estimating a project without any specifications, an underground duct bank with red concrete encasement is called for. I'm trying to find where or if the NEC actually spells out the requirements for steel reinforcement or for the installation of PVC spacers as a minimum requirement for the construction of the duct bank with multiple conduits in it.
Concrete Encased Duct Bank
- Thread starter MJPCAC
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kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
In short, no the NEC does not dictate the duct bank design. The NEC does recognize the limits on temperature. Duct bank design is an exercise in thermal analysis. The allowable separation of the conduits has to do with the material between the conduits, and the current in each conductor. Additional constraints are burial depth, duct size, cable grouping, soil thermal resistivity, soil temperature, and additional heat sources, i.e. circulating water pipes, steam pipe, or other duct banks/conductors.
The steel is dependent on structural integrity, such as going under or crossing a road, typically will have steel, there are other reasons of course.
The short of it is that typically a civil engineer is needed to design, or estimate the cost of a duct bank, once the electrical tells him how big it will be.
BTW: See if you can take exception to the red concrete, and instead go with the just the top of the concrete painted red, it's a heck of a lot cheaper and serves the same purpose.
The steel is dependent on structural integrity, such as going under or crossing a road, typically will have steel, there are other reasons of course.
The short of it is that typically a civil engineer is needed to design, or estimate the cost of a duct bank, once the electrical tells him how big it will be.
BTW: See if you can take exception to the red concrete, and instead go with the just the top of the concrete painted red, it's a heck of a lot cheaper and serves the same purpose.
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