The MGP1252L2N is a 1-pole-plus-neutral (1P+N) molded case circuit breaker from the Schneider Electric PowerPacT 4 range, rated 125 A at 40 °C with a TM-D thermal-magnetic trip unit providing LI (overload and short-circuit) protection. It is designed for distribution applications on 230 V AC 50/60 Hz circuits, with a 25 kA Icu / Ics short-circuit breaking capacity at 415 V AC — meaning it can safely interrupt a fault up to that level without upstream gear having to clear it. The breaker mounts to a backplate in either horizontal or vertical orientation, and its suitability for isolation is certified per BS EN 60947-2 — a requirement in many European panel specs.
Schneider Electric has marked the MGP1252L2N as obsolete. There is no official successor order code listed, so a direct drop-in replacement from the PowerPacT 4 family is not confirmed. The 25 kA Icu at 415 V and 125 A rating are the specs to match if you are looking for a functional equivalent.
Above that, the thermal curve starts its time-delayed overload response. The magnetic (I) element is fixed-trip, not adjustable — it responds to short-circuit currents without intentional delay. Rated insulation voltage is 750 V and impulse withstand is 8 kV, which covers the clearance and creepage requirements for 230/415 V systems. The electrical durability is 20,000 cycles at rated current at 277 V, dropping to 10,000 cycles at 2x In — typical for a distribution MCCB not cycled as a motor switch.