Concrete Encased Ductbank

[Darrell Wilson PE]

Is there a good standard that covers design of duct bank? NEC covers requirements when concrete encased duct bank is chosen, but except for a couple of places where it is one of the approved options is concrete encased duct bank there is no requirement.

I generally cross roads with concrete encased duct bank, and generally extend some few feet beyond the edge. I currently have an application running along the road, not under. The distance from the edge of the road varies from maybe a foot from the edge to 10 feet of more.

I am basically looking something that explains when the concrete encase duct bank makes sense.

 

[t_van]

Geotech investigation

Geotech investigation

A Geotech investigation with bore samples may tell you whether or not encased concrete is a recommended approach.

 

[Al Pike]

I don't install any encased duct banks other than for heavy traffic area's, medium voltage road crossings, or unfused secondary service drops at 480v. Usually a POCO or engineering spec.

 

[ron]

Depends on the criticality of the application. I also sometimes need concrete encasement to help with conductor ampacity in the duct bank (concrete is often rho 55 and soil is often 90)