Code Question of the Day with Charlie Trout

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The National Electrical Code is the bedrock of the electrical construction business.

Do you know all the ins and outs of the Code? NECA and Electrical Contractor magazine are pleased to present their daily online feature, “Code Question of the Day.”

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Code Question Of The Day

Friday, April 18, 2014
Thursday's Question:

500 kcmil Feeder for 400A Panelboard?

Hello Charlie.

Are we allowed, per the NEC, to provide a feeder comprised of 4#500Kcmil + #3 ground wire (75-degree, THHN) for a 400A panelboard? I personally don’t think this is allowed by the NEC since 500Kcmil cable can only hold 380A (which includes 125% of continuous +100% of non-continuous loads) under the 75-degree column of table 310.15(B)(16), but I have heard arguments that the commentary (blue background) of the 2011 NEC Handbook for 240.4-(B) explains that this is allowed. What is your take on this?

Thanks for all the helpful responses you provide through this forum.

Pathros O. Cardenas, PE



Wednesday's code question and answer:
Wednesday, April 16, 2014

Re: CQD published Mon, Mar 17, 2014 - EV Charger Overcurrent Protection

Charlie, you mentioned "continuous" load. I thought that there were no continuous loads in residential load calculations. Is this a residential continuous load?

Another comment. Most Listed (If I were the inspector, I would be requiring such) equipment nameplates have pertinent electrical information, but often times don't include minimum ampacity ratings of branch circuit and minimum and maximum OCP requirements. If the NEC required such information on nameplates, it would alleviate a lot of confusion. This is done on certain types of equipment such as HVAC, Welders, etc.

When I used to advise people, such as person submitting the question, on NEC issues and requirements, my old adage was: "It's better to turn on a light, then it is to curse the darkness!" and encouraged them to become active in submitting proposals to the NEC. However, it always seemed that many are called but few submitted.

Regards, Nick Abbatiello




Hey Nick, good to hear from you again and thanks for the comment.

I don't see anything that excludes continuous loads or the need to include them in calculations for dwellings. There are many examples appliances that are considered to be continuous loads regardless of the occupancy type. Office lighting is commonly used as an example of a load that would be continuous but it is not occupancy dependent.



Section: 210.19, 210.20, 422.10, 422.13, 424.3(B), 625.41

ABOUT CQD: NECA’s Code Question of the Day (CQD) is Charlie Trout’s flagship National Electrical Code® forum for NECA and the industry. The CQD continues to generate a lively dialogue and relative Code-based and practical responses to an ever-increasing and interactive audience.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, is a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training.

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IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

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