I'm not familiar with AWG cable sizes, difficult for me to tell if sizing is ok or not.
Did these noises and over-heating appear only recently? If yes, did anything change in your installation recently?
Some extra questions:
– Do you know the actual (rms) current going through this breaker? What kind of loads are fed by this CB ?
– Do you have the possibility to make an infra-red measurement, to show the temperature values around this CB ?
– Is there any relation between this CB and the transformer you mention in your other topic, which also makes noise? Is this CB fed by this transformer? How are they connected together, cable or busway?
What I'm thinking about is that you might have a high level of harmonics in your installation, which could be a reason for vibrations and over-heating. Or maybe a connection getting loose…