What it is and what it does
The Siemens 5SU9336-1CN40 is a 3-pole RCD-operated circuit breaker from the SENTRON family — a combined residual current device and overcurrent protection in one 6-module-width unit. It's rated 40 A at 30 °C with a 30 mA AC-type residual trip and a C-curve magnetic trip characteristic, giving it the short-circuit and overload response profile typical for motor and lighting circuits where inrush is moderate.
What the ratings mean for fit
The 6 kA breaking capacity is certified to both EN 60898 and IEC 60947-2 — the first governs domestic-type installations, the second covers industrial panel applications. That dual rating means the same part satisfies residential distribution boards and light industrial sub-distribution without a separate coordination study at the 6 kA fault level. The 30 mA residual trip is AC-type, so it detects sinusoidal AC earth faults only. For pulsed DC or smooth DC fault currents (common on VFD-fed circuits or EV chargers), you would need an A-type or B-type RCBO — this part is not a fit there. The C-curve (magnetic trip at 5–10× In) handles motor start and capacitor bank inrush without nuisance tripping, but on highly inductive loads verify the inrush peak stays under 400 A (10 × 40 A). Thermal derating is published: 40 A at 30 °C, 37.2 A at 40 °C, 35.2 A at 45 °C, 34.4 A at 50 °C, and 33.2 A at 55 °C. If the panel ambient runs at 40 °C, the usable continuous current drops to 37.2 A — size the downstream load accordingly. The insulation voltage is rated 440 V, overvoltage category III, pollution degree 2. That means it's designed for fixed-installation distribution boards with transient overvoltages up to 4 kV — standard for building-level sub-distribution. The IP20 rating applies only when installed in a distribution board with conductors connected; the device itself is not rated for wet or dusty environments.
Panel integration notes
The 5SU9336-1CN40 occupies 6 modular width units (108 mm) on a DIN rail, with a depth of 77 mm and an installation depth of 70 mm. Mounting position is any orientation. The supply cable can enter from either top or bottom. Touch protection is built in, and the unit is halogen-free and silicon-free — relevant for clean-room or corrosive-environment installations where outgassing matters.