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Hi,

I was wondering if anybody could explain why (per Chapter 9 Table 1 & 4) you are allowed a greater % of conduit fill for Over 2 Wires than you are allowed for 2 Wires.

Seems counter-intuitive, doesn't it?

I understand the concept of "jamming" explained in FPN No. 2, but as that is fro 3 conductors, I don't think it applies here.

Can anyone explain? I'd be interested to know.

Thanks!
 

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One might be able to run a smaller conduit/raceway even verses the individual fill for a single wire or two.

One will use 40% in the trade than the other two, they are there for purpose and of course safety.

They have experimented and cooked many a wire set up and came down to theses numbers from testing. Sure go a little farther in the Code Book in Annex A, it lists all the UL associations in our Code, and in Article 90(D) Relation to other International Standards.

ANSI, IEEE, and other testing and other professional organizations are also used in the CODE.

This all comes down to what the mean average gave through the use of physic's (physical properties) gave as the answer.
 
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