Originally Posted by 480sparky
Centerfrugal? The middle of being stingy?
I think he meant concentric and eccentric...which the OP mentioned.
Here's another application where it's necessary...
Ground Riser in a building...IF run in ferrous metal conduit. EMT, GAL, IMC...if it's in FRE or PVC it is not necessary. Problem with that is...many of the large engineering firms are now speccing a 500MCM ground riser...which is ridiculous. UL did a study that over sizing the wire to 500's from 3/0 does nothing. A major problem we have with high rise construction is that the engineer will spec out the 500MCM in a 2" conduit. There is no UL listed MIGB that can handle a wire that size. Besides...BENDING the 500 to get into the split lug would be a job for Superman!