Terminating MC Cable to Conduit

[That Man]

For the past several years, I've been designing electrical systems that are utilizing MC cable more and more. Every so often, it becomes necessary to transition from MC cable to conduit, like when an instrument of light is directly mounted to a conduit. Up to now, I have simply been specifying a TMC connector terminating to a straight coupling. I have misgivings about this, since there is no way to add the backing nut, but I think this might be alleviated by the threads of the coupling itself. I would like to stop guessing.

Is it technically possible to terminate MC cable to a rigid conduit coupling via a TMC connector, and run the unarmored conductors in a conduit for an arbitrary distance?

Is it allowed in the code?

Can such a connection be buried? This is the problem I'm facing at the moment, as we are specifying concrete and steel light poles for a project, and I don't want to embed the cable in the foundation, but terminate the MC cable at an underground conduit that runs through the light pole foundation, and run the conductors through the conduit. See attached image. It shrinks down too much, so you can't read it, but the blue lines are MC cables. They terminate at conduits with TMC connectors, and the conductors (red) run in the conduits to the inside of the light pole.


It works in my mind, but I don't actually install things, I just create drawings, and the construction folks don't provide feedback. I can't find any direct reference in any documentation (NEC, manufacturer info, internet search), but there might be an indirect reference, like if terminating to a conduit counts as a junction box, or something similar. I rely on Mike Holt forums for guidance on so many problems like this. I appreciate the help.

 

[luckylerado]

Are the conductors within the DB MC cable suitable for wet locations once the sheath is removed? If so, I do not know why this will not work. Why transition to pipe at all? Just sleeve the whole cable. Sheath and all.

I have never once had to use DB MC cable. UF?

 

[That Man]

One element the construction personnel have provided feedback on is the reticence to terminate MC cable via any means other than TMC connectors, which require a bulkhead or (as I'm proposing) a threaded coupling. They have even gone so far as welding plates inside an MCC to terminate through, rather than peel back and tape the armor. I'm not saying they are correct, but the AHJ is on staff on their construction side, and that's the method they have decided on, so the point is moot. For the same reason, I cant run the MC cable in a conduit, except as a sleeve, and there is no room in the light pole to terminate an MC cable like they prefer. The only option I can come up with is to terminate underground via a coupling, or not use MC cable at all, which is not what the client wants.

You brought up a good point about wet location rating. That's a yes/no question I can forward to the manufacturer and get an answer on.

I'm hoping that with the collected knowledge on these forums, others have encountered this situation, and I'm interested in how they have dealt with it.

 

[That Man]

luckylerado, sorry what does UF mean? My industry is Oil and Gas, primarily oil fields, oil shipping infrastructure, oilfield wastewater treatment & disposal, and gas, if that is what you are asking.

 

[luckylerado]

It is underground feeder cable. Non-metallic. Specs may prevent its use in your case.

340.2 Definition
Underground F eeder and Branch-C ircuit Cable, Type UF. A
factory assembly of one or more insulated conductors with an
integral or an overall covering of nonmetallic material suitable
for direct burial in the earth.

 

[That Man]

Ah, the cable type. I didn't get the context there, sorry.

I just got off the phone with the MC cable manufacturer. the insulation of the conductors is XHHW-2, so it should be OK; they said they'll call me back if they find out differently. As far as the TMC connectors, I couldn't get in contact with the manufacturer, so the question is still open: is it possible to terminate to a coupling as opposed to a bulkhead, and can that termination be buried? Thanks for your help so far.

edit: dyslexic cable type changed from HXXW to XHHW

 

[That Man]

No one has any other input? Does anybody have physical installation experience with TMC connectors? Is it possible to terminate them to a straight coupling instead of a bulkhead?

 

[ADub]

No one has any other input? Does anybody have physical installation experience with TMC connectors? Is it possible to terminate them to a straight coupling instead of a bulkhead?

My guess is most people will find another way to accomplish this installation without some cobbled up ug transition. So good luck


Sent from my iPad using Tapatalk

 

[dkidd]

Have a look at post #7 in the thread http://forums.mikeholt.com/showthread.php?t=162685

 

[Smart $]

Crouse-Hinds TMC fittings have NPT threads, which are standard rigid conduit threads. There should be no problem transitioning directly to RMC via a standard RMC coupling.
http://www.cooperindustries.com/con...inds/resources/catalog-sections/f_section.pdf. See page 87.

 

[That Man]

Don't get me wrong, I appreciate every answer, but why even bother replying if all you have to say can be summed up as "someone will figure it out". That's my job, to figure it out. And this isn't a cobbled up transition. TMC connectors are a fundamental part of MC cable terminations. So much so, that the clients I am working with want to use them for every termination. If you aren't familiar with MC cable, then this question is not for you.

I'm hoping someone on Mike Holt has dealt with these connectors physically, and can tell me if they are compatible with straight couplings. I have already verified that the conductors within the MC cable will be just fine. A secondary question is whether or not these TMC connectors can be buried. This question is completely separate from the first, more fundamental question. I provided a picture to make the scenario easier to understand. The particular picture happens to take place underground, but the same scenario happens often above ground as well.

Regardless, I'll find out a definitive answer eventually. Like I said, that's my job. But I know it will save lots of research time to simply talk to someone who has installed these fittings in the field themselves, which is why I'm asking.

 

[That Man]

dkidd, Smart $, thank you for taking the time to respond. The linked thread was especially useful. Since the AHJ is embedded with the client (as is common in the oil field), they shouldn't object. I would still like to hear from someone who has actually installed these at some point. And I'll likely have to talk to a manufacturer about the underground question, but any code violation would put an end to this, and it sounds like there is no direct code violation so far. I'm still researching this as time allows.

 

[MasterTheNEC]

Greetings That Man -

I can speak on the issue of the Type MC Cable (jacketed) and since I have a close relationship with various fitting manufacturers as well I have had this discussion with a select few as well. Remember, these are my opinions and only mine.

1) The transition between JMC (Type MC-Jacketed) below ground leaves the installer in a bit of a pickle. The fittings that are designed for termination to enclosures and junction boxes (for brevity) and not to rigid metal conduit or nipples below ground or above ground for that matter. They do make and list fittings for EMT to Type MC transitions but again none of the fitting manufacturers I have spoken with endorse this transition as you have described underground. Even if the concept is solid and does seem to work well the fitting manufacturers will be quite protective of the intended use of their fittings.

2) Type MC Cable can be cut and stripped for use with various transition fittings (e.g. EMT to Type MC Cable) because the conductors within the Type MC Cable is marked in accordance with the original conductor standard to which they were produced (UL 83-Thermoplastic and UL 44- Thermosetting). The manufacturers have no issue with the transition as long as a listed transition fitting is used and not fabricated at the will of the contractor due to a weird condition of use....which this would fall into. Weird only in the sense of the nature of the transition.

3) When JMC (Jacketed Type MC) is started in a dry location, then transitions to a wet location, and then back to a dry location, the terminations would only need to be dry location type and the jacket material can be removed and ignored in that aspect of the installation. It must only remain intact in the "wet" locations of the installation.

4) As it would stand now I would think it would be a violation of the fitting (110.3(B)) to use it in the manner you describe based on my conversations with a leading fitting manufacturer. However, with that said if you convince a local AHJ that it is equivalent in use and they agree then 90.4 would allow you to continue the process. Keeping in mind that the local AHJ is assuming quite a bit of responsibility at this point for approving the use when the manufacturer does not approve of the use...but thats not our call.

Now the fitting that "Smart" has proposed may work "physically" and would more than likely present no issues. However, the question remains does the manufacturer of that fitting endorse the use of it to a rigid metal coupling?. The best course of action would be to ask the fitting manufacturer directly and ask for a letter of acceptance. The fitting manufacturer we work with said they would not.

In many cases the contractor will actually bring the Type MC (Jacketed) up to the top of the pole base. the devils advocate argument for termination the Type MC jacketed Cable is found in 312.5(C) and 314.17(B) or (C), which really do not apply. That leads to 300.10 which has a last paragraph that says " cable assemblies shall be mechanically secured to boxes, fittings, cabinets or other enclosures."...and I have seen brackets that mount (like an "L" bracket" that pushes down in the top concrete after the pour and has KO's on it to secure the cables as they emerge.....and of course bond accordingly.

So I can't tell you the transition is acceptable...only the fitting folks can 100% say that for the fitting you intend to use but I can comment on the Type MC Cable itself, it it was THHN/THWN-2 or XHHW-2 then it would be acceptable for the transition.

 

[That Man]

Greetings That Man -

I can speak on the issue of the Type MC Cable (jacketed) ...

Goodness, that was thorough. I feel like I should pay a consulting fee . I'll be doing some more research on other MC cable terminations. Maybe I'll install a small JB to the outside of the pole, since vandalism isn't an issue. My research continues...

 

[dkidd]

Have a look at http://productspec.ul.com/document.php?id=PJOX.GuideInfo for UL Product Category PJOX information.

 

[That Man]

Thanks dkidd. I have lots to think about.

 

[Smart $]

Have a look at http://productspec.ul.com/document.php?id=PJOX.GuideInfo for UL Product Category PJOX information.

The Crouse-Hinds TMC are PJOX category listed. However, on catalog page it is also stated under Certifications and Compliance: NEMA 4 and IP56. These are enclosure standards... not fittings. So now I'm wondering how that weighs into their use...???