I am getting tired of comression fittings. When I tighten one, it graps the preceding conduit with an offset in it and twists it out of alignment. Sometimes the pipes pull out. Wrenches don't fit very well on them. They aren't really water proof.
I know they cost more which may be why they are specified but are they really any better than set screw connectors?
Something like the "Rainboot" connectors and couplings for rigid would be nice.
If they are being specified for indoor work, keep in mind that some architects & engineers get a % of the toal job cost.
Some feel that compression fittings make for better equipment ground continuity, but I've never seen one bit of scientific evidence to support this.
If physical strength is an issue here, perhaps RMC should be installed instead of EMT.
Peter it all depends on the quality of the fittings.
The ones I get as part of a large negotiated purchase are junk, I could tighten them up as much as possible and they are still loose. Usually they have a "Made in Mexico" label
On the other hand when I do T&M jobs and order small quantities I get top quality parts. Compression fittings with deep throats and glands that grab.
I guess it all about what your willing to pay for.
IMO a compression connector properly used is much better than the set screw type. It can be re-tightened if necessary. Try that with a set screw. Just my 2¢
[This message has been edited by electricman2 (edited 08-09-2004).]
More and more of our commercial work is spec'd with all steel compression fittings. I always assumed it was for bonding continuity, but it certainly does drive the cost up.
I found on some cast ridgid copression in the 1 1/4-2" range the ring inside is too big. If I use large adjustable wrinches and get it as tight as possable the pipes are not tight, will spin, and may pull apart. If I take it apart and clip just a hair off both ends of the sealing ring it works great. When I put the pipes back together BY HAND ONLY I can't even twist them let alone pull them apart. Of coarse I crank it down still. A quality issue I guess. I don't know what it does when the rain comes but keeping the pipes together is priority 1.
I did a horse barn with comp fittings and they were fine. I use steel fitings for all emt so maybe thats the difference.