National Electrical Code

There exists confusion now n then when gents ask electrical questions and myself and others refer to the National Electrical Code or NFPA 70 (which has no legal authority in itself) in our feeble attempts to help. Usually unless I forget (yep that has happened lol) I TELL THEM TO CONSULT WITH THEIR LOCAL GOVERNING AUTHORITY (if any such exists) because its them NOT ME OR ANYONE HERE OR THE NEC that can issue any final (if needed) ruling or inspection or sign off on their project.

Nowwwwwwww heres the deal:

1) The NEC ONLY suggests certain MINIMUM STANDARDS and thats NOT to say an institution or a municipality or some "local authority" or even myself may design/require things to be different, maybe above and beyond what the NEC calls for.

2) A "local authority" may or may not have adopted the absolute latest version of the NEC or any version whatsoever or see the above.

NOTE When I was a distribution design engineer my old boss was a stickler for safety and doing things above and beyond even what the NEC called for, so sometimes I may advise a certain way of doing things slightly different (maybe even better), but thats just how I was taught (NEC was the MINUMUM) and how I practiced mind you HOWEVER its been years and Im rusty as an old nail on the NEC and even if I wasnt REMEMBER TO CONSULT WITH YOUR LOCAL AUTHORITY and its them NOT any of us here who has the final say so.

EXAMPLE there are obviously situations in the NEC where say a "grounding electrode" is required at the buildings electrical service entrance. Now, in addition to conductive buried utility pipes and/or foundation structural steel or "made grounding electrodes" such as copper rods driven into mother earth etc., at our facilty we drove a rod, tested it and if it didnt pass we drove another rod, but then we were NOT required to drive a third regardless BUT I DIDNT RECALL THAT WAS ANY PRECISE NEC REQUIREMENT its just how we did it. Likewise the NEC may allow a certain voltage drop when calculating wire size and distances BUT ANYTIME ITS EVEN CLOSE I BUMP THE WIRE SIZE UP ONE GAUGE!!

Sooooooo when I answer a question my old habits tend to OVER ENGINEER a bit so you will just have to bear with me BUTTTTTTTTT if what the NEC or ultimately the "local authority" says is different GO WITH THEM AND NOTTTTTTTT ME, its been too long...

Nuff said

John T

Seen a bunch of questions and answers on the board about electrical installations. I've been an electricion for 40+ years and think it's like asking a bartender for leagal advice. I agree the NEC says in no uncertain terms that the final dicission is up to the local authority, and have seen some inspectors, over the years ,that weren't that sharp either. Mostly I agree with you John, if in doubt, over build.

The same goes for the rest of the IBC (International Building Code) or any other engineering authority that gives guidance on design (API, AISC, ASCE, ACI, etc). Local municipality will change the requirements as they see fit. With structural engineering according (strictly) to ASCE you should check EQ loads everywhere in the nation. Many local municipalities waive this requirement in low risk areas.

I'm a retired City inspector, building, electrical, plumbing, zoning, etc., and I found over the years that the best and easiest - understood NEC book is the latest NEC handbook. Not the Code book, but the handbook. The latest handbook version includes the Code text, plus numerous color examples showing in great detail what all the verbiage means. For example, there is a color picture of grounding, that shows all the various grounding requirements, wire sizes, locations and types of electrodes, etc., al in one drawing. A person has to study it a bit, but it's all there.
And yes, the Code is just a document. Unless it has been legally adopted by a jurisdiction, it has no legal meaning. And the jurisdiction will have the authority to interpret it, administer it, and sometimes enforce it.

Bartender for legal advice! I gotta use tht line sometime in my future...

Thanks,

D.

They have probably listened to enough sob stories that they know what not to do, if they can remember it right. A lot of far out stories come out of bars!

John T :: IF YOU look down about 4 or 5 post you will see my question about a generator plumbing. Now forget that, what got me was you explic advice about powering a shop off a house in a four wire system. The photo shows the middle conduit comes FROM main power transformer then we split two cut off and go into the house to two seperate 300 am boxes b ut if you look at the left box you will see a conduit drop. That is what powers my shop and I know for fact that there IS a ground rod there that is fasten to the copper buss in the box. My concer after your post is I am thinking the coper and nutral are one and the same in that box and if I understand you that is not good. May be ok because there on the side of the house is where it starts an not from a breaker down in one of the boxes. Anyway have a electrican comming and going to let him read your previous post just to be sure.

Okay I took a quick glance at the photo but obviously cant tell whats in the conduits n what goes where HOWEVER I CAN TELL YOU THIS:

If you have a generator and you

1) Want to switch/transfer 120/240 volt single phase three wire typical home service from the genny or the utility, and

2) If you ONLY use a two pole transfer switch (switch the two hots NOT Neutral)

A) THE UTILITY NEUTRAL AND THE GENNYS NEUTRAL GET BONDED TOGETHER

B) The utility Neutral (and consequently gennys Neutral since they are bonded) is bonded to a grounding electrode such as a driven ground rod or rods

C) The equipment Ground Buss and the Neutral Buss in the main panel are bonded together.

D) You carry an equipment grounding conductor from the main panel out to the gennys metal frame the same as you carry it to any non current carrying metallic junction box or appliance etc

E) AT THE GENNY YOU DO NOTTTTTTTTTTTTTT bond the genny Neutral to the frame and if its already there then you must sever that connection

If the genny is A SEPERATELY DERIVED SOURCE and you use a 3 pole transfer switch (i.e. you switch the neutrals) then this is all different.

John T

John,

Bottom line is that your local municipality is going to have the final word. What I have found, is that many municipalities base their codes off of NEC, and will tweek them as and where needed. There are some municipalities that have their own codes completely, one being the city of Chicago. Was a time for instance when we couldn't put telephone cable in a building that was not in conduit, at the same time the city of New York was allowing teflon coated sheath plenum cable in walls and ceilings, no conduit. Bottom line, your local code guys are going to have the final say so. Pickup a copy of their code, and it might even say that is based off of NEC. I have run into that before, so NEC they got. And then again, NEC allows for romex for residential so long as does not go 3' below ground level, and I lived in a village that did not allow romex. The electrical inspector of my village back then had romex throughout his home. I asked what if his house ever burns down, village code says no romex, and insurance inspectors come in and find romex, "What then?". I don't remember what his answer was. I sold the house long before the housing bubble and made a pretty good profit though, that I remember, no romex.

Mark

Good post Mark, I enjoy your sparky posts as Im so rusty on the latest code practice. Yep we agree CHECK WITH THE LOCAL AUTHORITY... I remember years back at an NEC Seminar led by one of the gents on the committee (was it Joe McPartland or Holt I forget been too long) talking about a "rumor" that Romex was on the way out and I wondered if the conduit manufacturers or unions etc were lobbyying regarding that hmmmmmm lol Billy Bob and his brother in law can so easily go to Home Depot and stock up on Romex and string it up while they may hesitate if they have to run conduit and pull wires I betcha.

John T

what if there is no code or inspection. we have neither here.

Then do it SAFE AND RELIABLE would be my advice (which following the latest NEC would accomplish) and if youre not able to accomplish that yourself hire a professional (or consider having one at least look at your finished product???). But hey its your home and your money and your familys safety at stake so its your call

Best wishes, keep safe now

John T

I understand basic home wiring well enough that I feel comfortable buying what is needed for any given project at the local farm store, or at any of the discount building and home stores.

When it was time to put 240 volt electricity out to my new shop though, I didn't want to play guessing games, or take the advice of the pimple faced kid at the home center, so I went directly to one of the local electrical contractors who does that kind of work, and was busy enough that he didn't really care if he got one more job. He was more than happy to sell me exactly what was needed. Wiring, connectors, breaker box and breakers, and even gave advice on how deep to bury the wire. It all worked just as expected. No glitches anywhere. Going on 14 years now, and still no issues.