What this MCCB is and what it does
The Siemens 3VA1140-6MH32-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed specifically for starter protection — meaning it's built to sit ahead of a motor contactor and handle the high inrush and short-circuit stress that comes with motor starting, not just general distribution. Rated 40 A continuous at 40 °C, it carries a TM120M thermal-magnetic release that handles both overload and short-circuit trip curves. The 220 kA breaking capacity at 240 V is the headline number, but out here in the grease what matters is that it holds 154 kA at 415 V and still manages 121 kA at 440 V — that's serious fault-clearing for a motor branch circuit in a 400 V class panel.
Ratings that decide the fit
Three poles, 800 V rated insulation voltage, and a front IP40 protection class — it's meant for a clean, dry enclosure, not a washdown zone. The thermal derating curve is honest: 40 A flat from 40 °C to 50 °C, then 39 A at 55 °C, 38 A at 65 °C, and 37 A at 70 °C. If your panel ambient runs hot, you're not losing much headroom. At 10.8 W maximum power loss, it won't cook the enclosure, but it's not negligible in a sealed box — plan for some airflow if you're stacking several breakers. Operating temperature range is -25 °C to 70 °C, storage from -40 °C to 80 °C, so it handles cold storage just fine. Mechanical footprint: 70 mm deep, 76.2 mm wide, 130 mm tall. That three-inch width per pole is standard for a 40 A frame MCCB — it'll drop into a typical panel layout without surprises. No undervoltage release, no ground-fault monitoring, no communication module on this variant. It's a straight thermal-magnetic breaker with a trip indicator absent, so you won't get a visual flag on the front when it trips; you'll know by the load dropping out.