Siemens 5SJ6204-7 — 2-pole C-curve MCB for 400 V AC branch circuits
The Siemens 5SJ6204-7 is a 2-pole miniature circuit breaker from the SENTRON 5SJ6 series, rated 4 A at 400 V AC with a C tripping characteristic.
Rated 4 A at 400 V AC, this MCB protects a 2-pole branch circuit drawing up to 4 A continuous. The C characteristic means magnetic trip occurs at 5–10× In (20–40 A), so it holds through the starting surge of a small motor or a bank of fluorescent ballasts without nuisance tripping. Energy limiting class 3 means it lets through minimal let-through energy during a fault, which helps downstream components survive. The 2-pole configuration switches both poles simultaneously. The AC/DC voltage type means the arc chamber extinguishes arcs on both AC and DC. Terminals accept 1.5 mm² to 2.5 mm² conductors — the standard range for 4 A circuits. The 70 mm installation depth is shallower than many older breakers, which matters when the distribution board is mounted against a thin wall or in a tight enclosure. The mechanical service life of 20 000 switching cycles is typical for a residential-grade MCB; it will outlast the building's wiring but is not rated for frequent manual switching as a disconnect.
Snap-on DIN rail mounting in any position — the manufacturer allows any mounting orientation. The 2 width units let it fit alongside other 5SJ6 breakers.