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Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

(OP)
Is the following permissable:

A concrete, below-ground, ductbank system made up of PVC conduit.  At every point of stub-up, a transition from PVC to RMC is performed.  The RMC will have a grounding bushing on it and it will be connected to the system ground grid.  Is this an acceptable installation?  Note, each piece of equipment has its own ground.  Any motors will also have a dedicated stringer to the system ground grid.  

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RE: Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

Assuming you are in the US:

RMC = Rigid Metal Conduit??

It it fine to transition to steel conduit as you propose.  For grounding, all circuits should have a ground wire running with the phase conductors.  As a practical matter, if you are coming up through concrete, the interface between conduit, concrete and air is a prime spot for corrosion.  I'd recommend PVC-coated rigid steel conduit.  We normally use a coated steel elbow to make this transition.  Motors need a grounding conductor with the phase conductors in addition to any direct connection to the ground grid.

 

David Castor
www.cvoes.com

RE: Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

(OP)
Hi David.  Let me begin by saying "thank you."

Yes, by RMC I mean rigid metal conduit.  
Yes, all circuits will have a ground wire.
Thanks for the recommendation regarding corrosion.  It is duly noted.

RE: Going from PVC (concrete ductbank) to RMC (stubups/aboveground)

Another way to combat corrosion at the concrete/air/conduit interface is  wrap anti-corrosion tape around the conduit for a distance above and below the stub up point.

The tape is usually sold for protecting underground pipes.

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