The SENTRON 5SQ2160-0KA40 is a single-pole miniature circuit breaker (MCB) from the 5SQ T55 series, rated 40 A with a B tripping characteristic. It breaks fault currents up to 3 kA per EN 60898 at 240 V AC — that's the standard for protecting final circuits in residential and light commercial panels where the prospective short-circuit current stays under that ceiling.
Rated for both AC and DC supply voltage, so it handles the same branch circuit whether you're feeding a control transformer secondary or a straight 240 V line. Overvoltage category 3 and energy limiting class 3 mean it's designed for fixed-installation coordination — it limits let-through energy enough to protect downstream wiring and connected loads during a fault.