Revit MEP - Electrical Wire Sizes

[rudi.roux]

It would be amazing if Autodesk could revise the Revit Electrical Settings, mainly referring to the Wire Sizes and Ground Conductors. Currently, you can not create an existing Ampacity or Wire Sizes - e.g. You can't have a 10A Breaker with a 2.5mm² Cable and then create a New Ampacity of 20A with a 2.5mm² Cable. I'm not going to get too technical now, but this is a HUGE problem for me and quite a few other MEP users which I've spoken to. 

I require the ability to choose my own wire sizes and ground conductor sizes as I feel this is an area in the Electrical Settings which greatly be enhanced.

Possible Solution which could be Implemented:

• Add a column/drop-down selection where you need to assign certain amperage (A) to a Load Classification. 
• Then I would be able to have a e.g. - 10A, 2.5mm² Cable assigned to a Lighting Load and a 20A, 2.5mm² Cable to a Power/Socket Load.
• This way Revit should not get confused and the correct wire sizes would still be assigned correctly...

I would like to build a fully automated template which auto populates a Schematic Diagram/Single Line Diagram apart from Revit's Panel Schedule. Not being able to assign my own cable sizes limits me to do this and revert to manual work.

[fabiosato]

Hello Rudi,

Revit can calculate the wire for you, but you will need to test each configuration. Here in Brazil we use the same standard.

The workaround is to use a higher value in the ampacity for proper wire selection, for example a wire that can be used until 20A, you will need to input 21A. The amount starts from 4% to 8% on higher currents.

[rudi.roux]

Hi Fabio, 

The workarounds which we(me, you, MEP users) need to deal with electrically is so time-consuming from one project to another. haha... I do the same thing to get to the wire sizes which I require, but this is where it starts to "annoy" me, because now there are chances for human error again and where the information retrieved from the model/systems/panels become somewhat redundant. 

A typical example is, we have huge mining clients, and they require that we use specific wire sizes for specific amperages and vice versa. So I end up having to manipulate the "heck" out of wire sizes, ampacity and panel schedules to get to the desired result... Which leaves me thinking that this would have been easier/quicker in AutoCAD (standard schematic/single line diagrams) seeing as I have to manually manipulate so many things. 

This also leaves me thinking about a project from last year, currently the largest Cargo Terminal in Africa(under construction), where there was around +- 30 Panels and with around 20 - 250 circuits/loads on each, with so many "specific loads/load classifications" that thinking back now, if "this idea" already existed, it would have made that I only needed to worry about creating the load classifications and wiring/circuiting it to the panel and I could have been confident that the required wire sizes and ampacities would have been correct. 

Thank you for the interest and I hope to see further MEP developments, for both our sakes! haha

[Martin__Schmid]

@rudi.roux - thanks for the suggestion.. can you elaborate a bit more on why you would be protecting the same 2.5mm cable with different breaker ratings?  There are scenarios (as described here for motors) where there are different breaker/wire sizing requirements vs the current logic... so you may be on to something w/ your idea of having some association between the load classification and the sizing requirements, but I'd like to understand more.

Thanks,

MS

[Anonymous]

@rudi.roux Although I agree 100% with your request, I don't believe Autodesk will accept this... mainly because it would put Revit's wire sizing logic in a bind when you pick a 20A breaker. Revit's wire sizing would look at the two different wire size options and freak out because it doesn't know whether to give you a 14 or 16 AWG conductor. Would it be easier just to make autodesk give up on their whole wire sizing effort? or at least offer us an instance-based checkbox in each circuit's properties that allows us to override the automatic wire sizing? There are just too many situations where there can't be a hard link between a certain breaker size and a certain wire size... Motors w/o a VFD, Voltage Drop (since Revit does it all wrong), heat calcs... etc.