A rigid conduit threadless coupling. The 2002 NEC now prohibits this type of connection.

[This message has been edited by Joe Tedesco (edited 03-13-2005).]

Joe,

I'm a little tardy getting my new codebook, but I can gaurantee the '99 code prohibits this.

The people that see this everday probably think that it is relatively safe because the gap is so small that the wires aren't likely to be damaged. Little do they realize that the metal raceway is usually the only equipment ground & there is the possibility of a serious hazard downstream of this fitting.

Tom: When you get your 2002 NEC read the following, and see the new last sentence.
For IMC -- 342.42 Couplings and Connectors.
(A) Threadless. Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concretetight type. Where installed in wet locations, they shall be the raintight type. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose.

For RMC -- 344.42 Couplings and Connectors.
(A) Threadless. Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concretetight type. Where installed in wet locations, they shall be the raintight type. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose.

Joe,

This was not prohibited before?

Bill

Bill:

The last sentence is new in both sections, so that situation was not considered before the 2002 NEC. I found that the sentence is missing in the RMC article in my copy of the 2002 NEC, and the vertical rule is also missing in the IMC article. In addition the NEC CD Master PDF file is with the vertical rule in one section, but not in the other because of missing words.

I expect that we will see errata sheets on this soon from NFPA.

In the meantime I now have my copy of the NFC Fire Codes update CD and the corrections were made.


As far as the actual situation, this was found on a parking lot surface and the subject of EGC came to mind and the fact that the fitting was not designed to be used this way, and there were tripping hazards as well. Tom's points are well taken and it would violate 300.10.



[This message has been edited by Joe Tedesco (edited 11-18-2001).]

Bill;
Isnt that a emt coupling on rigid conduit ?
Didnt it have to be listed for the material used and approved for its use ?
It would be approved for emt because when you tighten it you dimple the emt helping to prevent it separation. Where with ridgid or imc it would be almost impossible to put that dimple in it.
Just asking ?

motor-T,

Set screw and compression fittings are available for rigid & IMC. Check out a Crouse-Hinds catalog.

Joe,

It seems that we've got 2 issues going with this one. I was questioning the use of a set screw coupling in a wet location.


Bill

Bill:

Both 2002 NEC and earlier rules indicate permitted use of threadless fittings in a wet location when they are of the raintight type.

The point I want to make is that the "new code" will not allow them to be used on threaded conduit ends unless they are listed for the purpose.

So now we should see a new product that will be listed.

Crouse-Hinds SSR series set-screw fittings for Rigid & IMC are concrete & rain tight. I don't believe they are acceptable on threaded ends. Page 9F-6 of the 2000 catalog.

(No, I don't work for CH)

Redsy:
Well thats a new one for me Never seen them and of course never used them. Yeah I would think that threaded end would not work well on a set-screw coupling. I sure prefer the idea of being able to make the conduit up wrench tite especially on ridig and imc. but thats just me.

Joe:
When I was first learning we used alot of conduit rigid of course and EMT was very new and not recomended at least not by our Boss. Generally to answer your question depending on the pipe size a 24-36 inch 'Rdgid' pipe wrench,and on 3inch pipe a chain wrench, our shop rule was to take down until it smokes. To be perfectly honest if those existed years ago I was never aware of them and our company never bought them, I was with the same company for 25 years before I started my own business, but that was always wrench tite.
So when I saw that I just Assumed it was an EMT coupling.

I thought that NPT was not the thread used by rmc conduit and imc conduit systems. Please correct me if this is untrue. The gentleman states a tapered thread is required. I don't know first hand but have all ways thought that electrical threads were nearly flat and opposed to the National Pipe Thread standard which is regularly used by plumbers. We have always purchased the "other" dies, I can't recall their proper name at this time, instead of the plumbers' NPT dies.

The thread required on conduit is NPT having a 3/4" per foot taper. See 346-8. Conduit couplings, unlike plumbing couplings, have a straight thread.
Don(resqcapt19)

I have seen "running thread" nipples,(electrical allthread?) which are straight due to being run completely through the dies, and then trimmed to length. This is not permitted to be used at couplings(342.42(B), 344.42(B)). In hazardous locations particularly, this would defeat the purpose of threaded joints, which provide a path with tolerances tight enough to quench a flame before it can propagate into an explosive atmosphere.

John: See the 2002 NEC, 500.8(D) Threading.

All threaded conduit or fittings referred to herein shall be threaded with a National (American) Standard Pipe Taper (NPT) standard conduit cutting die that provides a taper of 1 in 16 (¾-in. taper per foot).

Such conduit shall be made wrenchtight to prevent sparking when fault current flows through the conduit system and to ensure the explosionproof or flameproof integrity of the conduit system where applicable.

Equipment provided with threaded entries for field wiring connections shall be installed in accordance with 500.8(D)(1) or (D)(2).

(1) Equipment Provided with Threaded Entries for NPT Threaded Conduit or Fittings. For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit, conduit fittings, or cable fittings shall be used.

FPN: Thread form specifications for NPT threads are located in ANSI/ASME B1.20.1-1983, Pipe Threads, General Purpose (Inch).

(2) Equipment Provided with Threaded Entries for Metric Threaded Conduit or Fittings. For equipment with metric threaded entries, such entries shall be identified as being metric, or listed adapters to permit connection to conduit or NPT-threaded fittings shall be provided with the equipment. Adapters shall be used for connection to conduit or NPT-threaded fittings. Listed cable fittings that have metric threads shall be permitted to be used.

FPN: Threading specifications for metric threaded entries are located in ISO 965/1-1980, Metric Screw Threads, and ISO 965/3-1980, Metric Screw Threads.

Redsy,
You can buy running thread, but the code syas you can't make it in the field. See 346-8. All field threads must be tapered. Running thread can be used for short nipples between NEMA 1 types of enclosures for ease of installation.
Don(resqcapt19)

[This message has been edited by resqcapt19 (edited 11-30-2001).]