First, make sure the breaker you choose is GFCI or use a separate GFCI for protection.

Then, do some math.

Watts = Amps x Volts ... so ... Amps = Watts / Volts

Build in a 15-20% safety factor on the breaker (local code often requires this).

You're probably really getting closer to 220 volts than 240 volts from your utility.

So, 5500 watts / 220 volts X 0.80 = 20 amps. If you have a 30-amp breaker, you should have plenty of amps to handle the element, associated electronics (which typically only draw a few hundred milliamps), and probably a couple March or Chugger pumps, too. Adding that second 1650-watt element would put you at 26 amps - still under 30, but closer than I'd care to be if running other accessories (pumps. etc.).

If you want to run two elements at the same time, you're probably better advised to use a bigger breaker. I have a 15-gallon 3-vessel system with a 5500-watt element in the HLT and another 5500-watt in the BK. The system also has 2 Chugger pumps. I run both elements at the same time for back-to-back batches and/or to heat up cleaning solution while boiling. I have a 50-amp GFCI breaker for the whole system with both pumps running, the HLT element at 100% and the BK element at 80%. Both elements at 100% would be 11,000 Watts / 220 volts X 0.80 = 40 amps. So, that leaves another 8 amps at 220 volts to spare for the 120-volt pumps and electronics.

Also, don't overlook that you'll need heavier-gauge wire to handle the higher amperage. I bit the bullet and had a licensed electrician install the breaker and run the heavier-gauge cable to the 220/240-volt outlet.

Be safe and have fun.

Brew on!