Unlisted NPT Couplings

[Wire-Smith]

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).

Thanks, I didn't think of that.

 

[kwired]

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.

If I were inspector I probably wouldn't even notice - as long as whatever coupling you do use looks like those that are listed. If you obviously have a cast coupling that catches attention easier and I will then have to address it since I did notice it. First instinct will be - not listed, fail. If you gave a convincing enough reason why it needs to be there, maybe, but I am likely getting my supervisor involved and not giving an OK on the spot. That said as an installer and in a pinch I have used non listed couplings and pipe nipples. General hardware store that carries these is 40 miles closer than electrical supply house that has listed electrical fittings.

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

No doubt you can keep water out, they do the same thing with gas piping. Electrical we just generally don't make up as tight, don't ordinarily need to, and even if ends are sealed aren't necessarily sealed perfectly.

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

Underground gas and liquid lines are non metallic quite often these days.

 

[Wire-Smith]

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

I'm sorry that I offended you. I only meant I often spend more on items most others wouldn't, I didn't mean the way others do things is wrong. I guess one way to look at it is many of you have a lot more experience than me and therefore more confidence in the way things are normally done, I have came across a few things that make me question just towing the line, I "overbuild" because I lack confidence in those methods, not that I firmly believe they are bad. If I can think of a simple way to do things better, I try to do them that way, if that makes sense.

 

[infinity]

I'm sorry that I offended you. I only meant I often spend more on items most others wouldn't, I didn't mean the way others do things is wrong. I guess one way to look at it is many of you have a lot more experience than me and therefore more confidence in the way things are normally done, I have came across a few things that make me question just towing the line, I "overbuild" because I lack confidence in those methods, not that I firmly believe they are bad. If I can think of a simple way to do things better, I try to do them that way, if that makes sense.

I'm with you on the overbuild part, just as an example we spend extra time shaping in wires and using cable ties in panels and switchboards, just to make it neat. It's just that for some of us with what your trying to accomplish it just isn't worth the effort because it won't matter much in the end.

Raceways in concrete slabs on grade or outdoors are considered wet locations by the NEC because sealed or not they will end up with water in them. Instead of worrying about tapered couplings it might be better to just seal the outside of the standard couplings.

After reading through this thread I get the feeling that many agree that your approach to keeping water out of the raceway is commendable (because you feel that it's a better installation) but in the end it's still futile. In any case it does make for an interesting conversation.

 

[winnie]

Code is a minimum. There are many good design reasons to exceed what is required by code.

In my professional capacity I need to know code, but I do research on electric motors and am part of a design team designing advanced motors for aviation use.

When it comes to putting in conduit or a receptacle, however I am officially DIY, not a professional. I have also done my share of 'want to exceed code on a detail' only to find that the necessary hardware is not available.

Looking at my own history, I'd say that it is easy to get caught up trying to improve one design feature, bang one's head on it a while, and then realize that there is an easier way to get the desired benefit. electrofelon's suggestion of using USE to render the listing of the conduit irrelevant, for example.

Perhaps a _continuous_ non-metallic conduit would work for your application. No joints to worry about.

Good luck!

 

[tortuga]

Wow 5 pages on couplings, I am impressed.

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

:thumbsup:
I think Roger summed it up best. It's kind of like when we use rain tight EMT fittings without a lock-nut, such as threading them into weather proof 'Bell' boxes, a very typical non code compliant installation, that inspectors usually accept.

On a historical note I believe the listing requirement for Rigid conduit and fittings was new to the '99 code.

Anyone whom is supervising, designing and inspecting electrical work, whether Master Electrician, Inspector, EE, Foreman appreciates installers communicating questions and asking for permission rather than begging for forgiveness.
My recommendation would be to submit a proposed fitting, any supporting documentation from the manufacturer, and a letter to your inspector requesting special permission in writing under 90.4.
The local AHJ may be willing to research your product for acceptability and may allow it under conditions such as a wire type ECG is installed, or a megger test on the conduit after installation.
Who knows such special permission may end up being used as a state wide interpretation in your state.
Cheers

 

[Wire-Smith]

I'm with you on the overbuild part, just as an example we spend extra time shaping in wires and using cable ties in panels and switchboards, just to make it neat. It's just that for some of us with what your trying to accomplish it just isn't worth the effort because it won't matter much in the end.

Raceways in concrete slabs on grade or outdoors are considered wet locations by the NEC because sealed or not they will end up with water in them. Instead of worrying about tapered couplings it might be better to just seal the outside of the standard couplings.

After reading through this thread I get the feeling that many agree that your approach to keeping water out of the raceway is commendable (because you feel that it's a better installation) but in the end it's still futile. In any case it does make for an interesting conversation.

Yeah, the big reason I think I wanted to post this is because I thought it was an odd situation and am going back and forth on it myself. The bigger advantage to me is the better electrical connection at the joints, the water part is kind of I guess a desired bonus.I have a picture on my computer that I don't have with me but will post it later of a seemingly code compliant install where a ground fault in the rigid conduit never opened up the protective device and just torched the conduit on the wall of the building. I have also witnessed where smaller branch circuits are deadshorted to conduits to find the breaker and they took a lot longer to open than I expected and was melting the metal, I know this was likely a neglected breaker performing poorly, but still that's the way installs are maintained, so I figure look into lowering circuit impedance. No I don't look for breakers that way, I was an apprentice. And yes I compensate for voltage drop in wire size.
And I don't just mean the connection when new, I think it will be a much longer lifespan better connection as well. I have gotten the suggestions of the corrosion tapes on normal coupling joints and I like that idea to.
Thanks

 

[Wire-Smith]

Wow 5 pages on couplings, I am impressed.
:thumbsup:
I think Roger summed it up best. It's kind of like when we use rain tight EMT fittings without a lock-nut, such as threading them into weather proof 'Bell' boxes, a very typical non code compliant installation, that inspectors usually accept.

On a historical note I believe the listing requirement for Rigid conduit and fittings was new to the '99 code.

Anyone whom is supervising, designing and inspecting electrical work, whether Master Electrician, Inspector, EE, Foreman appreciates installers communicating questions and asking for permission rather than begging for forgiveness.
My recommendation would be to submit a proposed fitting, any supporting documentation from the manufacturer, and a letter to your inspector requesting special permission in writing under 90.4.
The local AHJ may be willing to research your product for acceptability and may allow it under conditions such as a wire type ECG is installed, or a megger test on the conduit after installation.
Who knows such special permission may end up being used as a state wide interpretation in your state.
Cheers

You might get a kick out of this or throw your hands up in the air. I know my inspectors around here wouldn't fail me on it. But I don't like going by that as a litness test. I understand why you may think that is the part of the problem I'm looking at, because of my first question, but I actually want the users on here opinions on the subject looking at it as an AHJ. Also, I do and would also pull an egc

Thanks

 

[Wire-Smith]

Code is a minimum. There are many good design reasons to exceed what is required by code.

In my professional capacity I need to know code, but I do research on electric motors and am part of a design team designing advanced motors for aviation use.

When it comes to putting in conduit or a receptacle, however I am officially DIY, not a professional. I have also done my share of 'want to exceed code on a detail' only to find that the necessary hardware is not available.

Looking at my own history, I'd say that it is easy to get caught up trying to improve one design feature, bang one's head on it a while, and then realize that there is an easier way to get the desired benefit. electrofelon's suggestion of using USE to render the listing of the conduit irrelevant, for example.

Perhaps a _continuous_ non-metallic conduit would work for your application. No joints to worry about.

Good luck!

Thanks,

You might be able to guess but you probably don't want me to go into why I don't like NM.

This is just a thought I have been kicking around, I'm not currently planning or needing to use it on a project.

 

[kwired]

Yeah, the big reason I think I wanted to post this is because I thought it was an odd situation and am going back and forth on it myself. The bigger advantage to me is the better electrical connection at the joints, the water part is kind of I guess a desired bonus.I have a picture on my computer that I don't have with me but will post it later of a seemingly code compliant install where a ground fault in the rigid conduit never opened up the protective device and just torched the conduit on the wall of the building. I have also witnessed where smaller branch circuits are deadshorted to conduits to find the breaker and they took a lot longer to open than I expected and was melting the metal, I know this was likely a neglected breaker performing poorly, but still that's the way installs are maintained, so I figure look into lowering circuit impedance. No I don't look for breakers that way, I was an apprentice. And yes I compensate for voltage drop in wire size.
And I don't just mean the connection when new, I think it will be a much longer lifespan better connection as well. I have gotten the suggestions of the corrosion tapes on normal coupling joints and I like that idea to.
Thanks

Rigid conduit typically has less resistance than the EGC you would pull through it, especially for the "small branch circuits" like you mentioned. Remember for a long circuit run you also have resistance in the ungrounded conductor that will limit fault current and result in longer time before tripping overcurrent device than it will take for shorter circuit length.

I have more concerns about locknuts not being tight enough and also have even seen bolt on hubs that weren't bolted tight enough and showed signs of arcing at mounting bolts after a fault, than I have with standard couplings that were made up wrench tight.

 

[roger]

I'm sorry that I offended you.

So suggesting you make a proposal for a change gives you the idea you offended me, rest easy you didn't. With that said, I see your worries on this a non issue if you haven't caught my drift yet.

Many before you have had grand ideas, many after will think they have the best methods or ideas and that tried and true methods are inferior.

I wasn't joking about compiling a list of documented problems with the listed coupling, when you have, it will go a long ways with getting a proposal accepted.

On the other hand, if you compile a convincing list of the advantages of non listed couplings it could go a long way too, so either way, you might want to get started researching.

Roger

 

[Wire-Smith]

Rigid conduit typically has less resistance than the EGC you would pull through it, especially for the "small branch circuits" like you mentioned. Remember for a long circuit run you also have resistance in the ungrounded conductor that will limit fault current and result in longer time before tripping overcurrent device than it will take for shorter circuit length.

I have more concerns about locknuts not being tight enough and also have even seen bolt on hubs that weren't bolted tight enough and showed signs of arcing at mounting bolts after a fault, than I have with standard couplings that were made up wrench tight.

On the first part about conduit being less resistive, I agree, I have looked over the soares data. This is actually a big reason as to why I am looking at the couplings, I figure it could be a substantial return on investment. My thinking is If the conduit is a good conductor then substantially better connections will possibly make it quite better or if nothing else add to the robustness for a longer effective life.

I completely agree on the second part too, those are easy to address as you know.

On a related note if anyone is interested I would also use 20' conduits for long straight runs.

 

[Wire-Smith]

So suggesting you make a proposal for a change gives you the idea you offended me, rest easy you didn't. With that said, I see your worries on this a non issue if you haven't caught my drift yet.

Many before you have had grand ideas, many after will think they have the best methods or ideas and that tried and true methods are inferior.

I wasn't joking about compiling a list of documented problems with the listed coupling, when you have, it will go a long ways with getting a proposal accepted.

On the other hand, if you compile a convincing list of the advantages of non listed couplings it could go a long way too, so either way, you might want to get started researching.

Roger

I agree it's not a problem to sound the alarm on, it's just a thought I have been kicking around. I really don't have any desire for this to be a code requirement, I think there are a lot of other areas of the code to work on that are quite legitatement before splitting atoms on something like this. I actually do try to keep documentation on those types of things already.
Thanks and if you didn't notice earlier in the thread, I have some Canadians looking in to if anyone up there makes them and lists them. Don says they may have used npt up to the 80's. I will also check on listing them.

 

[readydave8]

litness test.

sobriety check, cop wants to know if subject is lit:lol:

 

[ptonsparky]

The problem I have with burying galvanized rigid conduit is, just that. I’ve dug up enough of it to find rust marks in the dirt with the THW working just fine. Couplings were gone as well.

 

[Wire-Smith]

The problem I have with burying galvanized rigid conduit is, just that. I’ve dug up enough of it to find rust marks in the dirt with the THW working just fine. Couplings were gone as well.

Some situations require robroy, epoxy coating, or corrosion tape. Such as around Cathodic protection. Around here if you get It deep enough below topsoil it will last 100 years if done right, I.e. coating field cut threads and wrench cuts, then where it turns up through the topsoil level and 8" above, you just use supplemental protection like epoxy or tape or additional zinc coating. I've pulled out old lead cable and pulled new in, in some very old runs.

 

[Fulthrotl]

I use kopr-shield joint compound. The joints are water tight, I point people to plumbing(gas and liquid) pipes that don't leak when they say stuff like that, your keeping water out but it is same joint. I know npsm can be assembled to watertight but npt also makes better electrical connection.

cop-r-shield or led-plate will get you where you want to go with straight GRC couplings.
straight couplings are used both in vinyl coated rigid, and are listed for classified locations.

what do you need to be more resilient than explosion proof joints?
asking for a friend....

 

[Dzboyce]

I’ve never used Kopr-shield before. Looked it up. I see it’s made for T&B by Jetlube. Next trade show I’ll have to ask the jet-lube guys what the difference is between Kopr-shield and Kopr-kote. Other than the price that is. 8oz of Kopr-shield cost more than a gallon of Kopr-kote. And I do buy Kopr-kote by the gallon.

 

[Fulthrotl]

I’ve never used Kopr-shield before. Looked it up. I see it’s made for T&B by Jetlube. Next trade show I’ll have to ask the jet-lube guys what the difference is between Kopr-shield and Kopr-kote. Other than the price that is. 8oz of Kopr-shield cost more than a gallon of Kopr-kote. And I do buy Kopr-kote by the gallon.

i think it's extreme pressure anti sieze, but not postitive.
the kote is for drill pipe, i think.

led plate and cop r plate are about the same effectiveness, just one
is for conductivity, and better thermal transfer. the copper is what
i always ended up with in steam plants, and powerhouses.

not to beat a dead pipe coupling, but if you are using tapered couplings,
you will have several threads exposed that won't make up. bare threads
are the first point of corrosion and failure. if you use a straight GRC coupling,
all the threads will be buried inside the coupling, and if you use cop r plate or
whatever flavor you prefer, the threads will be full of the product, and no air,
or moisture will get to them.

and as long as we are on the subject, the absolute best product i've found for
penetrating rust and corrosion breaking, is aero kroil. nothing else even comes close.

 

[rambojoe]

So suggesting you make a proposal for a change gives you the idea you offended me, rest easy you didn't. With that said, I see your worries on this a non issue if you haven't caught my drift yet.

Many before you have had grand ideas, many after will think they have the best methods or ideas and that tried and true methods are inferior.

I wasn't joking about compiling a list of documented problems with the listed coupling, when you have, it will go a long ways with getting a proposal accepted.

On the other hand, if you compile a convincing list of the advantages of non listed couplings it could go a long way too, so either way, you might want to get started researching.

Roger

in other words, do not over think it, its not the space shuttle. I have demo'd explosion proof raceways with enough water in it to flood the trench. especially for surface run (not buried), its going to condensate. when I started in San Fran, heck, we were drilling holes in some conduit bodies for the heavy fog... funny thing about over thinking stuff, just to discover that a plumber stuck a empty Gatorade bottle and his lunch trash in a stick of 3'' while eating lunch by the trailer...