Siemens 5SU1354-3KK20 — SENTRON RCBO, 20 A, B-Curve, Type F
The Siemens 5SU1354-3KK20 is a 2-pole RCBO from the SENTRON series, combining overcurrent protection with residual current detection in a single 36 mm wide, 2-module-width unit.
The 20 A rating at 30 °C is the headline figure, but the derating curve matters more for a warm panel: at 40 °C the continuous current drops to 18.8 A, at 50 °C to 17.4 A, and at 70 °C to 14.6 A. If your enclosure ambient runs above 40 °C, the BOM current must be checked against the derated value, not the 30 °C number. The B-curve (3–5× In magnetic trip) is standard for residential and commercial lighting and socket-outlet circuits; it avoids nuisance trips on modest inrush from small motors or capacitive loads. Type F residual current detection is the key differentiator here. It responds to AC, pulsating DC, and mixed-frequency fault currents up to 1 kHz, which covers the leakage profile from single-phase VFDs, washing machine drives, and LED drivers. Standard Type A RCDs can miss high-frequency components; Type F catches them, so this RCBO is the correct choice when the load side includes frequency converters or switched-mode power supplies that generate smooth or high-frequency residual currents. The Super resistant K design indicates enhanced immunity to surge currents and voltage transients, reducing the risk of nuisance tripping in industrial environments with frequent switching events or lightning-induced surges. This is a robustness feature, not a rating change — the breaking capacity and trip curve remain as listed.
The 5SU1354-3KK20 snaps onto a 35 mm DIN rail per EN 60715, occupying 2 modular width units (36 mm).
It carries the SENTRON brand designation and is classified per IEC 81346-2 and DIN EN 61346-2 as function F (protection device).