The Siemens 5SU9356-7KM20 is a SENTRON RCD-operated circuit breaker — an RCBO combining overcurrent protection and residual current detection in a single 2-module (36 mm wide) package. The 1P+N pole configuration switches the phase and monitors the neutral; the protected pole count is 1.
Thermal derating and conductor sizing
Current rating is temperature-dependent: 20 A at 30 °C ambient, derating to 18.8 A at 40 °C, 18.2 A at 45 °C, 17.4 A at 50 °C, and 16.2 A at 55 °C. The maximum power loss is 1.5 W.
Halogen-free and silicon-free construction, rated IP20 with conductors connected and the distribution board installed. Overvoltage category III, energy limiting class 3. Touch protection is fitted as standard.