Panelboard MCB Rating Instance parameter bug 2020

[tkendrick]

In 2020 Autodesk converted the MCB Rating system parameter from Type to Instance. This has caused the field to be defaulted to a value of 1A. As we all know, a MLO panelboard does not have an MCB rating. And we are all well aware of the previous issue of filling in that field and being stuck with the error message "Enter a positive value". As long as you left it blank in the family settings and did not enter a value in the field it could remain blank. 

I have already found the workaround to correct this error. 

Edit the family, change the Family parameter Part Type from Panelboard to Equipment Switch. Go to the Type properties and you can now delete the MCB Rating parameter that remains. Go back to the Part Type and switch back to Panelboard. All the Panelboard system parameter will automatically be added back, including MCB Rating, and it will be blank. 

Additionally for all your information, the Electrical Equipment family template file, also contains this error. No one but Autodesk can edit the family template files, so they will need to correct that. 

[tkendrick]

Update: I submitted this as a support case as well. This is a known issue.

See link:

https://knowledge.autodesk.com/support/revit-products/troubleshooting/caas/sfdcarticles/sfdcarticles...

[stever66]

I've always just dealt with this by creating a panel schedule template that doesn't show the MCB rating.  I basically replaced that cell with a simple text cell so I can type whatever I want in it - numbers, text, 200A, or whatever.   Or I can delete everything in that cell and leave it blank. 

I did this about the same time I gave up on using separate panelboard families for MLO or MCB, or for different ampacities.   Back in earlier versions of revit, once a panel had enough connected circuits, you couldn't change the family type.   So to change a panel from 100A to 200A, or to change it from MLO to MCB meant disconnecting a lot of circuits, and then reconnecting.

[drewKULEA]

I entered in a value of 0.01 in the MCB field for the MLO panelboard and it accepted this as a positive value and rounded it to show 0A for the MCB.  This should be confusing enough to work with the Mains type shown as MLO.