Couplings acceptable for class 1 div 1

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don_resqcapt19

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Yes they are, but there are limitations on where you can use one. For example a coupling is not permitted between an explosion proof enclosure and the seal fitting. Same applies between a Division boundary and the boundary seal.
 

don_resqcapt19

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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.
501.15(A)(1) ... Conduit seals shall be installed within 450 mm (18 in.) from the enclosure. Only explosionproof 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 explosionproof enclosure.
However couplings are not permitted between a classification boundary and the boundary seal.
501.15(A)(4) ... The conduit run between the conduit seal and the point at which the conduit leaves the Division 1 location shall contain no union, coupling, box, or other fitting except for a listed explosionproof reducer installed at the conduit seal.
The same rules apply for Division 2 applications shown in 501.15(B).
 

kwired

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Every piece of RMC and IMC comes with a coupling, what else would you use for connecting lengths longer then one piece?
 

rbalex

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UL doesn't actually require an RMC coupling:
RIGID FERROUS METAL CONDUIT (DYIX)
USE AND INSTALLATION
This category covers rigid ferrous metal conduit that includes standard
10 ft. lengths of straight conduit, with a coupling, special lengths either
shorter or longer, with or without a coupling for specific applications or
uses, elbows, and nipples in trade sizes 3/8 to 6 (metric designators 12 to
155) inclusive, for installation in accordance with Article 344 of ANSI/
NFPA 70, ‘‘National Electrical Code’’ (NEC)
Also see Section 344.130:

344.130 Standard Lengths. The standard length of RMC
shall be 3.05 ill (10 ft), including an attached coupling, and
each end shall be threaded. Longer or shorter lengths with
or without coupling
and threaded or unthreaded shall be
permitted.
However, Section 501.10(A)(1)(a) does require it to be threaded for Class I, Division 1. By back reference in Section 501.10(B)(1)(1) it is required for Division 2 too. The rules are similar for IMC and other Classes and Zones and Divisions.

In general, couplings are considered integral to the raceway system
 

don_resqcapt19

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...
In general, couplings are considered integral to the raceway system
Have they actually been tested for the containment of the hot gasses in the event of an explosion? The thread fit on a typical conduit coupling is very sloppy as compared to explosion proof unions and other explosion proof fittings?
 

Smart $

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Location
Ohio
...
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.
501.15(A)(1) ... Conduit seals shall be installed within 450 mm (18 in.) from the enclosure. Only explosionproof 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 explosionproof enclosure.
...
The explosionproof adjective carries to each item in the list... meaning only an explosionproof coupling is permitted between XP enclosure and seal.
 

rbalex

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It’s been a while since I’ve dealt with this issue directly and I may leave a few gaps. Please forgive me.

This was easier to discuss with older UL White Books. With respect to this topic, UL has two “super-Category Codes”; AAIZ for “Hazardous Locations” and AALZ for “Ordinary Locations”. Older White Books had other Category Codes organized as subsets of AAIZ and AALZ. Theoretically, it is still that way with the subordinate Category Codes cross-referencing themselves back to AAIZ or AALZ.

The Category Codes for IMC (DYBY), ferrous RMC (DYIX), and nonferrous RMC (DYWV) all refer back to AALZ (Ordinary Locations) with no reference to Hazardous Locations in their “USE AND INSTALLATION” sections other than cross-references to their respective NEC Articles which also make no specific references to Hazardous Locations.

The general Category Code for couplings (DWTT) also refers back to AALZ with a reference in the “USE” section that some may be used in “hazardous locations” where “unclassified location” fittings are permitted.

SO, how can we even use a product not specifically listed for Class I, Division 1, such as RMC, in such a classified location? SIMPLE, the NEC specifically says I can in Section 501.10(A)(1)(a) if it is threaded.

Category Code DWTT also states female couplings are only evaluated for use with threaded rigid conduit. Section 500.8(E) requires threaded connections to be made wrenchtight both for bonding and explosionproof integrity.

In short, a coupling listed as required by Articles 342 or 344 and installed per Section 500.8(E) is suitable for installation in Classified Locations.
 

rbalex

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The explosionproof adjective carries to each item in the list... meaning only an explosionproof coupling is permitted between XP enclosure and seal.
FWIW, as a statement this is gramatically correct; however, only unions, elbows, capped elbows, and conduit bodies similar to L, T, and Cross are specifically listed for hazardous locations. (UL Category Codes EBMV and EBNV) Couplings and reducers are considered to be integral to the raceway.

Again FWIW you will never find a listed non-explosionproof union. ("Eriksons" and similar aren't listed as unions")
 

don_resqcapt19

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But my point is using a standard coupling between an enclosure that is required to be explosion proof and the conduit seal fitting for that enclosure is, in my opinion, very likely to permit the escape of gasses that have a temperature that exceeds the auto-ignition temperature of the flammable gasses that may be present in the area of the enclosure. I just don't see the coupling as being tight enough to cause the escaping gasses to be cooled enough to prevent ignition if there would be an explosion in the explosion proof enclosure.

This just based on my experience with the quality and fit of the thread on standard conduit couplings, and I have no testing or actual incident reports to back this up.
 

rbalex

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But my point is using a standard coupling between an enclosure that is required to be explosion proof and the conduit seal fitting for that enclosure is, in my opinion, very likely to permit the escape of gasses that have a temperature that exceeds the auto-ignition temperature of the flammable gasses that may be present in the area of the enclosure. I just don't see the coupling as being tight enough to cause the escaping gasses to be cooled enough to prevent ignition if there would be an explosion in the explosion proof enclosure.

This just based on my experience with the quality and fit of the thread on standard conduit couplings, and I have no testing or actual incident reports to back this up.
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.
 

Smart $

Esteemed Member
Location
Ohio
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.
...
The five threads "wrenchtight" rule is based on the NPT standard for creating a leak-resistant pipe joint. It is physically impossible to create a leak-resistant joint using NPT-threaded conduit screwed into the straight threads of a standard conduit coupling.
 

rbalex

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The five threads "wrenchtight" rule is based on the NPT standard for creating a leak-resistant pipe joint. It is physically impossible to create a leak-resistant joint using NPT-threaded conduit screwed into the straight threads of a standard conduit coupling.
Fair enough; however threading has been required to be NPT since 2005. Metric is now a recognized alternate.
 

rbalex

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Why do people keep talking about straight threaded couplings then?
I am confused.
IDK, I'm just citing the Section 500.8 requirements and listed couplings meet them. Otherwise, there hasn't been a compliant installation in my lifetime.

It is important to recognize listed NPT couplings are factory threaded and manufactured under the requirements recorded in Section 500.8(E)(1) IN No.2.

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

During the 1999 and 2002 cycles, the IAEI practically demanded all classified location products be specifically listed for the location - even Division 2. CMP 14 politely told them if they needed everything listed they probably weren't qualified to inspect. Some jurisdictions actually do require it, but no manufactures will comply - so what's an installer to do?

SIDE NOTE: If you have seen a coupling or stick of RMC "marked" for a classified location, it, the mark, or both are counterfeit.
 

Smart $

Esteemed Member
Location
Ohio
IDK, I'm just citing the Section 500.8 requirements and listed couplings meet them. Otherwise, there hasn't been a compliant installation in my lifetime.
...
Listed for hazardous location couplings?

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