wire fill calculations

[thejobjarinc@yahoo.com]

what is the purpose of a wire fill calculation, and were can i optain offical ruling on this matter

 

[Cavie]

Wire fill calcs are ment to allow you to only fill a conduit up to a given % of cross section area of a given size conduit with a given size wire to prevent overheating of the conductors. The conduit fill and box fill charts in the NEC do the Calcs for you.

 

[480sparky]

Wire fill is not devised to protect against overheating. That is the purpose of derating.

Wire fill is simply how many little circles (wires) can you fit into a big circle (raceway) without damaging any of the little circles in the process.

Annex C and Chapter 9, tables 4 & 5 is where you want to go.

 

[celtic]

Wire fill is simply how many little circles (wires) can you fit into a big circle (raceway) without damaging any of the little circles in the process.

Mind if I "borrow" that ?

 

[480sparky]

Mind if I "borrow" that ?

Go ahead. It's not mine anyway. It came from my 4th-year teacher.

 

[celtic]

It came from my 4th-grade teacher.

He's a genius!


(never mind the flagrant mis-quote :grin: )

 

[JohnJ0906]

what is the purpose of a wire fill calculation, and were can i optain offical ruling on this matter

"Official ruling"? Why would you want/need one?

 

[480sparky]

He's a genius!

He's also on a CMP.

 

[celtic]

He's also on a CMP.

Have you suggested he use that verbage in future editions of the NEC?
:grin:

 

[480sparky]

Have you suggested he use that verbage in future editions of the NEC?
:grin:

Hmmmmm, I can just image the question now:

"Hey, boss, how many 12 THHN little circles can I put in a 1" EMT big circle?"




His favorite story (as I remember it):

Two electricians retire and become ranchers.

Both were contemplating a name for their ranch that not only reflected their careers, but also to show they are better than the other.

One names his ranch 210.1.

So the other one names his ranch 210.1(B).

So the first one renames his ranch to 210.1(B)(4).

Then the second one ranames his ranch to 210.1(B)(4)(U).

So the first one renames his ranch again to 210.1(B)(4)(U)(2).

 

[danickstr]

BTW what year did thhn fills on 1/2" emt go to 9 from 7?

 

[480sparky]

It was 9 in the '96, and 7 in the '99.

And the '96 was the first to have the 10 tables for raceway fill.

 

[infinity]

BTW what year did thhn fills on 1/2" emt go to 9 from 7?

What size conductor? The 1993 says that you can fit 10-#12 THHN conductors in a 1/2" conduit when the trade size was all that was used and not the specific raceway. The 1996 says 9-#12 THHN in 1/2" EMT, 2005 says the same thing.