What this 3VA1 MCCB carries — and what that means on the panel
The Siemens 3VA1112-5EE42-0AA0-ZD00 is a 4-pole IEC frame 160 moulded-case circuit breaker with a 125 A continuous rating and a breaking capacity class M — Icu of 55 kA at 415 V AC. That 55 kA rating means it can safely interrupt a fault current up to that level without welding the contacts or cascading the arc upstream, which is the figure a panel builder needs to verify against the prospective short-circuit current at the point of installation. The thermal-magnetic trip unit is a TM220 with ATFM (adjustable thermal, fixed magnetic) — overload protection Ir adjustable from 88 A to 125 A, short-circuit protection Ii fixed at 10 × In (1250 A). The N conductor is unprotected, which is standard for a 3-pole + N configuration where the neutral is not switched. This variant includes a nut keeper kit and is specified for DC Power OEM in China.