Panel fit and derating
The Siemens 5SU1324-6FM20 is a 2-pole RCBO from the SENTRON 5SU1 series, combining overcurrent and residual current protection in a single 54 mm wide unit (3 width units). It's rated 20 A at 30 °C with a B tripping characteristic and Type A fault current detection, breaking 10 kA per EN 60898. That 10 kA SCCR at 400 V means it safely interrupts faults up to that level without cascading upstream — standard for final subcircuits in commercial and light industrial panels. The 77 mm depth (70 mm installation depth) fits standard distribution boards; mounting position is unrestricted. Terminals accept 0.75 to 35 mm² solid or stranded copper.
Thermal derating curve
The 20 A rating holds at 30 °C ambient. At 40 °C it's 18.8 A, at 45 °C it's 18.2 A, at 50 °C it's 17.4 A, at 55 °C it's 16.2 A, at 60 °C it's 16.2 A, at 65 °C it's 15.4 A, and at 70 °C it's 14.6 A. If the panel runs hot — say 50 °C inside a sealed enclosure — the usable continuous current drops to 17.4 A. The ambient operating range is -25 to +55 °C; storage range is -40 to +75 °C.
Compliance and approvals
Rated breaking capacity is 10 kA per EN 60898. Overvoltage category III. Energy limiting class 3. Halogen-free and silicon-free construction. IP20 with distribution board installed and conductors connected. Supply cord can enter from top or bottom. The product is classified per DIN EN 61346-2 and DIN EN 81346-2 as function F.