cldewalt
New member
- Location
- Kansas city, Mo
Are standard threaded rigid coupling acceptable for class 1 div 1 locations.
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.
However couplings are not permitted between a classification boundary and the boundary seal.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 same rules apply for Division 2 applications shown in 501.15(B).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.
Also see Section 344.130: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)
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.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.
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?...
In general, couplings are considered integral to the raceway system
The explosionproof adjective carries to each item in the list... meaning only an explosionproof coupling is permitted between XP enclosure and seal....
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.
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.The explosionproof adjective carries to each item in the list... meaning only an explosionproof coupling is permitted between XP enclosure and seal.
Isn't that what I just said in Post #9 In fact, it isn't even specifically listed for classified locations. It is identified.My guess is that RMC and IMC are not specificaly listed as explosion proof either.
maybe, I got lost with all the four letter non English words in thereIsn't that what I just said in Post #9 In fact, it isn't even specifically listed for classified locations. It is identified.
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.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.
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.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.
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Fair enough; however threading has been required to be NPT since 2005. Metric is now a recognized alternate.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.
Why do people keep talking about straight threaded couplings then?Fair enough; however threading has been required to be NPT since 2005. Metric is now a recognized alternate.
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.Why do people keep talking about straight threaded couplings then?
I am confused.
Listed for hazardous location couplings?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.
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