ECN Forum Forums Code Related Discussion NEC & other Code issues Table 310.15(B)(6)

This question comes up allot on these forums! The answer is NO; you cannot use that table for subpanels. The NEC does a TERRIBLE job of defining this situation. Buy "Electrical Wiring Residential (14th edition)" from this site's bookstore if you want some clarification.

The "(S)" and the “feeders” in the code pertain to certain specific situations. I'll give two examples. If you had a 320A meter socket feeding a large house, you could use that residential table to size the wires feeding from the meter to both a 200A and a 100A panel inside the home (two panels, hence the “(s)”). Also, imagine your service entrance conductors first terminate in a fused disconnect at the closest point inside the house. Then a single “feeder” left that disconnect and went some distance away to a panelboard (so that the wire ran inside the home was fused). In this case, both the S.E.C. and the feeder could be sized using 310.15(B)(6).

Some people will dispute my claim that the aforementioned table cannot be used for subpanels. However, nobody has ever been able to site a source that backs up his or her side of the issue. The last time this topic was raised, I practically begged the "opposition" to provide the name of an outside resource that substantiates their view. Nobody could. They were all just making their own interpretation of that VERY ambiguous part of the code (one of many such parts).

I would very much like to use table 310.15 (B)(6) for residential subpanels. Therefore, I’d like to offer $50 to anyone that can give me proof that this can be done. Provide me with a RELIABLE source that contradicts the one I already have. If the source you give me is extremely detailed, I will make it $100. No tricks or oddball cases. My offer applies to the average residential subpanel fed from the average residential main panel.

Let’s see it!

Peter, seriously, you must forget the article 100 definition of "FEEDER" and in this case, use the definition in 310.15(B)(6).

Roger

Triple no offense but what makes your interpretation more correct than others?

200 amp service, the service entrance conductors 2/0 cu are sized by 310.15(B)(6) now I add a 200 amp sub panel.

I will use 2/0 cu right?



[This message has been edited by iwire (edited 04-08-2004).]

will that be Paypal?

Iwire, I provided a source. I am not just giving my opinion. Please provide your source (if yours differs from mine). I am definitely not trying to say that I am better at interpreting the NEC than anyone else. I leave the difficult interpretations up to well-known, published experts. I realize that such people can also be wrong but their opinions hold far more weight, than those of the average electrician posting on a forum.

I want to reiterate that I do not consider myself to be an expert in any realm. However, I do rely on the "expert" view of those published few (relatively) to provide some degree of analysis since the codebook itself is far too vague.

Please people; do not dance around the issue yet again. If subpanels can be fed using 310.15(B)(6) then surely there is a book written by SOMEBODY, SOMEWHERE that says so. Give me the name of this book.

Triple I do not know the answer to this question.

My only point is that whatever book you are reading or whatever book I might find to support the other side is not the NEC so it is not an official interpretation, it is just the authors [options] edit opinions.

Their opinions must be based on the same confusing wording that you and I read.

The only true interpretation as to come from the NFPA or in some States the local AHJ.



[This message has been edited by iwire (edited 04-08-2004).]

Tripple, you and I agree with the jest of this thread, but at the risk of offending some "published experts", I don't agree with your statement
I don't agree!

Now, I do agree with Iwire here, .

With all this agreeing and disagreeing the published people aren't very convincing. .

Roger

Iwire, if you reread my posts slowly you will see that I also agree that anything from an outside source is only the author's opinion. Also, I provide a specific source to back me up, not just "whatever book". There are over 6 billion people in this World so surely there must be at least one, well-known, published writer that supports the use of that table for subpanels if indeed it can be done. If no "expert" is willing to write it down, then how could it possibly be true?

I have to believe that the code writers know EXACTLY what that table pertains to. Thus, there has to be an exact and precise answer to this question. We are not talking about a subject as wide open as "what is the meaning of life". The code is not meant to be a book of riddles even if is can sometimes seem that way. The code is written by humans (not passed down by God on stone tablets) so its meaning is known PRECISELY by those that write it. If it was not then my life and work are based on a myth!


[This message has been edited by triple (edited 04-08-2004).]

All I am saying triple is you gotta go to the source if you want the real answer.


Of course the CMP knows what they mean, but you can not get that info from any outside source, it must come from the correct agency.

Do you know that if someone here at the forum was a member of a code making panel that they would have to put a disclaimer up that says that their post is their opinion and not that of the NFPA, this would even be true if the person literally wrote the words in question.

Of course another way to handle this would be to use a screen name instead of their real name.

Roger, the forum members here could possibly run the gamete from having never run a wire in their life to being an electrician studying the code for 60 years. The average person could be someone that can only squeak by on his or her state Journeyman test. Can you honestly say that this person's interpretation of a part of the code will hold as much or more weight than a published writer selling books on the same site you moderate? If a moderator is publicly stating that the books sold on this site have that little merit then I definitely want my money back!

I'm just jerking you around. I realize, as a moderator, you probably feel compelled to stand behind fellow members. I'm not trying to put anybody down, as I don't feel I am any more knowledgeable than the "average" forum user. Unlike the average person though, I don't rely on my own guesses and accept them as fact.


[This message has been edited by triple (edited 04-10-2004).]