Direct Burried vs Duct Bank

[ElectDesigner]

Say you are subfeeding a new building (bldg A) from and existing building (bldg B), but to do so the feeder needs to cross a road (future road) to reach the new building. The existing bldg already has direct burried PVC ducts stubbed out from the electrical room. The code in the area allows for either concrete encased duct bank or direct burried (meaning running cable in direct burried PVC duct) configurations, what would you recommend and why?

I understand the mechanical protection a concrete encased duct bank provides, but if the code allows both - the direct burried option seems more economic method.

I would also like to know how condensation is dealth with in underground ducts? I understand that the cable is rated for wet location, but how does one deal with moisture build up in the ducts?

Thanks.

 

[mkgrady]

Say you are subfeeding a new building (bldg A) from and existing building (bldg B), but to do so the feeder needs to cross a road (future road) to reach the new building. The existing bldg already has direct burried PVC ducts stubbed out from the electrical room. The code in the area allows for either concrete encased duct bank or direct burried (meaning running cable in direct burried PVC duct) configurations, what would you recommend and why?

I understand the mechanical protection a concrete encased duct bank provides, but if the code allows both - the direct burried option seems more economic method.

I would also like to know how condensation is dealth with in underground ducts? I understand that the cable is rated for wet location, but how does one deal with moisture build up in the ducts?

Thanks.

You answered your own question about concrete encasement of ducts. It costs more but provides more.

Underground electrical conduits are generally full of water from condensation and or seepage from the surrounding wet ground. This water can be made to run out of the pipe by running it pitched like a drain pipe but the wire is supposed to be rated to be in a wet location so there is no real harm.

 

[GoldDigger]

...This water can be made to run out of the pipe by running it pitched like a drain pipe but the wire is supposed to be rated to be in a wet location so there is no real harm.

Just make sure that it will not cause problems where it runs out the end of the pipes. (Have seen some nice pictures on that subject here.)

 

[Hv&Lv]

I like to pour flowable fill over my duct when I don't just direct bury it. It keeps me from having to worry about tamping a ditch and the engineers are happy to see it, plus the cost is cheap enough to justify it.
Another bonus, if there is ever a need to get back to it, it doesn't take a jackhammer to reach the pvc.

 

[ElectDesigner]

I like to pour flowable fill over my duct when I don't just direct bury it. It keeps me from having to worry about tamping a ditch and the engineers are happy to see it, plus the cost is cheap enough to justify it.
Another bonus, if there is ever a need to get back to it, it doesn't take a jackhammer to reach the pvc.

Thanks for the tip.