Feeder conduit installed in concrete beam

[bkelly]

I have a contractor that has installed a 4" PVC feeder conduit in a grade beam for a concrete slab on grade. This conduit runs for about 100', in thebottom of a 12"w by 18"d exterior beam. I dont believe NEC covers this, I believe this would be a structural, engineering, or specification issue. I have never installed a conduit this size in a grade beam, other than crossing the beam. Any thoughts on this, or code reference? Thanks for this great resource.

 

[dicklaxt]

It is not done in most cases,even with RGS, about 99.9 % of the time unless engineered for it,,,,,,,,,,,that has been my experience.When going(crossing) under we used a design practice of staying 2 foot below undisturbed soil when possible or at least 2 feet below,when running adjacent or parallel to a foundation we never ran within a 45 degree cone of deflection off of the bottom edge of the foundation.

dick

 

[raider1]

This would be a question for the structural engineer of record on the project.

Chris

 

[paul]

This is a matter for the structural engineer to look at and approve. The NEC and the AHJ could care less.

 

[Jim W in Tampa]

NEC would not care but you might fail it on structual. Was an engineer stamp needed on the prints ? If not then i think it might be up to you the (ahj).

 

[dicklaxt]

Just as a note,,,,,the parameters I posted above were set forth by civil/structural engineering.

In coastal areas or where land subsidence is a problem both footings and duct banks were installed on drilled or bell bottom pilings,,normally tho UG is forbiden in these areas.I recall a recent job where a slack loop had to be left in the #2 grounding taps from the grid,just above grade.

dick