PVC out of a concrete slab

[pilot]

We used sch-40 rigid pvc j-m pipe 40" under a concrete slab. The steel building is used for storage & has no living area. It is 135'X60'X24'=8100SQ FT or 194400CU FT. We got tagged for not changing to "IMC" or "rigid" (writtem on the noncompliance) at the surface of the slab. This IMC or rigid must be at least 18" long (he said) & then may go back to pvc to the load center. Any thought?
My inspector says the one thing I failed to post on this is that this is an airplane hanger. Any new thoughts with this information?

[ September 28, 2004, 03:40 PM: Message edited by: pilot ]

 

[buck33k]

Re: PVC out of a concrete slab

Did the inspector give a code reference? Maybe he considered it necessary to use RMC and seals for a hazardous location??

 

[iwire]

Re: PVC out of a concrete slab

I think the inspector may be thinking of 300.5(D)(4) 2002 NEC

300.5(D)(4) Enclosure or Raceway Damage. Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 rigid nonmetallic conduit, or equivalent.

But it may be possible that you are on the 1999 NEC

300-5(d) Protection from Damage. Direct-buried conductors and cables emerging from the ground shall be protected by enclosures or raceways extending from the minimum cover distance required by Section 300-5(a) below grade to a point at least 8 ft (2.44 m) above finished grade. In no case shall the protection be required to exceed 18 in. (457 mm) below finished grade.
Service laterals that are not encased in concrete and that are buried 18 in. (457 mm) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 12 in. (305 mm) above the underground installation.
Conductors entering a building shall be protected to the point of entrance.
Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 rigid nonmetallic conduit, or equivalent.

Either way the inspector must feel the area the PVC come up is subject to physical damage.

In that case rigid metal conduit, intermediate metal conduit or Schedule 80 rigid nonmetallic conduit must be used.

 

[hbiss]

Re: PVC out of a concrete slab

300.5(D)(4) Enclosure or Raceway Damage. Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 rigid nonmetallic conduit, or equivalent.

This sounds like a warehouse type of building with the possibility that this conduit could be damaged by forklifts or material. I wouldn't even consider schedule 80 NMC in this instance, RMC or IMC is the proper way IMO.

You now have big problems with the conduit 40" under the slab. Is there any possibility that the conduit could be protected- possibly by forming it out and pouring concrete around it to a height of at least 18"? Something to talk over with the AHJ before getting out the jackhammer.

-Hal

 

[caj1962]

Re: PVC out of a concrete slab

Is the load center directly above where the PVC emerges from the concrete? If the inspector is worried about damage to the conduit, what about the panel? As other posters have said ask for the code referance.

 

[iwire]

Re: PVC out of a concrete slab

Originally posted by caj1962:
ask for the code referance.

Jeff you do not think 300.5(D)(4) covers this?

 

[petersonra]

Re: PVC out of a concrete slab

Originally posted by hbiss:
300.5(D)(4) Enclosure or Raceway Damage. Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 rigid nonmetallic conduit, or equivalent.

This sounds like a warehouse type of building with the possibility that this conduit could be damaged by forklifts or material. I wouldn't even consider schedule 80 NMC in this instance, RMC or IMC is the proper way IMO.

You now have big problems with the conduit 40" under the slab. Is there any possibility that the conduit could be protected- possibly by forming it out and pouring concrete around it to a height of at least 18"? Something to talk over with the AHJ before getting out the jackhammer.

-Hal

I have seen similar installations where they protected the plastic conduit from damage by putting a steel angle around it so you can't hit the plastic conduit. I think the theory was it was no longer subject to physical damage, or maybe it was just cheaper that way.

 

[don_resqcapt19]

Re: PVC out of a concrete slab

513.3(B) combined with 501.4(B)(1) will not permit PVC in this location. Also seals will be required at the classification boundries.
Don

 

[iwire]

Re: PVC out of a concrete slab

Originally posted by pilot:
My inspector says the one thing I failed to post on this is that this is an airplane hanger. Any new thoughts with this information?

That would change things a bit, forget my previous posts and pay attention to to Don's post.

 

[buck33k]

Re: PVC out of a concrete slab

An airplane hanger - hazardous location up to 18". My immediate feeling is to abandon the pvc conduit runs under the slab. I have never been faced with doing this in a hazardous location, and so I do'nt know what would be the correct procedure. I would have a talk with the inspector .

[ September 28, 2004, 05:36 PM: Message edited by: buck33k ]

 

[rbalex]

Re: PVC out of a concrete slab

Originally posted by don_resqcapt19:
513.3(B) combined with 501.4(B)(1) will not permit PVC in this location. Also seals will be required at the classification boundries.
Don

513.3 Classification of Locations.
(A) Below Floor Level. Any pit or depression below the level of the hangar floor shall be classified as a Class I, Division 1 or Zone 1 location that shall extend up to said floor level.
(B) Areas Not Cut Off or Ventilated. The entire area of the hangar, including any adjacent and communicating areas not suitably cut off from the hangar, shall be classified as a Class I, Division 2 or Zone 2 location up to a level 450 mm (18 in.) above the floor.

In general, except as specifically required, as say in Figure 514.3(B)(1), the underground beneath a Classified location is not itself required to be classified. Depending on how the riser sweep is installed a seal may not be required per 501.5(B) (2) Ex 1.
PVC underground is fine with an appropriate EGC. per 501.4(A)(1)(a) Ex.

[Edit Add] I should expand on this. While the wiring methods are to be comply with Div 1 per 513.8, the location itself is not necessarily classified. The wiring / sealing would comply per the exceptions noted.

[ September 28, 2004, 05:26 PM: Message edited by: rbalex ]