As an engineer who's looking in from the outside, rather than installing conduit day-in and day-out, here's my own opinion on the matter.
I've seen way, way too many pieces of EMT hanging by the wires after they've come loose from set-screw fittings. I've especially seen that a lot around my kids' schools. (I suppose an argument could be made that conduit within reach of the kids at a school is "subject to damage," but that's another discussion...)
Because of this, my feeling, coming from real-life observations, is that set-screw fittings are unreliable, to the point of being dangerous.
My gut feeling, before I starting reading this thread, was that compression couplings are more reliable. Now, this discussion suggests that my gut feeling may have been wrong. However, I wouldn't be at all surprised if the engineer who wrote the specs for compression fittings was coming from the same place I am.
I further note that my gut feeling is biased by the fact that there are far more set-screw connections around where I've been than compression connections. Therefore, I'm a lot more likely to see set-screw fittings that have come loose, just because of the numbers. So, if there were a lot of compression fittings around, perhaps I would be seeing those conduits hanging by the wires, too.
All in all, it still seems like a compression connection would be more secure...
[This message has been edited by SolarPowered (edited 11-28-2005).]
