ground size question

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charlie b

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Lockport, IL
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250.122(A) says the EGC is never required to be larger than the current-carrying conductors. But nothing prohibits it.
 

infinity

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New Jersey
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Is there a similar NEC article for service grounding conductors? 250.122(A) is for equipment grounding conductors.

Can you clarify, what do you mean by "service grounding conductors", that term is somewhat vague.
 

charlie b

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Lockport, IL
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Retired Electrical Engineer
Is there a similar NEC article for service grounding conductors? 250.122(A) is for equipment grounding conductors.
I can't conceive of a situation in which #10 wire would be used for the service conductors. So please clarify your question. Are you talking about the grounding electrode conductor, or perhaps about a "ground" wire that is run from the service transformer to the main service panel?

While we are on the subject, can you give us some context for the question? Is this an existing installation that you have come upon, or perhaps a design that has not yet been constructed?

 

kwired

Electron manager
Location
NE Nebraska
I can't conceive of a situation in which #10 wire would be used for the service conductors. So please clarify your question. Are you talking about the grounding electrode conductor, or perhaps about a "ground" wire that is run from the service transformer to the main service panel?

While we are on the subject, can you give us some context for the question? Is this an existing installation that you have come upon, or perhaps a design that has not yet been constructed?

Never seen a 30 amp service for limited load applications?
 

kwired

Electron manager
Location
NE Nebraska
Is there a similar NEC article for service grounding conductors? 250.122(A) is for equipment grounding conductors.
If you are talking minimum size "grounded service conductor", yes. It must be able to handle maximum imbalance load yet never can be smaller than the required supply side bonding jumper. See 250.24(C) and (C)(1).
 

kwired

Electron manager
Location
NE Nebraska
I've seen a 30A service on a single family home. We even installed solar on it. :happyyes:

Was the PV only 100 watt unit, or was it 30kW and exported more than was ever consumed from utility?

I'm sure I've seen a few 30 amp services to a single family home still in use a time or two as well, some maybe just 120 volt only.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
(Thread drift alert...)
I believe the solar was about 3kW, requiring a 20A breaker. The homeowner had a 1950s vintage 30A fused disconnect feeding a 1980s vintage 125A panelboard. If we had wanted to, we could have installed a 5kW inverter on a 30A breaker.

Lots of homes that don't have air conditioners or electric heating appliances never need more than 30A, especially if the lighting is efficient. My own home qualifies. I've had consumption monitoring for the better part of the year and I've never seen more than about 10A at 240V, at least when averaged over a 5 minute interval.
 
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