National Electrical Installation Standards

Standards as High as Your Own

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  • August 29, 2019

    I have just bought an old house (ca 1965) to serve as my primary domicile. I bought it with the knowledge that the existing electrical installation isn't up to snuff. The specific issues I'd like to address are that there are no grounded outlets anywhere in the house, many fewer outlets and lights than needed, no GFI circuits, an aluminum input wire to the 100 amp breaker box (the rest of the house is 12 gauge, or better, copper) and no ground stake. The major work will be done by professionals but putting in the missing ground wires, locating and installing the extra outlets and switches along with the attendant new wiring is something I can do. And now, finally, the question I need to have answered is, "When upgrading the existing, ungrounded outlets, will single, naked copper ground wire, ran alongside the existing copper supply and correctly connected to each new, three prong outlet meet code?William Key
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  • August 28, 2019

    Re: CQD answer published Thursday, August 22, 2019 - Demand Factor Hello Mr. Trout, I read the questions and answers every day, and it is greatly informative. Regarding the question by Rick Gardner, "How can a main breaker of 1200 amps support feeders of 400 amps, 800 amps and 1000 amps (2200 total amps)? I think there are many novice non-electricians, such as myself, who are interested in the theory of why this is allowed. I understand to an extent that the NEC has instituted certain calculations to determine proper sizing of breakers, and the proper sizing of wiring is straightforward enough that I understand that. What is confusing is that, contrary to the NEC, it is possible to run every light, the A/C, water heater, stove/oven, and operate three hair dryers simultaneously. I always thought the NEC erred on the side of ultimate safety, but in this case that doesn't seem to be true. I suppose should such an unusual overload occur, the main breaker would trip, but I thought that was also a situation to try to avoid, as breakers have such limited number of on/off tripping before they're suspect to failure. Thank you for your help.Kevin Kayden
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  • August 27, 2019

    Does the GE lamp #LED15DA21/850 without guards, satisfy the requirement of NEC 590.4(F) and thus NFPA 241-13 section Temporary Lights? Arthur Harris
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  • August 26, 2019

    Re: CQD answer published Tuesday, August 20, 2019 -EVSE Regarding the Mon 8/29 vehicle charger question: I assume that Greg meant that "It does NOT look like there is any protection . . . " - AND more critically, I assume that these "ran several hundred feet" cables are not for building system voltage, but rather for carrying vehicle charger output. (This would be a first for me, I have never seen vehicle charging cables longer than 20 to 30 feet long). I have to assume that he is writing about cables between the charger and the vehicle - I believe that these would be "Output Cable to the Vehicle" defined cables with an "Electric Vehicle Connector" at one end. As such, I believe that they must be a part of a factory designed, built, and listed assembly. These exceptionally long cables might be field-construction allowed if installed in accordance with listed installation instructions. In this case, I believe that the protection for the cables is within the charger. As I understand it, chargers run several cable safety/function tests after the connector is inserted into the vehicle charging port before the charger will energize the actual charging conductors which are also in the cable. Scott Cline
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  • August 23, 2019

    Can an offset nipple be installed between a 1900 box and through with locknuts? Being told by the AHJ that it is not listed for that type of installation due to tapered threads? Please reference the code section other than 110.3B Thank you,Stan Komorowski
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  • August 22, 2019

    Re: CQD answer published Thursday, August 15, 2019 -Portable Tool Carts 1)"Portable tool carts" are not listed in article 90.2 Scope. therefore not subject to nec Darren Benevento 2) Hello Charlie. In response to the August 14, 2019 Code Question of the Day, Metal Electrical Boxes Mounted on Portable Carts, I question whether NFPA 70 applies in this case. The application of NFPA 70 is stated in the last paragraph of page 4, and in article 90.2(A) and 90.2(B). A portable tool cart is neither part of a building or facility structure, nor an appliance (400.10(8) since it does not consume electricity as fuel. I can find no specific reference to portable tool carts anywhere in the NFPA 70 or NFPA 79. The Kobalt cart may fall under the advisory requirements of the NEC if the product was submitted to a lab such as UL for product testing and certification, however, that is not likely the case with retrofitted electrical boxes on portable tool carts. In today's work environment, the use of receptacles mounted on any portable tool cart may create problems given OSHA requirements including Ground Fault Circuit Interruption protection for personnel. Richard Sullivan
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  • August 21, 2019

    I need to understand how the main breaker (in this case 1200A) can support by code feeders of 400A, 800A, & 1000A. The question my customer posed to me was how does the main of 800A support what appears to be a total of (400 + 800 + 1000A) 2200A. I understand the breakers are sized to protect the conductor size but I find limited information on how the 1200A main can support the 2200A feeder loads. Rick Gardner
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  • August 20, 2019

    Hi, We are building a medical office in New Jersey and wanted to ask if we need hospital grade wiring. It is a basic care space where only minor procedures and examinations will be performed in this office. Thank you. Joseph
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  • August 19, 2019

    The question I'm asking would be under the 2017 NEC. It concerns charging cables from a level 3 electric vehicle charger. They operate at 150 to 850 volt with a maximum output current of 600 amp DC per specifications. They ran several hundred feet to vehicle dispensing units from the main charger. It does look like there is any protection on the conductors from the charger. How does the code address this?Greg Evers
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  • August 16, 2019

    How many ground wires can be used in ground bar terminal screw for size 12 awg?Joshua Ormsby
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  • August 15, 2019

    Can a refrigerator circuit in the kitchen be a 15 amp?Richard DeCicco
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  • August 14, 2019

    Can metal electrical boxes be mounted on portable tool carts and if so can these metal electrical boxes be powered by flexible power cords? I have seen a portable tool cart by Kobalt with the electrical box or power strip flush-mounted on the top or side of the Kobalt cart, but I also run across mechanics with old Snap-On portable tool carts where they screwed or bolted-on a metal electrical box they picked up at Home Depot on to the top or side of their portable tool cart (not flush-mounted, but protruding out from the attached surface) and then ran a flexible power cord into the metal box to power one or two duplex receptacles. Can you help explain the specific NEC Codes that address these situations? Thanks, Ed Porter
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  • August 13, 2019

    Charlie, I have a commercial 120/240V, 1 phase service with two main panels, each with a 200A, 2P main breaker. The panels are located inside the building and are fed directly from the utility meterbase. The owner wants to install an exterior enclosed circuit breaker between the meterbase and each interior panel for maintenance purposes. The two new exterior circuit breakers will now become the service disconnects. There are presently two grounding electrode conductors, the primary one from the metal water service and a secondary attached to a driven ground rod. My question has to do with where to GECs must now connect. They presently are routed to both existing interior panel enclosures. I know the GECs along with the main bonding jumpers will have to be removed from those panels. With the proposed new arrangement, my understanding is that both GECs can land on the neutral bar in the existing meterbase if the local POCO allows. If not, can they be connected to the service neutral in only one of the new exterior circuit breaker enclosures or would they have to be routed to both new enclosures?Thank you for your service to the electrical community! K. Hall
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  • August 12, 2019

    Hi Charlie, in an ambulatory surgery center operating room, are all electrical outlets, or all emergency electrical outlets required to be attached to a line isolation monitor? If some are connected a different panel, not in the room, must they have a means to see a fault/alarm in the room? how are non-emergency outlets involved? Christopher Walters
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  • August 9, 2019

    Double tapping at ground and neutral wires on bus bars in main electric panel. if all houses in this subdivision were built at the same time under same code why when you try to sell your home it would be flagged by an inspector as needing to be fixed.Janet Blume
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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.

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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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