What this MCCB is and what it does
The Siemens 3VM1112-3ED32-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — meaning it sits at the feeder or main in a distribution panel, not on a specific motor or load. It's a 3-pole unit with a TM210 thermal-magnetic overcurrent release, which gives you fixed thermal and magnetic trip settings for general-purpose branch-circuit protection. Rated 125 A continuously at 40 °C, it holds that same 125 A rating up to 50 °C before the thermal derating curve starts to pull it down — at 70 °C it's still good for 114 A, so you've got some headroom in a hot enclosure. The interrupting capacity is where this breaker earns its keep: 76 kA at 240 V, 53 kA at 415 V, 32 kA at 440 V, and 12 kA at 500 V. That's a strong SCCR for a 125 A frame — it'll clear high-fault events without cascading upstream, which matters when you're coordinating a panel's selectivity. Rated insulation voltage is 800 V, so it's comfortable in 480 V and 600 V class systems.
Panel fit and integration
The 3VM1112-3ED32-0AA0 measures 70 mm deep, 76.2 mm wide, and 130 mm tall — a compact footprint for a 125 A MCCB. It's designed for panel mounting, not DIN rail, so plan for screw-mounting on a backplate. Front protection is IP40, meaning it's splash-proof from the front but not sealed against dust ingress from the sides or rear — standard for enclosed distribution gear. No undervoltage release, no shunt trip, no ground-fault monitoring on this variant; it's a straight thermal-magnetic breaker with no auxiliary functions.
Thermal performance and power loss
Maximum power loss is 23 W at rated load — modest for a 125 A frame, so heat buildup in a dense panel is manageable. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The derating curve is linear from 50 °C upward: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, 114 A at 70 °C. If your panel ambient runs hot, size the breaker at the derated value, not the 125 A nameplate.