Today I was called out because the breaker for the oven was tripping. Upon diagnosis, I discovered that the cord on the oven is not wired properly and also did not have a connector. I rewired the cord and installed a connector and tested the oven. Everything is working properly. While I was working, I examined the main electrical panel and found a 15 amp wire on a 20 amp breaker. this is a safety issue because the breaker will allow the wire to pull more power than the wire can handle. Causing overheating, damage and potentially injury. I changed the breaker to the proper size. The breaker that I replaced (according to the panel cover) is circuit number 19. From an electrician standpoint going from the top right down it is circuit number 12.