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Joined: Aug 2022
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I have the 2017 and 2020 Editions of the National Electric Code. The language is often somewhat vague and is filled with conflicting statements, so I'm extremely confused. As a result, I need some clarification.

In 90.2(A), it says that the scope of the code covers mobile homes, carnivals, and floating buildings. Well, that is understandable because all are normally considered structures (albeit moveable) and not vehicles. However, why does the NEC apply to RVs, when it is normally considered a vehicle and not a building? If they apply it to RVs, why doesn't the NEC to all other vehicles, especially overnight coach buses, long-haul tractor-trailers, Amtrak trains, cruise ships, houseboats, yachts, wide-body airliners, and private jets, which all also have sleeping compartments and lavatories? Does the NEC classify a camper van as an RV? How about a skoolie, or even any motor vehicle with 115V 60Hz AC receptacle outlets installed at the factory by the OEM, such as minivans, 3-row CUVs, pickup trucks, and tractor units of tractor-trailers, so that it allows people to camp in them? Also, when an RV is under the jurisdiction of the DMV and not the buildings department, how can an RV ever be required to follow the NEC under any AHJ?

In 90.2(A)(2), it says that it covers yards, lots, parking lots, and industrial substations. Why mention parking lots when it is already included under lots? Also, what do they mean exactly by lots, which is a super vague term? If they mean land lots, then wouldn't all the other mentions in the "covered" section besides floating homes, mobile homes, and RVs be superfluous? Wouldn't it also make the "covered" section conflict with the "not covered" section, beccause no exception was given within either section regarding the overlapped areas of mention (so no hierarchy is estsblished)? Also, what about yards, another very vague term? Front yard, backyard, railyard, bus yard, truck yard, shipyard, aerodrome yard (apron)?

It also does not mention whether it covers public roadways (such as their lighting and traffic signalling circuits), onshore wind turbines that are not owned by electric utility companies, offshore non-floating structures that are not owned or leased by an electric utility company (such as oil rigs), embassies/consulates of the US located outside of the nation's own territory, and US CBP preclearance facilities located outside of the nation's own territory.

Also, in 90.2(B)(1), why does it classify floating buildings as watercraft and mobile homes as automotive vehicles, when they clearly aren't, having no means of propulsion, hydrodynamic features, or wheels and can't even be registered as a vehicle by the US Coast Guard or DMV?

In 90.2(B)(2), what exactly do they mean by railway? Is it limited to just mainline railways or does it also include non-mainline heavy rail rapid transit, light rail transit, monorails, funiculars, roller coasters, and maglevs (if they do get built here)?

Also, since the NEC is not a legal document per se, does this mean that all of the Code besides the "not covered" section can actually apply to items listed under that section under certain AHJs?

That is because basically the entirety of the "not covered" section contradicts the "covered" section, because no exception is given for the "not covered" section under the "covered" section. So, a government building department, if they had decided to follow the NEC entirely, could interpret it in such a way that all installations under "not covered" will have to comply with the "covered" section of the NEC as a matter of preventative caution, because its statements are conflicting. I think those who know about British/Irish, Indian/Pakistan (which is exactly the pre-WWII British standard, if done to full code like in government buildings), and Australian/New Zealand electrical mains circuits and appliances, would know about how much more clear and strict those codes are. Their electrical systems are way overengineered compared to those in the US and Canada. Is that why electricity prices are higher by a significant margin in those places (when accounting for purchasing power parity) compared to the US and Canada?

British/Irish plugs are famous for having a fuse in every plug. They are also infamous for prohibiting electrical mains receptacles and switches in lavatories besides power-limited shaver sockets. It was only until the 2007 code edition that allowed general sockets and switches on RCD (GFCI) circuits in lavatories, and they had to be located at least 3 metres away from the nearest faucet or wet basin.

I've studied physics, chemistry, and even super complicated calculus before, and all of them were straightforward for clear for me to understand, despite how complex they were. There were no ambiguities or conflicting statements, except where experiments haven't been capable of testing out the extreme conditions covered by the established theories yet, such as quantum field theories.

Fully understanding the NEC for me is even more difficult than super precise electronics standards (such as IEEE, ITU, TIA, CD, DVD, Blu-ray, USB, HDMI, Secure Digital, EV plugs), computer programming, general relativity, quantum mechanics, and calculus because of the indeterminism in its definitions. Is the NEC purposely designed to be vague so that it gives authorities having jurisdiction wiggle room in their implementation? Is it even possible to fully understand the NEC due to its ambiguity?

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Joined: Jan 2005
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Cat Servant
It’s going to take me some time to process your post. I, for one, have never had trouble understanding the code and its application.
Certain parts of your post suggest that your primary language can s not English, and your uncertainty over the different authorities suggest a basic unfamiliarity with our social organization. Is that perhaps the source of your confusion?

I’m glad to hear of your sundry academic accomplishments. I caution you against assuming the folks here lack such education. Indeed, your courses are all part of a basic engineering program — even the electrical ones.

Have you ever built anything? You can’t follow Shakespeare without first mastering grammar—and you can’t apply the code without first learning the trade. You have to understand the context.

Finally: While engineer school teaches one way to examine issues, it is not the only way. Law, business, and medicine are disciplines that use a different approach.

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