When creating a new Revit family based upon the Electrical Equipment template, there is a parameter already within the family named Voltage. This is a system parameter which is predefined in the template and cannot be removed. By default, this is a Type-based parameter. You cannot simply edit the parameter and change it from Type to Instance as can be done with other parameters. However, it is possible to change it to Instance-based and this article will show you how to accomplish that change.
I have previously written about a software named Tekla BIMsight which is a good option for collision detection for building models. (Click here for article) After I first encountered this program and wrote the article about it in February of 2011, Tekla has continued to improve the software. The great part about this software is that it is still FREE. It is still a very viable option for designers who need collision detection capability, but can’t afford software like Navisworks Manage.
Tekla has a new update out for BIMsight and I still believe that it is a decent program and should be investigated to see if it meets your needs. The current (new) version is 1.9.
Applying Technology to Architecture 