600A Service.
I only have two 3" conduit runs between the MD and ATS
Can I run two complete 350mcm cu sets (L-L-N), one in each of two 3" conduits or am I required to use 3 pipes with each current carrying conductor pair in a separate pipe?
Thanks in advance.
Generally, it is precisely the way you should plan to run it, by running run at least one of each "color" in the same conduit. By "color", I mean phase, polarity, neutral, EGC, and anything else that may distinguish one wire's purpose from the others. Each kind of wire becomes what it would need to be for its share of the amperes, with the exception of the EGC being a full size EGC as it would need to be for the full 600A rating.
This way the magnetic fields surrounding the conduit will balance to zero, and you don't end up with issues magnetizing steel conduit or steel conduit components (even steel locknuts on PVC conduit).
You can put multiple parallel sets in the same conduit, with only one full size EGC per conduit, provided that all parallel conduits have the same number of sets in it, so that they each have the same thermal condition of use. For instance, given three sets, you cannot put 2 sets in 1 conduit and 1 set in the other. But given 4 sets, you could put 2 sets in each.
There is an allowance for isolated phase installations, all underground and all non-metallic conduit, and it has its own set of context rules based on the fact that magnetic fields arise from isolating the phases.
