Voltage drop in feeder neutral

slick 50

slick 50

Senior Member
Location
6 super bowl ring city
Hello,

Customer needs a 50A, 240v subpanel installed in a barn. The feeder will be 620' from the source panel.

One 20A circuit connected to L1 will feed barn lighting and a convenience receptacle.

One 30A, 120v circuit connected to L2 will feed a camper.

Primarily the camper will be used and nothing in the barn will be therefore, thinking of voltage drop for 30A, 120v at 620'. Southwire voltage drop calculator is saying I would need a 2/0 feeder to keep it under 5% VD.

Ultimate question is, can I use mobile home feeder that has 2/0-2/0-1-4 conductors? Being the neutral is only a #1, would there be an issue with voltage drop? Realistically it is plenty large enough to carry the 30A. Thanks!
 
The Southwire calculator probably assumes the same size phase and neutral. Since your neutral is smaller, it will have some additional resistance (more V.D.). If you want to calculate it more accurately, you can look up the resistance of 2/0 and #1 and use both of them in a manual V.D. calculation.

Remember that the camper won't be pulling a full 30A though - it'll probably just have a fridge running most of the time (~6A?). You should be fine
 
slick 50 said:
Ultimate question is, can I use mobile home feeder that has 2/0-2/0-1-4 conductors?
Click to expand...
If you do, your voltage drop calculation will not be accurate.

You can get the voltage drop for a 120V circuit with 2/0 as the ungrounded conductor and #1 as the grounded conductor by doing the calculation twice, once for for 2/0 conductors and once for #1 conductors, and then averaging the two answers.

Cheers, Wayne
 
augie47 said:
Since the on;y loads are 120v why not simply supply the panel with 120v and use one of the 2/0s as a neutral
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Or use the #1 as the ungrounded that gets connected to the 20A 120V circuit, as that that leg will be less loaded than the other two conductors.

Cheer, Wayne
 
winnie said:
If you protect a #2/0 Al conductor at 50A because of voltage drop issues, wouldn't your EGC need to be a #1 Al?
Click to expand...
You can use the 60C ampacity column for doing the 250.122(B) comparison, so the baseline case for aluminum conductors on a 50A OCPD would be #4 Al with #8 EGC, a difference of 4. So that would mean a minimum #3 Al EGC for 2/0 Al ungrounded.

But increase the OCPD size to 60A, and now the baseline is #3 Al with #8 EGC, so 2/0 Al with #4 EGC is fine. If the panel supplied is only rated 50A, use a main breaker in the panel.

Cheers, Wayne
 
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