Unlisted NPT Couplings

[Wire-Smith]

Not to derail the thread much. But my pipe threading knowledge is basically nonexistent.. any good sources to learn more as I don't get it in the field?

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https://steeltubeinstitute.org/steel-conduit/wp-content/uploads/sites/4/2013/04/ConGuide.pdf

https://steeltubeinstitute.org/steel-conduit/resources/installation-guides/conduit-cutting-threading-guidelines/

https://steeltubeinstitute.org/steel-conduit/resources/installation-guides/

don't feel bad, most guys in the field don't know much about it either.

 

[infinity]

So use the standard conduit coupler with a thread compound. Or use a cast coupler with tapered threads, with a thread compound, and run the risk of the inspector rejecting it. Or machine your own couplers with a tapered thread. I would pick option 1.

Any threading compound that you use would need to be electrically conductive or otherwise not impede the continuity of the metal raceway.

300.10 Electrical Continuity of Metal Raceways and Enclosures.
Metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electrical conductor and shall be connected to all boxes, fittings, and cabinets so as to provide effective electrical continuity. Unless specifically permitted elsewhere in this Code, raceways and cable assemblies shall be mechanically secured to boxes, fittings,
cabinets, and other enclosures.

So, my only question was would any of you inspectors fail me on this. would you?

Yes.

 

[electrofelon]

Any threading compound that you use would need to be electrically conductive or otherwise not impede the continuity of the metal raceway.

Do they make such a product? Ive never been concerned with thread sealing RGS, just curious.

 

[kwired]

So, my only question was would any of you inspectors fail me on this. would you?

thanks

If using non listed couplings they have this they can cite:

344.6 Listing Requirements.
RMC, factory elbows and couplings, and associated fittings shall be listed.

 

[winnie]

Do they make such a product? Ive never been concerned with thread sealing RGS, just curious.

Thomas and Betts Kopr Shield claims to work for threaded conduit fittings.

https://www.sitepro1.com/resources/pdf/assembly-drawings/CP8-TB.pdf

 

[Wire-Smith]

If using non listed couplings they have this they can cite:

I completely agree it is a technical code violation. Though that's not my question. My installation would actually be better than the legal way, these couplings are listed to be used with galvanized npt pipe and direct burried as plumbing pipe

 

[infinity]

I completely agree it is a technical code violation. Though that's not my question. My installation would actually be better than the legal way, these couplings are listed to be used with galvanized npt pipe and direct burried as plumbing pipe

Better than the legal way? I think that you will hear opinions to the contrary. Any conduit outdoors or underground will eventually contain water even if it's completely sealed (like PVC) due to condensation. IMO using a non-listed fitting on an installation that will be no better than an installation with a listed fitting doesn't make much sense.

 

[Wire-Smith]

Better than the legal way? I think that you will hear opinions to the contrary. Any conduit outdoors or underground will eventually contain water even if it's completely sealed (like PVC) due to condensation. IMO using a non-listed fitting on an installation that will be no better than an installation with a listed fitting doesn't make much sense.

The electrical connection would be far superior, I can keep condensation out of conduit, not with explosionproof style seals but look up polywater fst and zipseal and you can also use purge systems on conduit. Also, the joints are stronger. And coupling is listed for gas and liquid pipes. I could actually measure the difference with DLRO and pressurizing the pipe, there would be substantial difference in both aspects, I could even do structural test and it would perform better, with tapered coupling you would have much more solid thread engagement. Anyway my post is not about that, it is asking if you as an inspector would fail it, I take it you would, thank you for the response.

 

[Wire-Smith]

Since it appears people would like more background on my question, where I would like to use this is on high current setting ocpd long runs, I want the conduit joints to be extremely good and robust for 100 years to be able to effectively and easily carry fault current and have as low impedance as practical on this path, so ocpd will open quicker. I add the timeframe because the tapered coupling will also add longevity to the electrical connection, rust in that joint is an insulator. With straight thread you only have one thread completely engaged, tapered you have all which gives greater contact surface(lower resistance) and more corrosion protection for longevity, and the conduit connections are the weakest links.

 

[roger]

So, my only question was would any of you inspectors fail me on this. would you?

thanks

If I were an inspector I wouldn't but I wouldn't really care anyways.

Not to derail the thread much. But my pipe threading knowledge is basically nonexistent.. any good sources to learn more as I don't get it in the field?

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Here is a link that both of you might want to study on and see if there is any mention of particular thread types.

https://steeltubeinstitute.org/steel-conduit/wp-content/uploads/sites/4/2014/12/GROUNDIN.pdf

As far as keeping condensation out of a conduit, no way, and it doesn't matter, you will be using a "W" type conductor and 225.22 tells you the NEC expects it.

Roger

 

[Wire-Smith]

If I were an inspector I wouldn't but I wouldn't really care anyways.



Here is a link that both of you might want to study on and see if there is any mention of particular thread types.

https://steeltubeinstitute.org/steel-conduit/wp-content/uploads/sites/4/2014/12/GROUNDIN.pdf

As far as keeping condensation out of a conduit, no way, and it doesn't matter, you will be using a "W" type conductor and 225.22 tells you the NEC expects it.

Roger

The reason for Keeping water out is not to allow for dry location insulation if that was what you are thinking.
I will make a video for YouTube one day on one of my old conduits, you can keep condensate out of pipes, you have to seal both ends and duct seal or explosion sealoffs are not sufficient, but there are means. And no it's not usually much of a benefit to try for it. I do a lot of things most electricians believe are unnecessary, I just try to look for better and more robust ways to do things. I'm not an economy grade electrician and usually overbuild with no apologies

 

[infinity]

The reason for Keeping water out is not to allow for dry location insulation if that was what you are thinking.
I will make a video for YouTube one day on one of my old conduits, you can keep condensate out of pipes, you have to seal both ends and duct seal or explosion sealoffs are not sufficient, but there are means. And no it's not usually much of a benefit to try for it. I do a lot of things most electricians believe are unnecessary, I just try to look for better and more robust ways to do things. I'm not an economy grade electrician and usually overbuild with no apologies

Exceeding the code is fine, I say go for it, that's until you start installing violations then your idea that it's "better" goes out the window.

 

[roger]

The reason for Keeping water out is not to allow for dry location insulation if that was what you are thinking.

So do tell, why are you trying to keep condensation out?

I will make a video for YouTube one day on one of my old conduits, you can keep condensate out of pipes, you have to seal both ends and duct seal or explosion sealoffs are not sufficient, but there are means.

I look forward to seeing it.

And no it's not usually much of a benefit to try for it.

We see eye to eye on that point.

I do a lot of things most electricians believe are unnecessary, I just try to look for better and more robust ways to do things.

Good for you but that doesn't mean you are better or somehow special.

I'm not an economy grade electrician and usually overbuild with no apologies

That's your prerogative and that is fine, but when you bid say 100+ dwelling units you better bid to the bid documents and code if you want to win the bid and make money.

Roger

 

[Wire-Smith]

So do tell, why are you trying to keep condensation out?


I look forward to seeing it. We see eye to eye on that point. Good for you but that doesn't mean you are better or somehow special. That's your prerogative and that is fine, but when you bid say 100+ dwelling units you better bid to the bid documents and code if you want to win the bid and make money.

Roger

When you have moisture in a conduit going to electrical equipment, the moisture from the conduit often migrates to the equipment just through air circulation. And I know this isn't the only source of moisture to equipment but it's easy to seal these conduits. It also does offer reliability, if water is in conduit and insulation has defect . also lengthens life of insulation and conduit, I know I'm splitting atoms on this one. Also air is better insulator than water so you have less dielectric stress on insulation in some types of installations. Water is a insulation killer for MV applications. I agree I am not better and in many aspects worse because I add cost. I try to compensate for the added costs by being as detail oriented in the processes I use for the actual installation as well.

 

[winnie]

It is plausible to me that tapered threading on couplings is better than straight threading, and that using compatible NPT threaded plumbing couplings will result in a better installation than using listed straight threaded couplings.

It is also plausible that such plumbing couplings would be deficient in some important but unexpected by you way, making the installation inferior to one with listed couplings.

The whole reason for listing is evaluation by a reputable lab as to suitability. Not your guess (or my guess) about what is 'better'.

You are still planning on putting steel into the ground. If you want it to last 100 years you will need to plan carefully; soil characteristics, metal compatibility, protection over the metal, etc. You might be better off with some sort of continuous plastic conduit, embedded in concrete, and then running a wire EGC.

-Jon

 

[Wire-Smith]

It is plausible to me that tapered threading on couplings is better than straight threading, and that using compatible NPT threaded plumbing couplings will result in a better installation than using listed straight threaded couplings.

It is also plausible that such plumbing couplings would be deficient in some important but unexpected by you way, making the installation inferior to one with listed couplings.

The whole reason for listing is evaluation by a reputable lab as to suitability. Not your guess (or my guess) about what is 'better'.

You are still planning on putting steel into the ground. If you want it to last 100 years you will need to plan carefully; soil characteristics, metal compatibility, protection over the metal, etc. You might be better off with some sort of continuous plastic conduit, embedded in concrete, and then running a wire EGC.

-Jon

I agree there could be something unexpected. They are UL listed for gas and liquid underground steel lines. I can get a field UL evaluation. I don't have the UL testing procedure for couplings, but other products testing I do have is not as thorough as I would have thought. I will try to find a bootleg copy on fittings. One thing I will point to is a recent article in I think ec&m about breaker failures and what many would consider inadequate testing

 

[Wire-Smith]

Exceeding the code is fine, I say go for it, that's until you start installing violations then your idea that it's "better" goes out the window.

I don't know of any other code section that I think violating would be a better installation, but this one I believe would. I currently don't have my computer but I have some ul testing standards that I will send you and I think you will be surprised of how little they do. I think the NEC and product testing are great, but in this unique instance I think the tapered coupling is far superior. I'm not sure you are explicitly saying this but i don't think just because something is wrote down means something else isn't better. It definitely offers a cover your ass for liability and I agree I would unneccesarily be accepting a liability. But I look at every electrical installation I do as my liability and do not trust that following common code interpretations of the code as a cover your ass, many "code compliant" installations have failed unsafely and you are on the hook, the lawyer just argues a different code interpretation that still may not have performed better.

I know ul listing testing electrical equipment can be something around 20k, does anyone have an idea of what listing this coupling might cost?

 

[roger]

I know ul listing testing electrical equipment can be something around 20k, does anyone have an idea of what listing this coupling might cost?

Uhhh, just a guess but maybe as much as 20K.

Roger

 

[roger]

Here's what you should probably do, come up with a list of deadly accidents and property damages due to the couplings and submit a proposal with the list as your substantiation.


Roger

 

[electrofelon]

One option may be to use USE conductors, then the conduit becomes optional and you can use whatever conduit and fittings you want (for underground applications).