In this panel there is 100 amp service, single phase, where the 3 main wires (2 hot, 1 neutral) running into the panel are aluminum.
There are 6 breakers total, running horizontal, which is the max (2- 20 amp, 4- 15 amp).
The 20's are on the far left and right side of the row of 6 breakers.
The neutral bus runs horizontally on top of the 6 breakers.
One of the cables leading into the box contains a black, white and red wire, the rest just have the black and white.
From the cable that contains the black/white/red wire, the black connects to the far left 20amp breaker, and the red connects to the 15 amp breaker that is 4th from the left, while the white goes into the neutral bus.
The 5th and 6th breakers (on the far right) appear to handle numerous outlets. In fact, most of the apt. lighting is handled through #6.
The problem is that the main neutral wire is heating up to the point of melting the wire insulation (mostly at the lug and a bit more beyond it). This happens when a decent amount of lights are on, and even more so when the A/C is on (A/C is on the 4th breaker, on its own circuit), but noticed it happening with other applicances on.
All connections have been tightened.
The neutral has been cleaned off and reterminated.
Any ideas? New box? Its an old Sq-D.