What this 0.3 A D-curve MCB is for
The Siemens 5SY6514-8 is a SENTRON miniature circuit breaker with a D tripping characteristic, rated 0.3 A at 230 V AC on a 50/60 Hz line.
Pole config and what it connects
Two-pole construction, wired as 1P+N — the neutral pole switches with the phase, which is required for TN-S or TT systems where you want a guaranteed disconnection of both conductors. Rated voltage is 230 V AC single-phase, with a maximum of 250 V AC in single-phase operation. That DC rating covers 48 V control loops and 60 V battery banks common in industrial backup supplies.
Temperature range -40 to 75 °C covers most unheated plant environments.
Rated breaking capacities are certified per EN 60898 (6 kA) and IEC 60947-2 (30 kA AC, 15 kA DC). UL 1077 and CSA C22.2 No.235 listing at 5 kA AC covers North American supplementary protection applications. Overvoltage category III, touch protection integrated, sealable for lockout/tagout.