A 5500W element will never work on 15A. To calculate the amps needed, you divide the wattage (5500) by the volts (120) 5500/120 = 45.83 Amps. If you do 240 volts, you will only need 22.92.
To answer your question, a 50 amp breaker is not going to be an issue hooked up to a 30A line.