Lugging 500kcm to 2-4/0 lugs

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RoadDad

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Is it allowed by the NEC to install a 500kcm conductor to a 2-hole 4/0 lug. We have a breaker with a dual feed 4/0 lug and we are feeding it with a 500kcm. The engineer has OK'd the untwisting of 1/2 the strands to make the second termination on the dual lug. I think it will overheat and trip the breaker. What does the code say about this?
 
RoadDad said:
Is it allowed by the NEC to install a 500kcm conductor to a 2-hole 4/0 lug.
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No, see 110.14

We have a breaker with a dual feed 4/0 lug and we are feeding it with a 500kcm.
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Order the correct replacement lugs from the breaker manufacturer. They should only be a few days away once ordered.

The engineer has OK'd the untwisting of 1/2 the strands to make the second termination on the dual lug.
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That really blows my mind. :-?

I think it will overheat and trip the breaker.
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It might work fine or it might fail, no telling. But if it does fail you will on the hook for the failure regardless of the engineers blessing or if the failure did not even have anything to do with the split conductors.
 
RoadDad said:
Is it allowed by the NEC to install a 500kcm conductor to a 2-hole 4/0 lug. We have a breaker with a dual feed 4/0 lug and we are feeding it with a 500kcm. The engineer has OK'd the untwisting of 1/2 the strands to make the second termination on the dual lug. I think it will overheat and trip the breaker. What does the code say about this?
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The engineer should be shot and quartered.:grin:
 
As Bob said it may work for the next 40 years or it may not. If not they'll be looking for you not the engineer. Either way you have a violation regardless of what the engineer said.
 
ask the engineer if he can do the first termination for you, just kidding, don't do it order the correct lugs
 
mpd said:
ask the engineer if he can do the first termination for you,
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LOL, great idea. :cool:



I was trying to imagine actually having to do it, I think it would be difficult and there would be a lot of bare copper.
 
RoadDad said:
The engineer has OK'd the untwisting of 1/2 the strands to make the second termination on the dual lug.
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Who first suggested doing this, the engineer or the installer?
 
RoadDad said:
The engineer has OK'd the untwisting of 1/2 the strands to make the second termination on the dual lug.
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Any chance you could have him put this in writing and post it here? It would become an instant classic.
 
chris kennedy said:
Any chance you could have him put this in writing and post it here? It would become an instant classic.
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Not to mention a great blackmail opportunity. :roll:
 
Need More Info

Need More Info

Here's the engineer's reply.

Bruce,
The design of electrical lug connection (Dual Vs Single connection) in 480v breaker feeding VFD's at bioreactor is considered acceptable for long term reliable service of this equipment. If you have any questions, Please feel free to give me a call.
JBM


However, I need more than opinions, even if I agree with them. I need code sections, chapters, and verses.....
 
RoadDad said:
However, I need more than opinions, even if I agree with them. I need code sections, chapters, and verses.....
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You could point out 110.3(B), the lug is labeled 4/0, putting a 500 into it ignores the products labeling which is a violation of 110.3(B).
 
RoadDad said:
Here's the engineer's reply.

Bruce,
The design of electrical lug connection (Dual Vs Single connection) in 480v breaker feeding VFD's at bioreactor is considered acceptable for long term reliable service of this equipment. If you have any questions, Please feel free to give me a call.
JBM


However, I need more than opinions, even if I agree with them. I need code sections, chapters, and verses.....
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I dont read anywhere in that him saying to split the wire,only says double lug is ok and i am sure it is but not for a split wire
 
mpd said:
ask the engineer if he can do the first termination for you
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I said the same thing today about a custom engineered stainless steel countertop and backsplash all one piece with holes cut in the splash and 1.5" deep HANDY BOXES welded on to the back side. I said I can't install anything in those handy boxes, maybe the designer can.
 
Need Written Proof

Need Written Proof

iwire said:
You could point out 110.3(B), the lug is labeled 4/0, putting a 500 into it ignores the products labeling which is a violation of 110.3(B).
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The lug is rated for two 4/0 feeds, so that is justifiable. I need written proof that this is a violation. My opinion, good work practices, experience, etc.... is not a valid argument when dealing with the mindset that I am dealing with.
You have to remember, power plants are not "governed" by the NEC. It is a reference for them.
 
RoadDad said:
You have to remember, power plants are not "governed" by the NEC. It is a reference for them.
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If you are not governed by the NEC than the question is moot. Let the engineer sign off on it. I have seen instances where in NEC appplications, an engineers stamp over rides NEC requirement. I am not that familiar with how that works, but I have seen it. I agree that it is bad practice. It may work, but you have no guarantee and I think there is just as strong a chance that you may have problems. Order the proper lugs. My only other suggestion is a split lug and reduce the 500 to two 4/0. Parallel and spacing rules would apply.

This is a great product. Check for applicable sizes.
http://www.polarisconnectors.com/black.html
 
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