The Schneider Electric A9R05240 is a 2-pole residual current circuit breaker (RCCB) from the Acti9 iID series, rated at 40 A with a 300 mA earth-leakage sensitivity. The selective time delay (S-type) means it coordinates with downstream RCCBs — it holds during transient earth faults and only trips on sustained leakage, keeping the rest of the distribution board live during a downstream fault. This is critical for selectivity studies in commercial panel builds.
Rated at 40 A continuous, this RCCB handles the full load current of a typical lighting or general-purpose submain. The 300 mA sensitivity is a common choice for fire protection in commercial and industrial installations — it avoids nuisance tripping from normal leakage in long cable runs or equipment with filters, while still clearing a ground fault that could cause arcing. The voltage-independent residual current tripping technology means the device does not need an external power supply to detect leakage — it will still trip even if the line voltage drops or the neutral is lost upstream. This is a reliability advantage over electronic RCDs in harsh supply conditions.
Installation and compliance notes
Designed for clip-on mounting on a DIN rail. IP20 rated (finger-safe) for the device body; IP40 when installed in a modular enclosure. Compliant with EN/IEC 61008-1 for RCCBs. The 8/20 µs impulse withstand of 3000 A ensures it survives surge events without nuisance tripping.