Is there a different formula for voltage drop...

[sbyrne]

when dealing with DC compared to AC?

I was flipping through a customers specifications and came across something on voltage drop. It said:

...because this is a DC circuit, you must use the "there and back length" (one way length x2) when calculating voltage drop.

I have never heard of this. Well, NEC shows formulas using reactance, etc. which is different from the typical

Vd = 2k*L*I/Area

I don't undestand where the customer is coming from. Which leads to another question I've always wondered:

Is the 2 in the equation above there to turn the one way length into a "there and back" length? or is it there for some other reason? If so, what is that reason?

 

[Doug S.]

You almost always go there and back via the wire. I've heard of (not seen) RARE, earth return systems. I'm guessing the worms don't like those?

 

[Smart $]

Is the 2 in the equation above there to turn the one way length into a "there and back" length?

Yes, that is what the 2 is for.

 

[drbond24]

You are correct; the 2 in the equation accounts for the 'there and back again' length.

The voltage drop equation you typed works for any single phase circuit, AC or DC doesn't matter.