The Siemens 5SU1354-6KK40 is a SENTRON RCBO (residual current circuit breaker with overcurrent protection) in a 1P+N configuration, meaning it switches and protects one phase plus the neutral. It carries a Type B tripping characteristic, so it trips on short-circuit currents between 3 and 5 times the rated current — standard for general-purpose residential and commercial final circuits where no special inrush or high-harmonic loads are present. Rated 40 A at 30 °C ambient, the part is designed for 50 Hz supply systems at 230/240 V AC.
Breaking capacity and standards
Two breaking capacity ratings are listed: 10 kA according to EN 60898 (the standard for MCBs and RCBOs in household and similar installations) and 15 kA according to IEC 60947-2 (the standard for low-voltage switchgear and controlgear). The higher IEC rating means this unit can interrupt fault currents up to 15 kA when applied in an industrial distribution board where IEC 60947-2 applies; the EN 60898 rating covers the domestic/commercial installation scenario. Both ratings are at 230/240 V AC.
Temperature derating — the real current rating
The 40 A rating holds only at 30 °C ambient. Above that, the continuous current must be derated: 37.6 A at 40 °C, 36.4 A at 45 °C, 34.8 A at 50 °C, 32.4 A at 55 °C and 60 °C, 30.8 A at 65 °C, and 29.2 A at 70 °C. If the panel ambient runs at 50 °C — common in a crowded enclosure — the usable rating drops to 34.8 A. The operating ambient range is -40 °C to 75 °C.
Panel fit and mounting
This RCBO occupies 2 modular width units (MW) on a DIN rail — 36 mm wide, 90 mm high, 77 mm deep, with an installation depth of 70 mm. It snaps onto the rail and can be mounted in any position. Supply can enter from either the top or bottom, which simplifies wiring in tight enclosures. The IP20 rating applies only when installed in a distribution board with conductors connected.
Construction and compliance
The housing is halogen-free and silicon-free, important for environments where outgassing could contaminate contacts or sensitive electronics. Pollution degree 2 (non-conductive pollution only) and overvoltage category III (fixed installation with downstream sub-distribution) are the rated environmental conditions. Surge voltage resistance is 4 000 V, insulation voltage (Ui) is 264 V. Energy limitation class 3 means it limits let-through energy to a low level during a fault, reducing stress on downstream equipment.