derating is giving me a headache....

[flexloop]

I'm buying supplies for a big job and an trying to figure out how big my conduits need to be. I'm a GC and my conversations with my electrician are not giving me a better understanding, and reading NEC is only making things worse.

I have long runs that contain 6 circuits each: 5 20A circuits for outlets in a bathroom and 4 bedrooms and 1 15A lighting circuit for all 5 rooms. I'd like to use 1" FMC and NEC says I can have 24 of #12 thhn so at 18 I'm ok.

Do I need to do ampacity derating? The electrician said yes so I read NEC and am quite confused. I don't know what people are going to plug in to those outlets.

Any thoughts?

Thanks!

-Flex

PS: My first post so let me know if I'm in the wrong forum.

 

[Little Bill]

What you have can be quite confusing as you have both conduit fill and derating. You need to trust your electrician and let him figure out what is needed. Forum rules prevent us from assisting those not in the industry.