- Location
- Connecticut
- Occupation
- Engineer
310.12(B) would NOT allow the #4 to be on a 100A OCPD. The feeder to the detached garage does not supply the entire load associated with the dwelling
Next size up
- Thread starter steve burke
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I disagree with that comment. Section 310.12(B) "feeders" states "OR the feeder conductor supplying the entire load ASSOCIATED with an individual dwelling unit". I believe a detached garage for a single family dwelling falls into the category of "associated with" and thus would be allowed to use table 310.12.
- Location
- Connecticut
- Occupation
- Engineer
You are skipping over the ENTIRE LOAD part of 310.12(B).
The feeder to the garage does not supply the ENTIRE LOAD associated with the dwelling unit.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
FWIW, you can use the 83% factor for a 100A garage feeder if the service is 100A.
Or if you turn your garage into an Accessory Dwelling Unit, then you could use the 83% factor. : - ) If you do that, do you have to go back and upsize your service conductors, as they are now supplying 2 dwelling units?
Cheers, Wayne
Or if you turn your garage into an Accessory Dwelling Unit, then you could use the 83% factor. : - ) If you do that, do you have to go back and upsize your service conductors, as they are now supplying 2 dwelling units?
Cheers, Wayne
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
As David said, you are not understanding the requirements of 310.12(B).
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Unless its in the 2020, I don't see 310.12 in the 2017 and 320.12 is for AC cable.
- Location
- Connecticut
- Occupation
- Engineer
2017: 310.15(B)(7)
it is the 2020 NEC
You are correct, I was reading that incorrectly. So if I now understand this correctly, a house with a 400 amp service could use table 310.12 for the service entrance conductors but could not size multiple feeders in the house (say one distribution panel on each level) using table 310.12.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Correct, although if there are any 400A feeders in the house, the table still applies to those feeders.
Cheers, Wayne
And parts of Car & NY are going to outlaw all gas in new homes in next 13 to 15 years then make in maybe 25 years make all older homes stop using natural gas. So along with internal engines being banned houses might require a 300 or 400 amp service especially in climates. Does anybody think that any ultility company can supply a double or tripeling of available power?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
not if they try to do it with wind and PV. maybe some kind of nuclear power but the politics on that makes it highly unlikely that any kind of nuclear power makes a comeback. it is not just the power supply either. the distribution system is not something that can be readily upgraded either. people act like it is just a matter of snapping one's fingers and somehow these trillions of dollars of upgrades just happen.
It does not work that way. The politicians control the state public utility commissions and they will not allow utility rates to go up by a factor of 2 or 3 or 5 (or whatever it ends up being) to pay for these upgrades. We have gotten about all we can get out of increased energy efficiency, so there is not much more to be wringed out of that side of the equation. You would have to make houses so they could literally be heated with body heat to get much better, the trillions of dollars it would cost to upgrade the housing stock to accommodate that idea is unimaginable.
There are something like 80 + million single family homes in the us. say you could upgrade them all somehow to a 400 A service. Just that alone would be an enormous amount of money. My guess is about $3000-4000 each. That would be about $300 billion just by itself. Where is that money coming from?
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wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
To put that number in context, we were talking about the next 30 years. US GDP (in current dollars, since the cost estimate was presumably in current dollars) is about $21 trillion/year, or $630 trillion over 30 years.
So we're talking 0.05% of US GDP for the particular infrastructure improvement you are discussing. There obviously are other infrastructure improvements required.
For comparison US energy expenditures as a fraction of GDP are currently about 6%:
Cheers, Wayne
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