> > Ok, here's one for the electricians....
> >
> > I have a great shop with marginal power and I need to upgrade.
> > The shop is
> > about 20 ft away from my main house panel which is a 200 amp service.
> > Unfortunately the existing wire is four ~8ga runs from two 15amp
> > breakers.
> >
> > The problem is that the wires run through a 1" conduit that's
> > burried in a
> > concrete slab. I really don't want to dig this up so I need to figure
>out
> > the largest wires I can get through the existing conduit.
>
>A quick Google turns up
>http://bwcecom.belden.com/Catalog/Conduitcc/cncpchtp.htm
>which says that a 1" diameter conduit is allowed (by the NEC) to have a
>total of .35 in^2 of cable installed (with 3 or more cables).
>
>Grainger has 2 AWG THHN wire listed at .381" od, which means 3 of them
>would
>only take up .342 in^2
>http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1612704035&c
>citem=
>
>2 AWG THHN is rated for 130 amps in conduit (assuming your slab never gets
>over 86F). If you don't have to pass inspection, you could probably get
>away with 150 amp breakers at the house (but 125 would meet code). Then
>put
>a sub-panel in the shop to split it up as needed.
>
>However, don't forget you're robbing power from the house, and 200 amps is
>none too big by today's standards. If you have high power electric devices
>in the house (dryer, range, furnace, water heater etc.), you may have to
>forgo using them while drawing 150 amps in your shop, or risk blowing a
>main
>breaker.
>
>If that's not big enough, you might be able to squeeze in (2) 1 AWG wires
>plus a 2 AWG; which would get you a rated 150 amps. That's a code
>violation
>(because the conduit is overfilled), but your inspector may overlook it.
>
>Randall - not a licensed electrician
>
Thanks Randal,
Fortunately I have city gas service for my water heater, dryer, oven and
heating (although that's not really an issue). My slab will probably get
over 86 deg in the summer though, air temp gets to ~115 here...
Cheers,
John
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