No there is not any code, but there are standards on conduit spacing. The U.S. Iron and Steel Institute has the best chart. I'll look it up in a little while and try to post it to this thread.
Leo G said:
Is there a minimum space that I can have between conduits?
Leo G said:
How many 12AWG THHN wires can I put into a 3/4" conduit, 1/2" conduit? I know it is 40% the cross sectional area of the conduit but I don't know the size of the wire with the insulation on it.
For 3/4 you can have up to 16 #12 THHN's. For 1/2 you can have up to 9 #12 THHN's. When you start to fill a pipe this full, you get into concerns about derating the conductor's ampacity. When you have more than 3 current carrying conductors (hots and neutrals, not grounds) in the pipe, it builds heat. This causes a #12 conductor to be rated at less than 20 amps under certain circumstances, depending on how many conductors you fill the pipe with.
Leo G said:
Do I need to run a neutral for each hot in the conduit? Or will one take care of all the hots. (I think it's got to be one for each hot)
For a single phase panel, two hots on different phases can share one neutral. For a 3 phase panel, three hots on different phases can share one neutral. If all your hots happen to originate on the same phase, then each need their own neutral.
Leo G said:
No problem Leo. The bill is in the mail.