What this MCCB is and what it does
The Siemens 3VA1112-5MH36-0DC0 is a SENTRON molded case circuit breaker (MCCB) designed for starter protection — meaning it's built to protect motor starters and their associated wiring against short circuits and overloads, not just general distribution. It's a 3-pole unit rated 125 A continuously at 40 °C, with a thermal-magnetic trip that can be adjusted for the motor's inrush. The interrupting capacity is 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 7.5 kA at 500 V and 690 V — so it handles high fault currents on the low-voltage side of a transformer, but derates significantly above 500 V.
Ratings that decide fit
The continuous current rating is 125 A from 40 °C up to 50 °C, then it derates: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If your panel ambient runs above 50 °C, you need to account for that drop — the breaker won't carry a full 125 A without nuisance tripping. The rated insulation voltage is 800 V, so it's suitable for 480 V and 600 V class systems with margin. Power loss at rated load is 30.6 W — factor that into your enclosure thermal budget, especially in a sealed panel.
Built-in auxiliaries and releases
This MCCB comes with an undervoltage release (UVR) already fitted — part of the base design. That means if the control voltage drops below a threshold, the breaker trips, which is standard for safety circuits that need to drop a motor on loss of control power. It also includes two auxiliary switches (HQ type) for remote status indication. The internal basic switch is a 3VA11125MH360AA0. No ground-fault monitoring, no communication module, no voltage-trigger or trip-indicator accessory — this is a straightforward thermal-magnetic breaker with UVR and aux contacts, not a smart breaker.
Physical footprint and panel fit
Dimensions are 130 mm high, 76.2 mm wide, and 70 mm deep. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C.