ECN Forum Forums Photo Discussion Forums Violation Photo Forum Does the 2002 NEC prohibit this?

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).]