The Siemens 5SU1353-1KL40 is a SENTRON-series residual current circuit breaker with overcurrent protection (RCBO) in a 1P+N, 2-pole format, combining ground-fault and short-circuit/overload protection in one 36 mm wide (2 MW) module. Breaking capacity is 4.5 kA per EN 60898 and 5 kA per IEC 60947-2 — enough for most sub-distribution boards downstream of a main breaker; the higher IEC figure covers industrial panel duty where the prospective fault current is known to be under 5 kA.
The 40 A rating holds only at 30 °C; at 40 °C it derates to 37.6 A, at 50 °C to 34.8 A, and at 70 °C to 29.2 A. Mounting position is any orientation (vertical, horizontal, flat), and supply can enter from top or bottom — useful when retrofitting into an existing board where the busbar layout is fixed.
Physical fit and compliance
Dimensions: 77 mm deep (70 mm installation depth behind the panel face), 36 mm wide (2 modular width units), 90 mm tall. Fits standard DIN-rail enclosures with 2-pole busbar takeoffs. Overvoltage category III, pollution degree 2, surge voltage resistance 4 kV — suitable for fixed-installation distribution boards. Halogen-free and silicon-free construction, energy limitation class 3.