PVC Conduit Emerging From Trench To Sub Panel

[N844AA]

In the past if I was running a PVC underground feeder to a structure to feed a surface mounted panel, I would use a rigid elbow and rigid conduit to come out of the ground and feed the panel.

But in reviewing the code, is there any reason I cannot just come up out of the trench and feed the panel with PVC? This is on the exterior of a detached residential garage, the PVC is labeled as sunlight resistant and I do not consider this location to be subject to physical damage.

PVC all the way? Is there a code that says I must transition to rigid?

Thanks in advance!

 

[Den]

Around here we can use pvc but it must be schedule 80. It must also have a slip joint "riser tube" if the pvc has an elbow to turn horizontaly but not needed if the pipe just goes to the ground and stops ( according to my inspector. ) I thought code was to have a slip joint anyway.

 

[Article 90.1]

PVC all the way, direct burial sleeved in PVC where it emerges from the ground, PVC all the way with RMC elbows are all acceptable. I can't locate the article that allows RMC elbows in a PVC run to not have to be bonded when buried, though. SCH. 80 PVC may be a local amendment in some areas, but generally it is only required to protect against physical damage.

And although I first scoffed at it, and others will shun me, I have been known to glue the end bell of the PVC right over the threads of the RMC as it makes a stronger mechanical connection than FA's.

 

[augie47]

........and I do not consider this location to be subject to physical damage.

Unfortunately, in most cases, it is more what HE (AHJ) considers it
Garage outside subject to weedeaters, lawnmower bumps, etc. most AHJs will say subject to physical damage.

.
PVC all the way? Is there a code that says I must transition to rigid?

Thanks in advance!

No Code that mandates rigid that I know of. as stated above, to many AHJs it would be a "physical damage". 300.5(D) is your basic reference.

 

[N844AA]

Thank you all. Yeah, the whole "subject to physical damage" is always so subjective.

Thanks again!

 

[satcom]

Thank you all. Yeah, the whole "subject to physical damage" is always so subjective.

Thanks again!

We like to use sch 80 for comming out of the ground, any conduit near a garage or any out building can be exposed to damage.

 

[peter d]

I highly doubt an expansion fitting is necessary in Los Angeles. Frost heaving isn't a problem there.

 

[G0049]

Unfortunately, in most cases, it is more what HE (AHJ) considers it

Or SHE...

 

[iwire]

And although I first scoffed at it, and others will shun me, I have been known to glue the end bell of the PVC right over the threads of the RMC as it makes a stronger mechanical connection than FA's.

That there would be an NEC violation and I will not believe it is stronger, PVC cement is not 'glue'.

 

[roger]

Schedule 80 PVC is listed as being protection from physical damage whereas schedule 40 is not, so in otherwords, schedule 80 PVC can be used in lieu of RMC for this application.

Roger

 

[cpal]

Around here we can use pvc but it must be schedule 80. It must also have a slip joint "riser tube" if the pvc has an elbow to turn horizontaly but not needed if the pipe just goes to the ground and stops ( according to my inspector. ) I thought code was to have a slip joint anyway.

Well
Are you referring to a slip joint as a true fitting listed for ground movement??

or are you referring to a slip joint that actually is listed as an expansion fitting (as in thermal)

they are quite different and an expansion fitting is not listed for ground movement. (or atleast I am not aware that they are)

 

[N844AA]

Schedule 80 PVC is listed as being protection from physical damage whereas schedule 40 is not, so in otherwords, schedule 80 PVC can be used in lieu of RMC for this application.

Roger

I'm gonna use schedule 80 from now on for this.

 

[Den]

Sorry for the slang. Meter riser is a floating pipe (pvc) over the pipe coming out of the ground letting things move up and down. Expansion joint is a special fitting for allowing pvc conduit to expand in horizontal runs and not for direct bury. I don't have the code book in front of me but there is a chart that shows how much pvc will expand with temperature and it is a lot. Surprised me how much expansion room is required.

 

[cpal]

Sorry for the slang. Meter riser is a floating pipe (pvc) over the pipe coming out of the ground letting things move up and down. Expansion joint is a special fitting for allowing pvc conduit to expand in horizontal runs and not for direct bury. I don't have the code book in front of me but there is a chart that shows how much pvc will expand with temperature and it is a lot. Surprised me how much expansion room is required.

but of course appox 4" per 100'

slip risers are fine for ground movement. just checking

 

[Article 90.1]

That there would be an NEC violation and I will not believe it is stronger, PVC cement is not 'glue'.

iWire, you don't have to believe if it is stronger or not. But it is! I cursed my foreman up and down when he asked me to do it for the first time 20 years ago on 6", but guess what, it works and it works well. PS this is one violation I'm willing to make, so please send the code police to any underground jobs I do in the future.

Test it for yourself if you don't believe me, or just ignore it all together if you prefer.

Code violation or not, that is how this industry evolves, by people finding superior ways of doing things; more efficient, faster, safer, better, etc.

 

[tkb]

The State of Maine addresses this transition.

http://www.maine.gov/pfr/professionallicensing/professions/electricians/new_board_action.htm

October 17, 2008 - The Board approved illustration #30 in the CMP Handbook of Requirements for Electric Service and Meter Installations, effective August 25, 2006, which does not require a transition fitting between the PVC and steel so long as the bell end of the PVC is installed over a threaded end of the metal conduit.October 17, 2008 - The Board approved illustration #30 in the CMP Handbook of Requirements for Electric Service and Meter Installations, effective August 25, 2006, which does not require a transition fitting between the PVC and steel so long as the bell end of the PVC is installed over a threaded end of the metal conduit.

See the second paragraph.

 

[220/221]

I'm a PVC all the way proponent.

Rigid doesn't last in our soil. Even wrapped, the insides get rusty.

And although I first scoffed at it, and others will shun me, I have been known to glue the end bell of the PVC right over the threads of the RMC as it makes a stronger mechanical connection than FA's.

GAH!! What about the exposed edge on the RMC? Aren't you concerned that it may tear up the conductors if they are pulled towards it?

 

[danickstr]

i don't like the glue on bell idea, not because its a code violation (although that is a reason not to do it) but because if someone dug it up and saw it, I would be embarrassed. Even if it works well, it looks like I am a corner cutter. I would rather screw a female..adapter on there.

 

[short circuit faulted]

My Take

My Take

Interesting installation method discussion, I tend to agree with I-wire on the connection. Around here the universal engineered specification regarding feeders and service entrance states "Transition from schedule 40 PVC to galvanized rigid steel ninety degree elbow coated with bitimius where in contact with soil or concrete". Coating elbows is a job reserved for a deserving apprentice, NASTY. Especially nasty on 102 degree day with humidity around 85%...of course those days aren't comfortable for anyone on the job. I have seen schedule 40 elbows installed by others where "Hopefully" the rope and not the conductors burnt out back side on longer pulls. Branch circuit in slab, the GRS elbows are at contractor's option depending on the length of the pulls, we normally use them at the panels and at the other end ot the run if it exceeds 200' transitioning to EMT withing 18" of FF if rising above. A tip you may want to incorporate with branch circuits in slab is what we call a cheap insurance policy, plus it gives you access to 120V to fire alarm door holders or other small 120V loads requirement, we stub up into the hallways from the first receptacle in the run and into the room with the last receptacle in the room so that should we lose a homerun we don't lose all the receptacles in the run.

Have a great day out there and be SAFE, a millisecond of inattention can cause a lifetime of pain or end your life!

Steve