The 5SM2326-0 is a Siemens SENTRON residual-current device (RCD) designed as a companion unit for the 5SL4 series MCBs. It is a 2-pole, instantaneous-trip device rated for AC residual currents only — meaning it detects sinusoidal AC earth faults but not pulsating DC or smooth DC faults. The headline 63 A rating applies at 40 °C ambient. The derating curve is published: at 50 °C the continuous current drops to 56.7 A, at 60 °C to 53.55 A, and at 70 °C to 50.4 A. If the distribution board runs hot — say, a packed enclosure near a boiler or in a roof space — use the 50 °C or 60 °C figure for your load calculation, not the 40 °C number. Insulation voltage (Ui) is 460 V, and the unit withstands a 4 kV surge (overvoltage category III). Operating frequency is fixed at 50 Hz.
Occupies 2 modular width units (MW) on a DIN rail. Fastening method is standard REG (regular) clip-on. Mounting position is any orientation. Depth is 70 mm, matching the 5SL4 MCBs it pairs with — the assembly sits flush in a distribution board without protruding beyond the MCB body. The IP20 rating is conditional: it applies only when the distribution board is installed and conductors are connected. During panel assembly or service, the live terminals are exposed — standard safe-working precautions apply.