Square D QOU3100 Miniature Circuit Breaker

No. The QOU3100 is a unit-mount circuit breaker meant for surface, flush, or DIN rail mounting in OEM panels and enclosures. It is not a plug-on breaker and will not fit standard Square D QO or QOB load centers.

While it is designed to be compatible with standard 35mm DIN rail systems, it does not snap on directly out of the box. It requires a separate Square D QOU mounting foot accessory to properly secure it to the rail.

Yes. Square D QOU miniature circuit breakers do not have restricted line and load markings. This allows them to be safely reverse-fed in field applications requiring alternate power flows.

Yes, factory-installed box lugs are included on both the line and load sides. They are rated to accept 12 AWG through 2/0 AWG copper or aluminum conductors.

Yes. Unlike many standard AC breakers, the QOU3100 is specifically rated to handle DC loads up to 60V DC with a 5kA interrupting capacity, making it suitable for control panels and DC power configurations.

The LI designation means the thermal-magnetic trip unit provides Long-Time (thermal overload) and Instantaneous (magnetic short-circuit) protection. This fixed trip profile is the standard requirement for most general-purpose branch circuit protection.

Yes. This 3-pole breaker uses an internal crossbar mechanism to ensure a common trip. If an overload or short-circuit occurs on any single phase, all three poles will open simultaneously to safely disconnect power.

Yes. The Square D QOU form factor has remained consistent over time. A new QOU3100 will physically match and directly replace older 100A 3-pole QOU units in existing enclosures or control panels.