# Grounding Bushing



## Chris Kennedy (Nov 19, 2007)

Service? Size as per 250.66

Feeders? Size per 250.122


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## local134gt (Dec 24, 2008)

360max said:


> If you have a panel and have 8- 4" conduits all with 500 MCM, and want to run one wire thru all the grounding bushings and then continue to the grounding bar from the last grounding bushing, what ground size wire would be required. The breakers are 400, 600, and 1200 amps. List code sec please.




8 500mcm = 4000mcm..... 250.66 says over 1100 use 3/0 CU


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## 360max (Jun 10, 2011)

local134gt said:


> 8 500mcm = 4000mcm..... 250.66 says over 1100 use 3/0 CU


...these are feeders


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## Chris Kennedy (Nov 19, 2007)

local134gt said:


> 8 500mcm = 4000mcm..... 250.66 says over 1100 use 3/0 CU


That doesn't work for service bonding jumpers. 250.102(C).


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## Chris Kennedy (Nov 19, 2007)

local134gt said:


> 8 500mcm = 4000mcm..... 250.66 says over 1100 use 3/0 CU





Chris Kennedy said:


> That doesn't work for service bonding jumpers. 250.102(C).





360max said:


> ...these are feeders


Never mind.:whistling2:


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## 360max (Jun 10, 2011)

250.102(D) the last paragraph is what I believe applies, which would mean a 3/0 conductor thru all grounding bushings and then back to gnd bar.


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## Chris Kennedy (Nov 19, 2007)

You have feeders here, over 250V to ground I assume. Unless you found an enclosure that has eight pre-punched KO's over 4", why are you worried about bond bushing and extra wire?



> 250.97 Bonding for Over 250 Volts.
> For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).
> 
> Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall be permitted:
> ...


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## Bionic Sparky (Jun 22, 2012)

*line side*

Maybe he was on line side in trough? Just a thought


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## 360max (Jun 10, 2011)

Chris Kennedy said:


> You have feeders here, over 250V to ground I assume. Unless you found an enclosure that has eight pre-punched KO's over 4", why are you worried about bond bushing and extra wire?





Bionic Sparky said:


> Maybe he was on line side in trough? Just a thought


its a spec requirement


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## Chris Kennedy (Nov 19, 2007)

360max said:


> its a spec requirement


OK then given...



360max said:


> ...these are feeders


and..



360max said:


> If you have a panel and have 8- 4" conduits all with 500 MCM,


Assuming 8×380=3040A and these feeders are protected by a 3000A breaker then T250.122 calls for a 400kcmil cu or 600kcmil al. If you have a wire type EGC in these 8 parallel conduits, it would be the same size.


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