Medium Voltage

[patpappas]

I can not find in either NEC or NES about constructing a building over medium voltage underground direct buried cables, aside from a very bad idea, is this "bad" idea covered anywhere.

 

[Sahib]

A bad idea especially when the MV cable belongs to POCO. If the MV cable is yours, a concrete cover of thickness specified in NEC will make it "outside" the building.

 

[ron]

I don't think you'll find it in the NEC.

Chapter 3 is used for 1000V and below. If it was 1000V and below, 300.5 in general says it should be in raceway with a few exceptions.

 

[patpappas]

Not Utilities primary, customers, 8320 volts

 

[charlie b]

I don't see a problem, at least given only the information listed above. I presume there are no handholes or manholes being covered by the building, so there should be no need to gain access to the portion of the run that is under the building. I believe that a Civil Engineer needs to sign off on a calculation that approves the design, specifically taking into account such things as the depth of the run, the nature of the soil, the nature of the concrete encasement, and the weight of the building. My concern would be that the weight of the building might deform the conduit run.

 

[ron]

My concern would be that the weight of the building might deform the conduit run.

The OP said direct buried cable, no conduit

 

[patpappas]

no conduit, direct buried cables, cable depth of 4 feet, footing must be below frost line of 42" in our area, mostly a clay base soil but cables were in-cased in sand.

 

[Sahib]

no conduit, direct buried cables, cable depth of 4 feet, footing must be below frost line of 42" in our area, mostly a clay base soil but cables were in-cased in sand.

I think NEC Art.310.60 may be consulted for cable burial depth and ampacity rating.

 

[ron]

I think NEC Art.310.60 may be consulted for cable burial depth and ampacity rating.

300.2(A) says no. 1kV nominal or less

 

[GoldDigger]

no conduit, direct buried cables, cable depth of 4 feet, footing must be below frost line of 42" in our area, mostly a clay base soil but cables were in-cased in sand.

The low clearance between 42" and 48" makes me nervous about the implementation of the design to avoid potential cable damage.
Better to incorporate pass through of the cable into the footing design?

 

[packersparky]

300.2(A) says no. 1kV nominal or less

Part II of Article 300 is for wiring methods over 1000 volts.

 

[ron]

Part II of Article 300 is for wiring methods over 1000 volts.

You are absolutely correct. My error.

Look in 300.50 for MV underground