What this MCCB delivers for the main switchboard
The Siemens 3VA2325-5KQ42-0AA0 is a SENTRON molded case circuit breaker (MCCB) sized for a 250 A continuous load — a common infeed or feeder rating in industrial switchboards and motor control centres. Its 4-pole construction handles three-phase plus neutral, with adjustable N-conductor protection from OFF up to 160 % of the phase rating, so it adapts to both solidly-grounded and impedance-grounded distribution systems. The ETU860 electronic trip unit provides true RMS sensing, communications (the breaker carries a communication function), and ground-fault monitoring via summation current formation on L + N. That makes it suitable for coordinated protection schemes where the breaker talks to a higher-level control system — not just a standalone thermal-magnetic device.
Breaking capacity — where it holds the line
At 240 V the interrupting rating is 187 kA; at 415 V and 440 V it still delivers 121 kA, and at 500 V it holds 75.6 kA. Only at 690 V does it drop to 7.5 kA — still adequate for most 690 V motor circuits, but the headroom narrows. For a site engineer building a selective coordination study, the 187 kA at 240 V means this breaker can sit upstream of smaller MCCBs on a high-fault-current service entrance without cascading open.
Thermal derating — flat across the panel ambient
The 250 A rating holds flat from 40 °C all the way to 70 °C ambient — no derating curve to calculate for a hot enclosure. That is unusual for a compact MCCB; most competitors begin stepping down above 50 °C. The maximum power loss is 37.5 W, which a standard IP40 front panel can dissipate without forced ventilation provided the enclosure volume is adequate.