Square D FI36040 Molded Case Circuit Breaker

This breaker is designed exclusively for Square D I-Line power distribution panelboards and switchboards. It utilizes a plug-on jaw assembly that connects directly to the I-Line bus system.

The FI frame is a legacy molded case circuit breaker. For modern panelboard upgrades, engineers typically specify the Square D PowerPact H-frame series, such as the HRA36040, which offers similar high-interrupting capabilities and fits I-Line panelboards.

As a current-limiting circuit breaker, it clears severe short circuits extremely fast, typically within a half-cycle. This rapid response reduces the peak let-through current and thermal energy, protecting downstream equipment from severe electrical faults.

Yes, this thermal-magnetic breaker is rated for DC applications. It provides an interrupting capacity of 10kA at 250VDC, making it suitable for industrial DC control circuits or battery systems.

The breaker features a plug-on line connection with a jaw assembly that pushes directly onto the panelboard busbars. A retaining bracket and mounting screw secure the breaker to the backpan, ensuring a solid mechanical and electrical connection.

No, the FI36040 features a fixed thermal and fixed magnetic trip unit. The Long-Time and Instantaneous trip curves are factory-set and cannot be adjusted in the field.

Yes, proper torque is critical to prevent thermal failure. While the lugs accept 14 AWG to 1/0 AWG copper or aluminum wire, the exact torque value depends on the wire size used and will be printed directly on the breaker faceplate label.

Regular visual inspections should verify that the I-Line jaw contacts are clean and free of pitting. Electricians should also periodically exercise the breaker mechanism to keep the internal contacts clear and verify that the load-side lugs are torqued to the manufacturer specifications.