I have a Square D box with 100 amp service. Everything has worked fine for the 12 years I have been here and for a total of 25 years between the last person here and me. An unlicensed electrician putting in GFI's, intentionally shorted out an outlet with a jumper wire to trip the breaker. That seemed like a bad way of doing things. It tripped the breaker for that outlets circuit as well as the main breaker. With the main breaker off there were still some lights on in the basement. Obviously if the main breaker is off nothing should have power. I told him the main breaker was probably old and by shorting out the outlet like he did, it tripped the breaker. He was trying to tell me I need a new circuit breaker box and rewiring for $850 to $1500. I sent a picture of my opened box to a licensed electrician to verify that I just need a new main breaker (about $27) He concurred and said that main breakers can cause this by not shutting off all the way more or less. My picture of the box is too big for this post. If you want to see it I can email it to you. Can you give me your opinions please?