Key ratings and what they mean for your panel
The Siemens 3VM1340-5GD42-0AA0 is a 400A molded case circuit breaker from the 3VM1 IEC frame family, rated for a breaking capacity of 55 kA at 415 V AC (class S). That Icu figure means it can safely interrupt a 55 kA fault current without damage to itself or upstream gear — critical for high-fault installations like transformer secondaries or large motor control centers. The TM210 thermal-magnetic trip unit provides overload protection (thermal) and short-circuit protection (magnetic) with a fixed short-circuit pickup of Ii = 10 x In (4000 A), so it coordinates well downstream of a larger feeder breaker.
Integration and mounting — checklist cadence
Packaged dimensions are 261 x 208 x 170 mm — verify your enclosure depth and bus-bar clearance. The 4-pole footprint matches standard Siemens 3VM1 mounting patterns; use the supplied nut keeper kit (included per) to secure bus-bar connections without loosening over time. For a 400 A continuous rating, plan for adequate ventilation or derating if enclosed above 40 °C ambient — typical for molded case breakers in this class.