National Electrical Installation Standards

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
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What is the min. depth to bury electrical conduct under cement Jerrell Boner
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Does 310.15(a)(2) apply to a sheet metal trough pertaining to the 30 current carrying conductor rule? Steve Potter
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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
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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: http://www.neca-neis.org/code-question-of-the-day/code-question/cqd-for-11-4-2005 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
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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
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For a temporary service can I feed a temp 800 amp panel from (2) existing 400 amp breaker (3) phase 480 volt? The feeders will be sized at 400 amps each feeding a 800 main panel. Is this permitted? Thomas Scimeca
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In a bathroom, can a 227v switch for lighting be installed in a 2-gang box along with a 120v switch for an exhaust fan? If so is a barrier required? Richard Cressotti
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When adding an outside disconnect to an existing system and the grounded conductor and frame grounds are all bonded together is it permissible to connect #4 bare copper straight to the ground electrode along with a #4 bare copper to the same ground electrode? Terry Nelson
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Using the 2017 code, is it permissible to nipple between two separately fed panels? Thomas Cosgrove
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I thought I knew how to wire transformers until a few days ago. There are some guys that say you don't need to bond the transformer to the building grounding electrode system when you aren't using the neutral on the secondary. Say when you have a 480 volt 3 phase 3 wire primary and a 208 volt 3 phase 3 wire secondary to some piece of manufacturing equipment or A/C unit. I have looked through the code book and asked several other electricians and haven't got any real substantial answers or code references. I talked to one person that mentioned the exception in 250.121. I tried to follow it through the code book and I still don't think I understand it. Please help me understand this and find me a code reference so that I can go back to the people asking me these questions and give them some answers. I hope I have explained my issue well enough and my terminology isn't to messed up. I have been reading Code question of the day for a couple of code cycles now and it has been a big help. Thank you for the forum. Vern
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Re: CQD answer published Wednesday, January 23, 2019 - Concrete Hole Raceway Regarding the CQD for 1/23/2019 about the concrete wall hole-raceway: My guess is that David's pronoun reference for "doing this a long time" meant that he had been doing electrical work a long time, not using holes in concrete as raceways. =}) Those darn pronouns can be pretty slippery. In any case, this would have to be an installation which an inspector used their 90.4 authority to accept as safe. It certainly could be, as long as an equipment grounding conductor properly bonds the metals on both sides as required in Article 250. The concrete hole could be acceptable as a raceway under 90.4 since it is fully non-combustible. I have indeed received just such an approval (ahead of construction of course) for a case of an old exterior service being refed by a new exterior service - the multi-hundred amp feeder (1200 as I remember it) was run in just this manner. The undisussed concern I would have is if one side of the wall of David's subject is exterior : How is the installation protected from water intrusion and corrosive damage? Scott Cline
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After designing and having built over 900 dealerships in 45 years I have never had this field review by a local electrical inspector: that states: "ALL DOMESTIC POWER PLUGS IN THE COMPLETE SHOWROOM AREA AND IN THE LANDSCAPE FURNITURE MUST 18" OFF FLOOR AND NO FLOOR PLUG ARE ALLOWED" Stanley Tkacz
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Hi Charlie, is there any rule about stranded vs solid thhn and lug nuts? I constantly find lugs with stranded wire jammed in and was once told they are only for solid and to use a crimp on terminal to connect Christopher Walters
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Hello, The term "physical damage is widely used along the NEC. so, I would like to ask if there is any formal definition for this term. Could you please tell me why there is not a formal definition for this term? Is it the AHJ the authority (depending on the country) who has the duty to make a formal interpretation? thank you so much. Diego Medina
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