National Electrical Installation Standards

Standards as High as Your Own

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  • March 31, 2020

    Good Morning Code questions, I have a working space question about a switchboard that is supplied by a 600/347-volt system. What is the minimum depth of working space required to a grounded surface installed directly in front of the equipment. I appreciate your views and response. Keep up the great work. Mark Summers
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  • March 30, 2020

    In reference to Monday's answer (on 2-25-2000) it is important to consider the available fault current of the commercial building when making this judgement call. Most residential panel main breakers are only rated for 10,000 amps of available fault current. In many cases, commercial installations can have a fault current that exceeds this rating, which would make the panel unacceptable for the installation. Jackson Roos
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  • March 27, 2020

    Dear CQD, Is a receptacle outlet required on the outside of a home? My home was built in the 1950s. There are no receptacle outlets on the exterior of this house. I'm not an electrician, but I want to know what the Code requires. I appreciate your help. Mr. Clark
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  • March 26, 2020

    Greetings Code People, I have a question about a motor disconnecting means. Section 430.102(B)(1) requires a disconnecting means be installed in sight from the motor and driven machinery location. If the motor is within 50 feet of a motor control center that controls it, and there is a glass partition on front or the motor control center, but the motor is 30 feet from the MCC, but clearly visible through the glass, does the installation meet the minimum requirements in the NEC. Some here say no, others say yes. Can you weigh in on this please? P.S. Really enjoy the questions and responses every day. Sam Thompson
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  • March 25, 2020

    Using the 2017 NEC, on an island in a kitchen, how many receptacle outlets are required? The island is 15 feet long by 4 feet wide. I was under the impression that a receptacle must be installed every 4 feet. I would really appreciate your opinion. Thanks, Mark Gregory
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  • March 24, 2020

    What NEC sections support using flexible cord (SJ or SOW) used to connect a LED luminaire (4-ft strip type fixture) if strain relief fitting are used on both connection ends? Thanks, Love CQD. Buddy the QC Inspector. Gary Beckstrand
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  • March 23, 2020

    Re: Code Question of the Day 02-10-2020: Hello Mr. Trout, Following up on your 2/7/2020 answer to the commonly asked question about receptacles, you mentioned the other debate of "which way does the ground go on a receptacle installation, up or down." It would be great if you could further explain, as the idiotic "penny challenge" seems to be a fad, much more ridiculous than the "pet rock" or others as this "challenge" has the potential to be fatal. So why doesn't the NEC require the ground on the up, where if the plug is somewhat ajar and something falls, it won't contact both prongs of the plug? Did somebody back in the early 1900's flip a coin and we're living with it ever since? I also can't understand how a GFCI receptacle could be completely burnt after the "penny challenge," as I thought it would cut the electricity instantaneously. Ironically this specific one was installed with the ground up. Always great to look forward to learning more every morning reading your answers. As a "regular person," it is somewhat amazing too how complicated and technical it is. Kevin Kayden Bartow FL
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  • March 20, 2020

    Hi CQD Staff, simple question today! Can a sprinkler pipe be installed 3 feet above a motor control center in a mechanical room? I thought this was a dedicated space that is for electrical equipment only. Am I wrong? Some people here are saying it's okay because it is a sprinkler pipe. Any opinion of guidance would be greatly appreciated. Michael Gracias
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  • March 19, 2020

    Good Day Code Lads, here is a question that has bothered me for quite some time. Does the Code prohibit back wiring of switches and receptacles in a wiring system. I was always told that you can’t back wire devices and that the wires have to be wrapped around the screws on the device. I appreciate the response or opinion you have. Charles Timmons
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  • March 18, 2020

    Thanks for this forum. It provides useful information. I have a question pertaining to emergency generators installed for a commercial building. When the utility power fails, is there a maximum time that emergency generator power must be restored so people are not left stranded in the dark? I can't seem to find a rule that clarifies this. Thanks for you help on it. Thomas Seneca
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  • March 17, 2020

    Hello Code Folks, I'm being told that the color code for a 480Y-277-volt system is Brown, Orange, Yellow, and Gray for the neutral. Is this required by the NEC? I can't seem to find a rule that spells this out. I would appreciate your views on this. Thank you. Darrin Watkins
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  • March 16, 2020

    Hi, my question is about cords. Can a cord be run above a suspended ceiling to supply a vending machine on the other side of the hallway? This doesn't seem to be the correct way to power this equipment. I look forward to your reply. Eddie Frost
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  • March 13, 2020

    Good Day to all at Code Question of the Day. Can splices be made in a panel? Some say yes, and some say no. What do you say ? Thanks. Eddie Madison
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  • March 12, 2020

    I read the Code Questions and responses every day. My question is if an optional standby generator system is installed in a dwelling unit, is there supposed to be some means to identify that the generator is connected to the property. I'm concerned about any emergency response. I'm not an electrician but I was told there needs to be a sign installed. I appreciate any help provided. Mark Simmons
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  • March 11, 2020

    Hello, Code Question of the Day. I enjoy reading the questions and responses each day. Thank you. Here is my question: What is the minimum depth of working space required from a switchboard supplied by an ungrounded 480-volt closed delta system. There is a concrete wall directly in front of the switchboard. I believe the minimum depth of the working space required is 36 inches. What is your opinion? Thanks for any assistance. Harry Cannaday
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ABOUT CQD: The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry, sponsored by EATON. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.

SUBMIT YOUR CODE QUESTION: Click here to submit a question to for inclusion in an upcoming edition of the Code Question of the Day, or email

CHARLIE TROUT: Charles M. Trout, better known as Charlie, was 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. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. NEIS can be purchased in the NECA Store in three formats: a printed or  PDF download of a standard or, as an  annual subscription service.

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IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

This correspondence is not a formal interpretation of the NEC® and any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, the NEC Correlating Committee any Code-making panel or other electrical 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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