For today’s job, I was called out to troubleshoot a loss of power in several rooms of the home. Upon inspection, I determined that only half of the power in the electrical panel was present. One leg of the 120V supply was missing, resulting in half of the breakers not working and all 240V two-pole breakers being inoperative. To verify the source of the issue, I checked the voltage at the line side of the meter to rule out a power company problem. The line side and feeder side of the main breaker showed correct voltage; however, the load side of the main breaker was only outputting 120V across both lugs. Additionally, the main breaker was producing a noticeable internal buzzing sound. These findings confirmed that the main breaker had failed. The scope of work included providing and installing a new main breaker at the meter location. After installation, all voltages were re-tested at both the meter and the panel, and the electrical system was restored to proper operation