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EMT coupling

Merry Christmas
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
don_resqcapt19 said:
NM is safer than MC only in the amount of toxic gasses when the cables are involved in fire.
Click to expand...
Perhaps you meant the opposite, MC is safer than NM in the amount of toxic gasses released when burning?

Seems like the wire insulation could be the same, so the difference is attributable to the non-metallic jacket. Southwire 12/2 NM has outside dimensions of 418x179 mils, and the jacket is 30 mils thick. Treating that as a rectangle, the approximate cross-sectional area is about 418*179 - (418-2*30)*(179-2*30) = 32,220 sq mils. [An overestimate geometrically, as it's more of a racetrack shape.] While the insulation on the conductors is 19 mil thick, with the conductors 81 mils in diameter [note 179 = 30 + 19 + 81 + 19 + 30], so the two insulated conductors have a cross-sectional area of 2 * pi/4 * (1192-812) = 11,938 sq mils. So it is true that the jacket uses almost 3 times the plastic as the conductor insulation does.

Cheers, Wayne
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
wwhitney said:
Perhaps you meant the opposite, MC is safer than NM in the amount of toxic gasses released when burning?

Seems like the wire insulation could be the same, so the difference is attributable to the non-metallic jacket. Southwire 12/2 NM has outside dimensions of 418x179 mils, and the jacket is 30 mils thick. Treating that as a rectangle, the approximate cross-sectional area is about 418*179 - (418-2*30)*(179-2*30) = 32,220 sq mils. [An overestimate geometrically, as it's more of a racetrack shape.] While the insulation on the conductors is 19 mil thick, with the conductors 81 mils in diameter [note 179 = 30 + 19 + 81 + 19 + 30], so the two insulated conductors have a cross-sectional area of 2 * pi/4 * (1192-812) = 11,938 sq mils. So it is true that the jacket uses almost 3 times the plastic as the conductor insulation does.

Cheers, Wayne
Click to expand...
I posted it backwards...
 
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