Sizing based on largest ungrounded condcutor

mbrooke

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United States
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*
What would you think if the NEC changed 250.122 to:

"Table 250.122 Minimum Size Equipment Grounding
Conductors for Grounding Raceway and Equipment"



"Size of largest ungrounded copper conductor" "Copper"

#14 #14
#12 #12
#10 #10
#8 #10
#6 #8
#4 #8
#3 #6
#2 #4
#1 #4
#1/0 #4
#2/0 #4
#3/0 #3
#4/0 #3
#250 #3
#350 #2

ect
 

Dennis Alwon

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Staff member
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Chapel Hill, NC
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Electrical Contractor
Why would you change this.. What is your substantiation.
You don't just make up numbers because you think it is better so Where did those numbers come from?

BTW, I hate the idea. LOL
 

mbrooke

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United States
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Why would you change this.. What is your substantiation.
You don't just make up numbers because you think it is better so Where did those numbers come from?

BTW, I hate the idea. LOL


Easier to understand and clears up confusion such as upsizing circuits for voltage drop.

I did increase the EGC size for a few cases, I think the impedance is to high at time- like a 200amp OCPD being opened with #6- but that is open for debate.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
IMO it's a great idea just replace that dumb Table 250.122 and get rid of 250.122(B). I believe that Don has been saying this for years.
 

mbrooke

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United States
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Well that's the substantiation you used when you answered Dennis.

Roger
Going into reactance, resistance and suseptance, average circuit runs and typical breaker pickup curves would take more effort to type out and make the thread more confusing. I know Dennis is smart, but, I want to save everyone the long list of numbers.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Going into reactance, resistance and suseptance, average circuit runs and typical breaker pickup curves would take more effort to type out and make the thread more confusing. I know Dennis is smart, but, I want to save everyone the long list of numbers.
So make the proposal and use that for your substantiation.

Roger
 
I might, but I want to get your thoughts/ideas/votes before I do.
If you have scientifically analyzed fault clearing and find the existing method flawed and have a better one, I don't see why it shouldn't be accepted.

The other option is go the route of a lot of these recent changes that happened and just say it seems like a good idea and don't give any evidence:rant:
 

mbrooke

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If you have scientifically analyzed fault clearing and find the existing method flawed and have a better one, I don't see why it shouldn't be accepted.

The other option is go the route of a lot of these recent changes that happened and just say it seems like a good idea and don't give any evidence:rant:
Well I'm not Eaton, so I will have to use route #1.
 

kwired

Electron manager
Location
NE Nebraska
Problem is even if you run conductors per current requirements, you still get different fault current levels and clearing times on OCPD's depending on length, upstream conductors and source impedance. There is no one size fits all method that won't have undesired results in certain situations. I think a one size fits all is a good basic requirement though and let designers decide if they want to exceed that requirement in specific situations.
 

mbrooke

Batteries Not Included
Location
United States
Occupation
*
Problem is even if you run conductors per current requirements, you still get different fault current levels and clearing times on OCPD's depending on length, upstream conductors and source impedance. There is no one size fits all method that won't have undesired results in certain situations. I think a one size fits all is a good basic requirement though and let designers decide if they want to exceed that requirement in specific situations.
Well said.

FWIW, in Canada code requires that in some cases EGCs be larger then our table, in others it lets them be smaller.
 
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