The 220 kA at 240 V is the headline number, but the real-world figure for a 400 V-class distribution board is the 154 kA at 415 V. That's still very high — this breaker is sized for transformer-secondaries or large motor-control-center buswork where fault current runs heavy.
Thermal derating — don't lose headroom
The 125 A rating holds steady up to 50 °C ambient. Above that it steps down: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, 112.5 A at 70 °C. Panel builders should account for that in the fill factor.
The 3VA1112-6EF36-0KC0 measures 76.2 mm wide, 130 mm tall, and 70 mm deep.