# Hub VS Compression fitting



## itsunclebill (Jan 16, 2007)

Definitely not news that the old style compression connectors for EMT weren't raintight - the hex on some didn't even cover the hole completely sometimes.

The new compression fittings are listed as raintight and for wet locations, implying they are reasonably waterproof and in fact they have a gasket where they make contact with a box or panel.

Myers hubs have the same listing, but is there any reason to use one on top of an outside panel or box when the new compression connectors have a gasket?

How about when using gasketed locknuts?


----------



## B4T (Feb 10, 2009)

I would Scotchkote the threads and the conduit under the fitting, above the split ring, if there is one :thumbsup:


----------



## CTshockhazard (Aug 28, 2009)

*Only in America where code = increased mfg. profit*



itsunclebill said:


> Definitely not news that the old style compression connectors for EMT weren't raintight......


Hogwash! Used these for years with nary a problem, cross the border and they're still good.


----------



## knowshorts (Jan 9, 2009)

If it's coming out the top, I use a meyers. Out the side, a green connector.



Black4Truck said:


> I would Scotchkote the threads and the conduit under the fitting, above the split ring, if there is one :thumbsup:


I figured.


----------



## oldtimer (Jun 10, 2010)

knowshorts said:


> If it's coming out the top, I use a meyers. Out the side, a green connector.
> 
> 
> 
> I figured.




( Scotchkote.)......... The Magic Bullet.:whistling2::laughing:


----------



## macmikeman (Jan 23, 2007)

A year or so ago I posted something over at Mike Holt about an article I came across put out by Mark Ode of UL. He states that UL has not ever listed threaded hubs for use with emt connectors of any type, they are listed for rigid conduit only. He is up against the Vatican with that theory, inspection departments are founded on the solid religion that you must put a myers hub first if you are running emt into the top or side of a raintight can. I showed a print out of that article to an inspector once who wouldn't believe me when I told him about it. Went over like a lead balloon. Remember now, this is the same UL that rejected old style compression emt fittings in the first place, and all the local inspection agency's across the nation seemed to get on that bandwagon really quick...


----------



## Dennis Alwon (May 9, 2009)

Ok, myers hubs and sealing locknuts-- the skinny.

I will absolve myself first and say this is from the white Book and is not my opinion.

A myers hub as well as sealing locknuts and washers are only listed for rmc and imc. Apparently there is a difference in the threads of a connector vs the threads on rigid pipe. One is tapered and the other straight threads.

From UL




> Sealing (Liquid-tight) Locknuts — Sealing locknuts are intended for use with threaded rigid metal conduit and intermediate metal conduit with one sealing locknut in the outside or the inside and either an ordinary locknut or sealing locknut on the inside of the enclosure for wet locations or liquid-tight applications. Sealing locknuts may also be used with Listed wet location or liquid-tight fittings where so marked on the fitting carton and used on the inside of the enclosure.


 ​


> Grounding and Bonding Hubs — Grounding and bonding hubs are Listed hubs (see DWTT) provided with a Listed grounding or bonding locknut. *They serve in a manner similar to grounding and bonding bushings except they are only for use with threaded rigid metal and intermediate **metal conduit*. Grounding hubs provide the electrical continuity required by NEC 250.92 at service equipment and the electrical continuity required by NEC 250.97 for circuits rated over 250 V.


​​​​


----------



## Dennis Alwon (May 9, 2009)

Here is the article Macmikeman is referring to.

Here is the thread at MH that was up the other day.


----------



## itsunclebill (Jan 16, 2007)

Pretty much what I figured.

I guess you could always add Scotchkote to both sides of the external gasket, the internal gasket, the end on the conduit, then overcoat the whole thing after assembly. A shrink sleeve over everything and another dose of Scotchkote ought to get it about right.


----------



## Mogie (May 26, 2010)

knowshorts said:


> If it's coming out the top, I use a meyers. Out the side, a green connector.
> 
> 
> 
> I figured.


This is my rule of thumb, also.


----------



## Dennis Alwon (May 9, 2009)

itsunclebill said:


> Pretty much what I figured.
> 
> I guess you could always add Scotchkote to both sides of the external gasket, the internal gasket, the end on the conduit, then overcoat the whole thing after assembly. A shrink sleeve over everything and another dose of Scotchkote ought to get it about right.


Some may say that is a bit overkill.


----------



## itsunclebill (Jan 16, 2007)

Dennis Alwon said:


> Some may say that is a bit overkill.


I'd swear I saw a copy of an invoice for a bunch of 55 Gal barrels of the stuff that had something to do with J-boxes or pull boxes. My suggestion is at best rank amature use of the stuff.................


----------



## jwjrw (Jan 14, 2010)

Dennis Alwon said:


> Some may say that is a bit overkill.


 


Don't let B4T hear you say that!!!:jester:


----------



## william1978 (Sep 21, 2008)

itsunclebill said:


> I'd swear I saw a copy of an invoice for a bunch of 55 Gal barrels of the stuff that had something to do with J-boxes or pull boxes. My suggestion is at best rank amature use of the stuff.................


 Was Black4truck name on the invoice???:laughing:


----------



## Shockdoc (Mar 4, 2010)

itsunclebill said:


> Definitely not news that the old style compression connectors for EMT weren't raintight - the hex on some didn't even cover the hole completely sometimes.
> 
> The new compression fittings are listed as raintight and for wet locations, implying they are reasonably waterproof and in fact they have a gasket where they make contact with a box or panel.
> 
> ...


 I've used them outside recently on 2 1/2 " into a troft......used plumbers teflon paste around compression rings. peeled gasket from locknut and siliconed it to fitting on outside of box. A meyers hub is best when priced into the job.


----------



## Al Lamke (Sep 15, 2010)

Myers hubs have tapered threads, EMT conectors(all) have straight threads! Forget about weather proof or not! What about efective ground path? Myers hubs not listed for emt connectors therfore code violation to use myers hub and emt connector together!


----------



## LJSMITH1 (May 4, 2009)

Al Lamke said:


> Myers hubs have tapered threads, EMT conectors(all) have straight threads! Forget about weather proof or not! What about efective ground path? Myers hubs not listed for emt connectors therfore code violation to use myers hub and emt connector together!


I agree...but it might not be a direct code violation. Do you have a specific code reference in mind?

UL has not developed a standard for such a combination, even though it has been done in the field for many years - especially with RT compression fittings. These also have a straight thread.

I had one customer use a 2.5" set screw connector into a hub. The inspector tagged it as not being 'made up tight' due to the fact that the fitting only threaded about 2 turns into the hub before it jammed. The inspector saw all the 'extra' thread and assumed that it was not fully engaged. The installer (not having the extra length of EMT to run directly into the enclosure) ended up cutting about 3/4" off the EMT coupling threads to make the fitting sit lower in the hub. It still only threaded a couple of turns into the hub.

Customer called us and said that our connector threads were NFG.:blink: I had to politely tell the customer that the threads were different between the ID of the hub (NPTF) and the connector (NPSM). It was all news to them.

Inspector passed it.:001_unsure: I guess that's all that matters anyway...

Personally, I think all these fittings should be additionally evaluated and listed to work in combinations with one or another (within reason). There is no such requirement in UL514B at the moment.


----------



## Al Lamke (Sep 15, 2010)

Larry Check code art. 110.4(B) Thanks Al


----------



## Al Lamke (Sep 15, 2010)

I am also having a "discussion" with inspectors about PVC connectors in a myers hub. Tests have shown that the different threads lead to allowing water to enter an encloser thru uneven threading. If this so with emt connectors, why is it not so for PVC connectors(with straight threads)?! It seems to me the simplest and most economic way is, to use a sealing locknut for ridig conduit, a raintight compression fitting for EMT ,and a sealing washer or sealing locknut for PVC. The inspector insists the electrical contractor must use a myers hub when PVC enters form the top. Thanks for letting me vent my frustrations! Al


----------



## LJSMITH1 (May 4, 2009)

Al Lamke said:


> Larry Check code art. 110.4(B) Thanks Al


I have the 2008 NEC and "110.4(B)" does not exist. However, 110.4 talks about operating Voltages.

You probably mean 110.3(B) Installation and Use. The FPN in the 2008 NEC talks in generalities regarding listing, instructions, and approval, and does not specifically prohibit the combination of a conduit fitting hub tapered thread and a EMT fitting straight thread. 

A 'Myers" type hub is not specifically listed for use with anything other than RMC/IMC, locknut, and an enclosure, and an EMT fitting is not specifically listed for use with anything other than EMT, a locknut, and enclosure. The UL514B tests are very specific as to how the product is to be evaluated. There are no options available to include other combinations not currently defined in the standard.

I was asking if you had any detailed code articles that specifically dealt with this issue. I could be wrong, but I don't believe that there is - hence the widespread use of such a combination. The idea is that if the NEC doesn't specifically prohibit this combination, then it is probably ok. Until you get to 90.4....

I think UL should conduct some kind of independent investigation regarding these thread combinations to see if they meet the basic mechanical pull, bend, moisture resistance, electrical resistance, and current requirements specifically called out in the UL514B specification. If so, there should be specific allowances made in future editions of the NEC and UL514B. 

The NEC cannot possibly cover all possible combinations, but it could certainly attempt to address the ambiguity of these types of applications.


----------



## LJSMITH1 (May 4, 2009)

Al Lamke said:


> I am also having a "discussion" with inspectors about PVC connectors in a myers hub. Tests have shown that the different threads lead to allowing water to enter an encloser thru uneven threading. If this so with emt connectors, why is it not so for PVC connectors(with straight threads)?! It seems to me the simplest and most economic way is, to use a sealing locknut for ridig conduit, a raintight compression fitting for EMT ,and a sealing washer or sealing locknut for PVC. The inspector insists the electrical contractor must use a myers hub when PVC enters form the top. Thanks for letting me vent my frustrations! Al


 
PVC connectors also have the same type of threading issue - tapered or straight. Some LT connectors have a tapered thread, AND use a tapered thread locknut for both types of applications. Other PVC connectors might have a straight thread. It all depends on brand and overall design.

Myers hubs are designed for RMC/IMC tapered conduit threads and attach such conduit to an enclosure in an outdoor environment. It is vibration proof, has excellent sealing and bonding characteristics, and is extremely strong to handle service entrance applications. The Myers hub was designed to replace the welding operation that was done prior to 1949 to attach a RMC/IMC coupling to an enclosure. They are not designed to be used with any type of EMT (straight-threaded) fitting - just RMC/IMC or other tapered thread fittings.


----------



## Jlarson (Jun 28, 2009)

Al Lamke said:


> Larry Check code art. 110.4(B) Thanks Al


:no:



Al Lamke said:


> I am also having a "discussion" with inspectors about PVC connectors in a myers hub. Tests have shown that the different threads lead to allowing water to enter an encloser thru uneven threading. If this so with emt connectors, why is it not so for PVC connectors(with straight threads)?! It seems to me the simplest and most economic way is, to use a sealing locknut for ridig conduit, a raintight compression fitting for EMT ,and a sealing washer or sealing locknut for PVC. The inspector insists the electrical contractor must use a myers hub when PVC enters form the top. Thanks for letting me vent my frustrations! Al





LJSMITH1 said:


> PVC connectors also have the same type of threading issue - tapered or straight. Some LT connectors have a tapered thread, AND use a tapered thread locknut for both types of applications. Other PVC connectors might have a straight thread. It all depends on brand and overall design.
> 
> Myers hubs are designed for RMC/IMC tapered conduit threads and attach such conduit to an enclosure in an outdoor environment. It is vibration proof, has excellent sealing and bonding characteristics, and is extremely strong to handle service entrance applications. The Myers hub was designed to replace the welding operation that was done prior to 1949 to attach a RMC/IMC coupling to an enclosure. They are not designed to be used with any type of EMT (straight-threaded) fitting - just RMC/IMC or other tapered thread fittings.


I just use common sense, a PVC MA can be made up wrench tight into a myers hub so can just about every other fitting. Common sense will always be better than what ever BS the UL nuts are pumping out :thumbsup:


----------



## Al Lamke (Sep 15, 2010)

NEC 2005 art.110.4 has been changed to NEC 2008 art.110.3 (your are right). Listed equipment SHALL be installed in accordance with any instructions included in the listing or labeling The way I read this is, that if the myers hub is not listed for use with an EMT connector or PVC connector, you can't use it. Myers hub are listed for use with RMC. The word SHALL means must or has to , not could or possible. Al


----------



## LJSMITH1 (May 4, 2009)

Al Lamke said:


> NEC 2005 art.110.4 has been changed to NEC 2008 art.110.3 (your are right). Listed equipment SHALL be installed in accordance with any instructions included in the listing or labeling The way I read this is, that if the myers hub is not listed for use with an EMT connector or PVC connector, you can't use it. Myers hub are listed for use with RMC. The word SHALL means must or has to , not could or possible. Al


What instructions are included with the listing or labeling? I think this is where things get 'fuzzy'. The listing only provides the specification to which the hubs were evaluated (i.e. 514B). The labelling for hubs typically does not include detail for what use the fitting is listed for - with exception of "Wet Location" or "Concrete Tight". However, manufacturer catalog spec sheets may provide additional clues as to what the fitting is designed for. Typically, installers don't look at these...:blink:

A manufacturer's catalog states: " To secure threaded rigid service entrance conduit to box or enclosure.." http://www.bptfittings.com/images/products/141%20thru%20196.pdf

So it is fairly straightforward that you are not supposed to install it with EMT fittings or the like. If that's the case, why do so many installers try to get away with it?


----------



## Jlarson (Jun 28, 2009)

LJSMITH1 said:


> If that's the case, why do so many installers try to get away with it?


Cause a working, high quality install is more important to most of us than what some label or sheet of paper says. And I have never seen a myers hub that came with instructions.


----------



## Shockdoc (Mar 4, 2010)

Al Lamke said:


> I am also having a "discussion" with inspectors about PVC connectors in a myers hub. Tests have shown that the different threads lead to allowing water to enter an encloser thru uneven threading. If this so with emt connectors, why is it not so for PVC connectors(with straight threads)?! It seems to me the simplest and most economic way is, to use a sealing locknut for ridig conduit, a raintight compression fitting for EMT ,and a sealing washer or sealing locknut for PVC. The inspector insists the electrical contractor must use a myers hub when PVC enters form the top. Thanks for letting me vent my frustrations! Al


They let us pop right into the top of a w/p service troft w/ just a sealing locknut around here. I end up altering the UL listing for the better by placing a o ring and silicone around my pvc male adapters when they enter on the top.


----------



## LJSMITH1 (May 4, 2009)

Jlarson said:


> Cause a working, high quality install is more important to most of us than what some label or sheet of paper says. And I have never seen a myers hub that came with instructions.


 
Maybe they should...:laughing:


----------



## Jlarson (Jun 28, 2009)

LJSMITH1 said:


> Maybe they should...:laughing:


Wouldn't read them anyway. :no:


----------



## Shockdoc (Mar 4, 2010)

Has anyone ever used teflon paste on emt compression fittings and down threads?


----------



## LJSMITH1 (May 4, 2009)

Shockdoc said:


> Has anyone ever used teflon paste on emt compression fittings and down threads?


 
Why would anyone ever do that?:blink:


----------



## Shockdoc (Mar 4, 2010)

LJSMITH1 said:


> Why would anyone ever do that?:blink:


 An ounce of prevention....I use it since I got it on my truck for all hub entries, ug gal connections, comp connections. There's a little plumber in my background.


----------



## LJSMITH1 (May 4, 2009)

Shockdoc said:


> An ounce of prevention....I use it since I got it on my truck for all hub entries, ug gal connections, comp connections. There's a little plumber in my background.


Teflon sealants (including paste and tape) should *not* be used on electrical conduit or conduit fittings as they will tend to insulate against a potential ground fault current going through the raceway. At minimum, it will increase impedance between connections. 

If you are going to use any kind of sealant, use something made for the application like Kopr-Shield by T&B. It is conductive and helps inhibit corrosion as well. I am sure there are others out there as well.

BTW, putting sealant on male hub threads, locknut threads, compression gland nut threads will do just about nothing about reliably sealing against moisture.


----------



## RIVETER (Sep 26, 2009)

Shockdoc said:


> An ounce of prevention....I use it since I got it on my truck for all hub entries, ug gal connections, comp connections. There's a little plumber in my background.


Although it would not be a perfect one it seems as if it could act as an insulator. Why not just caulk on the exterior if you feel the need?:thumbsup:


----------



## LJSMITH1 (May 4, 2009)

RIVETER said:


> Although it would not be a perfect one it seems as if it could act as an insulator. Why not just caulk on the exterior if you feel the need?:thumbsup:


 
..of course there's always ScotchKote.... LOL!


----------



## RePhase277 (Feb 5, 2008)

LJSMITH1 said:


> ..of course there's always ScotchKote.... LOL!


It's good for EVERYTHING.. I drank a quart of it this morning.

But seriously, on any threaded connection I use outdoors, I smear some good ol' Noalox© on the threads. Kopr-Shield© is great, but expensive and hard to come by 'round here.


----------



## Jlarson (Jun 28, 2009)

RIVETER said:


> Although it would not be a perfect one it seems as if it could act as an insulator. Why not just caulk on the exterior if you feel the need?:thumbsup:


That's what I do to outdoor vertical GRC/IMC, and EMT couplers and connectors.


----------



## one2question (Sep 2, 2010)

These are the little things that define a qualified person. Knowing the manufacture specs on each item. I can't count, the number of times that the inappropriate piece of material was used on a install. Which cause failure over a period of time. I have seen main breakers get water lodged from emt connector in myer hubs.


----------



## Jlarson (Jun 28, 2009)

one2question said:


> These are the little things that define a qualified person. Knowing the manufacture specs on each item. I can't count, the number of times that the inappropriate piece of material was used on a install. Which cause failure over a period of time. I have seen main breakers get water lodged from emt connector in myer hubs.


Not if you seal around the conduit and the compression nut, and put anti-seize on the threads. There is also a big difference between someone how just blindly follows directions and those of us who do stuff that works and is a better way to do it.


----------



## RePhase277 (Feb 5, 2008)

Jlarson said:


> Not if you seal around the conduit and the compression nut, and put anti-seize on the threads. There is also a big difference between someone how just blindly follows directions and those of us who do stuff that works and is a better way to do it.


Agreed. There are plenty of good safe uses for products outside of their listing or intended purpose. All a listing really does is give some assurance that a product should do the job it is intended to do. Your Kleins were never meant to drive nails and staples, or bust sheetrock but thousands of electricians do just that everyday.


----------



## LJSMITH1 (May 4, 2009)

InPhase277 said:


> Agreed. There are plenty of good safe uses for products outside of their listing or intended purpose. All a listing really does is give some assurance that a product should do the job it is intended to do. Your Kleins were never meant to drive nails and staples, or bust sheetrock but thousands of electricians do just that everyday.


 
Yet it is amazing that some of these folks bitch and moan about how their Klein's "don't work like they used to", or that they break prematurely..:blink: I love it when they call the manufacturer demanding a new product because theirs was 'defective'...LOL!


----------



## Jlarson (Jun 28, 2009)

LJSMITH1 said:


> Yet it is amazing that some of these folks bitch and moan about how their Klein's "don't work like they used to", or that they break prematurely..:blink: I love it when they call the manufacturer demanding a new product because theirs was 'defective'...LOL!


Some will bitch and moan no matter what. I have never broke a tool from "abusing" it. I use my Klein's as a hammer everyday never broke a pair doing it, and if on the off chance I did would just buy a new pair. You just got to know how far you can push stuff.


----------



## LJSMITH1 (May 4, 2009)

Jlarson said:


> Some will bitch and moan no matter what. I have never broke a tool from "abusing" it. I use my Klein's as a hammer everyday never broke a pair doing it, and if on the off chance I did would just buy a new pair. You just got to know how far you can push stuff.


I once broke a Craftsman 1/2" drive breaker bar by putting a 2' length of pipe on the end of it for extra leverage. I brought it back to Sears and they gave me a new breaker bar:thumbup:...no questions asked...Gotta love that!


----------



## Jlarson (Jun 28, 2009)

LJSMITH1 said:


> I once broke a Craftsman 1/2" drive breaker bar by putting a 2' length of pipe on the end of it for extra leverage. I brought it back to Sears and they gave me a new breaker bar:thumbup:...no questions asked...Gotta love that!


I do that all the time, I even beat on wrenches with hammers. Don't remember ever breaking one though.


----------



## one2question (Sep 2, 2010)

Jlarson said:


> Not if you seal around the conduit and the compression nut, and put anti-seize on the threads. There is also a big difference between someone how just blindly follows directions and those of us who do stuff that works and is a better way to do it.


I agree there are ways to improve items. It take's knownledge to improvise. Nothing wrong. I guess it depends on where you work and if it fails, who will be questioning the install. I was the question answerer, where I worked before. The people I answered too, critique everything and where very well prepare for my response. If there was, in any form of misuse or improper installs "a better in their opion" the cost was always more then the piece. But for jobs that you can leave, have no critiquers and the cost to repair are minor then I find silicon a great sealer.:thumbup: Note: only applied so not to inhibit proper grounding. Critiqued


----------

