What this MCCB delivers on the bus
The Siemens SENTRON 3VA1225-5GF42-0AH0 is a 4-pole molded case circuit breaker rated for 250 A continuous current (Iu) with a TM240 thermal-magnetic trip unit — fixed thermal and magnetic settings, no electronic adjustment. At 240 V it interrupts 187 kA; at 415 V it still holds 121 kA, which puts it in the high-interrupting category for industrial main or feeder duty. The frame is 140 mm wide, 158 mm tall, 70 mm deep — standard panel-mount footprint for a 250 A MCCB, no special cutout needed.
Interrupting ratings and thermal derating
The interrupting curve drops from 187 kA at 240 V to 121 kA at 415 V, then 36 kA at 440 V, and 17 kA at 690 V — that 690 V figure tells you this breaker can serve 690 V line-to-line systems, rare for a 250 A frame. Thermal derating starts at 55 °C: still 250 A at 50 °C, then 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If the panel ambient runs above 50 °C, size the breaker one frame step up or accept the reduced ampacity.
Auxiliary contacts and trip indication
Comes with 2 auxiliary switches plus 1 trip alarm switch (HQ version) — the alarm contact closes only when the breaker trips on fault, not on manual open. That lets the PLC or annunciator distinguish a maintenance disconnect from a real event. No undervoltage release, no shunt trip, no communication module on this variant — it's a straight thermal-magnetic breaker with local indication only.