Built for industrial applications, the Square D FCL34040 is a 3-pole, 40A current-limiting molded case circuit breaker. It provides reliable thermal-magnetic protection for demanding electrical systems. This unit-mount MCCB installs into Square D enclosures, switchboards, and motor control centers. As a legacy F-Frame component, it is officially replaced by the newer HJL36040 for modern upgrades. Rated at 65kAIC at 480VAC, it actively limits let-through energy to protect downstream equipment.
The FCL34040 is part of the legacy Square D F-frame family. For new installations, it has been superseded by the PowerPact H-frame series, though FCL breakers remain available for direct replacement in existing systems.
What does the current limiting designation mean for this breaker?
As a current limiting breaker, it is designed to clear severe short circuits extremely fast. This restricts the peak let-through energy, providing enhanced protection for downstream electrical equipment.
Can the trip settings on this breaker be adjusted in the field?
No. This breaker features a fixed thermal and fixed magnetic trip unit, meaning the long-time and instantaneous trip thresholds are factory set and cannot be modified.
Can I install this FCL breaker in an I-Line panelboard?
No. The FCL34040 is a unit-mount, feed-thru circuit breaker designed to be mounted with screws and wired with lugs. It does not have the plug-on jaw connections required for Square D I-Line panelboards.
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