The LUCCA A53's from 2017 and prior can be set to operate in 15 or 20 amp mode. The Clive default setting is 15 amp unless 20 amp is requested when ordered. In 15 amp mode the machine will only heat one boiler at a time, prioritizing the heating of the coffee boiler and then the steam boiler. In 20 amp mode the machine will heat both boilers at the same time whenever needed.
To change the 15 and 20 amp setting on the A53, turn the machine off, removing the phillips screw from the front center of the top panel, and then remove the panel (see this article for in-depth panel removal instructions). In the back right corner you'll be able to see the switch labeled 15/20, and flip it to the desired setting. Do not touch the switch labeled on/off.
After changing the machine to 20 amp mode, you may also need to switch off "ECO mode", which is a secondary setting that keeps the machine in functioning in 15 amp mode even (to protect from accidental amperage change). To enable or disable ECO mode, press and hold the boiler button for 10 seconds while the machine is powered on, until you see the ECO light turn on or off. If you don't hold the button long enough, the boiler light will turn off.