My guess is that it would be because 2 wires together that took up 40% fill may be too tight to pull through a conduit because they would be like >> oo or 8 << and together might approach the inside conduit diameter with the 40% fill limit. It would be a tight one for sure! Straight pulls might not be so bad, but 360 degrees would be another thing.
Does that make sense?
Bill
[This message has been edited by Bill Addiss (edited 10-16-2001).]