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Code Question Of The Day
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Tuesday, January 06, 2009
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Subject:Code Question of the Day: December 4, 2008
Your answer is incomplete and thus incorrect. Remember many people take your articles as gospel. There are both multipole AFCI as well as multipole GFCI breakers or a combination of a multipole AFCI with a GFI receptacle or device for exactly this type of circumstance.
Cordially,
Bill Nolte, C.S.H.O.
Project Manager
CEI Electrical Contractors
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code question and answer:
Friday, January 02, 2009
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Subject: Code question
In the 2008 NEC, with a branch circuit of 3 current carrying conductors, is it required to up-size the neutral regardless of derating?
Example; 3 #12 THHN and a #10 neutral.(3 phase 4 wire)
Regards,
Kevin
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Answer:
Hi Kevin,
Neutral conductors are required to be sized to carry the maximum unbalance of the load. The maximum unbalanced load is the maximum calculated load between the neutral conductor and any one ungrounded conductor (220.61). However, on a 3-phase, 4-wire, wye circuit where the major portion of the load consists of nonlinear loads such as computers, printers, electronic ballasts or adjustable speed drive motor equipment, harmonic currents are present in the neutral conductor (210.4 FPN) and it may be necessary to increase the size of the neutral conductor.
If you have a 2008 NEC Handbook (and you should have one) read the excellent commentary after 310.15(B)(4).
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Section: 210.61, 210.4 FPN
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Source: Charlie Trout
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ANSWERS: Answers are the author’s opinions and do not represent formal interpretations of the National Electrical Code.
All answers are based on the latest edition of the NEC, unless the question requests a response based on a specific edition.
CONTACT US: To submit a question, subscribe to Code Question of the Day, or remove yourself from this list, please send an e-mail to
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ABOUT THE AUTHOR: Charlie Trout is a nationally-known NEC expert and author. He served on three different National Electrical Code-Making Panels and is past chairman of CMP-12. He is also a member of the NECA Codes & Standards Committee. In 2006 Charlie Trout won the prestigious Coggeshall Award, given to recognize outstanding contributions to the electrical contracting industry in the technical and training area.
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