# Votage Drop Calc



## jsb (Apr 5, 2009)

i know how to do a voltage drop calc if the load is x feet from the panel, but i am trying to do a calc for some outside lighting need some help.

from the building i come out to a jbox and go one way to 4 building up lights, from the jbox i also feed out to 4 pole lights. how do i do that?

thanks for the help


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## 480sparky (Sep 20, 2007)

I wouldn't bother with figuring in the conductor running up the pole, just the branch circuit itself.

If you can figure out the top half of the image, this is how to figure the L needed for a Vd cal.


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## jsb (Apr 5, 2009)

i may be a little slow, but that makes no sense at all, maybe something will make sense if i stare at it longer???? 

load center?? what is this for?? am i missing something??

i am taking a single circuit out of a panel to some outside lighting


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## drsparky (Nov 13, 2008)

This may help to.:1eye:
http://www.southwire.com/voltagedropcalculator.jsp


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## jsb (Apr 5, 2009)

i was just there and that is great except i dont have a single load x amount of feet from the panel, the load continuously decreases as my distance increases


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## 480sparky (Sep 20, 2007)

jsb said:


> i may be a little slow, but that makes no sense at all, maybe something will make sense if i stare at it longer????
> 
> load center?? what is this for?? am i missing something??
> 
> i am taking a single circuit out of a panel to some outside lighting


 
_Load center_ means the mathematical 'center' of the load, and that's the number you need for the L in your Vd calc.

Simply substitute your numbers for those used in the image.


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## jsb (Apr 5, 2009)

still lost......the diagram makes sense, i can multiply acros and ad down to get the 14600, but then what the heck do they do?

then when i find the load center what does that have to do with sizing wire in my case?

still staring, still confused

where in iowa?


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## 480sparky (Sep 20, 2007)

jsb said:


> still lost......the diagram makes sense, i can multiply acros and ad down to get the 14600, but then what the heck do they do?
> 
> then when i find the load center what does that have to do with sizing wire in my case?
> 
> ...


 
So instead of using the 100, 40 and 20 amps in the diagram, use the amps each light uses.

Instead of 80, 100 and 130 feet, use the distances you have at the job site.

Use the final number, called the _load center_, as the L in your Vd calc.

Des Moines area.


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## jsb (Apr 5, 2009)

gotcha!!!!!
i was looking for the answer divide the 14600 by the added amps (160) to get 91.25 (the load center)
didnt follow their long division. damn kids and their calculators.
Wow dont i feel a little slow now

did a job in sioux city last summer. iowa's kinda interesting. i got through it and had fun.


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## jsb (Apr 5, 2009)

did this work


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## jsb (Apr 5, 2009)

hopefully u can see that last attachment. doing it 480's way u pull #8's through the wole run. anyone else have any other way they use??


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