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#48268 02/07/05 04:59 PM
Joined: Dec 2004
Posts: 1,064
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.

#48269 02/07/05 05:02 PM
Joined: Dec 2003
Posts: 751
parallel 250 kcmil alum.

#48270 02/07/05 06:48 PM
Joined: Jan 2003
Posts: 4,391
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. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
#48271 02/11/05 03:13 PM
Joined: Jan 2003
Posts: 4,391
Just bringing this up to the top, I was hoping for some more comments. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
#48272 02/11/05 03:35 PM
Joined: Apr 2002
Posts: 7,313
Likes: 7
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, usually 4/0.



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