The 5SY61 MCB B16: The Siemens 5SY6116-6 is a single-pole miniature circuit breaker from the 5SY61 series, rated at 16 A with a B-trip curve. It's the part you reach for when you need a standard MCB for a 16 A final subcircuit — lighting, general-purpose socket outlets, or small motor loads that don't need a C-curve's higher inrush tolerance. Single-pole construction means it protects one phase only, so it's a fit for single-phase branch circuits or for individual phase protection in a three-phase panel where you're using separate breakers per phase.
At 18 mm width (one module), it occupies a single 18 mm slot in the enclosure. The 90 x 18 x 76 mm dimensions mean it fits standard distribution boards and sub-distribution panels without crowding — you can stack up to about 12 of these per 225 mm of rail before you need a busbar extension. IP20 finger-safe terminals on the line and load sides. That's standard for indoor panel mounting; if this breaker goes into a washdown area or outdoors, it needs an IP54 or higher enclosure around it. The operating temperature range of -25 to 55 °C covers most indoor industrial and commercial environments, but derate the continuous current if ambient exceeds 40 °C — Siemens typically recommends 10% derating per 10 °C above 40 °C for the 5SY series.