Is it a requirement of the code to have rubber sealing rings on the threaded portion of a EMT compression fitting? I've noticed recently that they are available in at least the 1/2 and 3/4 sizes. All the years that i've used EMT comp connectors and couplings I've never seen the rubber washer right on the fitting. Always bought sealing washers when I would be going into a panel or enclosure. Is this just an added feature by maybe a particular mfg, or is it a requirement. Thanks.
Compression fittings
- Thread starter nizak
- Start date
- Status
- Location
- Massachusetts
I think it was a couple of years ago when UL changed the standards and the compression fittings we had always used were no longer listed for wet locations.
So now you can buy compression fittings for dry locations or compression fittings for wet locations. The ones listed for wet locations have the extra sealing washer.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
We either ask for compression or raintight fittings, the supply house knows the difference.
- Location
- Massachusetts
Some people believe that they provided better grounding continuity than set screw firings. In Rhode Island we are required to use compression fittings on fire alarm systems per local code.
I believe some manufacturers changed the "split" ring to a continuous one similar to compression fittings for copper tubing so their "standard" fittings are also raintight.
http://tnblnx3.tnb.com/emAlbum/albums//us_tc/gm101emt100_104_tc1.pdf
http://tnblnx3.tnb.com/emAlbum/albums//us_tc/gm101emt100_104_tc1.pdf
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
They're dusttight, we do a lot of work in ag buildings and hay cubing operations.
RICK NAPIER
Senior Member
- Location
- New Jersey
They use compression fittings in concrete.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
I've heard this before and I completely agree. I bet on the average install a set screw fitting is more likely to get installed correctly.
Not picking on engineers, but I wonder if they knew this they would still spec compression where the NEC doesn't require it?
renosteinke
Senior Member
- Location
- NE Arkansas
I suppose it helps to keep things in perspective.
It's not an issue of 'set screw vs. compression.' There are other ways to connect fittings to EMT. Set screws and compression have just been the most popular designs.
Some folks like the compression style for simple appearance; others see the screws as places that can collect grime or catch on clothing.
A minor point of history: it's not so much that the 'standard changed' that some bright youngster at UL noticed that the things had never been actually tested. He slipped a few into a test and found that they failed. Oops. Again. it's not that the folks at UL were lazy - it's just that the fittings predate the general acceptance of NEMA enclosures. (Even into the 80's UL simply refused to admit even the existance of NEMA, and had their own area definitions).
As a result, compression connectors were redesigned. They're still available in both styles.
It's not an issue of 'set screw vs. compression.' There are other ways to connect fittings to EMT. Set screws and compression have just been the most popular designs.
Some folks like the compression style for simple appearance; others see the screws as places that can collect grime or catch on clothing.
A minor point of history: it's not so much that the 'standard changed' that some bright youngster at UL noticed that the things had never been actually tested. He slipped a few into a test and found that they failed. Oops. Again. it's not that the folks at UL were lazy - it's just that the fittings predate the general acceptance of NEMA enclosures. (Even into the 80's UL simply refused to admit even the existance of NEMA, and had their own area definitions).
As a result, compression connectors were redesigned. They're still available in both styles.
- Location
- Massachusetts
OK, now explain a threaded conduit coupling.
Did they forget to test those as well? They pass water like a sieve.
renosteinke
Senior Member
- Location
- NE Arkansas
Ssssh ... don't let them hear you .... 
kwired
Electron manager
- Location
- NE Nebraska
A loose set screw has a chance of being seen and tightened.
A loose compression nut could be seen but you need to look harder to notice in most cases.
A set screw that got tightened is a better bond than a compression nut that did not.
In outdoor locations even with old style compression fittings there will always be more water in raceway from condensation than ever gets in through fittings - even with threaded RMC.
A loose compression nut could be seen but you need to look harder to notice in most cases.
A set screw that got tightened is a better bond than a compression nut that did not.
In outdoor locations even with old style compression fittings there will always be more water in raceway from condensation than ever gets in through fittings - even with threaded RMC.
- Status