Would 12 ga wire allow a microwave to draw more amperage than 14 ga wire? I had a microwave on a shared 15 amp circuit with 14 ga wiring. Whenever something else was switched on the breaker tripped. I ran 12 ga wire to the panel to a dedicated outlet for the microwave but only used a 15 amp breaker. The microwave is drawing 14 amps and is tripping the breaker. I will put a 20 amp breaker in the panel for this but my question is why didn't the breaker trip when it was wire with 14 ga?