Square D QOU225 Miniature Circuit Breaker

While they share the same internal thermal-magnetic trip mechanisms, their mounting styles differ. QO breakers are plug-on for QO load centers, QOB breakers bolt directly to NQ panelboard busbars, and QOU breakers like the QOU225 are unit-mounted. The QOU225 uses a bolt-on connection to secure to the panel backplate and features box lugs on both ends for feed-through wiring.

No. Although they share a 2-pole, 25A capacity, their panel connections differ. A QOU225 is designed to bolt onto a backplate or mount to a DIN rail, whereas QO225 breakers plug onto a busbar and QOB225 breakers bolt onto a busbar.

No. As a unit-mount breaker, the QOU225 is designed to be installed independently. It is commonly mounted directly in OEM equipment, control panels, DIN rail systems, or custom enclosures, rather than clipping onto a residential load center busbar.

QOU unit-mount breakers are fully compatible with DIN rail installations. However, depending on the rail profile, a separate Square D QOU DIN rail mounting bracket or adapter plate may be required to snap the breaker securely into place.

Yes. Standard QOU thermal-magnetic breakers do not have dedicated line and load terminal requirements. They can be safely reverse-fed, which is often required when utilizing the breaker as a standalone disconnect switch in a custom enclosure.

With its 48VDC rating and 5kA interrupting capacity, this breaker is frequently utilized in DC control panels, battery backup systems, and industrial telecommunications equipment. It provides reliable thermal-magnetic protection for low-voltage DC circuits just as it does for standard AC power.