Conduit Fill

[augie47]

Where am I making my mistake ?
Given 3" Sch 80 PVC and 600kcmil Cu.
I was asked how large a conductor I could add given 3 conductors in the conduit.
Table C9 shows 3 600 kcmils allowed in a 3" Sch 80 but when you go back and do the math using Chapter 9, (3) 600 kmil THWNs have a combined area of 2.6028 which exceeds the Table 4, over 2 wire, available area of 2.577.

 

[wwhitney]

Note 7 to the Chapter 9 Tables allows rounding up the allowable number of identical conductors when the first digit after the decimal place is 8 or 9. 2.577/0.8676 = 2.97, so it gets rounded up to 3.

Cheers, Wayne

 

[jumper]

Good catch Wayne. My math matched Gus and I was "huh?".

 

[K8MHZ]

edit

 

[Dennis Alwon]

That part gets everyone. When I was doing the tables for Annex C I had to come here and ask how to make my formula round up from .8 instead of .5

 

[augie47]

Thanks

 

[Little Bill]

Where am I making my mistake ?
Given 3" Sch 80 PVC and 600kcmil Cu.
I was asked how large a conductor I could add given 3 conductors in the conduit.
Table C9 shows 3 600 kcmils allowed in a 3" Sch 80 but when you go back and do the math using Chapter 9, (3) 600 kmil THWNs have a combined area of 2.6028 which exceeds the Table 4, over 2 wire, available area of 2.577.

By letting someone ask an old person to do math!

 

[augie47]