Siemens QF240A GFCI Ground Fault Circuit Breaker

Siemens QF240A is a 2‑pole, 40‑amp GFCI circuit breaker designed for 120/240‑V single‑phase systems, delivering ground‑fault protection with an integrated self‑test function. This plug‑in device provides 10 kA interrupt capability (AIC) and operates with a 5 mA ground‑fault trip threshold to quickly disconnect power when a fault to earth is detected. It is UL 943 compliant, featuring a self‑test and lockout design to verify proper operation, and is intended for use in Siemens load centers that accept QF series breakers. Ideal for branch circuits requiring personnel protection in residential or light commercial installations, the QF240A is suitable where moisture or outdoor exposure demands GFCI protection on 120/240 V circuits, such as kitchens, bathrooms, garages, and other areas where outlets may be used in damp environments. In practice, it protects downstream receptacles and loads by interrupting power on fault conditions while allowing normal operation on fault‑free loads, and it resets only after the fault is cleared and the device is manually re‑energized.