th111447 said:
I was planning on running 1/0 URD from my house to my pole barn located 125 ft away to install a sub-panel in the barn. I've dug the trench and there is a lot of rock so I'd like to put it in conduit.
This reply is late in the game, but I think the fact that there is a lot of rock has been overlooked, and that simply putting the cable in the conduit is not the fix all.
I think it needs to be pointed out that the rock can pose a problem for non-concrete encased PVC conduit. Especially where it will be buried in a location where traffic or heavy equipment will be driven over it.
352.12 says it is not acceptable for use where subject to physical damage.
Going back then to 300.5(D)(4) and 300.5(F), provisions need to be made for protection of the cable and conduit.
Rocks and other debris can cause damage to the point that they penetrate the conduit, piercing the insulation, and ultimately causing failure of the cable. Hence the NEC requirement for clean fill material around the conduit, not just in the bottom of the trench.