# transitioning from one type of conduit to another



## MDShunk (Jan 7, 2007)

If both ends are grounded (meaning the armor of the flex too), you're golden. 

There was some heated discussion, years back, whether or not you must use a listed transition fitting to transition from one conduit method to another. I think it was finally resolved that the mere existence of a transition fitting is not necessarily a requirement for its use. A TA into an FA, or two box connectors into a coupling, it was resolved, is compliant.


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## active1 (Dec 29, 2009)

IMO the transition couplers are produced for time saving, efficiency, less material needed at each location, more compact, and sometime less costly then building 2 different connectors and a rigid coupling. 

I know on nowhere in the NEC where it calls for certain adapters.
Only that the individual fittings be listed.

There was 2 types of problems with inspectors we ran into.
When the raceway size was reduced.
Such as from 1/2 to 3/8 when 3/8 was needed because that's all that would fit.
In theory the raceway shall be able to be pulled after walls are finished.
Reality is you pull the wire while the walls are open and the only reason your using flex vs MC is because of local amendments.

Few other times you get some inspector that will say "you can't make your own fittings". Ends up being easier to change the fitting vs fight the inspector.

Changing from non-matalic to metalic raceway, yes in theory the conduit should be bonded on both ends. Then I get all the flash backs about underground PVC to a ridgid 90 and vertical with PVC. Or a PVC stubbed out of the ground or floor to EMT.

Perhaps one day a fitting manufacture will make a transition coupling that has a spot to lay in the EG. Then lobby the code panel to make it a requirement. Just like those raintight fittings.


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## MDShunk (Jan 7, 2007)

This is what caused the rub, from the UL guide:

_Fittings with internal female threads (e.g., hubs, conduit bodies, couplings) have only been investigated for use with threaded rigid conduit._


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## macmikeman (Jan 23, 2007)

I actually had an inspector once tell me I could go ahead and thread schedule 80 pvc so it could go into a rigid coupling since his claim was that the threads on a male adaptor were not listed for grc couplings or threaded grc ends were not listed for going into a pvc female adaptor. He is such a dipchit that I ended up running schedule 40 all the way and to hell with using rigid metal conduit for a place that had lots of forklifts and luggage cart trains going to and fro and smashing everything to bits that they encountered. A bad dangerous situation just because he figured he knows everything there is to know after him spending too much time on Mike Holt and warping his sanity all to hell. Idiot. Clouseau.


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## splatz (May 23, 2015)

macmikeman said:


> I actually had an inspector once tell me I could go ahead and thread schedule 80 pvc so it could go into a rigid coupling since his claim was that the threads on a male adaptor were not listed for grc couplings or threaded grc ends were not listed for going into a pvc female adaptor. He is such a dipchit that I ended up running schedule 40 all the way and to hell with using rigid metal conduit for a place that had lots of forklifts and luggage cart trains going to and fro and smashing everything to bits that they encountered. A bad dangerous situation just because he figured he knows everything there is to know after him spending too much time on Mike Holt and warping his sanity all to hell. Idiot. Clouseau.


couldn't you just put in a box instead


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## MechanicalDVR (Dec 29, 2007)

Never been gigged on using a TA to FA.


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## cabletie (Feb 12, 2011)

Where there is a transition, the transition is supposed to be accessible. I'm certainly not going to be the first one to throw stones. The metallic raceway only has to be grounded at one end. Of course if it's a ferrous raceway enclosing a grounding electrode conductor it has to be at both ends, but that's a whole different topic, and a smack down one at that.


300.15 Boxes, Conduit Bodies, or Fittings — Where Required.
A box shall be installed at each outlet and switch point for concealed knob-and-tube wiring.
Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed.
Where the wiring method is conduit, tubing, Type AC cable, Type MC cable, Type MI cable, nonmetallic-sheathed cable, or other cables, a box or conduit body shall be installed at each conductor splice point, outlet point, switch point, junction point, termination point, or pull point, unless otherwise permitted in 300.15(A) through (L).


(F)Fitting.
A fitting identified for the use shall be permitted in lieu of a box or conduit body where conductors are not spliced or terminated within the fitting. The fitting shall be accessible after installation.


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## pudge565 (Dec 8, 2007)

MDShunk said:


> If both ends are grounded (meaning the armor of the flex too), you're golden.
> 
> There was some heated discussion, years back, whether or not you must use a listed transition fitting to transition from one conduit method to another. I think it was finally resolved that the mere existence of a transition fitting is not necessarily a requirement for its use. A TA into an FA, or two box connectors into a coupling, it was resolved, is compliant.





MDShunk said:


> This is what caused the rub, from the UL guide:
> 
> _Fittings with internal female threads (e.g., hubs, conduit bodies, couplings) have only been investigated for use with threaded rigid conduit._


So on top of the wording that MDShunk posted the UL "White Book" (now product spec available online as the White Book is no longer published) also said that fittings having male threads had only been investigated for use with a locknut. That was very recently changed to state that it may be used in boxes with threaded female hubs if so identified on the smallest shipping carton. However, the wording about the female threads is still there.

I do not know any inspector that calls it as a violation unless you are using that as the path of fault current.

This is all based on product category DWTT.


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## Cow (Jan 16, 2008)

What would happen if the flex ever became energized?

How are you going to create an effective ground fault current path with an isolated section of metal flex?


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## CTshockhazard (Aug 28, 2009)

It's been investigated by a whole helluva lot of electricians on millions of installs, so fire truck the UL guide. :biggrin:


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## MotoGP1199 (Aug 11, 2014)

Cow said:


> What would happen if the flex ever became energized?
> 
> How are you going to create an effective ground fault current path with an isolated section of metal flex?


That metal flex has to be grounded on one side. Either by a bushing, connected to a metal enclosure that is grounded, or any other approved method. Most likely if your doing this you will have a grounding conductor pulled in that conduit to ground the equipment or enclosure on the other end of the PVC etc. If the flex is in between two sections of PVC, the only way this would be approved is if you had a connector on the flex that has a built in grounding lug on the outside in which you could run an external grounding wire.


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## mikewillnot (Apr 2, 2013)

[OP]: OK, thx all. I would be particularly interested in the idea of transitioning from PVC liquidtight (no metal) to PVC rigid -- since I never again intend to ever use metal flex ... if I can possibly avoid it.


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## mikewillnot (Apr 2, 2013)

[OP]: So with the metal flex approach, this would be OK:

Main panel -> metal flex -> metal j-box/enclosure -> rigid PVC conduit -> Equipment

assuming a continuous ground wire from panel to equipment, and bonding (to the EGC) at both ends of the flex
?


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## cabletie (Feb 12, 2011)

I like to avoid carflex if I can. That stuff sucks to pull wire through. Now ENT is a different story.


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## Wiresmith (Feb 9, 2013)

mikewillnot said:


> [OP]: OK, thx all. I would be particularly interested in the idea of transitioning from PVC liquidtight (no metal) to PVC rigid -- since I never again intend to ever use metal flex ... if I can possibly avoid it.



using a box, or someone might make a transition fitting, for actual code compliance.

standard nm flex box connector to pvc female or vice versa if your in a dry location, arguably not technically code compliant in my opinion but it's satisfactory in my opinion. i think the code could use some exceptions in this area


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## Wiresmith (Feb 9, 2013)

mikewillnot said:


> I would be interested in opinions.



*110.3(B)Installation and Use. *listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing and labeling.


my opinion is that if you used a box connector into a coupling, then it is technically not code compliant, but only because the code is lacking in clarity not because in your exact scenario that it creates any potential problem


the big problem i see with this talk of transition fittings not being required are things like liquid-tight box connectors being screwed into straight thread fittings like rigid couplings. box connectors have straight threads they are not designed to be screwed into a straight thread fitting, when doing so you raise contact resistance, you lower liquid intrusion resistance and also you lower corrosion resistance of the joint. so if its a metal to metal transition you have installed a poor electrical connection for your raceway and if it is in an area subject to moisture you have installed a poor moisture resistant connection. a rigid coupling can have a straight thread because the conduit has a tapered thread which provides a good enough (and laboratory tested)connection.



the pictures i attached are box connectors(commonly called connectors, but they are box connectors), here is an excerpt of the description from the manufacture for the liquidtight flex connector "Use to positively bond the conduit to a box or enclosure. "
here is an excerpt for the emt connector "4in insulated compression connectors are used to bond 4 EMT thinwall conduits to electrical junction boxes or enclosures"
here is from the flex connector "Malleable iron straight squeeze flex connector is used to connect flexible metal conduit to a box or enclosure."


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