I am wondering if there is a minimum space required between rigid steel conduits installed in a new trench. I was reviewing annex B of the NEC but am not sure if those specified distances are an installation requirement for physical conduit clearances or for the calculation of conductor ampacities. We are clear on the ampacities but not sure on the physical clearances required. We work off of engineered drawings for the most part that details the trench and conduit but this time the engineer stated something like; install conduits in trench per code and reiterated that verbally when asked. The application is (1) 4? RSC and (1) 3? RSC to be installed in a common trench. They both are 3 phase 4 wire with 5th conductor as grounding conductor. They will be installed side by side on the same plane of the trench buried at 24?. There will be no other cables, conductors nor conduits in this trench. The voltage of both of these are 120/208 volt.
Thank you
Thank you