Wire size for 100 amp sub panel?

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  #41  
Old 05-17-01, 03:40 AM
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Hi Bill;
yes it's me, Sparky....my illiteracy has given me away!
Thank you for fixing that, i'll try your advice next post..

Virgil;
more like pulling hair! the 3-wire deal means the X-former 240/120 ok for residential....so if you had a 3 ph residence you can't use 310-15(b)(6)

boy, this issue is burnin' up a whole lotta cyberspace!

 
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  #42  
Old 05-17-01, 05:20 AM
s1nuber
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I hope the fish were biting for ya, WG.

I do not doubt the lighting & appliance panelboard requirement. That is not my question at all. My point hinges on the contention that 'main service disconnect' is a specific term. The NEC does not include the enclosure or all of the service equipment when 'main service disconnect' is used. A main service disconnect will disconnect utility power when turned off. The 100amp feeder breaker in the above example does not do this, it disconnects power to the feeder. This breaker is still inside of the service equipment, as well as the main service disconnect enclosure, but it is not a main service disconnect. If the source of power to the feeder in question is not a main service disconnect (even though it feeds a lighting & appliance panelboard), it does not meet the definition of 'main power feeder' in 310-15(b)(6). This means the feeder must be sized by 310-16, as it is not a main power feeder by NEC definition.

If the term 'main service disconnect' is interpreted to mean 'main service disconnect enclosure', then any feeder that originates at the service equipment, and supplies a lighting & appliance panelboard, would be a 'main power feeder'. I just think that if that is what the NEC meant, that is what they would have printed in 310-15(b)(6).

Enjoy your day!





 
  #43  
Old 05-17-01, 06:22 AM
resqcapt19
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The word do not say "connected to the main disconenct", they say "between the main disconnect".
don(resqcapt19)
 
  #44  
Old 05-17-01, 06:23 AM
resqcapt19
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The words do not say "connected to the main disconenct", they say "between the main disconnect".
don(resqcapt19)
 
  #45  
Old 05-17-01, 05:00 PM
Wgoodrich
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s1nuber

Read carefully just this sentence;

For application of this section, the main power feeder shall be the FEEDER[S] BETWEEN THE MAIN DISCONNECT AND THE LIGHTING AND APPLIANCE BRANCH-CIRCUIT PANELBOARD[S],


Now read carefully just this sentence;

and the feeder conductors to a dwelling unit shall not be required to be larger than their service-entrance conductors.


Think in detail what those two sentences said explicitly making sure you see the words BETWEEN THE MAIN DISCONNECT AND THE LIGHTING, ETC.

Now go back to your Code book and confirm those words are in that opening statement of 310-15-B-6.

Can you see what we are trying to point out, now ?

Hope this helps

Wg
 
  #46  
Old 05-17-01, 07:25 PM
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Warren, Don...
we are getting into some heavy linguistics here, which is probably the true root of the problem as seen in the ROP's.

I do not know of past changes, but i do see pending ones focusing on the grammar, even the punctuation!, has this been the case in past cycles???
 
  #47  
Old 05-17-01, 08:32 PM
resqcapt19
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The premise of the reduced wire size for "main power
feeder(s)" in dwelling units is load diversity. In my opinion all lighting and appliance branch circuit panels in a dwelling unit will have similar load diversity and the wire sizes in Table 310-15(b)(6) can be applied to the feeders for these panels.
Don(resqcapt19)
 
  #48  
Old 05-18-01, 05:10 AM
s1nuber
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I definitely see the other side of the arguement. I'm just not sure that I agree with it. If we follow the logic of just being between the main disconnect and the panelboard, what feeder is excluded from meeting 310-15(b)(6) requirements? All feeders are inherently between the main service disconnect and a panelboard in a residence, regardless of how it is wired.

So again I ask, why go to the trouble of creating and defining the term 'main power feeder', if it can be applied to any lighting and appliance panelboard feeder? Why not just say 'panelboard feeder'? It makes no sense to go to all of that trouble for no gain.

I think that I am starting to repeat myself, so maybe this thread is dead. I do enjoy these hypertechnical discussions, as they force me to re-evaluate my opinions. I don't think the regular Joe enjoys them, as they just want an answer: What size wire?

Enjoy your day!
 
  #49  
Old 05-18-01, 05:23 AM
s1nuber
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Don - I difinitely see what you are saying. I just think (from the NEC's increasing restriction of 310-15) that the NEC is trying to reduce/eliminate the practice. The funny thing is, I agree entirely with what you are saying as far as theory. I just think the code no longer allows it to be done, so I won't install feeders the old way.

Enjoy your day!
 
  #50  
Old 05-18-01, 08:26 AM
resqcapt19
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I think the only "correct" answer to this question is the response from your local AHJ, or a formal intrepretation from the NFPA.
don(resqcapt19)
 
  #51  
Old 05-18-01, 09:43 AM
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Wink Wire size for 100 amp sub panel.

Read article 215-2(d).
 
  #52  
Old 05-18-01, 10:32 AM
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Interesting chat. Wg, I just want to say that I did miss you, thought you'd been dating heavily or something. Also want you to bite your tongue for saying you are un-needed in any way. You bring a very valuable dimension to this forum and are definitely a factor in its overall character. Glad you enjoyed your fishin'.

Wirenuts, do you mean the "sprky" that disappeared from here a couple months back? The guy who misspelled durn near every word he wrote? You're THAT Sparky?

Juice

[Edited by JuiceHead on 05-18-01 at 01:38]
 
  #53  
Old 05-18-01, 01:56 PM
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JUice,
second that vote , i have learned much from you wg, and usually look for threads your involved in, keep up the good work!

juice, i go by sparky in the EC BB @
http://electrical-contractor.net/cgi...timate.cgi?...

good people, good advice, good chat etc....

 
  #54  
Old 05-18-01, 03:49 PM
Wgoodrich
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Juice, fish weren't biting that strong but had a great time anyway. Not been on heavy dating though am considering exercise and crash diet to go womanizing again. Got dumped a couple of weeks ago, said my nose was on the internet too much, go figure. Think I am getting too old to chase anymore, should stick with electrical, make less mistakes that way. Maybe that was why I went fishing, never know for sure though.

By the way I believe Thinman entered the 310-15-b-6 question on the IAEI forum. Maybe we can get some stronger knowledge on the subject there.

Good Luck

Wg
 
  #55  
Old 05-19-01, 07:10 AM
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S1Nuber,

I appreciate your comment that the regular Joe possibly doesn't appreciate the "hypertechnical" discussions we have in here sometimes. But I do believe s/he reads them, comprehends what s/he can, and takes the opinion that s/he most believes is the case. Or asks the question differently, or bags it and calls their favorite electrician believing electricity must obviosly be over their heads if they don't understand these discussions. Which may be true, may be to their benefit, or occasionally may cause us to lose somebody who may have had the capability to otherwise hang on and do the work safely and correctly if we hadn't messed with their brain.

At any rate, if their work is inspected, as I believe all of us would encourage, they'll find out soon enough what their local AHJ interprets the Code to mean, and either approves the work or has them "correct" it to comply ith their own personal belief as to what the Code intended, which in the end is safety for life and property, a most virtuous quest in any case!) And being able to hear a variety of opinions has always been the best way to make up one's mind in a free society.

Plus, I think it is gratifying to us juice-junkies to engage in such conversations. Goodness knows we collectively contribute a good deal to this forum, and provide valuable assistance vis-a-vie free and responsible-to-the-best-of-our-abilities advice to all the Joes/Josephines out there, and if we wander off the path and indulge ourselves in the technical aspects of code/methods/materials for the expansion of our own knowledge, and in the quest for what is truly correct, I feel it is not at the expense or chagrin of our more lay compadres.

But I want to express that raising the point alone exposes you as a thinking person S1, who imagines outside his own needs/desires, and therefore I believe you to be a scholar and a gentleman. For what it's worth.

Wg, sticking with electrical has only one advantage over dating - electricity is far more predictable. And logical. But what is love, anyway? Mysterious, enjoyable, sometimes stressful, sometimes painful, sometimes difficult, often expensive, often hard work, and very satisfying when done correctly...

Gee, that sounds a lot like electricity!

Oh, by the way, addressing the original electrical question, you can NEVER go wrong to increase your conductor size to conform to 60 degree C column of 310-16. Wire is cheap the first time it is installed, and incredibly expensive to tear out and replace because of a misunderstanding of the requirement. And FAR less frustrating. (Imagine hearing your inspector tell you that you have far exceeded the minimum requirement? I had that experience and I can tell you it feels pretty darn good.)

And it has been my own experience with my home wiring that one call to your AHJ at the beginning of a project, just to touch base and let them know you'll be working with them, is a big plus. And when I was in doubt and wondered what his opinion would be as it related directly to my passing inspection, one phone call cleared it up and told me that if I did it in the particular way he sees the requirement that he would obviously pass it when he arrived to inspect. Just can't go wrong this way, I think.

Have a nice weekend y'all.

Juice
 
  #56  
Old 06-12-01, 04:51 PM
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#6 cu max ampacity?

I tried to follow this thread but you guys are pretty technical.

I installed 150ft of #6 copper wire (black, red, and white) in an underground conduit from my main panel to supply a panel at a detached structure for a hot tub (50a 220v) and a few outlets and lights.

My question is, how much current can this wire handle (what size breaker should I put in my main panel?)?

I relied on advice from a guy at Home Depot and I hope this wire will work. I appreciate the help, I have no training but I'm trying to learn. Thanks!

Cliff
 
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