Voltage drop

[Obed.T29]

Hello I’m having issues with de rating here
Engineer wants :
•0- 75ft
4-6 CCC’s =12 awg
7-9 CCC’s = 10 awg
10-20 CCC’s =8 awg

•75’-150’
4-6= 10 awg
7-9= 10 awg
10-20= 8awg
•150’ +
4-6= 8awg
7-9= 8awg
10-20=8awg

There’s 1” emt
5 20amp 10awg circuits = 10 ccc’s
1 15 amp 240 10 awg = 2 ccc’s
This is a multifamily

 

[JoeStillman]

Looks like he derates using the ampacities in the 90°C column and the adjustment factors from 310.15(B)(3)(a). In your 1" EMT, the 10awg has a starting ampacity of 40A. With 12 CCC's, the adjustment factor is 50%, so you're good for 20A circuits, and certainly good for 15A.

My question is why is all this in one pipe, and not NM cable?

 

[Obed.T29]

Looks like he derates using the ampacities in the 90°C column and the adjustment factors from 310.15(B)(3)(a). In your 1" EMT, the 10awg has a starting ampacity of 40A. With 12 CCC's, the adjustment factor is 50%, so you're good for 20A circuits, and certainly good for 15A.

My question is why is all this in one pipe, and not NM cable?

It’s a take over job. Engineer is also accounting for 3% voltage drop which is why they mention 8 awg.