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#48268 - 02/07/05 12:59 PM Overhead 400A service
Dnkldorf Offline
Member

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
What do you guys use for the service drop wires? In PVc

500mcm copper thhn?
600 alum?
And the same question for wiring into the panels, in pvc,
2/0 copper, 3/0 alum
just curious of the costs.

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#48269 - 02/07/05 01:02 PM Re: Overhead 400A service
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
parallel 250 kcmil alum.
_________________________
Earl

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#48270 - 02/07/05 02:48 PM Re: Overhead 400A service
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Quote:
parallel 250 kcmil alum


Boy if those are in the same raceway that is pushing it as much as possible and is only acceptable if the calculated load is less than 368 amps.

250 AL rated 230 amps @ 90 C, four current carrying conductors in a raceway.

230 x 2 x .8 = 368 amps.

240.4(B) allows the next standard breaker however the calculated load must stay below 368 amps.

The last 400 amp overhead I did used one set of 600 Kcmil copper.

In my opinion you are not providing a 400 amp service with 500 kcmil copper (380 amps) or two sets of 250 kcmil aluminum (368 amps).

The service can only be rated as high as the lowest rated component.

Of course take this all for what it's worth, I do commercial work so Table 310.15(B)(6) is out of the question.

Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#48271 - 02/11/05 11:13 AM Re: Overhead 400A service
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Just bringing this up to the top, I was hoping for some more comments.

Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#48272 - 02/11/05 11:35 AM Re: Overhead 400A service
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Bob:
OK, it's on top, I'll bite...
500kcmil cu; 4" PVC or RGC dependent on spec's. Occasionally 600 al, but that's a rare bird.

UG is PVC, unless the 1 PE does the spec....
last time I got a change order & spec change in "clouds" when I verified the $$$ of RGC.

Going to the panels....cu, usually 4/0.

John
_________________________
John

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