Listed Conduit Hubs VS “Myers” Hubs

[kwired]

See

https://code-authorities.ul.com/wp-content/uploads/2014/04/ul_ConduitHubs.pdf

DWTT is Listing for service entrance. It can also optionally be Listed under KDER for grounding and bonding, not the other way around.

Kind of reminds me of when I’ve seen external bonding cables added to LFMC in division 1 (hazardous locations) service. Obviously the LFMC or connectors that are clearly Listed aren’t sufficient by themselves, Lusted or not. And many things do not require Listing (common hardware). It comes down to when do we cross the line.

Lusted connectors is a different game

 

[wwhitney]

This what shows up on my screen

Wild, that's not what shows up on my screen, or in the 2017 PDF I have. The only thing I can think of is some sort of stale cache so it's still showing you the 2020 version. You could try opening a private/incognito window, logging in to nfpa.org again, and going directly to the 2017 NEC without opening the 2020.

Cheers, Wayne

 

[kwired]

Wild, that's not what shows up on my screen, or in the 2017 PDF I have. The only thing I can think of is some sort of stale cache so it's still showing you the 2020 version. You could try opening a private/incognito window, logging in to nfpa.org again, and going directly to the 2017 NEC without opening the 2020.

Cheers, Wayne

Lately I have noticed it will take you to wrong places when you click on table of contents links. Particularly if I had left the window open for some time, even had computer sleep and wake. But when you first open the thing it takes you to right places. I don't know if it is problem with my computer, the site, the browser. Did get a new computer somewhat recently and never had noticed this happening on my old one.

 

[yesterlectric]

It doesn't say hubs listed for grounding and bonding. It says listed hubs. Either the code wasn't properly written and should be revised, or UL is just going overboard. If this statement from UL is right, then there's no need for 250.92B2, as the hubs with the ground lug would meet 250.02B4. The code requires following instructions with listing and labeling, but doesn't say follow every email from UL. UL has made new product listings through this procedure before................................
As an example of why I think the fact that it says listed hubs vs hubs listed for grounding and bonding matters, look at 250.8. It says you can use listed connectors for grounding and bonding (i.e.: wire nuts and not necessarily greenies) That's not a license to say it has to be listed for grounding and bonding, as is evidenced by the fact that some proposals have been made and rejected to change it to that. If that's the proper interpretation for 250.8, then why in 250.92 do we come up with a new idea of not accepting "listed hubs" and requiring that they be listed for grounding and bonding.
If UL is right on this, then bonding locknuts are also against the code? They are usually used for over 250V, and service entrances. UL Whitehbook even says they can be used. The time they can't be used without the wire would be when there's something like eccentric or concentric knockout. Otherwise, ULS says they can be used on the line side of a service.

 

[kwired]

Isn't all fittings supposed to be listed?

 

[Klockopotomis]

I feel a question I had 2 weeks ago that sheds light into an aspect of the OP question
The local AHJ in Colorado Springs does not see "Myers Hubs" as being approved for grounding and bonding of service equipment. So I did a deep dive into the Eaton "Myers Hub" I used on a 120/240v service. Eaton has it listed for service and grounding and bonding. AHJ wants the hubs' locknut to have a grounding lug attachment. Eatons' Myers Hub is listed for "Nut with grounding screw available for added safety" and "Unique serrations on both hub bite into metal, assuring a positive electrical ground (UL approved for use with service entrance conduit). UL definition of a listed Grounding and Bonding Hub "Grounding and Bonding Hubs are certified hubs (seeDWTT) provided with certified grounding and bonding locknut. They serve in a manner similar to grounding and bonding bushings except they are only for use with threaded rigid metal and IMC. Grounding hubs provide the electrical continuity required by NEC 250.92 at service equipment and the electrical continuity required by NEC 250.97 for circuit rated over 250v.
So I assume after reading this, standard Myers hubs are listed for grounding and bonding of service equipment at 250v or less

 

[paulengr]

I’ll follow this up with the fact that EMT set screw fittings are considered bonded. At least a Myers hub has lock nuts that bite into the paint and screw threads. EMT fittings have nothing that fancy yet pass.

 

[don_resqcapt19]

The code language is confusing, and I believe the "listed hub" the section is talking about is really the accessory hub that you buy for use for top entries into 3R enclosures.

 

[yesterlectric]

The code language is confusing, and I believe the "listed hub" the section is talking about is really the accessory hub that you buy for use for top entries into 3R enclosures.
View attachment 2557621

Yes I have heard this suggested but I think if that was truly the case they should have revised the code by now.

 

[don_resqcapt19]

Yes I have heard this suggested but I think if that was truly the case they should have revised the code by now.

No one has submitted a PI to make that change as far as I know.

 

[yesterlectric]

No one has submitted a PI to make that change as far as I know.

Yes. The people who think that so strongly don’t bother to submit a PI. And unless you have an opinion on which way it should go, you can’t submit a PI. There’s no option to submit a PI just asking they take a look at the language and make sure it’s clear.

 

[don_resqcapt19]

Yes. The people who think that so strongly don’t bother to submit a PI. And unless you have an opinion on which way it should go, you can’t submit a PI. There’s no option to submit a PI just asking they take a look at the language and make sure it’s clear.

While you can't do that exactly, as the rules require that the submitter provide new language, but submitting new language will either get a code change or a resolve statement saying why the language does not need changing.

In this case it would be easy to write language that says the only type of hubs that the rule is talking about is the type I posted a picture of. Either that change would be accepted, or it would be resolved with a statement that says it applies to that type of hub along with the typical conduit hub.

PIs just to get a panel statement on a rule are not uncommon.

 

[yesterlectric]

While you can't do that exactly, as the rules require that the submitter provide new language, but submitting new language will either get a code change or a resolve statement saying why the language does not need changing.

In this case it would be easy to write language that says the only type of hubs that the rule is talking about is the type I posted a picture of. Either that change would be accepted, or it would be resolved with a statement that says it applies to that type of hub along with the typical conduit hub.

PIs just to get a panel statement on a rule are not uncommon.

On this one I may try to do that next cycle but if I were to write one that is written to clarify that these Myers (and similar brand) conduit hubs are acceptable, I’m not sure what to call them that would differentiate them from the term “listed hubs” that the code uses.

I think these things have to be acceptable. For instance if you buy a Square D fused disconnect and order the service equipment accessories, you have the option of buying what are just the Myers hubs for use with RMC at the service entrance. They aren’t even made by Square D but Square D buys them and gives them a Square D part number as an accessory.

Additionally in some cases of using a fused disconnect as service equipment, the accommodations for a number of grounding, grounding electrode, and bonding conductors is limited and so you may not have enough to run a wire type lug. So you either use one of these or you use a bonding style lock nut with the setscrew that digs into the metal. If you’re coming into the top of the enclosure, this is probably the best option — thought by many to be better than the alternative of using a sealing locknut on the outside of the enclosure and the bonding style lock nut inside.

 

[don_resqcapt19]

On this one I may try to do that next cycle but if I were to write one that is written to clarify that these Myers (and similar brand) conduit hubs are acceptable, I’m not sure what to call them that would differentiate them from the term “listed hubs” that the code uses.

I think these things have to be acceptable. For instance if you buy a Square D fused disconnect and order the service equipment accessories, you have the option of buying what are just the Myers hubs for use with RMC at the service entrance. They aren’t even made by Square D but Square D buys them and gives them a Square D part number as an accessory.

Additionally in some cases of using a fused disconnect as service equipment, the accommodations for a number of grounding, grounding electrode, and bonding conductors is limited and so you may not have enough to run a wire type lug. So you either use one of these or you use a bonding style lock nut with the setscrew that digs into the metal. If you’re coming into the top of the enclosure, this is probably the best option — thought by many to be better than the alternative of using a sealing locknut on the outside of the enclosure and the bonding style lock nut inside.

Not sure exactly how you would word the PI. Maybe that conduits with interior locking nuts are not acceptable for the purposes of service bonding. I know that is the opposite of what you want to say, but it will get the CMP on record as to what is actually permitted.

I tend to treat the conduit hubs with lock nuts the same as lock nuts on threaded conduits for the purposes of this section.

 

[augie47]

"Myers" type hubs have been used for services for decades in this area and it is rare that an inspection authority even checks for DWTT vs KDER listing.

 

[yesterlectric]

Myers hubs usually have a serrated locknut it’s a lot more heavy duty than a regular lock nut. I view those as just about as good for grounding as the bonding type locknuts that don’t have a lug for wire but have a set screw that digs into the sheet metal of the enclosure. I think they’re better for grounding than a standard locknut and as such it seems to me that absent the code having made 250.92 more clear, that they should be allowed on the line side of a service without the need for a wire.