Voltage Drop Calculation Question

[21Bruce]

Mike's Explanation is pretty good:

Mike Holt Enterprises - the leader in electrical training.

Mike Holt worked his way up through the electrical trade from apprentice electrician through electrical contractor, to become one of the most recognized experts in the world as it relates to electrical power installations. He was a Journeyman Electrician, Master Electrician, and Electrical...

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(click on above for his technical note)
But I do struggle with one item, the definition of distance.
“D” = Distance: The distance the load is located from the power supply, not the total length of the circuit conductors.

What does this mean? A straight line from the meter to the load, regardless of any twists and turns?

Thank you

 

[tank728]

I believe distance is the conductor distance/length. The formula for single phase also has a multiply times 2. This is to account for the return path the current will take.

 

[winnie]

It is necessary to consider the total conductor length of a circuit (out to the load and then back again).

Usually formulas use the 'one way' length and then have a factor somewhere in the formula to account for the fact that the 'one way' length isn't the whole story.

As tank728 describes, the single phase formula will have a factor of 2 somewhere in it. The three phase formula will probably have a factor of 1.732. Other situations (odd phase count, unbalanced loading) will have different factors.

-Jon

 

[Dennis Alwon]

I think Mike Holt is saying the the distance is the length one way not the circuit conductor length which would be back and forth. I am thinking that is what he means

 

[Carultch]

What does this mean? A straight line from the meter to the load, regardless of any twists and turns?

It does not mean the "as the crow flies" distance, as that distance is not relevant to this calculation, unless your circuit actually travels that way. It means the one-way circuit length as others have mentioned. You still have to account for path that the circuit takes.

Best practices inside a building, is for circuits to travel rectilinear with the prevailing grid of structural members. There are times when you can strategically route at diagonal paths to minimize length, usually when buried in trenches, or embedded in slab.