Voltage Drop

[Jerry KES]

With a 480v source at a distance of 450 ft. to a 240v transformer, what size wire should be pulled? The xfrmr is feeding a 200 amp panel which is mainly be for lighting circuits.

 

[LarryFine]

Jerry, welcome to the forum!

With a 480v source at a distance of 450 ft. to a 240v transformer, what size wire should be pulled? The xfrmr is feeding a 200 amp panel which is mainly be for lighting circuits.

What's the calculated load? Voltage drop is a function of impedance and current.

 

[Jerry KES]

The load on the 200 amp panel for the work we will be doing is low. It will just be feeding around 50 2x4 layins, and some general purpose outlets. But I do want to size the feeders for possible future expansion.

 

[skeshesh]

Welcome to the forum.

Take a look at the article on mike holt site about voltage drop: http://www.mikeholt.com/technical.php?id=technicalvoltagedrop
The calculations are pretty straighforward (at least in the context of this darn business of electricity that we love so much ). You can find some calculators online too but you wouldnt know what assumptions they made so its upto you. Like Larry pointed out you need to know the load, if you're worried about future expansion assume a bigger load like 150-175A or something like that.

 

[augie47]

If you figure a full 200 amp load on the panel, that will equate to a 100 amp 480 volt load. At that distance, when you run the numbers, you will find you won't have to up your wire too much.

 

[don_resqcapt19]

Assuming 3 phase 480, a 100 amp load at 450' will have a 3% drop if you use #2 copper. I used this calculator.

 

[Jerry KES]

Thanks for the link to the calculator, but I am still wondering what I am doing wrong doing it by hand:
cm=2 x 12.9 x D x I / VD

2 x 12.9 x 450 x 100 = 1,161,000 / .03 = 38,700,000 cir mils??????

 

[raider1]

Thanks for the link to the calculator, but I am still wondering what I am doing wrong doing it by hand:
cm=2 x 12.9 x D x I / VD

2 x 12.9 x 450 x 100 = 1,161,000 / .03 = 38,700,000 cir mils??????

You divided by the precentage of voltage drop not the actual dropped voltage.

Chris

 

[Jerry KES]

Im such an idiot...

 

[raider1]

Im such an idiot...

Easy mistake to make.

Chris