DIYbanter - View Single Post - What is NEC Code For This Grounding Scheme ?

Doug Miller

In article , wrote:
On Sat, 29 Sep 2007 03:43:23 -0700, John Ross
wrote:

wrote:
On Fri, 28 Sep 2007 06:02:49 -0700, John Ross
wrote:

But as far as these wire sizes everyone is throwing around: is that
required or suggested? I hear this size 6 mentioned. Is that the code
from the rod to the panel or is that just suggested. Also, does that
change with the size of the service (this is 100 amp)? I think this
latest electrician said something about size 10 or 8.

It is really based on the size of the service entrance cables 250.66,
which is usually based on the service disconnect size but that varies
between residential and commercial. Residential generally gets away
with a smaller SE cable because of load diversity.
The other rules refer to the particular electrode used.
You never need more than a #6 to a ground rod/plate, #4 to a UFER.
When you are stringing several electrodes togerther you need the
minimum size for the best electrode down stream up to the 250.66 size.
Water pipes always use the 250.66 size.

250.66 (short version)
SE cable GEC size
copper aluminum Cu Al Res service
2 or smaller 1/0 or smaller 8 6 typical 100a
1 or 1/0 2/0 or 3/0 6 4 typical 150a
2/0 or 3/0 4/0 or 250 4 2 typical 200a

Thanks for the chart, but I have to admit I have no idea what those
abbreviations mean.

I asked the electrician today what size wire would go from ground rod
to panel and he said #8 since it was a 100 amp. It sounds like you are
saying it should be #6?

You never need to be bigger than 250.66 so if you have a typical 100a
service #8 copper is OK. If you upgraded the service you would have to
upgrade the GEC
SE = Service Entrance Cable
GEC = Ground Electrode Conductor (wire to the rod or water pipe)
Cu = copper
Al = Aluminum

And...
2, 1, 1/0, 2/0, 3/0, 4/0, and 250 are wire sizes.
"1/0" "2/0" etc are pronounced one-aught, two-aught, etc.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.