I got a call in the middle of the night that there was smoke coming out of the home owners mechanical room. Upon arrival pulled the cover off the unit and the contactor, a factory made up item had literally over heated and had melted wire that ran from the load side about 6 inches. Did not short out, but didn't blow the fuses in the disconnect. The wires ran through a Plastic grommet and never made contact with the casing. The over heating caused the main 200 amp. breaker to trip. The fuses are sized correctly, 50 amp. time delay but didn't blow. The disconnect is just a fuseable 2 pole 100 amp disconnect. What additional over load can be used here if any? The HVAC Tech. said a loose connection probably was the cause.