Q: When I run the Panel Edit command and try to modify the Bus Size / Mains field for a panel, the value is locked. How do I unlock it?

A: The Bus Size / Mains field uses Revit’s built-in “Mains” parameter. If Design Master is unable to modify that parameter, the field will be locked. The possible reasons and solutions are detailed below.

Bus Size / Mains Set in the Family Edit Command

In the Family Edit command for the panel family, if Device type is set to Distribution equipment: Panel, you can set the Bus Size / Mains for the family and each type within the family. If this value is set at the family level, it will be locked for the instances in the project.

The solution is to either modify the Bus Size / Mains field at the family level to what it should be for each type, or change the Device type to a type that does not use that field, such as Distribution equipment: Other.

After making any changes, use the Revit Load into Project command to reload the family definition in the project.

Revit Mains Parameter set to Type

Some Revit users prefer to change the “Mains” parameter from an Instance parameter to a Type parameter for their panel families. While this is more intuitive for how bus size relates to panels in the real world, it also renders the parameter uneditable in the project.

The solution is to undo this change in the panel family using the following steps:

1. Run the Revit Family Types command. Confirm the “Mains” parameter has a value; if it does not, enter a value.
2. Press the OK button to save your changes and close the dialog box.
3. Run the Revit Family Category and Parameters command.
4. Change the Family Category from Electrical Equipment to any other category, such as Generic Models.
5. Press the OK button to save your changes and close the dialog box.
6. Run the Revit Family Types command.
7. Select the “Mains” parameter and press the Edit Parameter button.
8. In the Parameter Data section, change Type to Instance.
9. Press the OK button, then the OK button again to save your changes and close the dialog box.
10. Repeat steps 3-5, changing the Family Category back to Electrical Equipment.
11. Run the Revit Load into Project command to reload the family definition in the project.

Revit Mains Parameter Associated With a Global Parameter or Formula

If the “Mains” parameter has been assigned a global parameter in the project, or has been assigned a formula in the panel family, it can no longer be edited directly.

To check if a global parameter has been assigned in the project, select the panel and, in the Properties panel, find the “Mains” parameter. If the button to the right of the parameter has a = symbol, a global parameter has been assigned. Press the button, select “<none>” from the list, and press the OK button to unassign the parameter.

To check if a formula has been assigned, in the panel family, run the Family Types command. Find the “Mains” parameter. Erase everything in the “Formula” column for the parameter, then press the OK button to save your changes. Use the Revit Load into Project command to reload the family definition in the project.