Siemens Q21540CT 15/40A Triplex Miniature Circuit Breaker

Yes. Siemens provides a UL-approved substitution letter authorizing Siemens QT series breakers as direct replacements for Murray MP series breakers. The Q21540CT is an exact replacement for the obsolete Murray MP21540CT.

This triplex breaker requires two standard 1-inch panel spaces. It provides two independent 15A single-pole circuits and one 40A double-pole circuit within that footprint to maximize panel density.

This breaker is compatible with Siemens EQ, PL, ES, and Ultimate series load centers that are listed to accept Type QT breakers. It includes a CTL (Circuit Total Limiting) rejection clip, so the panel busbar must be notched to accept CTL breakers.

Yes, the inner 40A double-pole circuit has a common-trip mechanism, ensuring both legs disconnect simultaneously during an overload or short circuit. The outer 15A single-pole circuits operate and trip independently.

The outer 15A poles accept 14-6 AWG copper or 12-6 AWG aluminum conductors. The inner 40A poles accept 8-6 AWG copper or 8-4 AWG aluminum conductors. Always torque the terminal lugs to the specifications printed directly on the breaker label.

No. This is a standard thermal-magnetic breaker designed for overload and short-circuit protection. It does not provide Arc-Fault Circuit Interrupter (AFCI) or Ground-Fault Circuit Interrupter (GFCI) functionality.