National Electrical Installation Standards

Standards as High as Your Own

NOTE: If searching by date you must select a full date.
  • March 1, 2019

    Re: CQD answer published Friday, February 22, 2019 Cords vs Cables I think the difference between cord and cable is one of the murkiest of gray areas in the code. After a lot of time pouring over NFPA 70 and 79, I have come to the conclusion that Cord is SJ or SO, anything else is cable. Michael Casey
    View Question & Answer

  • February 28, 2019

    Re: CQD answer published Thursday, February 21, 2019 - Re Wed Feb 20 CQD about phase conductors separated into different conduits. Your answer is perfect - and I am only accenting the excellent but easily missed concept of 300.20(B). We did this for a 3-foot long, 1600 amp, 3-Phase run between a buss-duct terminal and the machine's input box. Matching lengths of these very short conductors would have been very difficult had we not run them as lug-aligned A - B - C conduits. We used non-metallic (PVC) conduits as is necessary, BUT you must also remember to comply with 300.20(B) by cutting slots between the conduit holes if the enclosure is metallic . Otherwise that sheet of metal becomes an induction heater. Of course, full circuit-sized EGC conductors are required in each conduit. Scott Cline
    View Question & Answer

  • February 27, 2019

    Re: CQD answer published Thursday, February 14, 2019 - GFCI Location With regards to your answer on Feb 13th, how would this be different than having a receptacle in the ceiling for garage door openers? Would exception 2 to 404.8(a) apply? Bryan Berg
    View Question & Answer

  • February 26, 2019

    Re: CQD answer published Tuesday, February 5, 2019 - System Bonding Jumper Location Related to Wednesday's question, can one make the ground-grounded conductor bond in the transformer or should it be done in the disconnect? Michael Casey
    View Question & Answer

  • February 25, 2019

    Re: CQD answer published Friday, February 1, 2019 -Vehicle Showroom Classification 1) Good morning, I have run into this before. (And, no, it didn't hurt!) The issue is, the Class I, Div. 2 area in the shop area extends into the showroom when there are doorways between the two spaces unless efforts are made to prevent this. Positive-pressure ventilation is one method I have seen used. The repair shop area can also be declassified in accordance with Table 511.3(C). Placing the showroom receptacle outlets above 18" is an easy fix. If they need floor receptacles, one of the other methods would be necessary. However, if there are no openings in the demising wall between shop and showroom, there is no problem. Thanks for the forum! Grant Hammett 2) Receptacles 18" or more above floor, Thursday's question Jan:31:2019. The code section that you are looking for would be NFPA 101 Life & Safety - Ignition point. This would Not be a first here in town. 18" is the height that gasoline fumes rise to before being to heavy to fall back on itself. We have all seen switches spark or receptacles spark (when you yank a cord out especially if something is running at the time). This is an ignition/flash point. Whether it is a garage at home, repair garage, parking garage or in this case, a showroom - anywhere there could be gasoline fumes, the standard receptacle height would not be acceptable and must be over 18" off the floor. Many times, I have had an electrician tell me, "If it is not in the NEC, I am not doing it." As an inspector, we have to enforce all codes (and there are so many) no matter where it appears and will not sign off until compliance is met. As far as NFPA 70, where is the location for smokes & CO's (new and existing buildings)? The building code. Where is stair illumination (interior and exterior)? The building code. We also need to look at other areas of the NFPA, gas code (bonding), NFPA 1 & 101. Most of the time here, I see garage receptacles at three or four feet (convenience outlets) and yes, floor outlets would be a no no. I find electricity gets a bad wrap when it comes to fires, It is too easy to say it was an electrical fire. But shame on us should there be a fire and a Fire Marshal sees those receps are within the 18" range. Many times I have purchased a new vehicle and seen the staining on the ground when raining. New vehicles can leak (and stink). I would support the inspector in this case, he seems well read.Thank you for this treat every morning. Great job though I miss Charlie. Big Bad Busy Bob (or so I was called by a resident in a PB meeting)
    View Question & Answer

  • February 22, 2019

    Hi Charlie: Thanks for all you do with the code question of the day. On a recent job class 2 wiring was installed in PVC conduit to protect the wire in a wet location. Does strapping requirements apply for a conduit system if used for class 2 wiring. It is a bit grey, but it would seem to me it would. 725 does not require adherence to chapter 3 wiring methods for class 2 unless specifically stated. Thanks! Mike
    View Question & Answer

  • February 21, 2019

    What is the difference of multi-conductor cable versus a flexible cable? I use multi-conductor cables as feeders via cable tray from distribution board to panelboard. Are multi-conductor cables shall be installed in accordance with flexible cables or cords where cannot be used as substitutes for the fixed wiring of a structure? Jessie Santos
    View Question & Answer

  • February 20, 2019

    I have a short 14 foot run of 15 KV cables between medium voltage switches, Can I segregate each phase in separate conduits? Please advise Wayne Kantarek
    View Question & Answer

  • February 19, 2019

    Re: CQD answer published Thursday, January 31, 2019 - Wire Terminations 1) Charlie, I believe the question for CQD, 1-31-2019 is referring to WAGOS. They are listed for both solid and stranded wires according to the information on the package. Tom Ekstrom 2) Hi Charlie, product spec for RTRT is also interesting in regards to the question about stranded versus solid wire under "lug nuts", even though the submitter did not specify the product he was talking about. Terminals of the wire-binding screw, setscrew, or screw-actuated back-wired clamping types are suitable for use with both solid and stranded building wires. Have a great day. Greg McMurphy 3) IMHO all mechanical electrical connections are "pressure connectors" regardless of how the "pressure" is created & maintained. Crimped connections maintain continued "pressure" on the elastic deformation of metal(s). Obviously, this excludes soldered or otherwise similar metallurgical joints. Perhaps the definition in Article 100 can be more definitive (discriminating). Incidentally, you need to be complimented on the excellent job (service to the industry) you are doing giving continuity to what Charlie Trout started. R. Schneider, P.E. 4) What is meant by an upturned lug in 110.14 (A)? Josh Vinesett
    View Question & Answer

  • February 18, 2019

    When you burry. Conduit underground what type of tape do you put on the conduit. You don t put C 130 do you or can you? But what is the tape you apply to the conduit? David Bastean
    View Question & Answer

  • February 15, 2019

    What is the min. depth to bury electrical conduct under cement Jerrell Boner
    View Question & Answer

  • February 14, 2019

    Does 310.15(a)(2) apply to a sheet metal trough pertaining to the 30 current carrying conductor rule? Steve Potter
    View Question & Answer

  • February 13, 2019

    Can a GFCI receptacle get installed in a basement ceiling for a hot water heater and softener or is there a maximum height that it needs to be at or below? Ryan Ritacca
    View Question & Answer

  • February 12, 2019

    Greetings to you folks at CQD, while looking up some information regarding the definition of "coated" and "uncoated" wire, I ran across a CQD at the following link: In the answer part of that CQD is found this language: "The overall CSA of both bare copper and tinned copper for a given size was the same, therefore, you will find that the resistance values for tinned copper conductors is slightly more than that of bare copper." My question is this: What is meant by "CSA" in this answer? The word "diameter" would seem to make sense in place of "CSA," but I hate to assume… Thanks in advance for your help! Johnie Spruiell
    View Question & Answer

  • February 11, 2019

    I read on a webpage that you consider a RV pedestal as a “separate structure” and must contain a ground rod to be driven at each location. However, my reading of what follows contradicts that. Can you let me know if I’m wrong? The only equipment requiring grounding electrodes is the electrical service equipment. 250.54 contains permissive, but not required, language that allows for auxiliary grounding electrodes to be installed and connected to the equipment grounding conductor. Keep in mind that the pedestal is equipment, and NOT A STRUCTURE, so there are no NEC code requirements for having grounding electrodes on equipment that does not require them. Only equipment for separately derived systems and buildings or structures supplied by feeders or multiple branch circuits (other than multiwire) are required to have grounding electrodes. Auxiliary electrodes serve no real purpose, you will have to have an equipment grounding conductor installed with your feeder conductors to each pedestal. The EGC will bond all of the non-current carrying metal parts back to source of electricity, the electrical service. Some people will argue that extra ground rods are good for lightning protection, but that's not how grounding works. The earth is not an effective fault return path, but your EGC is. If lightning stuck a pedestal with rods attached, the energy will dissipate through the earth. As the potential dissipates, it spreads out from the location of the ground strike. As soon as this energy comes across other pedestals with ground rods, there will be a difference of potential between the pedestals and ground rods and the current will now be induced onto the equipment grounding conductor and will pass through every piece of equipment connected to the system. I have seen this many times with nonseparately derived system generators where installers connect an unnecessary ground rod to the generator frame because UL requires a terminal for such a connection. They see the terminal and assume it's required. The transfer equipment, not the generator determine if grounding electrodes are required. As soon as there is a lightning storm, the controller in the generator gets hit with a power surge and shorts out along with all of the electronics connected to the system. Unfortunately, this also happens where there are multiple building on structures connected to a common electrical service and requires the installation of multiple surge protective devices. Mike Lamberton
    View Question & Answer

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

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.

ABOUT CHARLIE: 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. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

NECA SAFETY PRODUCTS: NECA publishes valuable electrical safety books and CDs for the industry. Visit to view or purchase NECA safety products.

 CONTACT US: To submit a Code question, subscribe, or unsubscribe from this list, please e-mail: