What this MCCB is and what it does
The Siemens 3VA1225-6EF42-0BC0 is a SENTRON 4-pole molded case circuit breaker (MCCB) rated for 250 A continuous at 40 °C, with a 220 kA interrupting capacity at 240 V. That interrupting rating means it can safely clear a fault of that magnitude without the arc flashing over or the case rupturing — critical for high-fault panels downstream of a large transformer. It's designed for line protection, so its trip curve and construction are tuned to protect feeders and main buses, not individual motor loads. The 4-pole design handles three-phase plus neutral switching, common in North American and European distribution panels where you need to disconnect the neutral for service or where ground-fault protection is required downstream. It comes with an undervoltage release (UVR) built in, which drops the breaker if supply voltage falls below a threshold — a standard requirement for safety circuits on conveyors and presses so the equipment can't auto-restart after a brownout. Two HQ auxiliary switches are integrated. The rated insulation voltage is 800 V.
Sizing and thermal performance
This MCCB holds its full 250 A rating from 40 °C up through 50 °C — no derating needed in a warm enclosure. At 55 °C it's still good for 243 A, at 60 °C it's 237 A, and at 65 °C it's 230 A. At the maximum operating temperature of 70 °C it's rated for 223 A. That's a shallow derating curve; you don't lose much headroom even in a hot panel next to drives or transformers. The power loss at full load is 59.5 W, which is modest for a 250 A frame — you can plan the enclosure ventilation without oversized fans.
Interrupting ratings across voltages
The interrupting capacity scales with system voltage: 220 kA at 240 V, 154 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. That 220 kA at 240 V is a heavy-duty rating — it's sized for main breakers in large low-voltage switchboards where available fault current can exceed 100 kA. At 480 V the figure sits between the 440 V and 500 V numbers, so you're looking at roughly 50 kA class — solid for most 480 V distribution panels.
Panel fit and environment
The breaker measures 140 mm wide, 158 mm tall, and 70 mm deep.