Difference Between NEC and NESC

Merry Christmas


Senior Member
Well...... IMHO and all that......
The NESC is a good safety code for distribution and transmission, any utilities on-site will use that.
It's probably a good safety code for everything involved.
Any utilization equipment and wiring will need the NEC.
A lot will depend on the AHJ and their interpretations of where the two codes cross.

That’s rich. I have never seen a utility pull permits except new construction. I’ve personally pulled permits for an industrial twice in 30 years, playing NJ politics. Both are effectively permanently under construction. Something is always being modified somewhere.

And if you call the AHJ and ask them when NESC, NEC, RUS, and OSHA all disagree, you will just make their heads explode. Out of all of these the only ones likely to inspect are OSHA and NERC. I’d love to see the local Code inspector get into it with OSHA. Wonder who wins that fur fight?
For a real utility, sure, but is this installation a regulated utility or not? And the lines are blurry already. If there's something like an office or maintenance shed on site, I could see a zealous AHJ wanting a permit and inspections for that.

Exploded heads.... then they can't bother you :ROFLMAO: (I'd lock all of them in a room and say you folks figure it out, then let me know. In writing, with all of your signatures.)


Electron manager
NE Nebraska
Both the NEC and the NESC set the point of demarcation between the applicable codes as the service point. On the line side of the service point it is the NESC and on the load side of the service point, it is the NEC.
And unless the wind turbine is utility owned and operated, NEC is what should apply.

I don't read much of the NEC sections that are for over 1000 volts, but kind of doubt there is a ceiling on allowable voltage in those sections.


Electron manager
NE Nebraska
Not at all. Voltage has nothing to do with it.

Let’s step back to regulations. OSHA has 30 CFR 1926, 30 CFR 1910.269, and 30 CFR 1910.300-399.

1926 is for construction and major maintenance.

1910.269 covers generation, transmission, and distribution. This is you. I don’t know where the original came from. It doesn’t look like any standard.

1910.3xx covers utilization equipment. Half is a very old simplified NEC. The other half is taken from a 1980s edition of 70E. It is very out of date but it took OSHA 16 years to update 1910.269 so they’re not interested in writing more regulations.

So the vast majority of your equipment falls under 1910.269. However for instance lights inside the nacelle are utilization circuits and fall into .300-399. Read 1910.269 annex A. It is very clear how this works as well as commingled.

Now let’s bring up two major differences. Under 1910.269 everyone must be qualified. There is no general public. So it is assumed you know what you are doing or know when you are in over your head and avoid it. Second de-energizing is mandatory except under special circumstances under 1910.300-399. It’s encouraged under 1910.269 but most of the equipment and tools is designed for hot line work. Neither of these sound like a big deal but they are pervasive in the regulations and standards. Simply put they aren’t compatible. I am a contractor. I work in mines, government facilities, Duke, and Dominion among others. I’ve participated in drafting IS/Canadian/Trinidad corporate standards across different types of plants. So I’m familiar with all of them and the gotchas.

NESC is a consensus safety standard, not legally binding. So they have a scope but they are at odds with OSHA and NEC. Similarly read the scope in NEC and it’s obvious they are not legally binding either and thus will be state law. And they try to stick their heads in the sand when it comes to utilities. I’ll throw this out there too. The RUS standards are written for utilities (co ops) just starting out. It’s a lot more down to Earth. You may want to start there.

So you need to follow 1910.269 Annex A for “scope”. If it’s utilization use NEC as an equipment standard. If it’s anything else use NESC. For work methods follow NESC generally but make sure you are using it to fill in details 1910.269 doesn’t cover.

Get the voltage thing out of your head because that’s not how it works. Utilities try to just ignore NEC but they can’t quite get there and Annex A is where OSHA clarified this.

You could consider 70E for work rules but that is not written with utilities in mind. Don’t go there.

Stop with the voltage thing. If it’s utilization like lights and receptacles then NEC applies. Otherwise it’s all NESC. Very simple to understand. Just ask what it does and you have your answer.
That should allow for any sections in NEC that only apply to certain industrial applications where only trained individuals will install and maintain .....can possibly apply.


Electron manager
NE Nebraska
Low voltage is internationally recognized as 1000 V or less. Medium goes from there to 35 kV. High is from there to around 300 kV.

However the NEC somehow came up with 600 or less is low and above that is high. It got codified into OSHA. Due to the prevalence of power electronics and use in PV solar there is a recognized need for NEC to adopt international standards. They are reluctant to do so because of OSHA and OSHA isn’t too interested in changing the regulation due to the time and effort involved. They would rather drop the regulation and just reference standards as they have done with 70E but politically this isn’t possible.
NEC changed (2014 I think) from 600 to 1000.

Low voltage conductors still are predominantly using 600 volt max insulation though.