Fixing the NEC

[jim dungar]

Trying to find were the demarcation is

What part of the code have you seen that answers all of the choices required to make a complete installation? I think the requirement for GFCI protection of vending machines comes close, but it does not define what a vending machine really is.

 

[AC\DC]

What part of the code have you seen that answers all of the choices required to make a complete installation? I think the requirement for GFCI protection of vending machines comes close, but it does not define what a vending machine really is.

I guess you were answering my question with a question. I was just trying to figure out where the cutoff line is. I never heard it describe the way you describe. It makes sense actually.

So by your interpretation, any requirements they set for in here is article 90 approved as long as it’s not 100% the only way to do it.

I’m just trying to make sense of it. I’m not trying to argue. You already made a good argument . I’m just trying to figure out if that’s what you mean.

 

[jim dungar]

So by your interpretation, any requirements they set for in here is article 90 approved as long as it’s not 100% the only way to do it.

Sure, why not.

If someone says they want commercial grade white receptacles to be mounted horizontally in 4" square boxes with 1/2 mudrings, have they really designed the project for you or simply limited the choices you are allowed to make?

 

[AC\DC]

Sure, why not.

If someone says they want commercial grade white receptacles to be mounted horizontally in 4" square boxes with 1/2 mudrings, have they really designed the project for you or simply limited the choices you are allowed to make?

Someone paying the bill yes , an agency that says this books is not a design specification is the question? seems they can tell us pretty much anything. buy your logic they could dictate that white device be used on white walls since we can still decide to use decor-a or standard,

 

[going_commando]

Bro, the NEC totally isnt a design manual, because you can pick the color and orientation of receptacles, bro. For residential, it's a design manual that lets architects play a bit. You don't need an electrical engineer for a house, because the code tells you what to put in and where. You do get to pick colors and shapes though

 

[jim dungar]

...your logic they could dictate that white device be used on white walls....

Yes that would be possible if a proposal was accepted by the appropriate CMP and then was voted on by membership.

As I said the NEC is allowed to contain design requirements.
I know of no agency that considers any NFPA document to be a standalone design specification manual.

 

[AC\DC]

Good point I guess I’ll stop complaining that they can’t do that since technically they can

 

[Master Nater]

are you suggesting that 210.12 originate from proposals by CMP members or the NFPA. If so, I suggest you read the ROPs and ROCs starting with the 96 code cycle

i'm saying these blatantly obviously ridiculous codes were originated by manufacturers and lobbyists. i'm also saying they were APPROVED by code board members who do not put actual public safety before their own desires to line their own pockets. it astounds me how many of the electrical AHJ's do not realize that every stupid code they enforce and allow into the NFPA, only incentivizes our customers to hire unlicensed handymen to do their wiring. why? because those handymen will not follow these awful codes that do nothing but sell IMPRACTICAL materials, and promote nuisance tripping, that the lobbyist-paid code board members approved.

incentivizing customers to hire untrained and unqualified people to do their electrical work, instead of hiring licensed professionals, is the opposite of the purpose for establishing an electrical code in the first place.

 

[Master Nater]

People rely too heavily on the POCO for this. There are two purposes for knowing your available fault current and I am on the fence about submitting a PI for it.

1) Equipment selection - Your need OCPDs to operate in a contained event. If the available fault current is higher than the device allows you can have an explosion which I think we can all agree is not safe. That equipment selection value should be based on the highest available fault current. The main switchgears AFC and the one the utility says is the the size for the main.

2) Protection of people with PPE and trip curves. This is more complicated, usually requires an engineer and was put into the code because employers, contractors, and laborers were getting hurt while testing or working hot.

The idea of making sure fault current does not exceed the equipment's rating is as old as electrical work itself. Your OCPD and equipment should remain in one piece after a fault.

i absolutely understand the reason for knowing your fault code. what i'm saying is, we can do all of our due-diligence, and properly calculate our fault current, and properly select our switchgear/panelboards/breakers. but what happens when next month when the power company decides it's going to change out the transformer because the next-door neighbor is upgrading his service? the POCO just changed your entire fault current on all of our service.

whether you know or not, the POCO says that they are legally required to install a new tranformer with the lowest available impedence, all in the name of "being green." if you've done fault current calculations, you know that lower impedence transformers (Z) means that our fault current just went up. even better yet, what happens when they put in a larger transformer?

this is why i ask, what good did performing our fault current calculations actually do?

when the POCO isn't being held respsonsible for changing the fault current on everybody's equipment, what's the point?

 

[jim dungar]

this is why i ask, what good did performing our fault current calculations actually do?

If you, as the installer have performed your due diligence, it is not your problem if future problems occur. This is one reason that agencies like OSHA encourage, if not demand, compliance with NFPA 70E and it's requirements to reevaluate Arc Flash Incident Energy at least every 5 years.

As far as POCOs changing equipment, this is one reason many, if not most, SCCR evaluations are based on the use of infinite bus currents which by definition cannot be exceeded, without a change in the source impedance. I know of very few customers that would not be aware of the utility outage that occurs when POCO systems are upgraded, which also brings NFPA 70E into the discussion. Some utilities actually provide a not to exceed available fault current, rather than an actual value for equipment selection. They have minimum values of impedance which their general transformers must meet or exceed, of course dedicated transformers for specific customers may have contractural values.

 

[don_resqcapt19]

code board members who do not put actual public safety before their own desires to line their own pockets

That is 100% BS

 

[retirede]

That is 100% BS

This entire thread is….mostly.

 

[AC\DC]

So none of them stand to gain anything,
No stock options no personal investments that benefit them.
They may be doing it completely out of good faith, but our system is so crooked it we expect everyone to be screwing everyone
Hopefully, that will change, and hopefully they’re doing it out of the kindness of their heart

 

[Elect117]

when the POCO isn't being held respsonsible for changing the fault current on everybody's equipment, what's the point?

When you ask a utility to install a new service they provide you with the maximum available fault current and you buy the switchgear. If you mainly do residential or not a lot of service work then you might not see that. That number, for the switchgear, is the maximum available fault current. It is decided on the worst case. For example, 2000A main, That is about 1600kva. That isn't a nominal transformer size. They will check their inventory or service design manual and make a decision on what the largest size transformer they will install is. Lets say it is 2000kVA. That would put FLA at about 2408A. So 2408/.035 = 68.8kA. So the utility will look at their transformer inventor and say you need 100kA based on the largest transformer's impedance they would install for a 2000A main. Or they will say they carry a 1500kVA that will suffice, so 1806A is FLA and 51.6kA is the max, so install 65kA rated service. They can not exceed that. Which is why the switchgear is always a WAY larger number than the second one you get sent. If you are in a multiservice industrial area and they are doing more than one service off a transformer you will see larger FLAs, and kAs than that. But that information is for equipment selection. And equipment selection only.

After they designate a transformer for the service they will use the actual impedance and provide you with an available fault current letter. That is for PPE selection and LSIG coordination so you do not have a long trip time on some of the faults between 2000A and 65,000A. But your equipment selection is on the worst case. The utility bears no responsibility if you do not understand that. They tell you what the largest transformer could put on the service and if you use the wrong fault current numbers for buying equipment then that is on you. And it can be okay that way as well, as some people will more than likely point out. The code does not differentiate it properly and I believe that is why so many people have issues with fault current codes. They blame the utility for the size of the transformer when the equipment being installed is supposed to be sized to the largest possible transformer than can feed the service.

this is why i ask, what good did performing our fault current calculations actually do?

how do you select your PPE?

 

[jim dungar]

After they designate a transformer for the service they will use the actual impedance and provide you with an available fault current letter.

This is still not true for many POCOs.
My experience is they don't tell shared transformer customers anything about the actual fault current. Even the dedicated transformer customers frequently hear nothing about their available fault currents.

This is one reason Arc Flash Incident Energy studies should not be DIY.

 

[AC\DC]

So it’s based on not what transformer is there butt the largest one that possibly could be there in the future—-
It’s still power company’s control you just got to ask it the right way I guess ——
Wondering for next time

 

[jim dungar]

So it’s based on not what transformer is there butt the largest one that possibly could be there in the future—-
It’s still power company’s control you just got to ask it the right way I guess ——
Wondering for next time

This all depends on your specific power company and their policies.
During an extreme outage they may put in any transformer that fits where the old one was.

Yep, you got to ask.

 

[AC\DC]

If they put any transformer they want how how can you figure that out? How are you liable for that? I mean if that’s the case they should have everything should be like 65,000 AIC

 

[Elect117]

If they put any transformer they want how how can you figure that out? How are you liable for that? I mean if that’s the case they should have everything should be like 65,000 AIC

It is not likely. The number the utility tells you is likely going to be much higher than what you would use for a arc flash assessment. You are responsible for the equipment you install. If the utility says it is 65k and you put in 42k and the thing explodes then you made a mistake. That is also why so many engineers put the letters from the utility on the plans. Some jurisdictions require it on replacement services so they know what the maximum available fault current is. Some utilities treat it as a formal letter.

That is more than likely due to lawsuits or similar when it came down to the service's energization.

 

[jim dungar]

If they put any transformer they want how how can you figure that out?

They usually have a range of transformers but it is not really extreme. Say you have a 150kVA padmount, they might use a 225kVA during an emergency. Remember, they pay for the losses so they probably won't use one much larger than normal.