Breakers are designed to deal with inrush currents.
More so... to my knowledge _no_ breaker trips at it's rated current. For example European B type breakers have to trip on 1,45 times their rated current within one hour (only regarding the overload protection). So there's no way anything just slightly over 20 amps would trip a 20 amps breaker. That would probably require a 60 amps spike which the breaker recognizes as a short circuit and trips instantly (0.2 seconds with most Euro breakers).
