EMT To RMC/Hub Transition

[yesterlectric]

I know what many do when coming into the top of a NEMA 3R enclosure: use a conduit hub like a "Myers" hub and screw conduit male adapters into it. So many installations do it. And I personally think it's a better seal than a rain tight EMT fitting screwed directly into the top of the enclosure. However, "myers" hubs (I know myers is just one brand) are only listed for use with RMC. There's very few say raintight EMT to RMC adapters that could be used with an RMC nipple to screw into a hub. What "proper" ways do people see being used here that they might be comfortable with?

 

[tortuga]

I think the 'proper' way is not to go into the top of the enclosure by design.
I had EE tell me once that by going into the top of an enclosure I killed its UL 4X rating, even with the Myers hub and RT EMT fitting, she did not make me replace the enclosure so must have not been that concerned about it, but I had to do back flips to get all the other conduits to enter the bottom of all the other enclosures.

 

[electrofelon]

IMO the best way is to throw the gasket on the RT fitting immediately in the garbage, put a bead of silicone on the shoulder if the connector, and tighten it up good using the lock nut. Hope and pray that the connector isn't typical UL approved/passed garbage and you can actually tighten the lock nut up good to get through the paint without it skipping out (unlikely).

 

[letgomywago]

Use a sealing locknut it's what's listed for this. Then spray like crazy galvi spray then blackjack then galvi spray.

Or just user rigid, imc, pvc or fiberglass where you need to be outside. Emt works fine but the rain tight fittings are terrible

 

[electrofelon]

Use a sealing locknut it's what's listed for this. Then spray like crazy galvi spray then blackjack then galvi spray.

Or just user rigid, imc, pvc or fiberglass where you need to be outside. Emt works fine but the rain tight fittings are terrible

I'm pretty sure sealing lock nuts are only for rigid also.

 

[kwired]

I'm pretty sure sealing lock nuts are only for rigid also.

They are effective but yes only listed for use with RMC/IMC.

I throw away the gaskets that come with RT fittings and if penetrating above live components use myers hubs myself.

I used the RT fittings the way they say you should for only a short time when they first started pushing those things, came back to an install within a year or so only to find gasket deteriorated from sunlight, about 75% missing or at least no longer "sealing" leaving a gap between enclosure and fitting. Using the fitting without a gasket at all would have made a better seal than what it ended up being like. Not to mention no reliable bonding with the loose connection.

 

[electrofelon]

They are effective but yes only listed for use with RMC/IMC.

I throw away the gaskets that come with RT fittings and if penetrating above live components use myers hubs myself.

I used the RT fittings the way they say you should for only a short time when they first started pushing those things, came back to an install within a year or so only to find gasket deteriorated from sunlight, about 75% missing or at least no longer "sealing" leaving a gap between enclosure and fitting. Using the fitting without a gasket at all would have made a better seal than what it ended up being like. Not to mention no reliable bonding with the loose connection.

Yeah I agree just use the connector in a Meyers hub. Technically not listed for that but I'm not sure if that is ever enforced. I like my silicone idea but probably wouldn't do that on inspected jobs as I would be concerned the inspector would yell at me for throwing away the stupid supplied gasket.

 

[letgomywago]

I'm pretty sure sealing lock nuts are only for rigid also.

Then even more reason go avoid this situation

 

[wwhitney]

Yeah I agree just use the connector in a Meyers hub. Technically not listed for that but I'm not sure if that is ever enforced.

In 1/2", 3/4" and 1", apparently there are NPT-style connectors that are listed for that. E.g. Bridgeport 250-RTNPT, 251-RTNPT, and 252-RTNPT. Not sure if anyone makes anything like that for larger sizes.

Cheers, Wayne

 

[electrofelon]

In 1/2", 3/4" and 1", apparently there are NPT-style connectors that are listed for that. E.g. Bridgeport 250-RTNPT, 251-RTNPT, and 252-RTNPT. Not sure if anyone makes anything like that for larger sizes.

Cheers, Wayne

Yeah I did some quick searching too. It's odd how some of the stuff they only make up to 1 in or 2 in. Something like that if available in 2 in (and sometimes larger) would be the cat's meow.

 

[yesterlectric]

I actually found one company I never heard of. American Fittings. I think if more people were doing it right we would have more options. On the other hand one might wonder why the standard can't be changed to allow something that people have been doing for decades without incident. RMC is "tapered." Yea really. Screw an RMC coupling on and see how tapered it is compared to gas NPT piping fittings.

There used to be more options available back when compression EMT connectors with the steel ring were normally both listed for RMC and EMT, plus normally acceptable for wet locations. Then, UL "fixed" it by requiring those junky ones that are listed as "raintight."

https://amftgs.com/wp-content/uploads/2020/05/AMFICO-EMT-Adapter-EMT-to-Rigid-ETR-.50-4.0.pdf

 

[don_resqcapt19]

I actually found one company I never heard of. American Fittings. I think if more people were doing it right we would have more options. On the other hand one might wonder why the standard can't be changed to allow something that people have been doing for decades without incident. RMC is "tapered." Yea really. Screw an RMC coupling on and see how tapered it is compared to gas NPT piping fittings.

There used to be more options available back when compression EMT connectors with the steel ring were normally both listed for RMC and EMT, plus normally acceptable for wet locations. Then, UL "fixed" it by requiring those junky ones that are listed as "raintight."

https://amftgs.com/wp-content/uploads/2020/05/AMFICO-EMT-Adapter-EMT-to-Rigid-ETR-.50-4.0.pdf

The standard does not prohibit the fittings be evaluated for that use...it is just that each evaluation costs money, and it appears that the manufacturers have chosen not to spend that money on additional evaluations.

Only fittings for 2.5" and larger could be used with both EMT and rigid. For 2" and smaller the OD of EMT is less than than of rigid.

 

[TwoBlocked]

I agree to avoid going in the top of an enclosure. And if coming in from the bottom is a pain, the side is another option. But regardless, it's really tough to keep water out of a box that is outside. Doors, don't get closed tightly and door gaskets leak eventually. I like to drill a 3/16" hole in each corner of the the bottom of the box.