Increasing EGC Size for Voltage Drop

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stevee

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250.122(B) states "Where ungrounded conductors are increased in size, equip grounding conductors, where installed, shall be increased proportionately...."

Does this mean if I increase the size of my ungrounded conductors for voltage drop that I must do the same for the EGC?

Does 250.122(B) mean under any circumstances? What about for motor circuits, parallel circuits, and mulitple circuits as indicated in 250.122?

My inclination is to believe that it would apply to all circumstances. Whether you increase the ungrounded conductor size for voltage drop or any other reason.

I'm simply looking for verification of what I think? Any feedback would be great!
 
Most of us will agree to the "under any circumstances" part of your question. The debate that has run its course once or twice on this forum had to do with the "increased from what" aspect. In other words, for any given installation circumstances, what is the wire size for the ungrounded conductors that, if you go larger than that size, you must also increase the EGC?
 
I think this paragraph creates a lot of confusion.

I always use #10 AWG conductors + #10 AWG ground as a minimum for site lighting feeds. I had a project where I went to #6 AWG + #8 AWG ground because of voltage drop issues. The plan review told me I had to size the EGC for this length as a #6 AWG because of 250.122(B), stressing that it had to be proportional. I replied stating the EGC was size proportionally based on Table 250.122. I never heard anything about it after that.
 
Mr. Bill said:
I think this paragraph creates a lot of confusion.

I always use #10 AWG conductors + #10 AWG ground as a minimum for site lighting feeds. I had a project where I went to #6 AWG + #8 AWG ground because of voltage drop issues. The plan review told me I had to size the EGC for this length as a #6 AWG because of 250.122(B), stressing that it had to be proportional. I replied stating the EGC was size proportionally based on Table 250.122. I never heard anything about it after that.
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I took "proportional" to mean proportional to cm area. If you increase a #10 (10380cm) conductor (say a 30a circuit) to a #6 (26240cm) conductor you would be increasing the conductor by 252%. I would think this would require a 252% increase in the EGC. So if a 30A circuit requires a #10 (10380cm) conductor you would have to also increase it in size by 252% which would require a #6.

Now if you were installing a 20A circuit and increased the ungrounded conductors to #6 (26240cm) for voltage drop that would be an increase in conductor size of 400%. So you would increase the required EGC, a #12 (6530cm) by 400% which would require a 26120cm conductor which relates to a #6 also.

I think where you will see the difference is in the larger circuit sizes. Say for example a 200A circuit where you increase the conductor size by one from a 3/0 (167800cm) to a 4/0 (211600cm) an increase of 125% so your EGC would need to be sized at 125% of a #6 (24240cm) which would require that you install a 32,800cm conductor or a #4.

Does everyone agree with my method of "proportionately" increasing the size of the EGC? If it's not related to circular mil what would you use?
 
stevee said:
Does everyone agree with my method of "proportionately" increasing the size of the EGC? If it's not related to circular mil what would you use?
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I agree with you. :grin:
 
Mr. Bill said:
I had a project where I went to #6 AWG + #8 AWG ground because of voltage drop issues. The plan review told me I had to size the EGC for this length as a #6 AWG because of 250.122(B), stressing that it had to be proportional. I
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Mr. Bill Assuming the overcurrent device was a 15, 20 or 30 amp they where right, the NEC requires you use a 6 AWG EGC with 6 AWG circuit conductors.

The ratio of the EGC to circuit conductor with 15 , 20 and 30 amp circuits is 1 to 1.
 
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stevee said:
II think where you will see the difference is in the larger circuit sizes. Say for example a 200A circuit where you increase the conductor size by one from a 3/0 (167800cm) to a 4/0 (211600cm) an increase of 125% so your EGC would need to be sized at 125% of a #6 (24240cm) which would require that you install a 32,800cm conductor or a #4.
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I think that you meant 25%.
 
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