TimK
Member
- Location
- Tacoma, WA
Would a parallel run within the same conduit be the only time the grounding conductor is the largest conductor? Excluding specs and special engineering of course.
Grounding Conductor Largest Conductor
- Thread starter TimK
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Maybe I am misunderstanding your question but I can't see even in a single conduit parallel instalation where the EGC would be larger than the ungrounded conductors.
For simplicity take two 500KCMIL's and protect them with an 800 amp breaker, the EGC would only be required to be a 1/0
Roger
TimK
Member
- Location
- Tacoma, WA
Well, not that it is done often with smaller wires, but instead of 3/0 copper, we run parallel #3's to the service, now if I install them in the same conduit wouldn't my grounding conductor need to be #2?
I guess I am thinking more of grounding and not equipment grounding.
I guess I am thinking more of grounding and not equipment grounding.
travish
Member
- Location
- Central North Carolina
- Occupation
- Electrician
don't think you can paralle smaller than1/0 for amperage reasons
As Travish points out, you can not parallel conductors (excluding some exceptions) smaller than 1/0
Roger
I played with some numbers and don't think it could happen. The smallest you can parallel is 1/0 and as you increase the number of conductors in the conduit, the ampacity is lower (by derating ) to a point the EGC is still smaller.
TimK
Member
- Location
- Tacoma, WA
Well, let me do some reading then, maybe I am thinking of grounded, or am i chasing my tail on that one also?:ashamed:
Maybe it is parallel runs in parallel conduits that you are thinking of? For example, 7 parallel 1/0 runs in 7 conduits, protected by a 1000 amp breaker would require a 2/0 equipment ground in each conduit.
TimK
Member
- Location
- Tacoma, WA
250.122(F)
250.122(F)
You are correct, thats where i read that. I couldn't grasp my head around why we would need such a large EGC, when everything else was smaller, and we were allowed to bond the ground coming out of the conduit with it's own bond bushing.
250.122(F)
You are correct, thats where i read that. I couldn't grasp my head around why we would need such a large EGC, when everything else was smaller, and we were allowed to bond the ground coming out of the conduit with it's own bond bushing.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I used to think that an egc could be larger than the conductors in a parallel run and I even wrote a proposal about it. The comment was the egc never has to be larger than the CCC.
TimK
Member
- Location
- Tacoma, WA
So does that mean I am wrong in my last statement?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
My understanding is that the egc in each conduit would never need to be bigger than the CCC. So 1/0 egc is all that is needed if the CCC was 1/0- the 2/0 is not necessary
TimK
Member
- Location
- Tacoma, WA
IAW 250.122(F) it needs to be sized off the OCPD does it not?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes but look at 250.122(A)
TimK
Member
- Location
- Tacoma, WA
I could agree, and I know it does not say "accumulative" but I always took that as the total cross sectional.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The conductors in each conduit is being protected for ground fault. If the EGC is the same size as the CCC then it will have the protection for those conductors. That is how I see it.
TimK
Member
- Location
- Tacoma, WA
I took it to mean that if you "lost" a parallel run, or two (treancher crossing pipes?) that one single EGC needed to be capable of working the OCPD. In my head, that was for the additional amperage that could be sent on the other parallel conductors.
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