We are running 3" rigid conduit for a 200HP motor located on top of a grain elevator. The vertical rise is about 180', the conductors will be 500mcm THHN, pull boxes every 50'.
How would you support the conductors in the pull boxes??
In the past I've used kellum grips, but I've seen places where the grips can cut through the conductor insulation and that is a major concern.
I've also used sheet rubber wrapped around the conductors and tied off in the box with a rope or cable.....not materials listed or approved for this application.
I've seen, but not used, a rubber or wooden "bung" drilled to fit tight on the conductors which then wedges tight into the top of the rigid pipe.
Are these still available? who makes them?
When I asked these questions at the wholesale house I just get that glassy eyed look and a shoulder shrug.
What would you do??