The 5SJ3120-6RC: The B characteristic means the magnetic trip operates at 3 to 5 times rated current (60–100 A for this 20 A unit), making it the right choice for resistive or general-purpose loads where inrush is modest — lighting, socket circuits, control transformers. The 4.5 kA breaking capacity at 230/400 V is sufficient for most residential and light-commercial distribution boards; if your fault-current study shows available short-circuit current exceeding 4.5 kA at the panel, step up to a 6 kA or 10 kA MCB from the same series. The 1-pole form factor clips onto standard DIN rail and occupies one module width (approx. 18 mm).
Snap-on DIN-rail mounting for 35 mm rail per EN 60715. The screw terminals accept 1–25 mm² conductors; torque to 2.5 Nm. The Retail line shares the same busbar pitch and accessory footprint as the broader Siemens 5SJ series, so shunt trips, auxiliary contacts, and alarm switches from that family fit without adapters.