2-pole C-curve MCB for 400 V AC branch circuits
The Siemens SENTRON 5SQ2270-2YA02 is a 2-pole miniature circuit breaker with a C tripping characteristic, rated 2 A at 30 °C and 400 V AC, with a 3 kA breaking capacity per EN 60898. The C-curve means it trips at 5 to 10 times rated current — typical for moderate inrush loads like lighting banks, small transformers, or motor control circuits where you need to ride through the start surge without nuisance trips. The 3 kA SCCR at 400 V is the fault-clearing limit per the standard; upstream coordination must respect that ceiling.
Thermal derating — read the real rating at your panel temperature
The 2 A rating is at 30 °C ambient. At 40 °C it derates to 1.85 A, at 50 °C to 1.74 A, and at 60 °C to 1.6 A. If this breaker sits in a warm enclosure — common in packed panels — the continuous load must be sized against the derated value, not the 30 °C figure. The IP20 finger-safe terminals are standard for enclosed distribution boards; not rated for wet or washdown zones.
Panel fit — 2 MWUs, 55 mm depth
Occupies 2 modular width units (about 36 mm) on a DIN rail, with an installation depth of 55 mm. The 2-pole form factor switches both phase and neutral (or two phases in a split-phase or single-phase 400 V line-to-line circuit). Pollution degree 3 and overvoltage category III suit it for fixed-installation distribution panels in industrial environments.