Rigid metal conduit as defacto ground rod


Old 09-28-04, 05:50 PM
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Rigid metal conduit as defacto ground rod

I am doing a garage subpanel and was intending to install a ground rod. However, I ran my THWN conductors about 60 feet underground through rigid metal conduit. Can that act as my ground rod. It is buried 8 inches and runs for 60 feet.
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Old 09-28-04, 05:59 PM
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No. You must have a real ground rod.
Old 09-29-04, 08:44 AM
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If the S-P is located in a structure which is seprate from the structure where the Service is located, you are required to have both an Equiptment Grounding Conductor between the two stuctures, and a Grounding Electrode (copper rod) at the detached structure.

The U-G RMC can serve as the EGC IF it forms a solid metallic path between both ends of the "run", and both ends should be "Bonded" to the metallic enclosures at each end.

I advise that at the S-P you fit a "Bonding-Bushing" on the end of the RMC inside the S-P, and connect a Bonding Jumper between the Bonding-Bushing and a Grounding terminal bar which is throughly Bonded to the metal surface of the enclosure.

The Equiptment Grounding Conductors of the Branch-Circuit, the Grounding Electrode Conductor to the Ground-rod, and the Bonding-Jumper all will connect to the Grounding terminal bar.

The ONLY connections to the Neutral terminal bar are the Feeder Neutral conductor,and the Neutral conductors of the Branch-Circuits.

Good Luck & Enjoy the Experience!!!!!!!!!!!
Old 09-30-04, 04:16 PM
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Actually you are only required to have an EGC if there are other metallic paths between the structure, such as a water pipe or phone/cable between the buildings.
The point is moot though since you are only 8" deep. 3/4" galv pipe can be used as a grounding electrode in lieu of a ground rod but it must be driven to "at or below grade" or it can be laid in a trench 30" deep.

I honestly cannot say if I think the conduit run itself can be the grounding electrode if it were 30" deep. I have never run across such a situation and never considered the scenario.
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