electrical detached garage ?

Posted by Bill on February 25, 2009, 3:02 pm

Your electrical inspector would know.

>I'm not the expert but I'm thinking that because the subpanel is
>located in a detached building that it also must have a ground rod AND
>4 wires back. If anyone is sure about otherwise I'm glad to hear it
>cause it's save me a couple bucks on the ground rod :-)

Posted by Steve Barker on February 25, 2009, 4:02 pm

Bill wrote:

> Your electrical inspector would know.
>
>

What if he does not have an inspector involved? Then that's not an
option to ask.

s

Posted by John Grabowski on February 25, 2009, 5:14 pm

> Interesting.
> Code here in 2003 was only one grounding rod, (Actually two, 6' apart), at
> the service entrance only.
> All other sub panels needed 4 wires back to main panel.
> Wonder if it is worth changing?

> > NEC article 250-32(b)(1)
> > Its called a "grounding rod". He will also need the appropriate gauge
> > bare copper wire and copper clamp for the grounding rod.
> > The ground from the main panel is not connected at the secondary
> > location's subpanel.
> > --
> > Dave- Hide quoted text -

> - Show quoted text -

I'm not the expert but I'm thinking that because the subpanel is
located in a detached building that it also must have a ground rod AND
4 wires back. If anyone is sure about otherwise I'm glad to hear it
cause it's save me a couple bucks on the ground rod :-)

*You are correct. The ground rod is for lightning protection. Check with
your building inspector to see if he wants two.

Posted by Wayne Whitney on February 25, 2009, 7:40 pm

> I'm not the expert but I'm thinking that because the subpanel is
> located in a detached building that it also must have a ground rod
> AND 4 wires back.

That is correct for your situation. This configuration is always
required by the 2008 NEC, and it is required by earlier NECs if there
is any other metallic path between the detached building and the
building with the service.

Note that you need to have a grounding electrode system at the
detached building, and ground rods are just one option. All
electrodes present must be attached together, and the possibilities
include: ground rods you choose to drive; metallic water service pipe
that is buried for at least 10' before entering the building; and the
rebar in your foundation, if it is #4 or larger.

The rebar is required to be used if you are pouring a new foundation
(not for an existing building), and if you attach to it, there is no
need to drive any ground rods. The metallic water pipe is required to
be supplemented by at least one other electrode, e.g. a ground rod or
the rebar. Lastly, if you are using only ground rods, because no
other electrodes are present, you must drive two ground rods.

That's just a quick summary of the rules, see Article 250 of the NEC
for the exact text.

Cheers, Wayne

Posted by on February 26, 2009, 11:15 am

> > I'm not the expert but I'm thinking that because the subpanel is
> > located in a detached building that it also must have a ground rod
> > AND 4 wires back.

> That is correct for your situation. =A0This configuration is always
> required by the 2008 NEC, and it is required by earlier NECs if there
> is any other metallic path between the detached building and the
> building with the service.
> Note that you need to have a grounding electrode system at the
> detached building, and ground rods are just one option. =A0All
> electrodes present must be attached together, and the possibilities
> include: ground rods you choose to drive; metallic water service pipe
> that is buried for at least 10' before entering the building; and the
> rebar in your foundation, if it is #4 or larger. =A0
> The rebar is required to be used if you are pouring a new foundation
> (not for an existing building), and if you attach to it, there is no
> need to drive any ground rods. =A0The metallic water pipe is required to
> be supplemented by at least one other electrode, e.g. a ground rod or
> the rebar. =A0Lastly, if you are using only ground rods, because no
> other electrodes are present, you must drive two ground rods.
> That's just a quick summary of the rules, see Article 250 of the NEC
> for the exact text.
> Cheers, Wayne

Water is plastic and it's not worth the hassle to get at the rebar in
the footing. Walls are block up to 24" above grade. So I'll be going
copper rod at the power entrance.

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