The GE microwave may be tripping the breaker when the door is opened because there are other appliances on the same circuit that are in use at the same time. Because a microwave requires a significant amount of current, it should be placed on a separate circuit. If not, operating the microwave along with other appliances, such as the refrigerator or toaster, will either trip the breaker or blow a fuse.
An issue with the breaker itself may be causing it to trip when the microwave door is opened. Breakers have a limited lifespan and begin tripping more frequently when they are near the end of their life expectancy. Bob Vila states that many microwaves use 15 amp breakers, but recommends replacing them with 20 amp breakers for better performance —if you are using at least 12-gauge wiring.
The wiring for the circuit breaker may be causing it to trip when the microwave door is opened. Wiring less than 12 gauge may not be sufficient for operating some microwaves. For example, at least 10-gauge wire should be used for 30 amp breakers; at least 12-gauge wire should be used for 20 amp breakers; and at least 14-gauge wire should be used for 15 amp breakers.
A problem with the microwave’s door switch can also result in a tripped breaker when the door is opened. A microwave door has up to three switches. Take out each switch — but leave the wires intact — and push the tab on the switch to hear it click. You will be able to recognize the faulty switch because it will not click.