The Siemens SENTRON 5SU9346-1CN40 is a 4-pole RCBO — residual current operated circuit breaker with overcurrent protection — rated 40 A at 30 °C ambient, with a 30 mA residual trip threshold and a C tripping characteristic. This is the variant that combines the MCB and RCD functions in a single 7-module-width unit, saving a DIN-rail position compared to separate devices. The C-curve (tripping between 5 and 10 times rated current) is the standard choice for motor-starter and lighting circuits with moderate inrush; the 30 mA residual sensitivity covers personnel protection (indirect contact) and fire prevention in TN and TT systems.
Ratings and what they mean for the panel
The 6 kA breaking capacity per EN 60898 is the rated short-circuit capacity for domestic and light commercial distribution boards — adequate for most sub-distribution applications where the prospective fault current at the board is below that threshold. The insulation voltage is rated 440 V, matching standard 400 V three-phase networks with headroom. The 40 A rating holds at 30 °C; at 40 °C it derates to 37.2 A, at 45 °C to 35.6 A, at 50 °C to 34.8 A, and at 55 °C to 34 A (–) — so if the panel ambient runs hot, factor the derating into the load schedule. The Type AC residual current detection means it trips on sinusoidal AC fault currents only — not on pulsed DC or smooth DC. That is fine for general-purpose circuits feeding resistive, inductive, or conventional rectifier loads, but if the downstream equipment includes variable-speed drives, LED drivers, or UPS systems that generate DC fault components, a Type A or Type F RCD would be required. The product is halogen-free and silicon-free, which matters for installations with strict fire-load or outgassing requirements.
Mounting and integration
The 5SU9346-1CN40 occupies 7 modular width units on a DIN rail, with a depth of 77 mm and an installation depth of 70 mm. It can be mounted in any position, and the supply can enter from either top or bottom. The IP20 rating is standard for enclosed distribution boards — the touch protection is integral. Overvoltage category III and pollution degree 2 confirm suitability for fixed-installation sub-distribution panels.