emt fittings damp locations

[LJSMITH1]

How long have the emt fittings been around with the plastic seal? My local supply house still does not get these. I had to go outside my area to get them.



Anyone have any trouble using these. Even on a factory end they seem to take a bit of finess to fully seat the conduit.

We have been producing these since 2003 - ever since UL changed the requirements for compression type fittings.

As for the fitting assembly, the end of the conduit should be cut with a tubing cutter and have no burr. The tubing cutter should not distort the conduit OD so much as to cause a problem inserting it into a preassembled fitting. Due to the tolerance swings with some manufacturers emt, sometimes the fitting needs to be disassembled to place each piece onto the conduit separately (i.e. Nut, compression ring, seal, then body). While the fitting is designed to work best with the nominal OD of a trade size, an OD at the max may be required to be assembled separately.

 

[LJSMITH1]

LJ,
It apprears that UL and the code are in a bit of a conflict with each other and few electricians look to the UL White Book when making an installation. The issue is that you are telling us that "raintight" fittings are only for damp locations, but code rule specifies "raintight" for wet locations.

As far as rigid goes, the conduit has a tapered thread but coupling do not and rigid conduit leaks more in wet locations than the old style EMT compression fittings before UL made you add the seal.

Don,

I believe the single piece couplings that are typically supplied with rigid conduit, have a straight-tapped, female thread. This is why they probably don't seal too well. I don't think that this "fitting" is tested to UL514B. I went to Allied Tube's website and the only coupling that is UL-Listed is ther "Kwik-Couple RIGID".

We supply a 3pc rigid coupling that has tapered threads and is UL listed http://www.bptfittings.com/images/products/1121.gif . I am sure others supply other single piece, rigid couplings, but I am not sure if they have tapered threads or if they are listed.

 

[don_resqcapt19]

LJ,
All standard conduit couplings have straight thread. I have to assume that they are a listed product as they are supplied with the listed conduit. As far as the three piece couplings of the design shown in your link, they leak even more than a standard conduit coupling. If they pass the UL test, then a standard coupling will also pass the test, but my point is listed or not, both of those items let more water into the conduit than the old design EMT couplings and UL made you change the design of them.

 

[LJSMITH1]

From what I was told, UL realized that the standard compression design was not as raintight as thought when assembled in the field. They changed the requirements to make sure that the fittings passed the test when listed as raintight.

As far as the standard rigid, threaded, couplings go, I think there is a general assumption that they are raintight. This was the case with compression fittings prior to 2003 for 30 years.

I don't know if the standard straight couplings are separately listed or if they are listed for use only with the pipe (i.e. UL Recognized). I'll have to do some digging to find out more.

You bring up a good point worthy of some investigation. I am always eager to learn more.

 

[realolman]

Why don't they just make conduit couplings tapered? I can't believe a rigid threaded conduit with a tapered threaded coupling and some pipe dope wouldn't be better than any other coupling out there.

Do you really not do it that way if you need it in a really wet location?

There... I've said it. Flame away.:smile:

 

[don_resqcapt19]

Why don't they just make conduit couplings tapered? I can't believe a rigid threaded conduit with a tapered threaded coupling and some pipe dope wouldn't be better than any other coupling out there.

Do you really not do it that way if you need it in a really wet location?

There... I've said it. Flame away.:smile:

The reason is cost. You have to tap a tapered thread couplings from each end, but you only have to tap from one end of a straight thread coupling.
As far as using pipe dope or tapered thread couplings, I don't, and I just arrange the conduit system to drain and as far as I know there are no listed conduit couplings that have tapered threads.

 

[realolman]

well you're certainly right about the cost

Mc Master Carr:

Galvanized 1/2" merchant pipe couplings 2.48 ea
Galvanized 1/2" threaded conduit coupling 0.92

 

[realolman]

well you're certainly right about the cost

Mc Master Carr:

Galvanized 1/2" merchant pipe couplings 2.48 ea
Galvanized 1/2" threaded conduit coupling 0.92

Funny thing... I made sure to look today and the merchant pipe coupling is threaded straight through, and is good for 150 psi.

Why can't you keep water out if you can keep water in?

 

[don_resqcapt19]

Funny thing... I made sure to look today and the merchant pipe coupling is threaded straight through, and is good for 150 psi.

Why can't you keep water out if you can keep water in?

Are you sure that is not a special coupling? There are some straight thread piping couplings. Standard pipe couplings are not straight thread and are tapped from both ends.

 

[realolman]

Malleable iron pipe couplings seem to be threaded from both directions. This is a galvanized steel pipe coupling, called a merchant coupling.

I guess what bugs me is that it seems you can't use threaded rigid conduit to keep water out, and I can't see why that should be. That emt would be superior to rigid in this just seems ridiculous to me.

So the myers hub in the enclosure is water tight, but the threaded coupling at the other end of tha piece of conduit is not?!? That just seems absurd.