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-   -   how deep should PVC conduit be in slab? (http://www.diychatroom.com/f18/how-deep-should-pvc-conduit-slab-158209/)

skinut2234 09-27-2012 10:23 PM

how deep should PVC conduit be in slab?
 
OK in preparation for the kitchen island - I'm cutting a channel into the slab to run electric (about 2' from the wall)- I cut down about 2.5" and about 3.5" wide in the concrete - I rented a power chisel. To go deeper seems to really be a challenge- Can I lay the PVC in and cover with concrete from here? What determines the depth that it needs to be? I can't see weight being an issue- Once the concrete hardens around the PVC and the floor gets installed.....thoughts? suggestions?

jrclen 09-27-2012 10:37 PM

The National Electric Code determines this. Table 300.5 note 2 requires the conduit to be surrounded by 2" of concrete. What size conduit are you using?

skinut2234 09-27-2012 10:45 PM

3/4" PVC Conduit

electures 09-27-2012 10:49 PM

Quote:

Originally Posted by jrclen
The National Electric Code determines this. Table 300.5 note 2 requires the conduit to be surrounded by 2" of concrete. What size conduit are you using?

The NEC does not require the conduit to be surrounded by 2" of concrete. It can be laid on the soil and concreted over.

Gac66610 09-27-2012 11:05 PM

Quote:

Originally Posted by electures (Post 1018862)
The NEC does not require the conduit to be surrounded by 2" of concrete. It can be laid on the soil and concreted over.

It needs to be covered by 2" of concrete

mpoulton 09-27-2012 11:13 PM

The standard approach to solving this problem is to cut all the way through the slab with a saw, and lay the conduit under the slab. It is easier than making a shallower channel. Chiseling a channel through concrete is REALLY HARD as you discovered, but making two sawcuts through the slab a few inches apart is really easy. You still need a rotohammer or small jackhammer to break up and remove the pieces, but it's about a 30 minute job with the right tools, rather than all day with a rotohammer trying to chisel 3" deep groove in the slab.

electures 09-27-2012 11:14 PM

Quote:

Originally Posted by Gac66610

It needs to be covered by 2" of concrete

No. Since it is under the building it can be 0" deep. It is covered by the thickness of the slab.

Jim Port 09-27-2012 11:49 PM

Quote:

Originally Posted by Gac66610 (Post 1018877)
It needs to be covered by 2" of concrete

Could you cite the NEC rule for this?

Gac66610 09-28-2012 07:11 AM

Quote:

Originally Posted by Jim Port (Post 1018912)
Could you cite the NEC rule for this?

Table 300.5, Notes

electures 09-28-2012 07:57 AM

Quote:

Originally Posted by Gac66610 (Post 1019027)
Table 300.5, Notes

If you are refering to Note 2, it states;

2. Raceways approved for burial only where concrete encased shall require concrete envelope not less than 50 mm (2 in.) thick.


PVC does not require concrete encasement and is "Listed for direct burial without concrete encasement", therefore Note 2 does not apply. Refering to Table 300.5, Row 3, labeled "Under a building", Column 3, the required depth is 0". The OP just needs to break through the slab and lay the PVC on top of the dirt. Then concrete over the pipe. Done.


Code05 09-28-2012 08:19 AM

300.5, Note 2 is referring to conduit like EB20 - not PVC 40 or 80.

skinut2234 09-28-2012 09:01 AM

let me clarify- I don't know how thick the slab is- It's not a new house- it's an existing house built in the mid 70's in NJ. I was going with the channel since after chiseling down 2" or so- It's getting really hard to go any deeper and I thought by going down 2" and then laying the PVC in the slab- I could cover it back up with high strength concrete. Won't that keep the PVC well secured?

jrclen 09-28-2012 09:30 AM

Quote:

Originally Posted by Code05 (Post 1019058)
300.5, Note 2 is referring to conduit like EB20 - not PVC 40 or 80.

Can you cite something on this? I really would like to know. I have laid PVC in concrete channels cut in slabs and was required to cover the conduit with 2" of concrete. Evidently some slabs are not allowed to be cut through. But that's completely out of my field so I may well be wrong about this.

herdfan 09-28-2012 10:28 AM

Quote:

Originally Posted by jrclen (Post 1019114)
Evidently some slabs are not allowed to be cut through. But that's completely out of my field so I may well be wrong about this.

That would be tensioned concrete. They have steel cables running through them keeping tension on the concrete. If one gets cut, the concrete can lose some of its strength.

Gac66610 09-28-2012 12:13 PM

So you (a long with others) are saying that PVC can not be used in concrete?
I read Notes 2, and 5, both say minimum of 2" concrete, so how would a slab be any different?


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