Headdog
Member
- Location
- Central Florida
We have a project that requires us to attach to two separate, existing, 480VAC 3-phase, 75hp motor circuits (at the existing motor control enclosure) and run each circuit through a trench to a new location about 350 feet away. I believe I have correctly calculated the required minimum wire size(s) assuming I use two individual PVC conduit runs for each separate "circuit" (3 phase wires and a neutral or grounded neutral).
The conduit runs will be encased in concrete, in a trench that is 30" deep (conductors are 24+ inches below grade).
My questions are:
1). How do I know (or calculate) the required separation distance to maintain between the two conduit runs (with or without the concrete)?
2). I know I must de-rate the current carrying capability if I combine these two circuits (i.e. putting 6 current carrying conductors and two neutrals together). Is that acceptable to do under the NEC, or must I stick with two separate conduit runs in parallel?
The conduit runs will be encased in concrete, in a trench that is 30" deep (conductors are 24+ inches below grade).
My questions are:
1). How do I know (or calculate) the required separation distance to maintain between the two conduit runs (with or without the concrete)?
2). I know I must de-rate the current carrying capability if I combine these two circuits (i.e. putting 6 current carrying conductors and two neutrals together). Is that acceptable to do under the NEC, or must I stick with two separate conduit runs in parallel?