Notched hole for GEC

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timothy.collins

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I have been hearing recently there is a non-practiced requirement for the GEC entering an enclosure. Common practice seems to be; route the conductor thru an existing hole or drill one. I believe there may be some data that relates to elongating the hole or cutting a U shape to prevent the heating of the enclosure due to induction in that area in the event of a fault. Has anyone seen this information and can point me in the right direction. Any comment will be greatly appriciated.
 
You might be thinking about the requirments in 300.20(B) for individual conductors carring alternating current.

Just a thought.

Chris
 
timothy.collins said:
I have been hearing recently there is a non-practiced requirement for the GEC entering an enclosure. Common practice seems to be; route the conductor thru an existing hole or drill one. Any comment will be greatly appriciated.
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timothy.collins,

I think I know exactly what your talking about. Many GEC's are installed below transformers (CEE,ground rod, etc.). In my experience I have run across many of these violations. I would suggest reviewing 250.64 especially 250.64(E).

Unaware at the time, I have personally violated this code section. Funny thing is that on more than one occasion different inspectors did'nt see anything wrong.

Later after watching Mike Holts GvB series I learned about 250.64(E) as well as other sections. At first I was concerned that I installed an installation that was unsafe then I was comforted to learn that a GECs chief purpose is to give a path in the event of a lightning strike or line surge.

Im not saying that it was ok but since I live in SO California and there is hardly any lightning I could rest easier. If I was in Florida it would be a different story.

There are a few theories about why we bond to entrance and exits of metal enclosures and raceways. I have a novice level of understanding about the "inductive choke " that could possible aid in destroying the conductor in cetain case's.

I'm sure there is someone on the forum that could better explain.

I'm grateful this forum exists so I can deflate my ego and get some answers that are somtimes hard to come by anywhere else.

hope this helped

Ibew441dc
 
ibew441dc said:
timothy.collins,

There are a few theories about why we bond to entrance and exits of metal enclosures and raceways. I have a novice level of understanding about the "inductive choke " that could possible aid in destroying the conductor in cetain case's.


hope this helped

Ibew441dc
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Its no theory, but a phycial property of electrons. Since lightning is high frequency and high amperage, it behaves differently than AC 60 Hz. At the high frequency the inductive and reactive components are very large. Changing a conductor from 4 awg to 4/0 for lighting protecting makes very, very little difference since lighting currents travel on the skin. But using a flat copper sheet 4" wide makes a huge difference.

M&W mfg makes a Kenny Clamp for this purpose.
 
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Heres a picture of the kenny clamp. goggle kenny clamp for info.
They cost about $4.00 each and are excellent quality. I may be the only person on the west coast using them...
 
tom baker said:
Its no theory, .
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Tom Baker,

(I know what you were getting at but Im going to be a smart a@# ;) )

The examples you were giving are taught in ac and dc theory not, completely proven. Its starts with electron theory.

Anywho:grin:

Thanks for the graffic. What manufacture is M&W?
I think your right about nobody on the west coast using those kenny clamps. I think it is due to the wide spread lack of education on the effects of lightning , ( probably because the west coast doesn't suffer as bad as the east.)

You should rest easy , knowing that you have planted a seed of knowledge.
I am going to seek out these kenny clamps and continue to educate my peers on proper installation methods.

thanks ,

Ibew441dc
 
tom baker said:
Heres a picture of the kenny clamp. goggle kenny clamp for info.
They cost about $4.00 each and are excellent quality. I may be the only person on the west coast using them...
Click to expand...

Sheesh, I was telling my partner they should make a connector for the GEC that mechanically bonds to the panel, and poof 2 days later I find it exists. We have always used a romex connector for that reason, just so I felt it would still be somewhat grounded if the ground was removed in the panel for some onknown reason.
 
Jesse, I was told it was a Prince Georges co. MD inspector that invented it. The jurisdictions around that area like to see them:roll: . A former employer liked using them, I had never seen them before, but he did a lot of work in the DC area.
 
ibew441dc said:
Tom Baker,

(I know what you were getting at but Im going to be a smart a@# ;) )

The examples you were giving are taught in ac and dc theory not, completely proven. Its starts with electron theory.

Ibew441dc
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Do you have a copy of the IEEE Green Book? The choke "theory" is very well explained.
And if you have some other documentation that this effect is not proven I'll be interested to see it.
 
Tom's explanation is one that I have heard many times before. To add to what he has said;

When the high frequency current travels along a conductor and reaches where the conductor will pass into a metallic enclosure, whether it is a trough or raceway, 93% of the current will "jump" from the conductor to the metallic enclosure. If that metallic enclosure is not bonded to the conductor, as the current "jumps" across, it will create an arc that usually destroys the conductor and may inhibit the current before it completes its path. That is another part of the reason for bonding the GEC to the enclosures. I have seen the result of this twice. The conductor is scorched and cut clean through.
 
JohnJ0906 said:
Jesse, I was told it was a Prince Georges co. MD inspector that invented it. The jurisdictions around that area like to see them:roll: . A former employer liked using them, I had never seen them before, but he did a lot of work in the DC area.
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Inspector "invents" a cable clamp for the GEC and then gets his and adjacent jurisdictions to require it. They cost $4 each, maybe 2 per panel; he probably gets $2 for each one sold.

There ought'a be a law against using a government agency to compel someone to use something that you have an exclusive license to make money from.

Actually, they are nothing more than a slight modification to a tubing adapter that you can buy in the plumbing department at HD.
 
Bob
He actually paid for the testing and listing of the product, that is very expensive. I met the gentleman, and he spent years of his time and money developing this item. I am not saying I disagree with your statement, just adding to what has been said.
 
I often forget that these "Kenny Clamps" exist. My supply house normally only stocks one, and if somebody bought it, it's a week or so until they have another. Here's a pic of one I used a couple of months ago on a CT can.

HPIM0632.jpg


HPIM0633.jpg
 
tom baker said:
Do you have a copy of the IEEE Green Book? The choke "theory" is very well explained.
And if you have some other documentation that this effect is not proven I'll be interested to see it.
Click to expand...


Tom Baker

I do not own a copy of the Green Book but I have been wanting to get one .

I do not dispute the information and the sources about the choke theory. :smile:

ibew441dc
 
I have not seen any documentation that a GEC running through the enclosure wall is any type of a problem or choke as long as the GEC is connected to the metal enclosure at some point within the enclosure. There is lots of info on the problem when you run the GEC through a ferrous raceway without making a bonding connection. The small 1/4" KO on many meter cans is intended to be used to run the GEC into the meter can and is not designed for any type of connector.
Don
 
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