# 2014 NEC service feeder sizing?



## mgraw (Jan 14, 2011)

Ubersparky said:


> Its my understanding that in the 2014 NEC table 310.15 (B)(7) does not exist. My municipality has not begun enforcing the 2014 NEC. As I understand it, they did something a little tricky with the calculation here. By tricky, I mean that there is a certain way to calculate service feeders. I know that 310.15 (B)(16) is the table to be used. Isn't there a calculation that goes along with it?
> 
> Can anyone explain what the new procedure is?


The way I read it the feeder needs to be rated at 83% of the service size.


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## Ubersparky (Apr 26, 2013)

mgraw said:


> The way I read it the feeder needs to be rated at 83% of the service size.


Where was that 83% mentioned? Thank you for answering.


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## mgraw (Jan 14, 2011)

ubersparky said:


> where was that 83% mentioned? Thank you for answering.


310.15(b)(7)(1)&(2)


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## Dennis Alwon (May 9, 2009)

If you have a 200 amp service then you need a conductor rated 200 * .83= 166 amps.

In reality the calculation will be pretty much the same as the old table. Now you have to take de-rating etc into consideration.


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## Dennis Alwon (May 9, 2009)

Here is the article



> (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,
> ...


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## Ubersparky (Apr 26, 2013)

Thankyou all for the assistance. I have a journeyman, and apprentice trying to take their tests. As it will be on the 2014 code, I'm trying to help them prepare. I've encouraged them both to become members. So...you can expect a couple noobs to be posting code questions soon.


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## Carultch (May 14, 2013)

Ubersparky said:


> Its my understanding that in the 2014 NEC table 310.15 (B)(7) does not exist. My municipality has not begun enforcing the 2014 NEC. As I understand it, they did something a little tricky with the calculation here. By tricky, I mean that there is a certain way to calculate service feeders. I know that 310.15 (B)(16) is the table to be used. Isn't there a calculation that goes along with it?
> 
> Can anyone explain what the new procedure is?


If you don't have any default conditions of use for your service conductors above the default 30C temperature & not more than 3 CCC's in a raceway, then you can use the table from your previous edition of the NEC, and get the same results.

If conditions of use derate factors apply, then you take those in to consideration, and you need 83% of your service rating/service OCPD worth of ampacity.


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## donselect (Jul 21, 2015)

so will a #4 cu in 1in pvc for a 100 a or a 
2/0 in a 1-1/2 for a 200 be compliant ?


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## donselect (Jul 21, 2015)

so will a #4 cu in 1in pvc for a 100 a or a 
2/0 in a 1-1/2 for a 200 be compliant ?


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## telsa (May 22, 2015)

*You guys in the East have all the luck*



donselect said:


> so will a #4 cu in 1in pvc for a 100 a or a
> 2/0 in a 1-1/2 for a 200 be compliant ?


The Poco has a big say... since in most jurisdictions the Service -- and the conductors ahead of the meters -- have to be deeded over to the Poco as a condition of service. 

Thus becoming Poco assets, strictly speaking, the NEC excludes them. 

(This makes the Code language on Service conductors an oddity. My Poco operates on the basis that NEC Service provisions don't exist.)

Out my way we are not permitted to use PVC for a Service riser -- period. Indeed, we can't even get away with EMT for a Service riser. RMC/ IMC are the only selections permitted. Consequently, 'value engineering' in this specific area is no longer done out this way. 

You guys are so lucky. You get to design out every last dollar of materials.


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## Dennis Alwon (May 9, 2009)

donselect said:


> so will a #4 cu in 1in pvc for a 100 a or a
> 2/0 in a 1-1/2 for a 200 be compliant ?


Assuming you checked the wire fill then it should be fine as long as it is not a mast. Most power company's want a 2" mast thru the roof.

Also #4 means nothing without knowing the insulation type. Look at Annex C Table 9(A) for fill


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## don_resqcapt19 (Jul 18, 2010)

telsa said:


> ... since in most jurisdictions the Service -- and the conductors ahead of the meters -- have to be deeded over to the Poco as a condition of service.
> 
> ...


I have never heard of that before. It does not happen around here.


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