Square D LDL36400U31X Molded Case Circuit Breaker

No, the LDL36400U31X is a unit mount molded case circuit breaker equipped with mechanical lugs on both the line and load ends. For I-Line panelboard applications, you will need an L-Frame breaker with an I-Line bracket termination on the line side, such as the LDA36400U31X.

The Micrologic 3.3 electronic trip unit (indicated by the U31X catalog suffix) features adjustable settings for Long-Time (L) and Instantaneous (I) protection. This allows you to fine-tune the overcurrent and short-circuit pickup levels to match specific load requirements and coordinate with downstream devices.

No, this breaker comes standard with factory-installed mechanical lugs on both the line and load sides. These dual-rated lugs are ready to accept copper or aluminum conductors right out of the box, simplifying the installation process.

The only difference is the short-circuit interrupting rating. The LDL36400U31X features a standard D tier rating (18kA at 480VAC), whereas the LGL36400U31X features a higher G tier rating (35kA at 480VAC). Both share the exact same physical footprint, terminal lugs, and Micrologic 3.3 electronic trip unit.

Yes. PowerPacT L-Frame circuit breakers feature a specialized accessory cover that allows for the field installation of internal components like shunt trips, undervoltage releases, and auxiliary switches. These can be added safely without opening the main breaker mechanism or voiding the UL listing.

The integral push-to-trip button provides a safe, mechanical method to manually trip the circuit breaker. This allows maintenance personnel to verify that the internal mechanical linkage is operating correctly before performing service or diagnostic work.

No. While the LDL36400U31X provides the same 400A capacity, the PowerPacT L-Frame has completely different physical dimensions and mounting footprints compared to the legacy LA or LH frame series. Replacing an older LA or LH breaker with this model will require structural panel modifications or a specific retrofit kit.

The D in the LDL prefix indicates Square D's standard interrupting capacity for this frame, providing a maximum fault-clearing limit of 18kA at 480VAC. It must only be installed in electrical systems where the maximum available fault current at the line terminals does not exceed this value. If the fault current is higher, a breaker with a G, J, or L interrupting tier is required.