On Wed, 26 Oct 2005 16:08:13 -0400, "John Grabowski"
wrote:


wrote in message
roups.com...
If I am wiring a 100 amp subpanel in my detached garage with 240 using
2-2-2-4 AL, I am carrying the ground from my house's main panel (60 amp
breaker). Does NEC require that I have a grounding rod at my detached
garage? If that is the case, should I only be running 2-2-2AL?
thanks. Any arguments for using copper? The AL seems like it may be
overrated, but cheaper in the end.


Read article 250.32(A). Run the four conductors from your main service.
Install a ground rod or two for your detached garage. Install a grounding
terminal bar in the garage subpanel to connect the #4 aluminum from your
main feed and the grounding electrode conductor (#6 or #4 copper) from your
ground rods together. All grounding conductors for your branch circuits
should also terminate on this bar. Keep the neutral conductor isolated from
the grounding conductors. The #2 aluminum is good for 75 or 90 amps
depending on your terminal ratings. Have your work inspected.

It is okay to use aluminum, but I don't recommend its usage underground and
especially for direct burial. Moisture and aluminum don't go well together.


John Grabowski
http://www.mrelectrician.tv
Mr. Grabowski gave you the correct information.

Dan