What conduits are allowed to transition from underground to above ground

[freddyt7]

We have been told that there is specific NEC code as to what type of conduits are allowed to come above ground. Specifically HDPE must transition from HDPE below ground to either PVC or rigid steel. We were of the understanding that this is due to the sun and wire protection. Can someone please tell us the exact code section and what the reason for this is please.

Thanks - Tom

 

[petersonra]

The answer appears to be because the code says so.

Who knows why. Maybe the material does not deal well with sunlight.

Part II. Installation
353.10 Uses Permitted. The use of HDPE conduit shall be
permitted under the following conditions:
...
(5) Above ground, except as prohibited in 353.12, where
encased in not less than 50 mm (2 in.) of concrete.

353.12 Uses Not Permitted. HDPE conduit shall not be used
under the following conditions:
(1) Where exposed
(2) Within a building

Presumably, you could run it out of the ground if you encased it in concrete, but you could not run it inside the building so you would still need to transition to something else to go into the building.

 

[GerryB]

We have been told that there is specific NEC code as to what type of conduits are allowed to come above ground. Specifically HDPE must transition from HDPE below ground to either PVC or rigid steel. We were of the understanding that this is due to the sun and wire protection. Can someone please tell us the exact code section and what the reason for this is please.

Thanks - Tom

It's in the code book. I've never used it, but Art 353.12(1) in the 2014 code says "where exposed" under uses not permitted. So check the code book for whatever conduit you are running. The .12 section is "uses not permitted".

 

[FionaZuppa]

The answer appears to be because the code says so.

Who knows why. Maybe the material does not deal well with sunlight.

Presumably, you could run it out of the ground if you encased it in concrete, but you could not run it inside the building so you would still need to transition to something else to go into the building.

Carlon has anti-UV UL rated "Aerial HDPE", so if NEC wrote that thinking sunlight is an issue for HDPE, perhaps NEC was wrong?

Both PVC and HDPE give off toxic fumes when burning, so I not sure I see argument there. HDPE is also more difficult to glue fittings to (glues are typically 2part epoxies, a glue bond, not a chemical weld like with PVC), so why having it transition underground is an oddball requirement?

 

[Chamuit]

You may also have local amendments that come into play.

 

[petersonra]

Carlon has anti-UV UL rated "Aerial HDPE", so if NEC wrote that thinking sunlight is an issue for HDPE, perhaps NEC was wrong?

Both PVC and HDPE give off toxic fumes when burning, so I not sure I see argument there. HDPE is also more difficult to glue fittings to (glues are typically 2part epoxies, a glue bond, not a chemical weld like with PVC), so why having it transition underground is an oddball requirement?

it is a bit of a mystery to me why it is not allowed indoors, given that PEX used for plumbing is also HDPE, and it is commonly used indoors.

 

[GoldDigger]

it is a bit of a mystery to me why it is not allowed indoors, given that PEX used for plumbing is also HDPE, and it is commonly used indoors.

FWIW plumbing PEX is normally joined with internal metal barb fittings with an external compression ring. Not suitable for pulling wire through.

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[FionaZuppa]

FWIW plumbing PEX is normally joined with internal metal barb fittings with an external compression ring. Not suitable for pulling wire through.

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I don't think that's what he meant.
I think he was saying that hdpe has proliferated indoors by way of plumbing for water, so why is hdpe not ok for use as electrical conduit indoors. The plumbing fittings are not the only way to join hdpe, etc.

 

[norcal]

FWIW plumbing PEX is normally joined with internal metal barb fittings with an external compression ring. Not suitable for pulling wire through.

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And have read limitations on how long PEX can be exposed to sunlight,BTW, I don't care for the stuff, nobody has given me a proper answer about rodents & PEX.

 

[FionaZuppa]

And have read limitations on how long PEX can be exposed to sunlight,BTW, I don't care for the stuff, nobody has given me a proper answer about rodents & PEX.

Call Carlon and ask what limitations there are for their UL listed "Aerial HDPE". I cant imagine its any different than the "gray" they put in with PVC to make it UV resistant.