Need some Power Center help!

enbethlen covered the most important parts but you also want to check the connection of the main neutral (white) to the new bus bar. If the main neutral has become loose, it will offer a lot of resistance so that anything connected 120V AC in your rig will have to overcome that resistance. If you've already tried stripping and reconnecting to the neutral bus, it's definitely replacement time.

Look closely at the power section. You may need to only replace the neutral buss bar. You can get them at most hardware stores or electrical supply house.
Melted wires are mainly a sign of a loose connection. The neutral buss bars are commonly aluminum. The wire is copper. This is considered dissimilar metals and requires the use of an electrical de-oxidation grease.
If you have sufficient slack in the conductors cut the bad ones back to a point where there is good clean fresh copper, install the new neutral buss and re-terminate the wires applying a good coating of de-ox grease.

Hi,

There is too much voltage drop. The low voltage is drawing too many amps.

Continuous load on a 15 amp circuit should only be 12 amps.

Your problem is the plain fact you are overloading the circuit. You CANNOT run a RV AC unit on 15 amp service like you are doing. When you do this, SOMETHING has to give from the heat build up and it is obvious your wiring at the breaker panel is taking the hit. If you did a full research on these forums you would see that trying to run a RV AC unit adapted down to a 15 amp circuit is not the right thing to do. The odds are your buss panel strips in the panel box have oxidized and cannot get a good tight connection when you try to secure the bare wires in the slots/holes. As another poster stated, you need to replace the 120 breaker box panel, cut back the Romex wiring until you get GOOD non burnt wires and secure, then NOT run the Units AC on that house circuit. Doug

Wow!

I very strongly suggest you replace that load center completely, including the breakers, and a good length of the wires leading into it. The neutral bus has clearly gotten extremely hot, and may be compromised in ways that cannot be seen. It's hard to know what may be happening to the other components, too. Please don't use the AC electric system in the RV until it's been completely taken care of; that's a fire waiting to happen.

Heating can often be caused by a poor or loose connection. If the connection has a (relatively) high resistance, there is a fair bit of power being dissipated in a small area when there's a heavy current flow. Maybe the connections were not torqued down properly or worked their way loose, or the contact surfaces weren't clean.

Alternately, is there something that might produce heat next to the load panel? Is there a wire that runs there that may be is pinched or chafed?

Also, is the outlet in the house a working GFCI, and have you verified that it's wired properly? If there's a ground fault in the RV somewhere, and a hot/neutral reversal in the outlet, you could end up with trouble (that bypasses the RV load center breakers).