# Table 310.15(B)(7)



## HackWork (Oct 2, 2009)

Table 310.15(B)(7) covers all wiring methods for CU and AL? Meaning, if an installations qualifies for using that table, all other restrictions are ignored? For example, you could put 100A thru #2 AL SER cable that is 80% inside of insulation? 

What if AL romex was allowed, you'd be able to use Table 310.15(B)(7) on that too?


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## Deep Cover (Dec 8, 2012)

No, romex does not specify a type of conductor used inside its sheath.


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## B4T (Feb 10, 2009)

Deep Cover said:


> No, romex does not specify a type of conductor used inside its sheath.


I wish the one of the CMP would fix that.. it is a constant problem for us...


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## HackWork (Oct 2, 2009)

Deep Cover said:


> No, romex does not specify a type of conductor used inside its sheath.


In the context of my question, why does it have to? The table only lists CU and AL.


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## Deep Cover (Dec 8, 2012)

Read the title of the table.


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## HackWork (Oct 2, 2009)

Deep Cover said:


> Read the title of the table.


Well... they should have written that stuff in a more conspicuous spot than in the title 


I knew this made sense at one time, now I see what I was missing. :thumbsup:


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## Shockdoc (Mar 4, 2010)

B4T said:


> I wish the one of the CMP would fix that.. it is a constant problem for us...


If they printed THWN on NM cable then they wouldn't be able to sell you UF with the extra plastic for an additional $50 a roll.


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## 8V71 (Dec 23, 2011)

HackWork said:


> Well... they should have written that stuff in a more conspicuous spot than in the title
> 
> 
> I knew this made sense at one time, now I see what I was missing. :thumbsup:


I used to have the same problem when I used the yellow pages. For some reason I would miss the really big ads. :whistling2: :laughing:


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## raider1 (Jan 22, 2007)

FYI, Table 310.15(B)(7) is removed in the 2014 NEC and replaced with an 83% demand factor.

Chris


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## BBQ (Nov 16, 2010)

B4T said:


> I wish the one of the CMP would fix that.. it is a constant problem for us...


It is not the CMP, it is the manufacturers. They would have to pay for it to be listed and they have no motivation to do so.


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## Norcal (Mar 22, 2007)

raider1 said:


> FYI, Table 310.15(B)(7) is removed in the 2014 NEC and replaced with an 83% demand factor.
> 
> Chris


 
What was the reason for it's removal?


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## raider1 (Jan 22, 2007)

Norcal said:


> What was the reason for it's removal?


Confusion with the application of adjustment factors was one of the reasons. As written in the 2011 NEC it is not clear how to apply any of the adjustment factors to main power feeders or service entrance conductors.

The new 310.15(B)(7) requires us to use Table 310.15(B)(16) and then permits an 83% demand factor which will result in the same sized conductors that were permitted in the old table. The new informational note indicates that the ampacity adjustment factors may apply to this section.

Here is the new text for 310.15(B)(7)



> (7) 120/240-Volt, Single-Phase Dwelling Services and
> Feeders. For one-family dwellings and the individual
> dwelling units of two-family and multifamily dwellings,
> service and feeder conductors supplied by a single-phase,
> ...


Chris


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## Dennis Alwon (May 9, 2009)

I am glad they did this and I thought it was that way years ago but I may be mistaken.

Be careful because this *does not* mean that a feeder doesn't have to be larger in physical size than a service conductor. 

For example--- a 2/0 copper may be allowed to service a dwelling of 200 amp as a service conductor since 200*.83= 166 amps, but you may still need a 3/0 copper conductor as a feeder for 200 amp ( as in a feeder coming from a feed thru panel of 200 amps) if it doesn't carry the entire load.



> (3) In no case shall a feeder for an individual dwelling unit
> be required to have an ampacity greater than that specified
> in 310.15(B)(7)(1) or (2).


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> I am glad they did this and I thought it was that way years ago but I may be mistaken.
> 
> Be careful because this *does not* mean that a feeder doesn't have to be larger in physical size than a service conductor.
> 
> For example--- a 2/0 copper may be allowed to service a dwelling of 200 amp as a service conductor since 200*.83= 166 amps, but you may still need a 3/0 copper conductor as a feeder for 200 amp ( as in a feeder coming from a feed thru panel of 200 amps) if it doesn't carry the entire load.


I disagree with your interpretation of (3) and I can't see any inspector requiring a feeder from a 2/0 service to be run with 3/0.


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## Dennis Alwon (May 9, 2009)

BBQ said:


> I disagree with your interpretation of (3) and I can't see any inspector requiring a feeder from a 2/0 service to be run with 3/0.



So a 2/0 feeder perhaps in seu cable running thru insulation is fine for 200 amps if it has the total load of the service. BTW I know inspectors that will call you on that


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## HackWork (Oct 2, 2009)

Dennis Alwon said:


> So a 2/0 feeder perhaps in seu cable running thru insulation is fine for 200 amps if it has the total load of the service. BTW I know inspectors that will call you on that


That brings us back to the topic of this thread. 310.15(B)(7) says your inspector would be wrong, no?


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## Dennis Alwon (May 9, 2009)

HackWork said:


> That brings us back to the topic of this thread. 310.15(B)(7) says your inspector would be wrong, no?


Which code cycle are you questioning? Personally I agree with it not being clear in the 2011 but IMO 2014 made it clear


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## HackWork (Oct 2, 2009)

Dennis Alwon said:


> Which code cycle are you questioning? Personally I agree with it not being clear in the 2011 but IMO 2014 made it clear


2011.

Doesn't Table 310.15(B)(7) allow you to use 4/0 AL SER cable for 200 amps even if it's running entirely thru insulation as long as it is carrying the entire load of the dwelling unit?


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## Dennis Alwon (May 9, 2009)

HackWork said:


> 2011.
> 
> Doesn't Table 310.15(B)(7) allow you to use 4/0 AL SER cable for 200 amps even if it's running entirely thru insulation as long as it is carrying the entire load of the dwelling unit?


Sorry I had an errand to run. Yes it does-- I was reading 2014 and I mis-read what it was saying. I think it still applies

If you use 4/0 alum. for 200 amps as is allowed (200*.83= 166 amps), then we must use the same factor for a feeder. Look at the amp. of 4/0 ser running thru insulation--60C = 150 amps. Now we have a 200 amp sub panel that carries the entire load of the house. Now we need a conductor that is rated 83% of 200 which we know is 166 amps. 4/0 is not rated 166 amps so now you have to use a larger conductor such as 250mcm to get to 166 amps


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## HackWork (Oct 2, 2009)

Dennis Alwon said:


> Sorry I had an errand to run. Yes it does-- I was reading 2014 and I mis-read what it was saying. I think it still applies
> 
> If you use 4/0 alum. for 200 amps as is allowed (200*.83= 166 amps), then we must use the same factor for a feeder. Look at the amp. of 4/0 ser running thru insulation--60C = 150 amps. Now we have a 200 amp sub panel that carries the entire load of the house. Now we need a conductor that is rated 83% of 200 which we know is 166 amps. 4/0 is not rated 166 amps so now you have to use a larger conductor such as 250mcm to get to 166 amps


Using 2011, if it's carrying the load of the whole house (or individual dwelling unit inside of a house) than it shouldn't matter if it's running thru insulation and you shouldn't have to worry about using the 60 degree column since you use Table 310.15(B)(7) alone.

Are you saying that will change in the 2014 since the table is gone?


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## Dennis Alwon (May 9, 2009)

HackWork said:


> Are you saying that will change in the 2014 since the table is gone?


Yes that was the point I was trying to make


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## Dennis Alwon (May 9, 2009)

Actually I believe Gus at Mike Holt says their area will not allow it now as they interpret it differently. I have always argued that the code does not allow it in 2011 but I think it is unclear enough that many allow it.


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## HackWork (Oct 2, 2009)

Dennis Alwon said:


> Yes that was the point I was trying to make


I see. I don't know why they gotta make it harder, now I have to do math instead of just referring to a table.


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