# Problems on NEC code



## cocky (Sep 29, 2010)

I find it fairly difficult to solve the problems pertaining to NEC code. Can anyone suggest me a quick and easy material/book to get upto speed?

Thanks in Advance!


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## Dark Knight (Sep 29, 2010)

Try this thread.

NEC Practice Problems

There is a link at one of the posts where you can download practice problems.

Good luck


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## cocky (Sep 30, 2010)

Dark Knight said:


> Try this thread.
> NEC Practice Problems
> 
> There is a link at one of the posts where you can download practice problems.
> ...



That is some help, thank you


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## Dark Knight (Sep 30, 2010)

cocky said:


> That is some help, thank you


Hope you were able to download the material. Let us know if you have questions.


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## Gnana (Sep 30, 2010)

The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?"

They have an answer of 32 amps.

Does anyone think it's incorrect?

I got 30amps ( see table 310.16 and 240.4D) X 0.8 (see table 310.15.B.2.a) = 24amps


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## Gnana (Sep 30, 2010)

Gnana said:


> The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> 
> Does anyone think it's incorrect?
> 
> I got 30amps ( see table 310.16 and 240.4D) X 0.8 (see table 310.15.B.2.a) = 24amps



Be careful with this article, example 18 and 19 are also incorrect.


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## VectrenEng (Oct 1, 2010)

Gnana said:


> Gnana said:
> 
> 
> > The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> ...


Is the methodology incorrect? On the utility side, I rarely use the NEC, so I am trying to learn/understand these problems.


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## cableguy (Oct 3, 2010)

Gnana said:


> The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> 
> Does anyone think it's incorrect?
> 
> I got 30amps ( see table 310.16 and 240.4D) X 0.8 (see table 310.15.B.2.a) = 24amps


Isn't the 30 amp limitation for 240.4D new for 2008, and this set of questions based on 2005? So my 'guess' would be for 2005, the answers are correct, but not for us using 2008.


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## GabeM (Oct 3, 2010)

Gnana said:


> The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> 
> Does anyone think it's incorrect?
> 
> I got 30amps ( see table 310.16 and 240.4D) X 0.8 (see table 310.15.B.2.a) = 24amps


I agree that it seems incorrect. However, I think the answer should be 30 amps because 240.4D states that the 30 amp limit is applied after correction factors are applied.


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## GabeM (Oct 3, 2010)

VectrenEng said:


> Gnana said:
> 
> 
> > Gnana said:
> ...


I would also appreciate an explanation of what is wrong with examples 18 and 19.


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## Dark Knight (Oct 4, 2010)

GabeM said:


> Gnana said:
> 
> 
> > The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> ...


You are probably right. That 2005 version was the one I used in 2006.


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## cocky (Oct 4, 2010)

All,

How different is NEC 2005 from NEC 2008? I got my hands on 2005 handbook and wondering if that will make any difference if I take that with me to the exam. All those NEC code experts please share your views.


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## Flyer_PE (Oct 4, 2010)

^Just an opinion: All those little changes from 2005 to 2008 make great fodder for exam questions.


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## Gnana (Oct 4, 2010)

GabeM said:


> VectrenEng said:
> 
> 
> > Gnana said:
> ...


Problem 18

Per 2008 NEC code section 430.32(1), for motors with service factor 1.15 or greater

1.25 * 28 = 35A and not 1.4 * 28 = 39.2A as indicated.

Problem 19

Per 2008 NEC code section 430.32(1) for motors with temp rise over 40 deg, all other motors

1.15 * 26 = 29.9 and not 1.3 *26 = 33.8


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## GabeM (Oct 4, 2010)

Gnana said:


> GabeM said:
> 
> 
> > VectrenEng said:
> ...


The NEC does allow the 39.2 A and 33.8 A values, but only if 35 A and 29.9 A are not high enough to prevent the motor from tripping on start up. The problems didn't seem clear what it was asking, but I assumed they meant the 39.2 A and 33.8 A values because problems 16 and 17 already used 35 A and 29.9 A.


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## patelpe (Oct 5, 2010)

GabeM said:


> Gnana said:
> 
> 
> > The example number 11 " What is the ampacity of a #10 ZW2 conductor in a raceway with 5 current carrying conductors?" They have an answer of 32 amps.
> ...




Question # 11 states what is the ampacity of a # 10 ZW2 conductor with total 5 current carrying conductor in a raceway. Article 240.4D should be considered to find out the protection of conductor only and should not be considered for ampacity itself.

Answer 32 Amps seems to be correct for ampacity of the condutor.


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## Dark Knight (Oct 20, 2010)

I know there has been some discussion about the results not being accurate or something like that. But have received some e-mails asking for this material. So here is the link...

NEC Problems

The problems are in that link. Just in case, I worked the problem with the 2005 version of the NEC.


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## Dark Knight (Feb 1, 2011)

Sorry to quote myself but there have been more requests for these problems.



Dark Knight said:


> I know there has been some discussion about the results not being accurate or something like that. But have received some e-mails asking for this material. So here is the link...
> NEC Problems
> 
> The problems are in that link. Just in case, I worked the problem with the 2005 version of the NEC.


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