Earth grounding rod needed for detached garage?


Old 08-09-07, 11:05 PM
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Join Date: Jun 2007
Posts: 6
Earth grounding rod needed for detached garage?

I have an older 2 car garage that is detached from the house by about 25'. The garage is on one 15 amp breaker via a buried 2 wire 14 gauge non-metallic cable. The wiring inside the garage is all 14 gauge run in 1/2" metal conduit. I have made sure that all the recptacles and switches have ground wires connecting them to their boxes. I can see that there is a 3/4" conduit stub coming into the building with the underground cable in it and the house has the cable leaving out 1/2" conduit at a box on the inside wall. According to the neighbor who watched the original construction, they don't think that the builder ran metal pipe the whole distance between the buildings though.

If that is true, don't I have to add one of those copper grounding rods into the earth next to the garage and wire it up to the 3/4" metal conduit for the building to be grounded if they didn't run the metal pipe all the way?

I am not an electrician but I think that it would not be good to add another ground IF they did run metal conduit all the way between the buildings. Do I have to do a connectivity test between the pipe leaving the house and the one entering the garage to know if any more needs to be done?

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Old 08-09-07, 11:39 PM
Join Date: Dec 2006
Location: orange county
Posts: 285

Just curious ____Is the location of this 15A c/b you are referring to at the MAIN PANEL? ( I am a novice and mostly get my knowledge from reading these posts) As you probably already know and if I am understanding my own interpretations correctly you are allowed to run one circuit to a de-tached building without installing a Sub. As far as driving a ground rod as I am a novice I wouldn't bet my life on it but I would bet 100 bucks that would not be necessary. At least I've not yet read in the archives that I read of any such necessity for a single circuit to a de-tached structure?? But what do I know. We'll find out shortly when the pro's come around.
Old 08-09-07, 11:53 PM
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,808
if this is only one single or one multi branch circuit wire then you don't need the ground rod at the garage location but if you run subfeed box then yes you have to .

but before i can get any more futher in this you mention that you have both half and threequarter pipe in the ground what you have to do is check the wires make sure they are not damaged and both are same namebrand etc

i know from time to time we do have underground splice in there but not too often unless it propley used

Merci , Marc

P.S. buy a simple three light repecactle tester to verify the wireing is correct in there
Old 08-10-07, 06:49 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
I hope you are mistaken about the cable type. NM (non-metallic) cable is not appropriate for outdoor use underground, even if in conduit. The proper cable would be UF (underground feeder).

In your case, if you have no ground then using grounded receptacles in the garage is improper, unless your provide GFCI protection. Since GFCI protection is a very good idea (and is now required for garages), I would do this if it is not there already.

Installing a ground rod to this setup would be wrong, and would serve no purpose. You would only install a ground rod if you have a sub-panel at the detached garage.
Old 08-10-07, 12:15 PM
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Join Date: Jun 2007
Posts: 6
More Info

I learn so much from this forum! Even when I think that I've included everything that might be needed in order to answer a question, I find out that I didn't. So...

- the 15A c/b for the garage is at the main panel

- the wire leaving the house and the wire entering the garage are the same kind as best as I can tell (color, # of conductors). The amount of excess wire in the box at the house is very, very little and I can not read its identification printing to be positive that it is the same, but is sure looks the same.

- I used the wrong term for the wire. It is UF cable. I used the term non-metallic to mean it was absent of any metal jacket, which I now understand was not the best way to describe it.

There is no sub-panel at the garage. The line comes in and feeds a pair of GFCI's. The rest of the garage (lights and outlets) are connected to the Load end of the GFCI's. Is this correct?
Old 08-10-07, 12:48 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
As long as the receptacles are on the LOAD side of the GFCIs, yiou are fine.

Why are there two GFCIs? For a 120 volt circuit, one will suffice.

If no ground exists then the receptacles SHOULD be labeled "NO EQUIPMENT GROUND" to be up to code, but this is often not done.

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