Quote Originally Posted by hhsting View Post
Halcyon linac Manufacturer instruction does not indicate to use PVC or metal conduit. It says provide 2 two inch conduit for power.

In the cable/conduit of the instruction section says all conduit runs underground shall be dry and watertight. Therefore, all PVC pipes must be glued together, and metal conduits must be properly sealed.

It further says route conduit from the panel to floor pit of linac and provide appropriate fitting to connect the linac manufacuter provided with machine flexbile metal conduit (FMC). The FMC will route the 3 phase and ground power wires in the floor up to the stand PDU.
That's a little different than the accelerators I've seen. They are usually provided with special cables that are provided by the manufacturer that run up to the base. No telling exactly what is in those cables - it could be a mix of power and control wiring.

In your case, since the contractor is providing a FMC cable to take power clear into the base, that does sound more like a branch circuit or feeder. I think I'd error on the side of caution and use some type of metal conduit, like IMC.

The ones I have seen also say to make the conduit watertight - which just isn't possible because water will condense inside the conduit from temp. changes. Per the NEC, the inside of any underground conduits are wet locations. I guess one could seal the conduit ends, but that might just trap more water inside the conduit.