Rigid galvanized coupling to liquid tight flex connections

I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
The contractor ran 3/4” LFMC into a 3/4 GRC coupling -
Our client is saying this is an ‘illegal’ connection because the coupling is NOT listed for flex conduit. Where is this stated the NEC?


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Isaiah said:
The contractor ran 3/4” LFMC into a 3/4 GRC coupling -
Our client is saying this is an ‘illegal’ connection because the coupling is NOT listed for flex conduit. Where is this stated the NEC?


Sent from my iPhone using Tapatalk
Click to expand...
technically he is correct, but come on its done 2,376,472 times a day. Can't he find something else to worry and complain about? IF you really want to blow his mind, tell him to also rip off the stupid gasket on the LFMC connector so he can actually tighten it up to the RMC coupling. Have mental health crisis services standing by. Seriously that is all I care about is throwing that gasket in the garbage. If I can go to sleep knowing that gasket is on the way to the landfill and the fitting is actually tight, I will sleep well.
 
infinity said:
The issue is the straight threads on the connector. It's a listing issue which IMO is bogus given that there is no readily available fitting to transition from one to the other wiring method.
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Female threads never require taper, only male nipples.

Visualize a tap & die set, the tap is always straight, only the die is tapered.

UL category for conduit fittings is (DWTT), which allows sealing locknuts.
All male threaded fittings and nipples have only been investigated for use with locknuts.
..Sealing (Liquid-tight) Locknuts — Sealing locknuts are intended for use with threaded rigid metal conduit and intermediate metal conduit
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UL simply hasn't investigated the use in such applications. To me, that doesn't disqualify it automatically. I like to use my brain and can see that I don't need UL to investigate whether I can screw a male NPT thread into a female NPT thread.
 
electrofelon said:
technically he is correct, but come on its done 2,376,472 times a day. Can't he find something else to worry and complain about? IF you really want to blow his mind, tell him to also rip off the stupid gasket on the LFMC connector so he can actually tighten it up to the RMC coupling. Have mental health crisis services standing by. Seriously that is all I care about is throwing that gasket in the garbage. If I can go to sleep knowing that gasket is on the way to the landfill and the fitting is actually tight, I will sleep well.
Click to expand...

Lol. Agreed!


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ramsy said:
Female threads never require taper, only male nipples.

Visualize a tap & die set, the tap is always straight, only the die is tapered.

UL category for conduit fittings is (DWTT), which allows sealing locknuts.
Click to expand...
I'm not sure what any of this has to do with the straight thread on the connector which is the problem. Here's the Article from Mark Ode that got this ball rolling back in 2010:

 
electrofelon said:
I've never bought the whole straight thread argument, because RMC couplings are straight thread. I don't see how someone can preach that those are okay but another combination is not okay.
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I agree, but remember this is from UL not the real world. The simplest thing would be to require that the fitting with the straight threads into the coupling be required to be made up wrench tight and that's the end of it.
 
ramsy said:
Female threads never require taper, only male nipples.

Visualize a tap & die set, the tap is always straight, only the die is tapered.

UL category for conduit fittings is (DWTT), which allows sealing locknuts.
Click to expand...
Nearly impossible to start the tap if it is not tapered. The taper may not be same as taper of a die though.

If tapping a hole for straight thread like a bolt, you need to run the tap past the taper or the bolt will stop when it reaches the tapered part of the threads.
 
infinity said:
The issue is the straight threads on the connector. It's a listing issue which IMO is bogus given that there is no readily available fitting to transition from one to the other wiring method.
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I've seen female thread to LT flex fittings a time or two already installed. I know my supply house doesn't stock any such thing though.
 
infinity said:
I agree, but remember this is from UL not the real world. The simplest thing would be to require that the fitting with the straight threads into the coupling be required to be made up wrench tight and that's the end of it.
Click to expand...
Somehow the taper thread will give a water tight seal whereas the straight thread would require a gasket to get a water tight connection. Not sure of the engineering that makes it so. The way I see it if these connections (non code straight/taper connection) are in a wet area as more an issue than if used in a dry area.
 
Fred B said:
Somehow the taper thread will give a water tight seal whereas the straight thread would require a gasket to get a water tight connection. Not sure of the engineering that makes it so. The way I see it if these connections (non code straight/taper connection) are in a wet area as more an issue than if used in a dry area.
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Is there any requirement in the NEC or the product standard that rigid connections be watertight?
 
Fred B said:
There are applications that you don't water getting in such as you meter enclosure.
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With no pressure leakage is pretty minimal if threaded wrench tight. Same raceway you mentioned for meter enclosure likely gets more water inside via condensation than it will ever have from leakage at fittings.

Raintight EMT fittings they forced us to use probably getting close to 20 years ago are still a joke for similar reason. I been using a lot of those and hate them. The nylon ferrule that supposedly makes them water tight is a big pain to get onto the tubing, usually making you disassemble the fitting in order to get it over the tubing, and the rubber washer that is supposed to seat against the enclosure does not stand up to the elements and once it starts to crack and pull apart you have a bigger leak than if you had used a set screw fitting:mad:. There is also no bonding going on at that point between fitting and enclosure anymore, not that it was very good to begin with. But on the same line of discussion of straight and tapered thread they also are not listed to put in a Myers hub. Too bad, I always put them in a Myers hub and haven't been turned down yet.
 
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