The Schneider Electric G12T3F20 is a GoPact MCCB 125 molded case circuit breaker — a 3-pole, 20 A thermal-magnetic unit with TM-D trip technology providing LI protection (overload L and short-circuit I). It is rated for distribution duty in panels up to 415 V AC 50/60 Hz, with a breaking capacity of 10 kA at 380/415 V AC (performance level T). The thermal-magnetic TM-D trip unit means the overload curve is thermal (bimetal) and the short-circuit response is magnetic (solenoid) — no electronic adjustment, no auxiliary power needed. Rated insulation voltage is 440 V AC, operational voltage 415 V AC.
Mounts fixed to a backplate (not DIN rail) — screw terminals on both front connections, 25 mm pitch. Dimensions are 75 mm wide, 130 mm high, 60 mm deep. Altitude derating starts above 2000 m.
That is the SCCR (short-circuit current rating) for the device — the maximum fault it can clear. Electrical durability is 8000 cycles at rated current and voltage; mechanical durability is 30,000 cycles. The electrical endurance figure governs replacement intervals in switching applications — 8000 operations at full load is typical for a distribution breaker used as a disconnect. Power dissipation per pole is 18.7 W — three poles total 56.1 W at full load. That heat must be considered in panel thermal design; tight enclosures without ventilation may require derating or forced airflow.