# Concentric KO and when to use Grounding bushing



## MikeD (Jul 7, 2008)

if you have eccentric or concentric ko's, you are _supposed _to use bonding bushings...if you cut the hole yourself, you can use a bonding locknut....


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## Idaho Abe (Nov 28, 2007)

Read 250.92 (B) and you will see that if the hole is concentric knockout you will need a jumper.


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## Losrod (Apr 30, 2008)

But if i am dealing with 250V or less is that still required?


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## MikeD (Jul 7, 2008)

What's the voltage have to do with it?


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## Losrod (Apr 30, 2008)

I was told by a foreman that a ecentric ko is rated up to 250V. 
So he said that i did not need one.


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## MikeD (Jul 7, 2008)

I don't know what he is talking about...locknuts by them selves are not an acceptable means of bonding...you need a bonding bushing along with a jumper


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## Losrod (Apr 30, 2008)

ok thanks. 
I will look it up on my code book and read that code.
Once again thanks.


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## Stickboy1375 (Jul 23, 2007)

Losrod said:


> I was told by a foreman that a ecentric ko is rated up to 250V.
> So he said that i did not need one.



Ding Ding Ding, we have a winner...


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## Stickboy1375 (Jul 23, 2007)

MikeD said:


> What's the voltage have to do with it?


Everything...


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## Stickboy1375 (Jul 23, 2007)

Idaho Abe said:


> Read 250.92 (B) and you will see that if the hole is concentric knockout you will need a jumper.


That section is for Services, try 250.97


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## MikeD (Jul 7, 2008)

point is....it's high voltage...it needs to be bonded...and isn't that what i said earlier...concentric ko's=bonding bushing w/ jumper....no ko's=bonding locknut


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## MikeD (Jul 7, 2008)

he's also using 240 delta, not 480


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## Stickboy1375 (Jul 23, 2007)

MikeD said:


> point is....it's high voltage...it needs to be bonded...and isn't that what i said earlier...concentric ko's=bonding bushing w/ jumper....no ko's=bonding locknut



No special bonding is required... only on 277 and higher voltage with ringed knockouts.


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## Stickboy1375 (Jul 23, 2007)

MikeD said:


> he's also using 240 delta, not 480



Are you agreeing no bonding required or not?


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## MikeD (Jul 7, 2008)

agree, it needs to be bonded..i was going by 250.92b...


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## Joefixit2 (Nov 16, 2007)

The way I understand it the bonding bushind is not required at that voltage, unless it is at the service enclosure, on the LINE side. I don't see where you are even required to use a bonding bushing on concentric KO's when leaving the service enclosure with load side conductors.


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## Stickboy1375 (Jul 23, 2007)

MikeD said:


> agree, it needs to be bonded..i was going by 250.92b...



I was never agreeing with you... No bonding is required, his voltage is not met....

250.92b is for services....


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## Stickboy1375 (Jul 23, 2007)

Joefixit2 said:


> The way I understand it the bonding bushind is not required at that voltage, unless it is at the service enclosure, on the LINE side. I don't see where you are even required to use a bonding bushing on concentric KO's when leaving the service enclosure with load side conductors.



Your correct, I posted a picture, doesn't get much easier than that....


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## John (Jan 22, 2007)

My point of view is that IT does need a Grounding bushing. This is for the sole reason of “Craftsmanship”. The NEC is for minimum requirements and not to be read as absolute. Use a little common sense when doing electrical work. If it makes sense that a grounding bushing may be needed, just do it even if the code does not require it.
My trade mark on installing any conduit is that I will use bushings on all conduit and fittings ¾” or larger. The NEC does not require this but I do it anyway. This is what is called “Quality Craftsmanship”. Take pride in your work give it a little extra Craftsmanship. :thumbsup:


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## MikeD (Jul 7, 2008)

thank you ...JOHN....this was all I was trying to say, but I was trying to justify it with code(i know that section is for services),,,but doesn't it make sense to use bonding bushings and locknuts anyway?...I think it's good practice to do so


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## MikeD (Jul 7, 2008)

and on top of that...congrats on knowingthis nit-picky code...this is another example of how ridiculous the NEC gets...use bonding bushings and you'll never have a problem, no matter the Voltage...oh yeah and Geaux Tigers 2007 National Champs


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## Joefixit2 (Nov 16, 2007)

Sure most of us agree it is good practice to use a BB on every concentric KO, but when asked if it is _requi__red _
then I will reply with the correct answer to the question asked. We can always offer our advice and opinions, but trying to force our opinions as code requirements by not truthfully answering the question asked is not fair to the OP and it is how wrong information gets passed. A lot of inspectors do this, either out of ignorance or the reason I mentioned.


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## Stickboy1375 (Jul 23, 2007)

I think you guys are just wasting material. There is no reason to install a bonding bushing so why do it?


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## Stickboy1375 (Jul 23, 2007)

John said:


> My point of view is that IT does need a Grounding bushing. This is for the sole reason of “Craftsmanship”. The NEC is for minimum requirements and not to be read as absolute. Use a little common sense when doing electrical work. If it makes sense that a grounding bushing may be needed, just do it even if the code does not require it.
> My trade mark on installing any conduit is that I will use bushings on all conduit and fittings ¾” or larger. The NEC does not require this but I do it anyway. This is what is called “Quality Craftsmanship”. Take pride in your work give it a little extra Craftsmanship. :thumbsup:


Do you pull EGC's in EMT or choose not to?


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## John (Jan 22, 2007)

Stickboy1375 said:


> I think you guys are just wasting material. There is no reason to install a bonding bushing so why do it?


Because it is the right thing to do under certain installs.


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## John (Jan 22, 2007)

Stickboy1375 said:


> Do you pull EGC's in EMT or choose not to?


Sometimes.


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## Bkessler (Feb 14, 2007)

You do not need a bonding jumper under 250 volts to ground. If you use one there is nothing wrong with that. But it does not make it a better "install" it just makes it a tiny bit more expensive.


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## Stickboy1375 (Jul 23, 2007)

Bkessler said:


> You do not need a bonding jumper under 250 volts to ground. If you use one there is nothing wrong with that. But it does not make it a better "install" it just makes it a tiny bit more expensive.


I agree 100%..., never understood the un-needed material equals better install logic...


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## Bkessler (Feb 14, 2007)

When you lack skills in one area you over compensate in others.


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