I have seen heat damage once in a bundle, but the case was extreme.
3' of bundle in 42 circuit panel (All of the circuits), 2' bundled in 2" EMT, another 2'+ bundled in a gutter, essentially 5-6' of the same conductors tightly bundled. They were pretty warm, and all the whites had yellowed, and insulation crispy long before thier time. They must of thought it looked real nice when they closed it up.
So yeah, I too don't like bundling in the panel, and consider it part of the 24" if it is done. I always bundle grounds and neutrals (24"), but leave the hots free. And will often cut the hots loose when I see it done by someone else.
[This message has been edited by e57 (edited 12-12-2004).]
"Well - I oughta....." -Jackie Gleason