What this MCCB carries — and what that means for your panel
The Siemens SENTRON 3VA1112-3EF36-0HA0 is a 3-pole molded case circuit breaker rated 125 A at 40 °C, with a breaking capacity of 75.6 kA at 240 V AC. That 75.6 kA at 240 V is the headline interrupt rating — it clears a fault up to that level without welding contacts or cascading upstream. At 415 V it still holds 52.5 kA, and at 690 V it's 11.9 kA. The thermal-magnetic TM240 release handles the overload and short-circuit trip curve; the shunt trip (STL) auxiliary release lets you remotely trip the breaker via a control signal. Rated insulation voltage is 800 V, so it's comfortable in 480 V and 600 V class panels. Maximum power loss is 28.1 W — factor that into enclosure heat rise if you're packing several breakers in a sealed cabinet.
Panel fit — dimensions and derating
Width is 76.2 mm (3 in), depth 70 mm (2.76 in), height 130 mm (5.12 in) — standard SENTRON 3VA form factor, mounts on a DIN rail or panel-mount adapter. The 125 A rating holds flat from 40 °C to 50 °C; above that it derates to 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If your enclosure ambient runs hot, use the 60 °C or 65 °C column for sizing.
What it's designed for
This is a line-protection breaker — no ground-fault monitoring, no communication module, no undervoltage release. It's a straight thermal-magnetic MCCB for feeder or main breaker duty in distribution panels, motor control centers, and switchboards. The shunt trip gives you remote open capability for emergency-stop circuits or interlocking schemes.