Re: Voltage Drop and wire sizing

Anonymous · ‎09-10-2010

I am running circuits for a residential building. MEP 2011 automatically figures the voltage drop and the appropriate size wire. However I believe it measures the complete distance of the circuit which is not necessarily how it will be wired. Is there a way to change wire size or change the way it measures length of wire.

Thank you,

Micah Toftness

Electric Etc.

Anonymous · ‎06-10-2011

I too, have been looking at this. Revit tends to double the run length of a circuit, and doesn't actually calculate voltage drop in accordance with the NEC. Are there any plans to make this so that we can change the way voltage drop is calculated, or at least manually change the wire size?

embolisim · ‎06-11-2011

Read this thread, it has a lot of useful info.

http://forums.augi.com/showthread.php?t=128224

Anonymous · ‎06-13-2011

I am Jimbob from that link and have many years of research on the voltage drop. If you are using revit 2011 there is no way you will ever get a correct voltage drop because the lengths are never right. I frequently have revit show lengths of wire that exceed the length of the building I am working in. So that in itself is most detremental. The other thing is the crude formula which they use to calculate vd. It may be close but never exacty.

For anyone who wants voltage drop calculator second to none please go to www.powersofteng.com and install a free program called EPS. There is a voltage drop calculator in it, as well as a conduit fill calc. There is a cut and paste formula for anyone who wants to output results. Works for parallel runs too.

embolisim · ‎06-14-2011

Thanks JB, I'll have a look.

Do you know if its any better in 2012? If not. how do we get them to fix this last bit so our engineers will actually use revit?

Currently the VD calcs are a major impediment to gettig our electrical guys to use Revit for anything more than a drafting tool. Because they already have tools that they know well, which work.

Anonymous · ‎06-14-2011

I have a very difficult convincing myself to continue to use revit as new projects are coming on our drawing boards now. If those guys would EVER give engineering more than 80 hours of developers time, they may convince. Anything short of 6 months this time around will be detrimental I think. Major improvments is required.

But if not, EPS is in the pro phases now with tab delimited format importing. It is very cool to see all circuits and panels to be circuited in less than one minute, with schedules and proper wire sizes and of course vd. There is no two way, but maybe one day it will. That would be very cool. Soon I will have risers and aic ratings and be able to tie in all panels together as a system. Researching now. EPS and revit might be a good fit together. Try the lite version and judge for yourself.

Anonymous · ‎06-14-2011

I have a great utility for calculating VD and wire sizes already. If Revit doesn't fix this in the next release, or even better, the next update, I doubt very highly I will ever be able to convince our Electrical Dept. Head to EVER begin using Revit. He is already opposed to it for many valid reasons. If it doesn't work correctly, and doesn't do whats advertised, he will probably never give it another chance.

jaboone · ‎05-14-2013

For those of you who are still using Revit, the Pro version of EPS is almost ready and is weeks from final marketing. There is a great revit import tool if you want great power for scheduling. EPS Pro will export to acad drawings. Check it out. There is a video of what EPS Pro can do and user guide will be ready soon.

www.powersofteng.com

Learning as I go

David_Robison · ‎06-01-2017

I know it's been seven years since this question was first asked, but since Revit still doesn't handle this request well, I don't feel too bad posting our solution.

We had an electrical add-in for Revit that allows you to correctly calculate voltage drop on feeders and branch circuits. We have replaced the Revit wire sizing with our own, which includes the ability to specifically set wire sizes on circuits. We pull distances from Revit as best we can but always give you the ability to override with a specific value.

You can learn more or download a trial on our website:

http://www.designmaster.biz/revit/voltage-drop.html

David Robison
Design Master Electrical RT