from being able to dissipate heat.
--------------------------------------------------------------------------------

If the space and heat dissipation from non current carrying conductors is an issue, then why does exception #1 permit an unlimited number(subject to raceway fill rules) of control conductors in the raceway with the power and lighting conductors? In this case only the power and lighting conductors are counted for derating purposes.
Don "


Good question, of which I do not know the answer.
 
Re: Are ten wires always derated @ 50%?

Pierre,
Was that intentional or an oversight, or something that is to be taken for granted?
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I really don't know, but we have an opportunity to find out. Just submit a proposal that exempts one of the travelers from being counted and then look at the ROP for the panel statement. We would have an answer in July of 2006.
Don
 
Re: Are ten wires always derated @ 50%?

Pierre I think :)

I might as well mention I have been off my feet for the last few days and may be for some more days.....so....you all are stuck with even more frequent posts from me. :D

You all here are much more interesting than anything on TV. :cool:
 
Re: Are ten wires always derated @ 50%?

Bob, I had noticed you were posting during times you're usually not, I thought you were enjoying some vacation days.

I hope you will be up and about soon and what ever has you down is only minor.

Roger
 
Re: Are ten wires always derated @ 50%?

Originally posted by roger:
I hope you will be up and about soon and what ever has you down is only minor.

Roger
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Just some arthritis in my foot, I am on meds and they say I should be back to work Monday.
 
Re: Are ten wires always derated @ 50%?

Bob
As you are aware, we will all do what we can to help you feel better sooner, as we cannot stand more posts - oops... I meant we really hope you will feel better soon. Good Luck, as I cannot imagine much of anything being able tokeep you down !!!


Ahh... the meds - I hope some good stuff ;)

[ September 10, 2005, 10:56 AM: Message edited by: pierre ]
 
Re: Are ten wires always derated @ 50%?

First, the NEC does not have an explicit definition for a "current-carrying conductor." But if it did, I am certain it would define the term somewhere along the lines of, "a conductor that carries current." If I were to have three wires, and if by virtue of the manner in which they are connected it is physically impossible for more than two to be carrying current at any given moment, then I will count the set as having only two "current-carrying conductors."

So as to Bob's question (two feeders in a conduit, interlocked so that only one component can run at a time), my answer is a clear and unequivocal "this is 3, and not 6, current-carrying conductors."

Secondly, it is clear enough that installing more conductors in the same conduit will make it harder, to some degree, for any conductor to dissipate its internally-generated heat. True, but irrelevant. It is for the purposes of facilitating heat dissipation that we are limited to 40% of conduit fill. This is what I mean:
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Situation 1: Three current carrying conductors in a conduit, and no other conductors in that conduit. Total conduit fill is 15%.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Situation 2: Three current carrying conductors in a conduit, and nine other non-current-carrying conductors in that conduit. Total conduit fill is 40%.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">Clearly, in Situation 2, the heat dissipation will not be as effective as in Situation 1. True, but irrelevant, because the heat dissipation will at least be "acceptable" in both Situations.

Like I said at the beginning: 70%.
 
Re: Are ten wires always derated @ 50%?

I have not read even one post of this thread so I should not be making a post. If you would please forgive me just this one time I would like to make a comment based on the thread title.

Are ten wires always derated @ 50%?
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To answer just this part of this thread with out bias of any other post;

My Answer
Personally sometimes instead of taking these conductors at 50% I will just take half of the current rating. I find this works as good as 50% sometimes.

:D :D :D
 
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