Duct bank separation

[Plastichucker]

I am trying to figure out the amount of separation needed for (2) 4" rigid conduits that will be in the same trench encased with concrete. I am unsure if it is 2 inches or the full 12 inches or something in between. Thanks for the help in advance.

 

[ron]

The spacing depends on how you figured out the ampacity of the conductors.

If this is low voltage (<600V), and you used the prescriptive tables in Appendix B, then likely 7.5" center to center per the detail. If you did Neher McGrath calculations, then you need to refer to the calculation data.