define new min. wire sizes

[HVAC-Novice]

under "Manage - MEP Settings - Electrical Settings" I can see the default min wire sizes for each ampacity. For example for 20A circuit it uses #12 wire or larger (larger being a smaller number...).

How can I change that definition? for example I want a min. size of #10 for 20A regardless of voltage drop.

I know based on voltage drop it calcualtes the size,  but is till want it to use #10 wire or larger regardless of voltage drop.

I tried deleting and creating a new ampacity, didn't work (besides that amapcity disappearing)

[pteague]

In the wire sizes part of that box, there is a check box for each wire size "Used by sizing". You can uncheck that box to remove any sizes you don't want it to use. This will cause it to use the next larger size (ampacity) that is on the list.

[HVAC-Novice]

The problem with that approach is, this also takes the sizes out for the next sizes. For example I want to change my 15A to #12, my 20A to #10 etc. but unchecking all of them just makes them all go to the very largest wire that still is checked.

The way I understand is that this method eliminates that size from being used entirely, not just for that specific amapacity.

I also just noticed thee is an error in length calculation (I know Revit only takes into account length up and horizontally and in practice runs are longer). But when a set of receptacles is to the right of a panel, all is fine. If I add one receptacle to the left (on same circuit) it nearly doubles the length. (It must assume some weird wire run). Maybe I forget about the whole Revit calculation of wire sizes and voltage drops.

[chrisplyler]

Delete the row designating 20amps to use #12, and create a new row designating 20amps to use #10.

[HVAC-Novice]

It doesn't let me create a new wire size that already exist. So I also have to delete the next wire size. For example, when creating a new 20A/#10 wire, I need to delete the original 30A/#10 wire as well and so on.

this seems quite cumbersome to delete all wire sizes, recreate all of them and also manually re-eneter the Diameter (no, it is not smart enough to know what diameter #10 wire has - when creating an amapacity of 20 and wire #10, it offers "0" diameter, which is pretty thin).

It also seems this has to be re-done for all insulation types and all temperature ratings. Besides the work this seems to require, it requires quite some quality control on my side to ensure I entered all the diameters etc. correctly.

[chrisplyler · Accepted solution]

Look under Electrical Settings > Wiring > Wiring Types. You'll only have to change the values for the wiring type you want to use.

You might make one type that's copper, 90deg, THHN, for which you change the amp/sizing of only that wire. You might create another type that doesn't have a modified amp/sizing table.

[David_Robison]

This is one of the features we included in our electrical calculations add-in for Revit.

http://www.designmaster.biz/revit/index.html

Using our add-in, you specifically choose the default wire size for each ampacity. This page of our documentation shows you what that customization dialog looks like:

http://www.designmaster.biz/docs/elecrt/index.html?wire_ampacities.htm

You can override the value for specific circuits when necessary. We size the breakers based upon 125% of the connected load on the circuit. There are some situations where that is not correct (motors and motor-compressors, for example). When you run into those circuits, you can choose the correct size for the circuit.

http://www.designmaster.biz/docs/elecrt/index.html?edit_circuits.htm