Square D HJA36040 Molded Case Circuit Breaker

This breaker features an I-Line style plug-in connection and is specifically designed for use in Square D I-Line panelboards and switchboards. It is not compatible with standard NQ, NF, or QO series load centers.

The "J" indicates the specific interrupting rating tier within the Square D PowerPacT H-Frame family. It denotes a higher short-circuit fault capacity compared to the standard "D" or "G" rated versions, making it suitable for systems with higher available fault currents.

All three models share the exact same physical dimensions, continuous current rating, and I-Line mounting footprint. The difference lies entirely in their short-circuit interrupting capacity. The HJA provides a higher interrupting rating than both the standard-duty HDA and the intermediate-duty HGA.

Yes. The PowerPacT H-Frame series was designed to directly replace older legacy F-Frame models. The HJA36040 will fit in the same footprint and attach to the same busbar as obsolete FA, FH, or FC series I-Line breakers.

The line side utilizes I-Line plug-on jaws that clamp directly onto the energized vertical bus in the panelboard, allowing for fast line connections without cables. The load side is equipped with standard mechanical lugs for landing your branch circuit wires.

"LI" stands for Long-Time and Instantaneous protection. The Long-Time (thermal) component provides fixed continuous overload protection. The Instantaneous (magnetic) component detects short circuits and is adjustable, allowing electricians to change the magnetic trip threshold to improve downstream selective coordination.