National Electrical Installation Standards

Standards as High as Your Own

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  • December 17, 2019

    Re: CQD answers published November 28 and December 10, 2019 -Water Piping Replacement Electrode retrofitting replacement is not in the NEC that I know of, but since so many inspectors read this excellent CQD, I will offer up my solution for losing the metal main water supply line. It details Chuck Mello's mention of a 250.53(D)(2) supplemental electrode. The replacement of the water supply line essentially always requires that a trench be dug. At this time it is very easy to install a supplemental electrode system [250.53(D)(2)]. Place a bare copper conductor in the trench with the new plastic pipe, with at least one but preferably two ground rods [250.52(5) & 250.53(A)(3) & 250.53(B)]. These rods are also driven in the trench, then use direct burial conductor clamps. This creates a "permanent" retrofitted electrode which is not easily damaged. Bare #6 copper would be allowed, but I used 25+ feet of #2, more in compliance with 250.52(A)(4) - an extra $20 cost - and put the rods 20' apart. Scott Cline
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  • December 16, 2019

    Sizing a 480V 3-phase 4-wire service for a waste water pump station. There are (4) 60 HP motors however the mechanical system will only allow (2) pumps to ever run simultaneously. What is the correct way to size the main utility service using the load for the (2) pumps? or do you have to size the service using the load for all (4) pumps.Bob Poteste
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  • December 13, 2019

    Is a conduit under a building slab (inside the perimeter of the building foundation) considered a direct buried conduit? Is there any cover requirement for a conduit under a building slab?Michael Oles
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  • December 12, 2019

    Can a three phase electrical sub panel be installed in a kitchen area in a commercial business?Mark Schultz
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  • December 11, 2019

    Re: CQD answer published Wednesday, December 4, 2019 - Service Point I do not agree. If the transformer primary is supplied by the utility then the transformer is the service point. A grounded conductor would be required to the service disconnect. ThanksMike Bressler
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  • December 10, 2019

    Can you have a kitchen GFCI attached to a bathroom GFCI. When kitchen GFCI is tripped the hall bathroom lights go off.Louis Montalvo
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  • December 9, 2019

    Charlie and Friends, Thank you for this wonderful resource and the continued support to the industry. I read the CQD everyday and get a lot out of the questions and interpretations provided. This response is in regard to the question where the hot and cold water piping was being replaced with PEX and what to do with the grounding electrode conductors from the service. I would have to assume that the PEX replacement is just on the interior piping so it is unknown if the supply water line is still metal or not meeting 250.52(A)(1). As the answer stated, if the water supply is still a valid electrode as described then reconnection of the grounding electrode conductor to some point on the metal water pipe up to 5 feet from the entry to the building is still required. This may mean replacing or extending the existing grounding electrode conductor. If extended then the splice would have to comply with 250.64(C). I believe a good addition the answer given would be to mention 250.53(D)(2) where an additional supplemental electrode is required and that grounding electrode conductor installed to be independent of the metal water pipe. Keep up the good work and look forward to the question and answer everyday.Chuck Mello
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  • December 6, 2019

    Re: CQD answer published Tuesday, November 26, 2019 - Flexible Cord Outdoors Charlie in the question about using SO cord outside you said that it had to be weather or water resistant. What if it is also exposed to the sun? Shelby
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  • December 2, 2019

    Re: CQD answer published Monday, November 11, 2019 -Service Conductors in Building I know, I am mostly retired but still love the Code Question of the Day and still miss Charlie at the Western Section IAEI meetings. We have has some of the best conversations about the Code (what else?) and I loved to win an argument (that didn’t happen often). RE: the Code Question of the Day for Friday, November 8, 2019 It is interesting to me that Mr. Tucker referenced an electric utility actually entering a building. Most electric utilities DO NOT permit their conductors to enter a building since we normally do not use conductors that are tested by a NRTL and they have not passed the vertical flame test. Most of the secondary conductors we use are polyethylene covered for overhead and cross-linked polyethylene for direct burial. For entry into a building, the cross-linked polyethylene URD (normally USE) cable has to be marked USE/XHHW or similar to meet the Code requirements. Take care, Charlie Eldridge
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  • December 3, 2019

    A client owns a 12.6 KV X 480Y277 transformer. This transformer primary is supplied by the utility and is the sole power source for the building. The project electrical engineer shows bonding and grounding of X 0 at the transformer, then just 3 phase conductors to the first disconnecting means. We objected. He replied the the grounded conductor will not serve any neutral load loads, and seems to be treating this like a separately derived system instead of what we think it is, a service entrance. We cited the code requiring that the grounded conductor was required to be brought to the first disconnecting means regardless, and grounded and bonded there in addition to the bonding at the transformer. He is adamant, and we are not willing to knuckel under. The argument seems to center on the private ownership of the transformer. In our opinion, who owns the transformer doesn't matter. Your thoughts might help us bring some sanity. Ron Robertson
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  • December 4, 2019

    Re: CQD answer published Monday, November 25, 2019 -Warning Ribbon for Underground Service Conductors Question regarding the Warning tape over HDPE. We are on a project now. They are doing horizontal boring to install feeders to carports that supply the AC to inverters. With horizontal boring there is no way to install warning tape. How is this addressed? It there an exception? Vern Detweiler
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  • December 5, 2019

    Re: CQD answer published Wednesday, November 27, 2019 - 2020 NEC Emergency Disconnects 1) AGREE with KEN.. it’s a Stupid idea some engineer came up with brought it to other engineers and over thought the process and added it to the 2020 code. WE ALL Still have time to voice out public objections on the 2020 NEC Bill Schell 2) "The concerns you express about burglary and mischief can be dealt with by locating the disconnecting means outside and locking it in the on position but locating the panelboard inside the building. The really evil people will find a way to defeat everything. The benefit to having the disconnecting means outside is for emergency responders so they can deenergize the interior wiring before entering the building." If it's locked in the on position, how do 1st responders deenergize it? Dave 3) Thanks for all your hardwork keeping us all on track. The poster that responded to the Nov 8 discussion on placing of breaker boxes on the exterior may be failing to understand what I believe to be the best reason to do so. The main breaker being accessible from the exterior favors when the fire department is dispatched to the building. First thing they do is to shut power down for safety reasons that I don't think needs to be explained. As you said, those "bad guys" will access a panel if they are in or outside the building if there intent is to disconnect security. Happy Thanksgiving to all! Jeff Frishof
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  • November 29, 2019

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  • November 28, 2019

    Min size conductor in a commercial branch circuit under 600 volts Vince Tomasino
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  • November 27, 2019

    Replacing HW and CW lines with PEX. Electrical Panel is grounded to existing CW line which is now discontinued. What is the proper method to now ground the panel?Franklin Dysthe
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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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