The Siemens 5SU1656-7KK20 is a SENTRON RCBO (residual current circuit breaker with overcurrent protection) in a 1P+N configuration — one protected pole plus a switched neutral — rated 20 A at 30 °C with a Type C tripping characteristic. It is designed for instantaneous operation and mounts in any position on a DIN rail, occupying 2 modular width units (36 mm). The 6 kA breaking capacity per EN 60898 covers most residential and light commercial final circuits; the higher 15 kA rating per IEC 60947-2 applies when the device is used in industrial distribution boards where the prospective fault current is higher. Supply can enter from either top or bottom, and the RCBO is rated for 230/240 V AC at 50 Hz, with an insulation voltage (Ui) of 264 V and a surge voltage resistance of 4 000 V — suitable for overvoltage category III environments with pollution degree 2.
Derating and ambient temperature
The 20 A rating holds at 30 °C ambient. Above that, the device derates linearly: 18.8 A at 40 °C, 18.2 A at 45 °C, 17.4 A at 50 °C, 16.2 A at 55 °C and 60 °C, 15.4 A at 65 °C, and 14.6 A at 70 °C. If the panel runs warm — common in crowded enclosures or near heat sources — size the upstream protection accordingly. The operating temperature range spans -40 °C to 75 °C, so the RCBO can be installed in unheated outdoor enclosures or near furnace lines without concern.
Physical fit and compliance
The device measures 36 mm wide, 90 mm high, and 77 mm deep, with an installation depth of 70 mm. It is halogen-free and silicon-free, which matters for clean-room or sensitive electronic environments where outgassing can cause contact corrosion. IP20 rating applies once installed in a distribution board with conductors connected — standard for enclosed panel use. Energy limitation class 3 means the let-through energy is low, reducing stress on downstream wiring and components during a fault.