medium voltage duct bank

[mshields]

I'm dealing with a contractor who is looking to cut every corner he can evidently. My clients PM just inspected a new 35kV ductbank pre-pour and found that contrary to our detail showing lots of reinforced rebar and a continuous ground conductor, the contractor merely had the Carlon spacers and the schedule 40 PVC.

He then pointed to a spec section that didn't make clear what the rebar requirements were. I have no doubt that I own what we need here as per our detail. My question for the group is; isn't this just plain old not acceptable for a medium voltage ductbank. And assuming it is, what code or standard may I point to where this is defined?

Thanks,

Mike

 

[MEP_PM]

Most spec?s have general language that states if there is a conflict between the drawing and spec?s you must follow the more stringent. Beyond that what is the purpose of the rebar? My understanding is it?s to add strength for protection of the feeders. My experience has been if the ductbank is more than a couple feet wide (with or without rebar), you have to try pretty hard or have a really big excavator to damage it. I guess soil conditions and seismic requirements may also be consideration. With that said, I?ve seen it done both ways, more so without rebar. I have also watch the utility company direct bury their primary feed to the edge of the property line then pull the rest of the way in duct bank provide by the building project. At that point the ductback seemed like a waste if the whole service wasn't protected.

 

[masterinbama]

If your detail shows a certain rebar layout, the contractor must follow it.

 

[mkgrady]

I have installed miles of mv duct bank without rebar or ground wire. You have to look for what the contract calls for when there is a conflict in the documents. Often there is something called an order of precedence which could resolve a conflict.