Do all 20 amp circuit breakers respond to inrush surges the same way?
NO! Circuit breakers have widely varying trip responses depending on their intended use. For most audio power amplifiers you need breakers with a HM rating. The High Magnetic rating allows a substantial inrush current, about double, for the first 100 milliseconds to eliminate nuisance trips. Nuisance trips are common on circuit breakers not rated for High Magnetic duty. For instance, a standard Square D QO120 breaker will trip with as little as 120 amps in the first cycle compared to 240 amps for a QO120HM. In Square D, the HM rating is only available for 15 and 20 amp breakers. The 30 amp QO breakers sustain inrush currents of 300 amps for the first 10 cycles @ 60 Hz, sufficient to light up most of the largest power amplifiers without nuisance tripping.
