What the 1000 A continuous rating means for your feeder
The ETU350 electronic trip unit lets you dial the long-time pickup (Ir) from 0.5 to 1.0 × Iu, so you set it to match the actual load, not just the breaker frame. At 415 V it interrupts 121 kA symmetrical; at 240 V that jumps to 187 kA. Those numbers tell you this breaker clears a bolted fault upstream of a large motor control center or a transformer secondary without the arc re-striking — it's sized for high-fault installations, not branch circuits.
Derating and thermal reality in the panel
This breaker holds its full 1000 A rating up to 55 °C ambient. At 60 °C it derates to 955 A, at 65 °C to 885 A, and at 70 °C to 815 A. The frame measures 320 mm high × 210 mm wide × 120 mm deep. That's a standard SENTRON 3VA2 drawout cassette footprint; it fits the same cubicle as other 3VA2 breakers in the line.