Schneider Electric LJA36400CU31X Molded Case Circuit Breaker

The C indicates that this circuit breaker is 100 percent rated. Unlike standard 80 percent rated breakers, this unit can continuously carry its full 400A capacity without overheating, provided it is installed in a properly sized and ventilated enclosure.

It features the MicroLogic 3.3 electronic trip unit, designated by the U31X suffix. This provides True RMS sensing and adjustable Long-Time and Instantaneous (LI) protection for precise system coordination.

The LJA36400CU31X utilizes a plug-on design for the line side. The breaker jaws snap directly onto the bus assembly of a Square D I-Line panelboard or switchboard, while the load side uses traditional mechanical lugs.

The load side mechanical lugs accept two cables per phase, ranging from 2/0 AWG to 500 kcmil. The terminals are dual-rated for either aluminum or copper conductors.

No. This breaker is specifically designed for the heavy-duty bus structure of Square D I-Line panelboards and switchboards. It will not fit in QO, NQ, or NF series enclosures.

While they share the same 400A capacity, the newer PowerPacT L-Frame has different physical dimensions and utilizes electronic trip technology. You must verify that your specific I-Line panel has adequate physical space before upgrading from a legacy thermal-magnetic frame.

Yes. Within the PowerPacT L-Frame family, the J interrupting class is UL Certified as current limiting. This reduces the peak let-through current and thermal stress on downstream equipment during a severe short circuit fault.

Yes, it includes an integral push-to-trip button on the front cover. This allows maintenance personnel to safely trip the breaker manually to ensure the internal mechanical linkages operate freely.

Yes, but with strict limitations. According to manufacturer guidelines, 3-pole PowerPacT L-Frame breakers with MicroLogic trip units are marked for single-phase use on 240VAC circuits only. You can use any two poles for this specific application.