What it is — and what the ratings mean for fit
The Siemens SENTRON 3VA2340-6KP42-0AA0 is a 4-pole molded case circuit breaker (MCCB) rated 400 A continuous, designed for line protection in distribution panels. The 400 A frame is the headline number — but the real selection driver is the ETU850 electronic trip unit, which gives you adjustable long-time, short-time, instantaneous, and ground-fault protection curves. That makes it a coordination-friendly breaker for selective tripping downstream of a main, not just a thermal-magnetic brute-force device. Breaking capacity is what gets an MCCB spec'd into a fault study. This unit delivers 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 7.5 kA at 690 V. At 415 V — the common industrial low-voltage distribution voltage — 187 kA SCCR means it safely interrupts faults up to that level without cascading upstream. That's a high-interrupting-capacity (HIC) class breaker, not an economy line. Thermal derating matters when you're packing breakers into a warm enclosure. The breaker holds 400 A up to 50 °C ambient; at 55 °C it derates to 375 A, at 60 °C to 350 A, at 65 °C to 325 A, and at 70 °C to 300 A. If your panel sits in a non-conditioned space — say, a Saudi switchroom hitting 55 °C — you're losing 25 A of headroom. Factor that into the load schedule. Mechanical footprint: 248 mm tall, 184 mm wide, 110 mm deep. Four-pole frame, so it takes up four module spaces on the DIN rail or panel-mount plate. IP40 on the front — dust-protected, no water jets — so it's fine in a clean indoor panel but not for washdown zones without an enclosure.
Where it bolts in
Mounts on a standard DIN rail or panel plate via the 4-pole frame base. The 110 mm depth fits into 400 mm deep enclosures with room for outgoing cable lugs. Terminal spread on a 4-pole frame means phase-to-phase clearance is built in — no need for additional phase barriers up to the rated voltage. The ETU850 trip unit supports communication — that's the 'Communication Function Yes' flag in the specs. That means it can talk to a higher-level energy management system or PLC via the 3VA communication module (ordered separately), giving you remote trip status, current metering, and alarm annunciation. If you're retrofitting an older panel that had a dumb thermal-magnetic breaker, this adds a data stream without rewiring the load side.