The Siemens 5SU9354-8KK10 is a 1P+N RCD-operated circuit breaker (RCBO) from the SENTRON 5SU9 family. It combines overcurrent protection with residual current detection in a single 36 mm wide unit — that's two width units on a DIN rail. The Type A fault current detection catches pulsating DC residual currents, which standard AC-only RCDs miss. Ambient temperature range is -25 to +45 °C, with derating above 40 °C — at 45 °C it carries 9.1 A, at 50 °C it's 8.7 A. That's the figure to watch if the breaker sits near other heat sources in a crowded enclosure.
Supply can land on either top or bottom terminals; no polarity restriction on the line side.