Locating a neutral buss bar

I see this problem a few times a year. One of the neutral wires (usually the one for the Air-conditioning circuit) gets a little loose and this generates heat. The buss bar is riveted to the plastic housing that contains all the AC breakers and fuses. It is typical to see 4 or 5 other neutral wires that also have the white wire coating burned or melted.

I normally have to shorten all the neutral wires to get good wire. This sometimes turns into a big job because I have to pull all the 120VAC farther into the main distribution box. Then I end up shortening all the wires because of the excess ground and black wiring.