For a 20 amp breaker, a continuous load of 20 amps will not trip the breaker. For a 27 amp load, the breaker can take up to 1 hour to trip. For a 40 amp load, the circuit breaker has to trip within 2 minutes.
So, most likely the initial voltage drop was mostly due to high amp loads for short periods of time.
So, most likely the initial voltage drop was mostly due to high amp loads for short periods of time.