What this breaker is and what the ratings mean for your panel
The Siemens 3VA1340-5GE42-0AA0-ZD00 is a 4-pole IEC frame 400 molded case circuit breaker with a class M breaking capacity — Icu of 55 kA at 415 V. That interrupting rating means it can safely clear a fault up to 55 kA without welding contacts or rupturing the case, which is the spec you check for upstream fault current at the panel main. The TM220 thermal-magnetic trip unit gives you adjustable overload protection (Ir from 280 A to 400 A) and a fixed short-circuit pickup at Ii = 10 × In (4000 A). The N conductor is protected at 100% — no derating for the neutral pole.