The Turn Centerlines On command turns conduit and cable tray centerline layers on. These layers are typically on a non-plotting layer that will not appear on your printed drawings. It is often helpful during the design to turn these centerlines on and off to see what your final drawing will look like.
To turn the centerlines on, go to
Ribbon: DM Electrical->3D-BIM-> 
Turn Centerlines On
Pulldown Menu: DM Electrical->Layer Management->Turn Centerlines On
The centerline layers will be turned on and will be visible on the drawing.