Properly configuring layout for 400 A service/meter socket with 3 downstream panels

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wwhitney

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Location
Berkeley, CA
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electrofelon said:
I think you know my philosophy Wayne, that I am vehemently opposed to this nanny state/dumbing down /"brother -in-law proofing" of the code where electricians are becoming mere "installers" and can't make any judgements based on actual conditions in the field to make things work.
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I somewhat sympathize with that attitude, but I don't think this is a good example of the issue. The minimum safe distance between live parts isn't something a typical electrician has learned through experience--at least I hope not, as that would imply having participated in a number of short circuit and arc over events. Rather it strikes me as something determined through engineering tests, etc.

Anyway, UL 414 "Meter Sockets" Table 8.1 has the answers. For voltage differences of 300V or less, "parts of opposite polarity" need to be 3/8" apart through air, and 3/4" apart measured over a surface. And if one of the parts is "grounded metal" then it's 3/8" through air, 1/2" over a surface. Plus there are some footnotes and details that probably need digesting.

I don't know what the typical stud spacing is on a meter socket such as is being discussed, but it sounds like some pretty wide lugs would still comply.

Cheers, Wayne
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
wwhitney said:
I somewhat sympathize with that attitude, but I don't think this is a good example of the issue. The minimum safe distance between live parts isn't something a typical electrician has learned through experience--at least I hope not, as that would imply having participated in a number of short circuit and arc over events. Rather it strikes me as something determined through engineering tests, etc.

Anyway, UL 414 "Meter Sockets" Table 8.1 has the answers. For voltage differences of 300V or less, "parts of opposite polarity" need to be 3/8" apart through air, and 3/4" apart measured over a surface. And if one of the parts is "grounded metal" then it's 3/8" through air, 1/2" over a surface. Plus there are some footnotes and details that probably need digesting.

I don't know what the typical stud spacing is on a meter socket such as is being discussed, but it sounds like some pretty wide lugs would still comply.

Cheers, Wayne
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Well I would have guessed to have no less than 3/4" separation, so I would have been fine and I suspect most electricians would have been too.
 
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wwhitney

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Location
Berkeley, CA
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Retired
electrofelon said:
Well I would have guessed to have no less than 3/4" separation, so I would have been fine and I suspect most electricians would have been too.
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I'm still wondering if there's some NEC requirement at play that would require more space. I guess the bending space requirements don't directly apply, but in practice keeping the conductors from interfering with each other might still require a larger separation between lugs (or maybe not).

Cheers, Wayne

P.S. UL 414 6.1.10 says that "Friction between surfaces may not be used as the sole means to restrict turning of an uninsulated live part." I guess that's why the lug you posted has a rib on the back, and the lug Larry posted has two mounting holes. So your lug requires a single post with a suitable recess or end of bus to prevent rotation? And Larry's lug requires double studs, or a ribbed one stud to two stud adapter?
 
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ctsparks

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Location
Connecticut
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Electrician
gcammerata said:
This is my first post on this forum. As a quick overview, I have a large shop/equipment building that is adjacent to where my new home will be constructed. The equipment building is complete, the home won't break ground until next year. The new pad mount utility transformer is adjacent to the new equipment building. The service size is 400A. Ultimately, I want the shop to have a 150A load center (sub panel), and the main house to have two, 200 A load center (sub panels). Inside the equipment building, immediately after the meter socket, I am assuming would need a 400A fused disconnect, followed by a 600A trough that would allow me to connect each of the 3 sub panels. Here are my questions:

1. Is this the best way to do this or is there a better way?

2. Is the 400A fused disconnect better than a 400A breaker in an enclosure?

3. I have never used a trough, but if that is the best way to go, the ones I have seen have bus bars inside. How do I make the connections to the bus bars.

4. Any links to specific equipment would also be helpful.

Thank you for the help!

Greg
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Better option would be to have separate service for the house and barn. This way if something happens with the business or you decide to close the doors, you could rent the barn to someone else without having to worry about paying the utility fees.
You can have the single utility transformer and feed the two buildings with their own service.
This might also be a benefit depending on the rate class you will be paying. If the building is considered commercial space the utility may bill it differently then they would for your home. There may also be rebate or solar programs that are available for the different rate structures.
 
V

VirutalElectrician

Senior Member
Location
Mpls, MN
Occupation
Sparky - Trying to be retired
ctsparks said:
Better option would be to have separate service for the house and barn. This way if something happens with the business or you decide to close the doors, you could rent the barn to someone else without having to worry about paying the utility fees.
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Around here the PoCo charges a flat $35/mo for a meter, so that adds up quickly.

If you wanted to do that in the future, you could just add a CT to the barn feed and bill accordingly.
 
S

stedder

Member
Can triple load side lugs be installed in the meter feeding three breaker enclosures grouped beside or below the meter?
Or has that already been said?
 
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