What this MCCB is and what the ratings mean
The Siemens SENTRON 3VA1112-5EF32-0DH0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, with a TM240 thermal-magnetic overcurrent release. It carries 125 A continuous current at 40 °C and holds that rating steady through 50 °C, then derates to 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C — so if your panel runs hot near the top of the enclosure, you still have solid margin before you need to upsize. The interrupting ratings tell you where this breaker can live without blowing upstream: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 690 V. That 187 kA at 240 V is the number that matters for most North American 480Y/277 V panels where the line-to-ground fault current can spike — this MCCB handles it without needing a current-limiting fuse ahead of it. The auxiliary contact configuration is 2 auxiliary switches plus 1 trip alarm switch (HQ type), and it comes with an undervoltage release (UVR) built in — the release design is a separate order code 3VA9608-0BB25 for the integrated auxiliary trip. That UVR means the breaker drops out if control voltage falls below a threshold, which is handy for safety circuits or emergency-stop chains where you want the breaker to open on loss of control power. Rated insulation voltage is 800 V, so it's good for 690 V systems with margin. IP40 on the front means it keeps out tools and small wires but isn't sealed against water — fine inside a clean panel, not for washdown zones.
Panel fit and integration notes
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep — that 70 mm depth is shallow enough to fit most standard panel depths without hitting the backplate. Width at 76.2 mm is about 3 inches, so it takes up three pole spaces on a DIN rail or panel-mount footprint. No communication function, no phase failure detection, no ground fault monitoring — this is a straight thermal-magnetic breaker with an undervoltage release and auxiliary contacts. Storage temperature range is -40 °C to 80 °C; operating range is -25 °C to 70 °C. That -25 °C low end means it's fine for unheated enclosures in most climates, but if your panel sits outside in a Minnesota winter, the storage minimum covers shipping and idle time.