Nipple fill 60%

[Therealcrt]

Just doing a for fun equation.

3” EMT nipple (under 24”)
Conduit fill is 60%
#12 THHN conductors

60% fill of 3” emt over 2 wires is 5.307in squared

#12 THHN area for 1 is 0.005in squared

So how many conductors can I fit without exceeding the 60% fill

 

[Therealcrt]

Typo… #12 is 0.0133in squared sorry

 

[wwhitney]

60% fill of 3” emt over 2 wires is 5.307in squared

5.307 in^2 is 60% of the total area of 3" EMT, so you have the right number, but the way you worded it is confusing. Because normally in this context "over 2 wires" means a condition where you get to use 40% fill, whereas you have a condition where you get to use 60% fill.

Typo… #12 is 0.0133in squared sorry

So now all you have to do is divide. : - )

Cheers, Wayne

 

[kwired]

divide your allowable fill by fill per conductor

I get 399 conductors (with your numbers) Better make each one a different color so you can differentiate them at each end.

 

[infinity]

Table C1 lists #12 for 266 conductors in 3" EMT which would be 40 % fill. 60% fill would be 50% more or 133 more conductors. So 266+133=399.

 

[electrofelon]

I get 399 conductors

Are you allowed to round up to 400? I like to pull MWBCs and need 100 of them.....

 

[Tulsa Electrician]

Table C1 lists #12 for 266 conductors in 3" EMT which would be 40 % fill. 60% fill would be 50% more or 133 more conductors. So 266+133=399.

That's so funny.
I remember my father teaching me as an lad.
6/4=1.5 (.60/.40)
I was so confused when he said it's 50% more.
266*1.5= 399
I swore it was only 20% more.
266*1.20 = He laughed and now I get to as well, I sure miss him.

Thank you for that.

 

[infinity]

That's so funny.
I remember my father teaching me as an lad.
6/4=1.5 (.60/.40)
I was so confused when he said it's 50% more.
266*1.5= 399
I swore it was only 20% more.
266*1.20 = He laughed and now I get to as well, I sure miss him.

Thank you for that.

You're welcome. I'm a path of least resistant guy and I loathe the conductor property tables. Looking up the 40% fill in C1 and adding 50% just seems easier.

 

[kwired]

Are you allowed to round up to 400? I like to pull MWBCs and need 100 of them.....

I've likely violated the 60% fill a time or two. Not so bad with straight nipples but can be fun with offset nipples.

 

[Carultch]

There is a blindspot in the 60% fill rule, for 2 conductors. Since it is impossible to pack 2 identical circles in the same circle to more than 50% fill by area, you wouldn't be even able to fit them with a 60% fill. By the logic behind the 60% fill rule, it really should be a 41% fill for 2 conductors. The typical fill limits represent about 75% diametral fill, and the 60% fill rule represents about 90% diametral fill.

 

[electrofelon]

There is a blindspot in the 60% fill rule, for 2 conductors. Since it is impossible to pack 2 identical circles in the same circle to more than 50% .

Not if you use oval or elliptical raceways

 

[kwired]

There is a blindspot in the 60% fill rule, for 2 conductors. Since it is impossible to pack 2 identical circles in the same circle to more than 50% fill by area, you wouldn't be even able to fit them with a 60% fill. By the logic behind the 60% fill rule, it really should be a 41% fill for 2 conductors. The typical fill limits represent about 75% diametral fill, and the 60% fill rule represents about 90% diametral fill.

Assuming both conductors are identical diameter. Though if both carrying same current they sort of should be if they are same conductor type.