What this MCCB is and what the ratings mean for fit
The Siemens 3VM1112-3ED12-0AA0 is a SENTRON molded case circuit breaker (MCCB) — a 1-pole line-protection device with a TM210 thermal-magnetic overcurrent release. It's rated 125 A continuously at ambient temperatures from 40 °C through 50 °C, then derates to 114 A at 70 °C. That flat 125 A band across 40–50 °C means it holds its full rating in a warm panel without needing to oversize; the derate curve only engages above 50 °C. Breaking capacity is 53 kA at 240 V AC and 8 kA at 415 V AC — the 240 V figure covers most North American panelboard fault levels, while the 415 V number is the relevant one for 400 V-class European distribution. The 1-pole form factor (25.4 mm wide) fits standard Siemens panelboard slots; depth is 70 mm, height 130 mm. Rated insulation voltage is 500 V, and the front face carries IP40 protection — fine for a closed panel, not for washdown.
Panel integration and deployment context
Mounts in a standard Siemens panelboard or loadcenter on the DIN-rail or direct-mount bus. The 25.4 mm width (1 inch) occupies one pole space. No trip indicator, no voltage trigger — it's a basic thermal-magnetic trip unit. Maximum power loss is 8 W, so heat dissipation in a densely populated enclosure is manageable. Storage temperature range is -40 °C to 80 °C; operating range is -25 °C to 70 °C. The IP40 front rating means the breaker face is protected against tools and small wires but not against moisture — keep it inside a closed panel.