"knockout seals" that come with Raintight EMT compression connectors

[tortuga]

Are the gasket (black or yellow O rings) that they call a "knockout seal" supplied with Raintight EMT fittings required by UL or the manufacturers installation instructions when used with outdoor "bell" type boxes or cast conduit bodies that have internal tapered threaded hubs? I am told that using these O rings on boxes with threaded hubs prevents the full seal of the tapered hub or become distorted and useless when threaded "wrench tight" into these types of boxes.
Comparing a EMT "raintight" fitting with a regular compression type I see there is in fact a plastic piece in the compression part of the connector of the raintight ones that is not present in the concrete tight ones. So the O rings may not be the main watertight seal.
I have access to a copy of UL 514B and it does not mention these gaskets either.

The fact that the manufacturer refers to these gaskets as an "included Knockout seal" may infer they are only required for use with knockouts and not threaded hubs.
I looked on several different manufacturers cartons, looked up installation instructions and in the white book and see no indication either way.
Thanks in advance

http://www.cooperindustries.com/con.../resources/pdfs/instruction-sheets/if1655.pdf

The Hubbell Raco catalog states "
All connectors are supplied with a factory
installed knockout seal. No need to add the
expense of buying a gasket separately"

 

[Smart $]

...
The fact that the manufacturer refers to these gaskets as an "included Knockout seal" may infer they are only required for use with knockouts and not threaded hubs.
...

EMT connectors are only listed for use with holes... and I believe you will find that hubs are only suitable for threaded conduit or fittings specifically made with NPT threads.

 

[iwire]

EMT connectors are only listed for use with holes... and I believe you will find that hubs are only suitable for threaded conduit or fittings specifically made with NPT threads.

I agree with you, and it is stupid.

 

[infinity]

I agree with you, and it is stupid.

LOL I agree too. This is done everywhere, every day. :slaphead:

 

[tortuga]

EMT connectors are only listed for use with holes... and I believe you will find that hubs are only suitable for threaded conduit or fittings specifically made with NPT threads.

Sorry I am talking about the "Internal Hubs" in a standard bell box. The Bell Box catalog states
"Hubs accept all threaded fittings and threaded conduit."
Going to the UL Whitebook QCIT "Wet location"

Boxes with threaded conduit hubs will normally prevent water from entering except
for condensation within the box or connected conduit.

Here is an example photo right from the T&B fittings catalog. These do not come with the "Gasket" and depict the installation I describe right in their catalog. A raintight EMT fitting into a bell box without the gasket. They go on to state "* Gaskets sold separately. In some jurisdictions, sealing gaskets are not required when installed in a threaded opening."

 

[Fulthrotl]

Sorry I am talking about the "Internal Hubs" in a standard bell box. The Bell Box catalog states
"Hubs accept all threaded fittings and threaded conduit."
Going to the UL Whitebook QCIT "Wet location"



Here is an example photo right from the T&B fittings catalog. These do not come with the "Gasket" and depict the installation I describe right in their catalog. A raintight EMT fitting into a bell box without the gasket. They go on to state "* Gaskets sold separately. In some jurisdictions, sealing gaskets are not required when installed in a threaded opening."

this is getting annoying.
raintite isn't "submersible".
it isn't "washdown".

i've *never* used a sealing washer when threading a fitting into a bell box,
or any other threaded entrance.

when i need a watertight entrance into a sheet metal enclosure,
i've taken to using these cutting edge devices that were just developed for
the purpose. they are called myers hubs.

and i don't use a sealing washer to screw a raintight fitting into a myers hub, either.
i've seen that done, and it's queerer than pink ink.

 

[tortuga]

i don't use a sealing washer

So you would discard this when threading into a bell box

 

[Smart $]

So you would discard this when threading into a bell box

There's a lot of missing information that I cannot seem to locate on UL's web site. For example, I cannot verify the "Hubs accept all threaded fittings and threaded conduit" statement.

If it comes with the gaskets, I'd use them... but IMO by the time that fitting is truly wrench tight, the gasket will be squeezed out from between the flange and the box. I've not used any of this particular type, so I cannot speak from experience.

 

[tortuga]

There's a lot of missing information that I cannot seem to locate on UL's web site. For example, I cannot verify the "Hubs accept all threaded fittings and threaded conduit" statement.
.

Judging from experience reading the UL white book they get very specific about when fittings should not be combined like that, for example with cable clamps. Looking at the Whitebook it is silent on the internal hubs under "Metallic Outlet Boxes (QCIT)", yet is so detailed and specific on cable clamps indicates to me that if they were not permitted it would say so.
UL 514A see section 9.4 "Openings for rigid conduit, electrical metallic tubing, and conduit hubs" would be the relevant standard, but really if they were not intended for use it would make it to the whitebook.
The manufacturers catalogs depict a raintight EMT connector installed in a outdoor box (photo), it would be strange for steel city to depict a product not being used as listed.
These fittings get threaded into conduit bodies as well.

If it comes with the gaskets, I'd use them... but IMO by the time that fitting is truly wrench tight, the gasket will be squeezed out from between the flange and the box. I've not used any of this particular type, so I cannot speak from experience

Wow really? You have not run into these in the field? Well yeah thats the crux of the problem some come with the gasket some don't. Both types infer its optional if going into a threaded entry. I need to determine if they are required. Reading the standard (section 39) for how they do the 1 hour "Raintight" spray test I think they use the gasket on a "sheet metal knockout" and discard it when threading into a NPT tapered hub.
I emailed UL for clarification and will post a follow up.

 

[Smart $]

... Wow really? You have not run into these in the field? ...

I've not done any conduit work since 2008 and that was all industrial, rigid steel or aluminum. Also, I've never run EMT in my entire career in a location where it could be rained upon. I'm not even sure if raintight EMT fittings existed the last time I ran EMT.

 

[tortuga]

I've not done any conduit work since 2008 and that was all industrial, rigid steel or aluminum. Also, I've never run EMT in my entire career in a location where it could be rained upon. I'm not even sure if raintight EMT fittings existed the last time I ran EMT.

Wow I have never worked with rigid aluminum. What kind of work requires that?
Rigid steel I use on service masts and thats about it.

 

[hbiss]

Wow I have never worked with rigid aluminum. What kind of work requires that?

Used to use it quite often. Outdoors for services for instance as well as other outdoor applications as long as there are no corrosive conditions and not in direct contact with concrete. Lasts forever where EMT and GRC will rust away. I've even direct buried it where soil conditions permit, (no alkalines or corrosives) have some that's still in use after 50 years. Easier to bend (use a size larger EMT bender for 1/2 and 3/4) and thread.

As to your original question, I rarely run EMT outdoors but with raintight compression connectors no, you do not use the sealing washers when threading the fitting into a threaded opening such as with a Bell box. But you should use a silicon sealant such as clear RTV on the male connector threads first per the Bell box instructions. Wipe off the excess.

The washers are intended for use where the connector is installed in a knockout or punched hole in the sheetmetal of like NEMA raintight enclosure but I would only use them on the bottom. I would much rather rely on a Meyers hub then the connector on the sides and especially the top.

-Hal

 

[curt swartz]

The rubber washers on RT EMT fittings are 100 % useless for any application. The shoulders on the EMT filling are narrow and rounded. Even hand tight the washer just squish over the shoulder of the connector and serve no purpose. If they want the washers to be useful they need to design the connector with a large flat surface similar to a Myers hub.

 

[ptonsparky]

So you would discard this when threading into a bell box

Those fittings are a waste of time. Even if you just snug them up so the gasket stays in place, they are gone or all but in just a few years. Pathetic.

 

[tortuga]

Thanks everyone for the feedback! We have around 40 bell boxes to make up next week looks like the gaskets will be discarded.

 

[ptonsparky]

Thanks everyone for the feedback! We have around 40 bell boxes to make up next week looks like the gaskets will be discarded.

use a different brand of fitting. Those with the hard plastic seal seem to Last longer.

 

[tortuga]

use a different brand of fitting. Those with the hard plastic seal seem to Last longer.

Thats a good idea, the Steel City ones show the gasket as 'optional depending on the AHJ' when used with threaded hubs. So I'd go with those.
There are about 15 bell boxes roughed in without the gasket. No wire pulled yet so would be still be easy to Re-do if needed.
I'll post a follow up when I here back from UL.

 

[ptonsparky]

Put a weep hole in the box, whatever kind you use.