For decades on large 480v services most folks here would use the "six disconnect:" rule to avoid the 230.94 GFP requirement (and later the 240.87 requirement). For those areas still under Codes prior to 2020, do you still see the six disconnect allowance or has 70E pretty much mandated a main ??
Service 480/277 > 1000 amps.
- Thread starter augie47
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electrofelon
Senior Member
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- Cherry Valley NY, Seattle, WA
Interesting question. None of my clients were ever large enough to know or care about 70E. Am curious though if a main was ever speced by someone for future compliance with 70E.
I know some people didn't like to use MLO's and didn't, don't think it specifically for 70E however. Note also you can still get around the GFPE requirement with multiple disconnects in separate enclosures.
- Location
- New Jersey
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- Journeyman Electrician
We're still under the 2008 and every new building we build has the 6 disconnect rule. I've never seen a main on a 4000 amp service.
hillbilly1
Senior Member
- Location
- North Georgia mountains
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- Owner/electrical contractor
The blue boxes have gfp mains, but most (not all) orange boxes use two mains in separate cans with a future empty can for a third to get around the gf requirement. They still have all of the distribution breakers in the same cans.
Most DC’s will have gf mains. I just done an industrial plant with two 800 amp mains, but all of the distribution is in different cabinets. The old six switch rule in a MLO cabinet makes it real difficult to hook up a temporary generator, and know of a lot of contractors that backfeed the extra main lugs with a generator with less than desirable results!
Most DC’s will have gf mains. I just done an industrial plant with two 800 amp mains, but all of the distribution is in different cabinets. The old six switch rule in a MLO cabinet makes it real difficult to hook up a temporary generator, and know of a lot of contractors that backfeed the extra main lugs with a generator with less than desirable results!
Tulsa Electrician
Senior Member
- Location
- Tulsa
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- Electrician
Pics from facility I'm work in presently
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mayanees
Senior Member
- Location
- Westminster, MD
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- Electrical Engineer and Master Electrician
Yikes!!! That last picture of the trip unit shows factory default settings on a 4000-amp trip unit. That's what's called an uncoordinated electrical system! Someone needs to determine the POCO source's ocpd and make adjustments to the breaker's trip unit using SKM or some other power system analysis software to avoid an uncoordinated trip.
Tulsa Electrician
Senior Member
- Location
- Tulsa
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- Electrician
Thanks for pointing that out.
Next week I will look the whole gear over a little closer and ask some questions. The facility is going thru some changes so this may be a good time address it. They did discuss after rework is done doing a new study though out. I will make them aware of this.
hillbilly1
Senior Member
- Location
- North Georgia mountains
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- Owner/electrical contractor
Wouldn't of helped on the load side either since GFI protection doesn't protect against a short circuit.
JAP>
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
The only thing I can figure, is the original installing electricians, used the hole saw extension as an Allen key. Then laid it on top of the breaker and forgot about it. The generator tech turned the main off to test the generator, when he was done, he turned the main back on, and the extension rolled into the buss! I imagine he needed a clean set of drawers after that! It had probably been laying there since the store was built 20 or so years ago.
hillbilly1
Senior Member
- Location
- North Georgia mountains
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- Owner/electrical contractor
I've witnessed that exact same scenario.
Those are the one's where you hug all your guys after you make sure everyone is ok.
JAP>
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