Bonding at Ground Ring

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hill900505

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Texas
I have a concrete equipment pad encircled by a 4/0 AWG ground ring. There are (2) 3" steel pipes and unistruts built to support 3 electrical panels. Do I need to ground this supporting structure (the 3" pipes or unistruts)? If so, should I run an EGC to a ground bus bar in any of the three panels or should I run a grounding electrode conductor to the ground ring directly? Thanks very much for the help!
 
Ponchik

Ponchik

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Once you mount the electrical panel enclosures to them, they (the unistrut and the 3" pipe) become bonded with the grounding system. I don't see the need to install additional EGC.
 
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pcanning87

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Location
New York
edward said:
Once you mount the electrical panel enclosures to them, they (the unistrut and the 3" pipe) become bonded with the grounding system. I don't see the need to install additional EGC.
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I agree with Edward, you don't need to do any additional grounding (this is a pretty typical set up in my industry). If you want to go the extra mile, either approach would work in my opinion. You could size the additional ground however you want since it's not required.


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petersonra

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Location
Northern illinois
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engineer
hill900505 said:
I have a concrete equipment pad encircled by a 4/0 AWG ground ring. There are (2) 3" steel pipes and unistruts built to support 3 electrical panels. Do I need to ground this supporting structure (the 3" pipes or unistruts)? If so, should I run an EGC to a ground bus bar in any of the three panels or should I run a grounding electrode conductor to the ground ring directly? Thanks very much for the help!
Click to expand...

Pretty much by definition this would not be a grounding electrode conductor. I don't know that you would gain anything by running some kind of a bonding conductor between the pipe and the grounding electrode system. Seems to me the primary issue is if there is some chance of the metallic parts becoming energized. If so it needs to be bonded in a way that ensures that the overcurrent protective device will trip in the event of a ground fault, or at the very least if it's an ungrounded power system there would be no or low voltage to ground. It seems to me that there is a low risk of this metallic structure becoming energized since whatever power there is is probably inside the box that is already grounded. Having said that there are some structures that are required to be grounded by the code. You might want to look and see if your structure qualifies for the required to be grounded rule.
 
Ponchik

Ponchik

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Location
CA
Occupation
Electronologist
luckylerado said:
That may or may not be true. What is the voltage? Concentric knockouts? Too little information to make this broad of a statement.
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I believe most of the enclosures that have the concentric/eccentric are tested for bonding for below and above 250V.
 
luckylerado

luckylerado

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Location
Lake of the Ozarks
ActionDave said:
Most metal junction boxe's concentric KOs are listed for over 240V, enough panel KOs are not that it's easier to just figure they are not.

The topic under discussion here is mounting the gear to a metal pole so I don't think concentric KOs play a part.
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The implication was made that the raceways did not require any additional bonding which is not always the case making it a relevant question IMO.

OP mentions raceways as well.
 
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hill900505

Member
Location
Texas
luckylerado said:
The implication was made that the raceways did not require any additional bonding which is not always the case making it a relevant question IMO.

OP mentions raceways as well.
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Sorry, I should have made it more clear. The (2) 3" pipes are just used as mounting unistruts, the panels are then mounted onto unistruts. 3" pipes are not used as raceway.
 
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