In May of 2006, I installed a 50 amp circuit for a spa in a 100 amp Bryant meter distribution panel with pop-in breakers. I noticed at that time that the main breaker body had melted around the areas that clip onto the buss on both phases. I replaced the main breaker. On 8/25/06 I got a call to the same residence that there was no power to the house. When I arrived on site, I noticed the same problem with the main breaker. I changed the main breaker again, and went back on 8/26 to inspect, and already noticed that heat damage was starting to occur. Besides the usual convenience lighting and regular household circuits, the only large amperage draws are for a 30 amp oven circuit and a 40 amp AC circuit. Customer keeps AC circuit off and cools his house with 2 120 volt evaporative coolers powered by existing plug circuits. No individual circuits trip and all other breakers appear to be in good condition. My theory is that there is too much load on the buss system, collectively from all circuits, and it is causing the buss to overheat. I reccommended that the customer upgrade his service to 200 amps. Am I on the right track, or am I missing something?