Equipment Grounding Conductor

[hancock electric]

Installing 120v/20a circuit @1000 ft. from the source. According to calculation, a 2/0 cu. conductor is required to account for 3% vd.
Does 250-122B indicate the EGC be 2/0 as well or is there another method to determine the EGC size?

 

[roger]

250.122 needs some work, but as it stands at present, the EGC will have to be a 2/0 as well.

Roger

 

[raider1]

Welcome to the forum.

I agree with Roger.

250.122(B) requires that when we increase the ungrounded circuit conductors that we also increase the equipment grounding conductor proportionately.

So, in you example a 20 amp circuit would require a #12 EGC and most likely a #12 ungrounded conductor. Since they are both the same size after you have done your voltage drop calculation then they must again be the same size.

Chris

 

[hancock electric]

Thanks! I just wanted to make sure I wasn't missing something.

 

[zbang]

Second-guessing your design, do you have to run 120v or can you step up to 480v or 600v for the run. Check out the cost of the transformers v. the cost of the wire and installation. (You'll find a number of conversations about that in the various formus here.

 

[Dennis Alwon]

Installing 120v/20a circuit @1000 ft. from the source. According to calculation, a 2/0 cu. conductor is required to account for 3% vd.
Does 250-122B indicate the EGC be 2/0 as well or is there another method to determine the EGC size?

You do realize that the 3% is an FPN and is not enforceable by the NEC. It is good design but if this is for lighting you may be able to cheat a bit on that.

 

[LarryFine]

Thanks! I just wanted to make sure I wasn't missing something.

We are: what is the load current?

Added: No, it doesn't change the answer, that the EGC must be equally upsized. I was just pointing out that you may not need that large a wire size.

 

[ptonsparky]

If this is a test question I agree with the others, pia that it may be.

Increase the feeder overcurrent protection size to a 60A, 100A or more and you can decrease the size of the EG compared to that of the 20A circuit.

 

[rpjaj5]

Installing 120v/20a circuit @1000 ft. from the source. According to calculation, a 2/0 cu. conductor is required to account for 3% vd.
Does 250-122B indicate the EGC be 2/0 as well or is there another method to determine the EGC size?

Is it possible to "re tap" the trans and get the voltage up to about 125v and thus decreasing the the wire size needed per your voltage drop calcs?

 

[LarryFine]

Is it possible to "re tap" the trans and get the voltage up to about 125v and thus decreasing the the wire size needed per your voltage drop calcs?

The only issue with that is the voltage drop goes away as the load decreases. It is better to boost as close to the source as you can, by the way, because the primary current increases to provide the voltage boost.

I agree with the two-transformer idea, using 480 or 600v between them. You'll need a new grounding electrode system, but your transmission line will be smaller. 20a x 120v = 2.4kva = 5a x 480v = 4a x 600v.

How about using a 240v supply for the long run and step it down to 120v at the far end? Even that will halve the transmission current, saving on wire cost, and require only one transformer. Price all the options.

 

[tom baker]

Is the load 20A or did the customer say " I need a 20A receptacle"? I had a similar installation that was 1,000 ft and even at 5 Amps load it was large conductors. We've done similar installations by going 120>480 and then 480>120. And then we ran 12 AWG in 3/4" PVC.