# Upsizing ground wires for distance and parallel sets - 250.122(B)



## 1.21gigawatts (Jun 22, 2013)

Im assuming you have a 400a OCPD. With your increased ampacity of (2) sets #350. Giving you a 1.4 multiplication factor your next EGC would be #1 cu. in each conduit. I know a #3 seems more than reasonable but my understanding is that the OCPD could be upsized or adjusted up at some point in the future and with that the #3 EGC would be too small and not capable to handle the fault current.

It also makes sense that with distance the impedance of the wire increases so having a larger EGC would provide lower impedance allowing the OCPD to trip faster.


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## Dennis Alwon (May 9, 2009)

The equipment grounding conductor in each conduit must be sufficient to trip the overcurrent protective device as t. 250.122 recommends. when the distance increase the impedance changes and so the equipment grounding conductor must be increase when the current carrying conductor's are increased. Each raceway must have sufficient ability to trip the overcurrent protective device if a ground fault should occur. So IMO, each raceway must have the equipment grounding conductor increased proportionally to the other conductors in the raceway. Also look at 250.122 (F)


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## chicken steve (Mar 22, 2011)

This seems to address VD well>



> *(B) Increased in Size. * Where ungrounded conductors are
> increased in size from the minimum size that has. sufficient
> ampacity for the intended installation, wire type equipment
> grounding conductors, where installed, shall be increased in
> ...



And 'F' addresses parallel .....


~CS~


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## Carultch (May 14, 2013)

Dennis Alwon said:


> The equipment grounding conductor in each conduit must be sufficient to trip the overcurrent protective device as t. 250.122 recommends. when the distance increase the impedance changes and so the equipment grounding conductor must be increase when the current carrying conductor's are increased. Each raceway must have sufficient ability to trip the overcurrent protective device if a ground fault should occur. So IMO, each raceway must have the equipment grounding conductor increased proportionally to the other conductors in the raceway. Also look at 250.122 (F)



"Each raceway must have the equipment grounding conductor increased proportionally to the other conductors in the raceway."

In my example, the wires in each raceway actually decreased in size, upon upsizing for voltage drop by adding more raceways.


What I am getting from these responses, is that _I cannot take advantage of the de-facto doubling of the EGC's kcmil_, from having separate EGCs in each raceway, when it comes to upsizing the ground wire. Am I correct?


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## Carultch (May 14, 2013)

1.21gigawatts said:


> Im assuming you have a 400a OCPD. With your increased ampacity of (2) sets #350. Giving you a 1.4 multiplication factor your next EGC would be #1 cu. in each conduit. I know a #3 seems more than reasonable but my understanding is that the OCPD could be upsized or adjusted up at some point in the future and with that the #3 EGC would be too small and not capable to handle the fault current.
> 
> It also makes sense that with distance the impedance of the wire increases so having a larger EGC would provide lower impedance allowing the OCPD to trip faster.


I was actually thinking of a 350A OCPD, but the example can work for a 400A OCPD when taking advantage of the "next size up rule".

I wouldn't think that an OCPD would be expected to be changed in the future. If so, it is the responsibility of the future contractor to assess whether anything else needs to change.

The intent is that the OCPD will remain at what it is (perhaps 350A), and that the default 500kcmil Cu wire simply had to be upsized to address the same current over a long distance. Same load, same breaker. If the load increases in the future, it is the responsibility of the future contractor to change the wire and raceways as required for current and voltage drop.

Unless I am told to plan for future expansion, when doing the original work.


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## Dennis Alwon (May 9, 2009)

Carultch said:


> "Each raceway must have the equipment grounding conductor increased proportionally to the other conductors in the raceway."
> 
> In my example, the wires in each raceway actually decreased in size, upon upsizing for voltage drop by adding more raceways.
> 
> ...


If there is a 350 amp overcurrent protective device then according to T250.122 you would need a number 3. You cannot take the #3 and downsize it because there are 2 raceways. Each raceway must have the #3 simply because that #3 is what is needed to safely trip the 350 amp overcurrent protective device.


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## Carultch (May 14, 2013)

Dennis Alwon said:


> If there is a 350 amp overcurrent protective device then according to T250.122 you would need a number 3. You cannot take the #3 and downsize it because there are 2 raceways. Each raceway must have the #3 simply because that #3 is what is needed to safely trip the 350 amp overcurrent protective device.


My question was:
Is it OK for the EGC to *remain* a #3 in each conduit, even though wire was upsized for voltage drop?


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## Pete m. (Nov 19, 2011)

Carultch said:


> My question was:
> Is it OK for the EGC to *remain* a #3 in each conduit, even though wire was upsized for voltage drop?


No. Due to the last sentence of 250.122(F).

"Each EGC shall be sized in accordance with 250.122."

Pete


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## Dennis Alwon (May 9, 2009)

I agree with Pete you need to upsize the equipment grounding conductor in each conduit based on the upsize of the conductors in that conduit


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## denny3992 (Jul 12, 2010)

What about 1/0 being smallest size parallel conductors?


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## denny3992 (Jul 12, 2010)

denny3992 said:


> What about 1/0 being smallest size parallel conductors?


Never mind....phase conductors only


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