+ 1 Hotline the cover is an important part, in the example if the cover were metal it likely would have caused the breaker to trip as soon as the plastic melted away, thus eliminating the heat source. Also the cover limits the air supply in the box(duh) and attempts to smother the fire. How many j-boxes have you opened that had charred connections? Twist the joint tight, use a listed connector, and put a cover on it!
Jimmy
Life is tough, Life is tougher when you are stupid
