Bonding 400 mcm

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elbee

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Location
Deerfield, Florida
Hello! New to the forum here.

I searched this forum for about an hour now, but have not seen a similar question posed. If I missed it, please just send me the link to the proper thread and I apologize for the waste of time.

I have been banging my head against the wall over this for a few days now. There is no way around this as far as I can see. This site has a 3000A main breaker which is fed by 8 3-1/2" EMT circular raceways. The EMT is going to server as ground, but needs to be bonded. Looking at 250.122, it appears we need to use 400 mcm copper to bond the EMT. I have never seen a bonding bushing or anything similar to fit 400 mcm. Does anybody have a hint for me? :ashamed1:
 
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elbee

Member
Location
Deerfield, Florida
Chris, I can only find bonding bushings/locknuts that accept 250 mcm, not 400 mcm. If you can find 400 mcm, please send me a link. I would much appreciate it.Bob, I am aware of 250.66 for sizing. The issue is that on one side (breaker box) the emt comes through the floor do it can not be bonded to the box because there is no bottom to the box, just concrete. Masterinbama, yes, this is a main service. There may be a second in the future (way later). All the replies are giving me hope. Thanks guys!
 
augie47

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
Take a look at 250.102(C). If these are service conduits and you install a separate jumper to each bushing, that jumper can be sized based on the size conductor in each conduit,

In cases where the conductor is larger than the factor supplied lug, I always changed the lug.
 
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elbee

Member
Location
Deerfield, Florida
Augie47, 250.102(c) is for supply side. I am actually doing this on supply side, but I am looking for load side (which NEC fails to mention an exception for parallel raceways). Also, changing the lug, then nullifies the UL of the product. This job is under a microscope due to its uniqueness.

I have looked at at bonding clamps, bushings, locknuts, and everything ilsco, Appleton, Caldwell/erico, thomas and betts, etc. I can not find anything that will bond 400 mcm to my 3-1/2 emt.

Thank you for the replies. I am still looking. Please let me know if I am failing to interpret the code properly.
 
Dennis Alwon

Dennis Alwon

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Location
Chapel Hill, NC
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Retired Electrical Contractor
I am confused. You mention the emt as the ground - I assume you mean egc- and then say it needs to be bonded. This makes me think this is not a service. If this isn't service equipment then it would not need bonding unless 250.97 comes into play.
 
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elbee

Member
Location
Deerfield, Florida
This is service equipment. This is a feed from our ATS (switching from utility to generator) feeding our switch gear (with a 3000A main breaker). I believe I have found my answer after searching manufacturer catalogs for hours. It is UL and looks like it will suffice for NEC as well as our EE and inspector.

http://www.erico.com/part.asp?part=LPA5964

Please let me know your thoughts/concerns. It appears it will for up to over 6" OD as well as UL rated for all wire sizes.
 
augie47

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
It appears the wire size is determined by the size of the lug you select to attach.
While I agree, changing the lug on a bushing might construed as "altering a U.L. listing", I would tend to accept that as a better choice, but that's me.:D



on a side note, while it has little to do with the problem being discussed, I am a bit confused at calling this "service" if it feeds from your ATS.
Per the NEC:
Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

This wiring appears to me beyond the Service Point.
 
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Fladude38

Member
Location
United States
elbee said:
Hello! New to the forum here.

I searched this forum for about an hour now, but have not seen a similar question posed. If I missed it, please just send me the link to the proper thread and I apologize for the waste of time.

I have been banging my head against the wall over this for a few days now. There is no way around this as far as I can see. This site has a 3000A main breaker which is fed by 8 3-1/2" EMT circular raceways. The EMT is going to server as ground, but needs to be bonded. Looking at 250.122, it appears we need to use 400 mcm copper to bond the EMT. I have never seen a bonding bushing or anything similar to fit 400 mcm. Does anybody have a hint for me? :ashamed1:
Click to expand...

It seems to me that you should be looking at 250.102 (C). Your "Service Point" is your ATS so are you sure its not the "Load Side" you are looking to bond? If so, that would be 250.102 (B). Unless I'm missing something?
 
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