Siemens 5SU1646-6FP20 SENTRON RCBO — 4P, 20 A, Type B
The Siemens 5SU1646-6FP20 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) from the SENTRON family, rated 20 A at 30 °C with a Type B tripping characteristic. It operates at 400 V AC, 50 Hz, and carries a 6 kA breaking capacity per EN 60898 and IEC 60947-2. The 72 mm width (4 modular width units) fits standard DIN-rail distribution boards, and it can be mounted in any position.
What the ratings mean for your panel
The Type B characteristic trips instantaneously at 3–5× rated current, making it the standard choice for residential and commercial final circuits supplying socket outlets, lighting, and general-purpose loads — not motor circuits or high-inrush equipment. The 6 kA breaking capacity (per both EN 60898 and IEC 60947-2) is sufficient for most domestic and light commercial installations where the prospective short-circuit current at the board stays under that threshold. The 400 V AC rating across 4 poles means it can protect a three-phase plus neutral circuit, or be used in single-phase split configurations. The 50 Hz operating frequency is fixed — not suitable for 60 Hz systems without verifying the manufacturer's derating. Temperature derating is published: 20 A at 30 °C drops to 19.5 A at 40 °C, 18.9 A at 50 °C, and 17.8 A at 70 °C. If the distribution board is in a warm enclosure or adjacent to heat-generating equipment, use the 40 °C or 50 °C column for your continuous load calculation. The IP20 rating applies only when installed in a distribution board with connected conductors — the RCBO itself is not rated for exposed or washdown environments.