Get ampacity which is used for specifying size, the unit is ampere. 
   Namespace:   Autodesk.Revit.DB.Electrical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Namespace:   Autodesk.Revit.DB.Electrical  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0)