What this MCCB is and what it does
The Siemens 3VA2450-8HK42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 500 A continuous current at 40 °C, with four poles and an ETU340 electronic trip unit. It is designed for line protection — the primary feeder or main disconnect in a distribution panel, not for motor or generator protection. The ETU340 release gives you adjustable long-time, short-time, instantaneous, and ground-fault protection curves, which means you can coordinate it downstream of a larger feeder breaker and upstream of branch panel MCCBs without nuisance tripping.
Interrupting capacity — what the numbers mean for your fault level
This breaker carries a rated ultimate short-circuit breaking capacity (Icu) of 440 kA at 240 V AC, 330 kA at 415 V and 440 V, 220 kA at 500 V, and 52.5 kA at 690 V. Those are very high values — the 440 kA at 240 V is typical for a large-frame MCCB intended for transformer secondary or high-fault utility service entrance applications. At 690 V, the 52.5 kA rating still covers most industrial motor control center bus faults. The 5 500 A minimum and maximum short-time withstand (Icw) rating tells you the breaker can hold closed under fault for at least the short-time delay setting, which is essential for selective coordination.
Temperature derating — don't size by the 40 °C number alone
The 500 A rating holds at 40 °C, 45 °C, and 50 °C. At 55 °C it derates to 477 A, at 60 °C to 455 A, at 65 °C to 432 A, and at 70 °C to 410 A. If this breaker sits in a non-air-conditioned enclosure or near other heat sources, use the 55 °C or 60 °C column for your ampacity calculation. The maximum power loss is 99 W — that's the heat you need to vent through the enclosure. Panel builders should account for this in the thermal budget, especially in a sealed NEMA 12 enclosure.
Physical fit and panel integration
Dimensions are 248 mm high, 184 mm wide, 110 mm deep. That 184 mm width across four poles is wider than a typical 3-pole MCCB of the same frame — verify the DIN-rail or mounting-plate space before committing the panel layout. The 110 mm depth is shallow enough for most 600 mm deep enclosures, but check gland-plate clearance for the incoming cable lugs. Operating temperature range is -25 °C to +70 °C; storage from -40 °C to +80 °C.