Square D QOB335-1021 Miniature Circuit Breaker

The -1021 suffix indicates that this breaker includes a factory-installed shunt trip mechanism. This allows the breaker to be opened remotely via a 120/208/240V AC control signal.

This bolt-on circuit breaker is designed specifically for Square D NQ and NQOD series panelboards. It cannot be installed in standard QO load centers, which require plug-on breakers.

QO breakers are plug-on units typically used in residential and light commercial load centers. QOB breakers, like the QOB335-1021, feature a bolt-on design that secures directly to the panelboard bus bar, providing the robust mechanical connection required in commercial and industrial environments.

The Square D Visi-Trip feature provides clear visual confirmation when the breaker trips. The handle moves to a center position and a bright red indicator appears in a dedicated window, allowing electricians to quickly identify the tripped circuit in a fully populated panel.

The thermal-magnetic mechanism delivers dual protection. The thermal element responds to gradual overloads by heating and tripping the breaker, while the magnetic element provides instantaneous tripping in the event of a severe short circuit.