voltage drop

[schole]

we need to service a 30A 120V single phase load approx 800feet from it's source, a 2pole 30amp breaker in a meter pedestal. Assuming we may need to use a 4/0 aluminum conductor for the voltage drop, does NEC allow a pigtail from the breaker to splice onto the larger conductor? Can't seem to find a reference in the handbook.

 

[kingpb]

Run the large conductor into a j-box, then pigtail with a conductor that will go into the breaker. No issue with Code.

Might want to consider using a higher voltage, i.e. step it up at panel, and step in back down at load. You would have to do cost analysis to see if that is actually cheaper. But 800ft of cable, pull boxes, and up sized conduit can't be cheap.

 

[Dennis Alwon]

You can make the splice directly in the panel.

 

[LarryFine]

Might want to consider using a higher voltage, i.e. step it up at panel, and step in back down at load. You would have to do cost analysis to see if that is actually cheaper. But 800ft of cable, pull boxes, and up sized conduit can't be cheap.

I concur. At the very least, run the circuit as 240v and use a 240/120v transformer at the load end, including a bond and electrode.

That alone will halve the current and resultant drop along the run.

 

[luckylerado]

Based on what I see a 4/0 aluminum is not going to cut it. You need 4/0 copper or 300 kcm aluminum. 120v 30 amp 800 feet.

even at 240 volts you are looking at 1/0 copper or 3/0 aluminum. Are you sure that it is 800'? 50 foot could mean as much as a whole wire size. are you sure that the load actually draws 30 amps.

if it is a motor load and it can be retapped for 240 and the FLA is only say 10 amps at the new voltage now you are only looking at a #4 copper to stay within 3% and if the motor is rated at 230 volts then you are good with a #6

 

[kwired]

You can make the splice directly in the panel.

Assuming you have enough room in the panel. Try running 3 - 4/0AWG into a 2 space panel rated only for 30 amps

I agree with others - step up voltage at source and step it back down near the load would likely cost less than the larger conductors needed if no transformers are used. Also calculate voltage drop based on actual load and not the breaker size.

 

[LarryFine]

even at 240 volts you are looking at 1/0 copper or 3/0 aluminum

if it is a motor load and it can be retapped for 240 and the FLA is only say 10 amps at the new voltage now you are only looking at a #4 copper to stay within 3% and if the motor is rated at 230 volts then you are good with a #6

Whether the motor is wired for 240v, or it's wired for 120v and supplied by a a 240-to-120v transformer, the current on the 240v line would be the same (ignoring transformer losses).