Voltage drop when sizing equipment ground wire...?

[Danny89]

So was talking to a journeyman yesterday and the gentleman stated we should upsize our ground wire due to the distance and voltage drop.

Situation 250 feet distance 60 amp branch circuit.

Table 250.122 says #10 Cooper for 60amp.

Should I upsize or does it matter? Is there a code reference if upsizing is a good idea?

Thanks!

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[Dennis Alwon]

Art. 250.122(B) is what you want. The upsizing is based on the conductor sizes that you increased for whatever reason.

 

[Danny89]

I'll check that out...thanks


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[kwired]

So was talking to a journeyman yesterday and the gentleman stated we should upsize our ground wire due to the distance and voltage drop.

Situation 250 feet distance 60 amp branch circuit.

Table 250.122 says #10 Cooper for 60amp.

Should I upsize or does it matter? Is there a code reference if upsizing is a good idea?

Thanks!

Sent from my Moto Z (2) using Tapatalk

Did you upsize the ungrounded conductors because of voltage drop? If not then #10 copper still is acceptable, if you did upsize then the EGC must be increased by same proportion as your ungrounded conductor was increased.

 

[infinity]

So was talking to a journeyman yesterday and the gentleman stated we should upsize our ground wire due to the distance and voltage drop.

Situation 250 feet distance 60 amp branch circuit.

Table 250.122 says #10 Cooper for 60amp.

Should I upsize or does it matter? Is there a code reference if upsizing is a good idea?

Thanks!

Yes you must up-size if the ungrounded conductors are up-sized too because it's required by the section that Dennis posted. What size ungrounded conductors are you using?

 

[Danny89]

Did you upsize the ungrounded conductors because of voltage drop? If not then #10 copper still is acceptable, if you did upsize then the EGC must be increased by same proportion as your ungrounded conductor was increased.

Yes we did upsize to a #4 awg copper


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[Danny89]

Yes you must up-size if the ungrounded conductors are up-sized too because it's required by the section that Dennis posted. What size ungrounded conductors are you using?

4awg copper for ungrounded conductor

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[infinity]

4awg copper for ungrounded conductor

Sounds like you'll need a #8 AWG EGC.

 

[kwired]

4awg copper for ungrounded conductor

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What you need to do is find cross secitonal area of 6 AWG and find out what percent increase there is to 4 AWG, then multiply CSA of 10 AWG by the same percent, your new EGC can not have a CSA smaller than the result.

 

[Dennis Alwon]

Here is something to read in our FAQ's https://forums.mikeholt.com/threads/2020-nec-faqs.2551625/page-2#post-2556808

 

[winnie]

What you need to do is find cross secitonal area of 6 AWG and find out what percent increase there is to 4 AWG, then multiply CSA of 10 AWG by the same percent, your new EGC can not have a CSA smaller than the result.

As a small addendum to this: the code requires you to go by % increase. However because of the way AWG is defined, the same # change gives the same % increase, with one exception.

By definition, the % increase in size from #6 to #4 is equal to the % increase from #10 to #8. However because the values in AWG tables get rounded, you may find situations where if you do the % calculation doesn't match if you use the tables. Since the code specifies % change, the AHJ might permit change by AWG difference or might require change by % difference.

-Jon

 

[DBG]

Interesting discussion, question, using a 3 conductor Cable TC, current carrying conductors upsized for Vd and integral cable EGC is too small, can a larger single conductor EGC be installed alongside and external to the cable?