conduit fill

[mjac]

How can I figure out how many 12-2 romex cables can be ran through a 4" pvc schedule 40 nipple? The nipple is going into a 10"x10"x15' troff for lighting control circuits.

 

[iwire]

Re: conduit fill

I would cut myself a pile of 12" pieces of the wire stick them in the pipe and just see what looks good.

How long is the nipple?

Less than 24"?

 

[ryan_618]

Re: conduit fill

I am assuming that an NM cable is about 3/8" wide, or .375 inches. Notes 5 and 9 of the chapter 9 tables must be used.

So, pi*R(sqaured)=circle area. 3.14*0.140625=0.4417" of area. We go to table 4 and find the schedule 40 table, and go to the nipple part of it (assuming less than 24"). 7.532 is the allowance of space in the nipple. 7.532/0.4417=17 12-2 NM's permitted.

 

[ryan_618]

Re: conduit fill

Or save yourself a bunch of math and do what Bob said!

 

[mjac]

Re: conduit fill

The nipple is less than 24". However I like the idea of cutting 12" pieces of romex to see how many will fit, probably easier than doing the math.

 

[don_resqcapt19]

Re: conduit fill

You still have to do the math!! Nipples no longer have an "all you can fit" fill rating. They are limited to a 60% fill. See Note 4 to Chapter 9, Table 1.
Don

 

[iwire]

Re: conduit fill

Don I was not suggesting to cram the pipe, I have a pretty good eye for 40% fill, which is where I like to stop anyway.

Just try filling a pipe to 60% fill it is not as easy as it sounds.

 

[ryan_618]

Re: conduit fill

I had someone send me a PM regarding my math. In my example, I mistakenly used the diamter as the radius in my formula. I should have used 0.1875 for my math. This would result in an area of 0.110 per conductor. 7.532/0.110 would result in an allowance 68 12-2 NM cables allowed.

When I did the math, I thought my answer looked low...I should have double checked it!!!

 

[mjac]

Re: conduit fill

Thank for your help.

 

[mjac]

Re: conduit fill

Correction: Thanks for your help