# Thread: drop voltage and cable setting

1. Login to Give a bone

## drop voltage and cable setting

Maybe I miss the right way to post this..

from mine experience and from the previous post, I understood, that VD (voltage drop) seems to be quietly "ununderstandable" in terms of calculation origin.
With a simple test based on 2 identical panels (230V), I found the reason that the cable setting (Ampere, dimension, diameter, used in calculation) represents the most important scenery to be taken into consideration.
Unfortunately, by the preset cable (revit 2014 default file, USA standard, es. THWN), the drop voltage has a sense, but by simple personalized cable, there is no way out to figure with drop voltage calculation different from zero.
What's gonna be the wrong/mistake/error?

waiting your response, I thank you.

2. Login to Give a bone

## Re: drop voltage and cable setting

The method Revit uses for calculating wire size vs voltage drop is consistent and matches the method used by all of the Electrical engineers that I've personally analyzed it with.

The short description of calculations:
wire size is driven by max voltage drop
voltage drop is calculated by using the distance (cumulative x,y,z from panel to farthest load) and the load (the largest of either the breaker size or connected load)
it also assumes that the entire load for the entire circuit all goes to the farthest load

More detailed descriptions are available here: http://revitoped.blogspot.com/2012/0...culations.html

3. Login to Give a bone

## Re: drop voltage and cable setting

thanks a lot, but even trying to find a solution, I got some trouble again in drop voltage (VD) calculation of revit 2014.
In a simple case (same panel and same light), the VD is strongly influenced by wire setting and electrical setting (and electrical starting country template).

In my personal case, the italian electrical template and wire defualt setting doesnt give me a right VD calculation. Our cable size (ampere, dimension, diameter) are proportional to the current that across the cable.

By a standard italian electrical default template, If I can substitute the wire name (=dimension=14,12,10,8,6,4,3,2,1,1/0,2/0,ecc) with the desiderate/personalized one (es. 1mmq, 1.5mmq, 2.5mmq, ecc), the diameter will be editable (by normal tool), and the drop voltage, will be calculate rightly.

(respecting NEC/AWG) Can you help me in finding "where" I can edit the wire name = dimension in the revit source code and obtain a (right) VD? Actually.
es. 2 light 500W each (tot 1000W) / 230V = 4.34 A
result: wire 2#12, VD 0.46V
If I change #12 with 2.5mm the VD = zero.

waiting your response, I thank you.

4. Login to Give a bone

## Re: drop voltage and cable setting

Hi,
I normally use an italian electrical template, that has wire default setting according to NEC/AWG. I've tryed to test an UK template, and by simple circuit

es1. tempalte Electrical-DefaultGBRENU.rte
2 light 500W each (tot 1000W) / 230V = 4.34 A
result: wire 2#1mm,1#1mm,1#1.5mm VD 0.00V
If I change the wire #1mm with 2.75mm the VD = zero anytime.
correction factor: not editable.

es2. tempalte Electrical-DefaultITAITA.rte
2 light 500W each (tot 1000W) / 230V = 4.34 A
result: wire 2#12,1#14,1#12 VD 0.46V
If I change the wire #12 with 2.75mm the VD = zero anytime.
correction factor: editable.

Can you help me in finding "where" I can edit (and how) the wire name = dimension in the revit source code of second example and obtain a (right) VD?
waiting your response, I thank you.