400 A MCCB with ETU350 — what the ratings mean for your panel
The Siemens SENTRON 3VA2440-5HN32-0CL0 is a 3-pole molded case circuit breaker (MCCB) rated for a continuous current Iu of 400 A, with an ETU350 electronic trip unit configured for line protection — meaning it protects feeders and main distribution from overload and short-circuit faults, not motor or generator circuits. Breaking capacity is 187 kA at 240 V, dropping to 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 17 kA at 690 V — the 415 V figure governs most European industrial distribution panels; the 690 V rating is the limiting case for 690 V line-ups. Rated insulation voltage Ui is 800 V, suitable for 690 V systems with margin for transient overvoltages. Temperature derating is minimal up to 50 °C (full 400 A), then drops to 384 A at 55 °C, 376 A at 60 °C, 368 A at 65 °C, and 360 A at 70 °C — the 55 °C step is where you lose headroom; plan the enclosure ventilation if ambient exceeds 50 °C.
Panel fit and integration
Dimensions are 110 mm deep, 138 mm wide, 248 mm tall — the 138 mm width is standard for 400 A frame MCCBs on DIN-rail or backplate mounting; verify the gland plate cutout against the existing panel layout if retrofitting into a tight enclosure. Auxiliary contact block is populated from factory with 2 auxiliary switches (NO/NC configurable), plus 1 trip alarm switch and 1 electrical alarm switch HQ — that covers remote status indication without adding a separate auxiliary module. Maximum power dissipation is 66 W at rated current — factor that into enclosure thermal calculations; a 400 A breaker dumping 66 W in a sealed cabinet needs forced ventilation or a larger enclosure than a derated unit would. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C — the storage limit governs warehousing, not running conditions.
Lifecycle and sourcing posture
The ETU350 trip unit is a fixed-configuration electronic release; there is no communication module or phase-failure detection on this variant — the basic switch base is 3VA2440-5HN32-0AA0, and the integrated auxiliary trip is 3VA9608-0BB24. An undervoltage release (UVR) is built in — the design of the auxiliary release is an undervoltage release, so the breaker trips when control voltage drops below the dropout threshold.