Siemens Q21540CT Type QT molded‑case circuit breaker is a quad‑style, 2‑pole unit for 120/240 VAC circuits, rated 15–40 A with a 10 kA interrupt rating. It uses a thermal‑magnetic trip with common‑trip design to ensure all poles disconnect together during a fault. Designed for Siemens load centers, it is compatible with QT quad‑style installations in Type EQL, SEQ, and EQG panels. The catalog number Q21540CT corresponds to a 40 A rating at 120/240 VAC, with QT family variants spanning the 15–40 A range.
