Conduit Spacing (and More)

Leo G

Is there a minimum space that I can have between conduits?

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.

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)

Thanks (MD or SP)

Leo

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Custom Cabinets in Hartford County Connecticut

mdshunk

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.

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.


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.

No problem Leo. The bill is in the mail.

mdshunk

To use the chart, do as follows. If you have, for instance, a 1" conduit next to a 1/2 inch conduit look up 1/2" on the top of the chart and 1" on the left hand side. You can see that the proper spacing is 1-3/4" apart CENTER TO CENTER.

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Leo G

OK MD checks in the mail!!:Thumbs:

__________________
Sawdust Follows Me Everywhere

http://lrgwood.com
Custom Cabinets in Hartford County Connecticut