What this MCCB is and what the ratings mean
The Siemens 3VA1125-6GD46-0AA0 is a SENTRON-series molded case circuit breaker (MCCB) for line protection — the main disconnect and fault interrupter in a distribution panel, motor control center, or feeder circuit. It is a 4-pole device rated 25 A continuous, meaning it protects a 25 A branch circuit and will not nuisance-trip at that load under normal conditions. The breaking capacity is where this part earns its place: 220 kA at 240 V, 154 kA at 415 V, 121 kA at 440 V, and 17 kA at both 500 V and 690 V. Those numbers tell you it can safely interrupt a fault current up to those levels at the respective system voltage — critical for high-fault installations like large transformer secondaries or industrial substations where available fault current exceeds standard 65 kA or 100 kA breakers. The TM210 designation means a thermal-magnetic trip unit — the thermal element handles overload protection (time-curve shaped), and the magnetic element handles instantaneous short-circuit protection. No undervoltage release, no shunt trip, no communication module on this variant; it is a straight, hardwired line-protection breaker.
Panel fit and thermal derating
Dimensions: 130 mm tall, 101.6 mm wide, 70 mm deep. That 70 mm depth is the can depth behind the panel face — important for gland-plate clearance and busbar stacking in a shallow enclosure. The 4-pole width (101.6 mm) is roughly 4 inches, standard for a 4-pole MCCB frame; verify the DIN-rail or mounting-plate pattern matches your existing backpanel layout. Thermal derating is minimal for this frame: it carries the full 25 A from 40 °C through 50 °C ambient, then drops only to 24 A at 55 °C and 60 °C, and 23 A at 65 °C and 70 °C. In a hot panel — near a transformer or in a non-climate-controlled enclosure — you lose only 1–2 A before the trip curve shifts. Maximum power loss is 8.5 W, so the breaker itself does not add significant heat to the enclosure. Front protection is IP40 — finger-safe from the front but not sealed against dust ingress. Not for washdown or outdoor exposure without an additional enclosure. Storage range is -40 °C to 80 °C; operating ambient is -25 °C to 70 °C.