Couplings acceptable for class 1 div 1

[kwired]

Listed for hazardous location couplings?

344.10 requires all RMC products to be listed. So standard couplings must be listed too.

They are listed, but usually not marked. I assume they are not required to be marked or they would be.

 

[Smart $]

They are listed, but usually not marked. I assume they are not required to be marked or they would be.

Yes, listed... but to what category?

500.8(E)(1) says, in part...

All NPT-threaded conduit and fittings shall be threaded with a National (American) Standard Pipe Taper (NPT) thread.

...which would exclude the use of a standard coupling, right?

 

[rbalex]

I have already posted this information in Posts #9 and 10:

Couplings are listed under UL Category Code DWTT.They are not required to be specifically listed for classified locations. Neither is IMC nor RMC.

Fittings for classified locations are listed under Category Code EBNV and does not include "standard" couplings or any other form of coupling except flexible explosionproof couplings.

 

[don_resqcapt19]

Over many years (LONG before most of us were even in the business ) experience has shown, five threads (seven in a few cases) "wrenchtight", will be sufficient for the purposes stated in 500.8(E). That's why I used the term identified in my previous post.

BTW have you ever seen any coupling, standard or not, marked for classified use?

AFTERTHOUGHT: Flexible couplings are listed and marked for classified locations.

But there has been a huge change in the quality and fit of the threads on the couplings since I started in the trade. The couplings I used when I started in 73 may very well work, but I really have my doubts that the ones I see today would.

 

[rbalex]

But there has been a huge change in the quality and fit of the threads on the couplings since I started in the trade. The couplings I used when I started in 73 may very well work, but I really have my doubts that the ones I see today would.

If you believe there is an serious ongoing problem, you know how to make a PI. You're one of the few I'd give serious consideration (and even sponsor) if I were still active in the process. As it is, CMP14 doesn't seem too concerned.

 

[Smart $]

I have already posted this information in Posts #9 and 10:

Couplings are listed under UL Category Code DWTT.They are not required to be specifically listed for classified locations. Neither is IMC nor RMC.
...

Ummm... the question was rhetorical.

And I hear what you are saying about not being specifically required to be listed for classified locations... but 500.8(E)(1) says that fittings [for classified locations] must have NPT threads. The requirement for fittings having NPT threads goes back to the NEC 2002 edition.

Standard couplings do not have NPT threads.

And that takes us back to a comment you made earlier...

...
Non-listed couplings may be a case similar to listed and non-listed LFMC. They can be made and sold, but not legally installed.
...

...only in this case, the product is listed, but not Code compliant for classified locations.

 

[don_resqcapt19]

Based on Article 100, a conduit coupling is a "fitting". The conduit couplings that are supplied with the conduit are straight thread couplings. It appears that the wording in 500.8(E)(1) prohibits the use of the couplings that are supplied with the conduit in classified areas.....if so I have violated that thousands of times.

Is this just an unintended consequence of the use of the word "fitting" much like in older codes where the conduit rules said that you could not have more than 360° of bend between fittings, or is there a real intent to require the use of couplings with tapered threads in classified locations?

Did we ever use tapered thread conduit couplings in the US? I know that up until sometime in the early 80's the CEC required the use of tapered thread conduit couplings in Canada.

 

[rbalex]

...if so I have violated that thousands of times.
...

I confess I'm at a loss. I was on CMP14 at the time "Threading" was introduced to Section 500.8. At the time UL, FM, ETL, CSA, NEMA, etc. were all quite happy with continuing to use "standard" couplings. The IBEW and NECA reps seemed happy too. I believe the process to arrive at the conclusion that I outlined in Post #9 is essentially correct. BTW, the original content was actually from Section 505.3(B) in the 1999 NEC. Conduits and couplings have never been specifically UL listed for hazardous locations.

As for unintended consequences, that's possible. Although they usually follow a cycle behind, Canada adopted Zones one cycle before the US. In 1999, Art 505 was something of an amalgam of several opinions.

SO - as I mentioned you and Smart $ are both quite capable and competent to make a PI correction OR, better yet, request a Formal Interpretation. An FI has the benefit of not requiring a whole new Code cycle.

Remember it took 25 years for UL to reveal seal sizes were only based on 25% fill.

 

[don_resqcapt19]

I think for the 2020 code I will submit a PI that says you can't have a "standard" coupling between an enclosure that is required to be explosion proof and its seal fitting. I don't see as much issue with standard conduit couplings in other parts of the conduit run.

 

[rbalex]

I think for the 2020 code I will submit a PI that says you can't have a "standard" coupling between an enclosure that is required to be explosion proof and its seal fitting. I don't see as much issue with standard conduit couplings in other parts of the conduit run.

I've been giving this a lot of thought. I still believe a request for a Formal Interpretation (FI) is best. They ARE painful to get, but if you wait to make a PI, odds are it will be rejected without heavily documented substantiation that a problem actually exists. As you mentioned, if an "NPT" coupling is​ required, it has been violated millions of times - mostly because no one makes them. And, if a problem actually exists, why wait four years to correct it? CMP14 has been one of the panels least likely to accept a PI simply because it sounds like a good idea. (Not that it hasn't)

The NEC is replete with unentended consequences. As I mentioned, the origin of Section 500.8(E) was from the introduction of Zones in 1999.

The FI would read something like:

In light of the requirements of Section 500.8(E) are simple couplings, where used, required to have NPT threads when installed between enclosures required to be explosionproof and their required seals?
​

If it is answered in the negative, the CMP is obligated to "clarify" the Code (in possibly several locations) in the next cycle and possibly issue a Tentative Interim Amendment (TIA).

 

[MechEdetour]

I think for the 2020 code I will submit a PI that says you can't have a "standard" coupling between an enclosure that is required to be explosion proof and its seal fitting. I don't see as much issue with standard conduit couplings in other parts of the conduit run.

I wonder if this is one of those things that wasn't factored in considering how unusual it'd be. Sealing fittings are required within 18" of an explosion-proof enclosure. Couplings are used to join two pieces of conduit together. Why would anyone want a coupling between the seal and the enclosure anyways? There is barely any real estate there as is. Especially since most of the time I've seen unions there to be able to make the required connections. . .

I'd be curious to know the history of what rbalex posted earlier regarding length of conduit that can be provided with or without couplings. Maybe when couplings first emerged they were limited to a 10ft run of conduit (ie. can't use a coupling with a 7ft and a 6ft piece of conduit, but would need a 10ft and 3 ft)? Seems silly, but is it possible that changes were made outside of the scope of how couplings are used in hazardous locations which inadvertently affected the application in such locations?

Standard A for product B can be used in location C because it complies with requirements for location C. Now standard for product B is revised to A', and unintentionally product B is no longer suitable for location C. . .

 

[HECEngineering]

Unrated couplings

Unrated couplings

I don't think that there is anything that specifically says you can use conduit couplings in classified areas, however, in general there is nothing that says you can't.

It appears that I was incorrect in saying that you can't use a coupling between an enclosure that is required to be explosion proof and the seal fitting.

However couplings are not permitted between a classification boundary and the boundary seal.

The same rules apply for Division 2 applications shown in 501.15(B).

My electrical inspector will only allow rated couplings or and/or fittings between an enclsoure and a conduit seal. I do a bunch of work in Canada and this is in their code also. They also do not allow reducing bushing or adapters between enclosure opening and seal. Typically I will reference 501.15 (A) (1) page 736 of the 2011 handbook (NFPA 70) says " Conduit seals shall be installed with 450mm (18 inches) from the enclosure. Only explosion proof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosion proof enclosure." So normal couplings are not permitted to be used between seal offs and enclosure. If they are not listed and identified as such, they cannot be used.

 

[kwired]

They also do not allow reducing bushing or adapters between enclosure opening and seal. .... Only explosion proof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosion proof enclosure."

Seems to be some contradiction there, or were you trying to point that out?

BTW this thread is pretty old, you just revived it with your post.

 

[rbalex]

My electrical inspector will only allow rated couplings or and/or fittings between an enclsoure and a conduit seal. I do a bunch of work in Canada and this is in their code also. They also do not allow reducing bushing or adapters between enclosure opening and seal. Typically I will reference 501.15 (A) (1) page 736 of the 2011 handbook (NFPA 70) says " Conduit seals shall be installed with 450mm (18 inches) from the enclosure. Only explosion proof unions, couplings, reducers, elbows, capped elbows, and conduit bodies similar to L, T, and cross types that are not larger than the trade size of the conduit shall be permitted between the sealing fitting and the explosion proof enclosure." So normal couplings are not permitted to be used between seal offs and enclosure. If they are not listed and identified as such, they cannot be used.

Beginning with the 2017 NEC, "... conduit bodies similar to L, T, and cross types ..." are also prohibited between the explosionproof enclosure and the seal. Don't know if I agree with this as there was no hard evidence presented that any actual events had occurred. I do understand the theory that the conduits bodies increased the potential volume.

I wonder how your inspector can determine you have a "rated coupling" beyond a standard threaded coupling. Neither RMC nor standard couplings are rated for classified locations; they are identified.

Also beginning in 2017, threadless coupling will be permitted in Division 2. I can see a PI for 2020 or possibly TIA to specify the couplings between the explosionproof enclosure and seal be threaded. This may not be necessary since 501.15(B) already requires compliance with 501.10(A), but my experience tells me it will cause confusion. ("But 501.10(B) says I can use threadless couplings")