What this MCCB is and what it carries
The Siemens 3VA2440-5HN42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current across the full ambient range from 40 °C to 70 °C — no derating needed up to the top of the operating band. The four-pole design with an ETU350 electronic overcurrent release makes it a line-protection breaker for distribution panels feeding heavy loads like large motor control centers or transformer secondaries. Interrupting capacity is the headline number here: 187 kA at 240 V, 121 kA at 415/440 V, 75.6 kA at 500 V, and 9 kA at 690 V. That 187 kA at 240 V is a high-fault rating — this breaker handles a stiff transformer secondary without needing a current-limiting fuse upstream.
What the ratings mean for panel fit
At 110 mm deep, 184 mm wide, and 248 mm tall, this breaker fits standard SENTRON 3VA switchboard mounting patterns. The 400 A frame is physically larger than the 250 A frame in the same series — verify busbar spacing and lug kit compatibility if replacing a smaller 3VA unit. Rated insulation voltage is 800 V, so it's comfortable on 480/277 V or 600 V systems with margin. Power loss at rated current is 63.5 W maximum — that's the heat the enclosure must vent. In a sealed panel with multiple breakers at full load, factor that into the thermal budget. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C.