What it is and what it does
The Siemens 5SU9326-1CN16 is a 2-pole RCD-operated circuit breaker (RCBO) from the SENTRON family, combining overcurrent and residual current protection in a single 4-module-width unit. It's rated 16 A with a 30 mA residual trip, Type C characteristic, and a 6 kA breaking capacity per EN 60898. That means it protects both against overload/short-circuit and earth leakage in one device — saving a DIN rail slot versus separate MCB + RCD.
Ratings that matter for fit
The 16 A rating holds at 30 °C; derate to 14.6 A at 40 °C, 13.9 A at 45 °C, 13.3 A at 50 °C, and 12.5 A at 55 °C. If your panel ambient runs above 40 °C, size the load accordingly — the 16 A nameplate is only good at the lower end of the operating range. The 30 mA residual-current trip (Type AC) catches sinusoidal AC fault currents to ground. Fine for general-purpose circuits feeding resistive and electronic loads, but not for pulsating DC faults — that would need a Type A device. Overvoltage category III and pollution degree 2 suit it for fixed-installation distribution boards. Breaking capacity is 6 kA per EN 60898, adequate for most residential and light commercial sub-distribution boards where the prospective short-circuit current stays under that threshold. The 4 kV surge voltage resistance (impulse withstand) covers typical mains transients.
Mounting and integration
Snaps onto standard DIN rail, 4 module widths (72 mm wide). Depth is 77 mm overall, with 70 mm installation depth — check your enclosure's internal clearances. Feed from top or bottom.