Conduit fill with XHHW with #6-4 conductor cable, and THANKS!

[JasonMT]

Im trying to figure out the correct conduit size (schedual 40 PVC) to use with a 4 conductor cable. The cable contains 4 #6 XHHW-2 conductors. I know that Nec says: A multiconductor cable or flexible cord of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. I measured the cable, It measures 5/8 of a inch, and is perfectly round. I used the formula, A= 3.14* R squared. Which comes out to be 1.23 inches squared. Chapter 9 tables tell me schedual 40 PVC with one wire 53%. So I used this column which I came out with 2 inch PVC= 1.744 In. Sq.. 1 1/2 = 1.052 In. Sq.. 1.23 In. Sq. is between these 2 numbers. So I should use 2 inch sch 40 PVC. Is This correct?

I also recently passed my state Journeyman test recently. I used this site for studying for the exam. I had alot of questions. That alot of people helped me with. I just want to say thank you for your help.

 

[ActionDave]

What are you working on and why are you using conduit with cable in it instead of individual conductors?

 

[JasonMT]

I work in substations for a Utility. The Nec does not apply there. I try to use it on every thing I do there. The cable is installed in trend way. Its what they used for every thing. The trend way tends to fill up with water. So I cant convert it with a J-Box. I have to pull it through the trendway then through a pipe that plugs into the trend way, to the first Box that serve the yard lts.

 

[Dennis Alwon]

I believe you calculated the fill correctly..:thumbsup:

 

[GoldDigger]

Are you using 5/8" as the radius rather than the diameter in the area formula? A diameter of 5/8 inches will not give you more than 1 sq. in. of area!

 

[JasonMT]

Opps. Yes I did. I will recalculate. 2 inch seemed a little big. Nice catch.

 

[JasonMT]

Now when i recalculate my mistake, it says I can use a 1" pipe. The cable is pretty tight going through a 1" pipe. Plus I have to use a blanket heater to bend it around the concrete going up to the first lt box. Theres no way 1 inch pvc will hold its form after those bends.

 

[ActionDave]

I work in substations for a Utility. The Nec does not apply there. I try to use it on every thing I do there. The cable is installed in trend way. Its what they used for every thing. The trend way tends to fill up with water. So I cant convert it with a J-Box. I have to pull it through the trendway then through a pipe that plugs into the trend way, to the first Box that serve the yard lts.

Go forth and boldly calculate away then.

I try to avoid cable in conduit calculations by never doing something where I need to do them.