PVC Conduit

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olly

Senior Member
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Berthoud, Colorado
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Master Electrician
Is it legal to run pvc conduit in a residential attics and wood stud walls? I have heard that it is not allowed do to gases emitted if it catches fire.
2nd Pvc question do you think the inspector will want to see schedule 80 in the attic?
PVC in attic do to a terra dome style home.
 
olly said:
Is it legal to run pvc conduit in a residential attics and wood stud walls? I have heard that it is not allowed do to gases emitted if it catches fire.
2nd Pvc question do you think the inspector will want to see schedule 80 in the attic?
PVC in attic do to a terra dome style home.
Click to expand...

Yes, see 352.10, uses permitted. PVC is not allowed in plenums or spaces for environmental air; see 300.22.

I dont know about terra dome style houses, but in any standard attic you will see a 100* swing in temps, so for any decent amount of run, you will likely need expansion fittings; 352.44.
 
olly said:
Is it legal to run pvc conduit in a residential attics and wood stud walls? I have heard that it is not allowed do to gases emitted if it catches fire.
2nd Pvc question do you think the inspector will want to see schedule 80 in the attic?
PVC in attic do to a terra dome style home.
Click to expand...

schedule 80 PVC is a substitute for GRC.

schedule 40 would be used in walls, etc.
it's the same thickness as ENT (smurf)
smurf is used in walls and ceilings.

before i used schedule 40 in the attic, i'd ask the AHJ,
but it should be ok.
 
Fulthrotl said:
schedule 80 PVC is a substitute for GRC.

schedule 40 would be used in walls, etc.
it's the same thickness as ENT (smurf)
smurf is used in walls and ceilings.

before i used schedule 40 in the attic, i'd ask the AHJ,
but it should be ok.
Click to expand...
Whoa, hold on there!

Sch 80 PVC is tougher then sch 40 but is not even close to an equivalent to GRC when it comes to the physical abuse it may be able to take.

Then the Sch 40 compared to ENT isn't exactly apples to apples either. The thinner portions at the corrugations of ENT are much weaker then the consistent wall of sch 40 and for that reason ENT isn't really supposed to be exposed.
 
kwired said:
Whoa, hold on there!

Sch 80 PVC is tougher then sch 40 but is not even close to an equivalent to GRC when it comes to the physical abuse it may be able to take.

Then the Sch 40 compared to ENT isn't exactly apples to apples either. The thinner portions at the corrugations of ENT are much weaker then the consistent wall of sch 40 and for that reason ENT isn't really supposed to be exposed.
Click to expand...

i'm holding.....

i didn't mean it was as strong... i meant that schedule 80 plastic is what the AHJ's
around here will let you substitute GRC with.

again.... the ENT is often ran in attics.... no, it's not as durable as sch 40 pvc.
 
kwired said:
Whoa, hold on there!

Sch 80 PVC is tougher then sch 40 but is not even close to an equivalent to GRC when it comes to the physical abuse it may be able to take.

Then the Sch 40 compared to ENT isn't exactly apples to apples either. The thinner portions at the corrugations of ENT are much weaker then the consistent wall of sch 40 and for that reason ENT isn't really supposed to be exposed.
Click to expand...

Taking notes, plastic not as tough as steel, got it. :D
 
Toxic fumes from burning PVC are a problem if the PVC is installed in an air return ceiling or plenum; residential attics are neither.

As for sch 40 or 80, I see no need for 80; as mentioned above, NM cable is installed in attics all the time w/o protection other than the way it's run.

Some stud/joist bays and even entire crawlspaces might be plenums, tho they are fairly rare. I cant imagine an attic used as an air handling space by design.
 
olly said:
Is it legal to run pvc conduit in a residential attics and wood stud walls? I have heard that it is not allowed do to gases emitted if it catches fire.
2nd Pvc question do you think the inspector will want to see schedule 80 in the attic?
PVC in attic do to a terra dome style home.
Click to expand...

If you do intend to use PVC inside, make sure that it is permissible for your specific application. I work with applications where the wiring has to be in metal. The rough-in contractor, who was unfamiliar with this application and rule, put in PVC for us to use. It was not an easy work-around, as the solution was to run metal-clad cable inside the PVC. And where exactly do you terminate that?
 
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