What this MCCB carries — and what it means for the panel
The Siemens 3VA2325-6HK42-0AA0 is a 4-pole SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current at 40 °C, carrying the ETU340 electronic trip unit. Line protection version — no ground-fault monitoring, no communication module. The 242 kA breaking capacity at 240 V tells you this breaker can interrupt very high fault currents at that voltage, which matters for main incoming feeders in industrial switchboards where the upstream transformer can deliver that kind of energy. At 415 V the rating holds at 187 kA, and at 690 V it drops to 11 kA — a steep derate that reflects the arc-extinction physics in air at higher voltage. The 800 V rated insulation voltage (Ui) confirms it is designed for 690 V systems with margin.
Current derating — the real-world continuous rating
Full 250 A is available up to 50 °C ambient. Above that the unit derates linearly: 242.5 A at 55 °C, 237.5 A at 60 °C, 230 A at 65 °C, and 220 A at 70 °C. If your panel internal temperature runs hot — say a non-ventilated enclosure near a dryer section or a crowded MCC lineup — the 55 °C or 60 °C figure is the one to size against, not the 40 °C nameplate. The 37.5 W maximum power loss is the heat the breaker dumps into the enclosure; factor it into your thermal budget.
Trip unit and selectivity
The ETU340 is an electronic overcurrent release with adjustable N-conductor protection (OFF, 50%, or 100%). The thermal memory and long-time pickup settings (tr min and tr max both listed at 1500) are part of the coordination toolkit for achieving selective tripping downstream. For a mill electrical engineer building a selective coordination study, the ETU340 gives you the adjustability to hold in through motor-start inrush while clearing a bolted fault on a branch feeder. The 20 000 mechanical endurance cycles are adequate for a main or feeder breaker that sees infrequent operation — not a switching duty device.
Mounting and integration
Dimensions: 248 mm high, 184 mm wide, 110 mm deep. IP40 on the front — suitable for a dry indoor panel, not for washdown. The 4-pole form factor (3 phases plus switched neutral) is standard for TN-S or TN-C-S systems where the neutral needs to be isolated and protected. Bolts into a fixed mounting plate or a withdrawable cradle depending on the SENTRON 3VA system frame.