Engineered for commercial and industrial applications, the Square D FC24040AB is a 2-pole, 40A molded case circuit breaker. It provides reliable thermal-magnetic protection with long-time and instantaneous (LI) trip functions. This legacy F-Frame breaker installs into Square D I-Line panelboards and features a specific phase A-B connection. For modern upgrades, it is replaced by the PowerPacT HJA26040. Rated for 65 kAIC at 480VAC, it delivers extra-high interrupting capacity.
HACR Rated, Visual Trip Indicator, Extra High Interrupting Capacity, Phase A-B Connection, 2-Pole in 3-Pole Housing
Product FAQs
9 answers
What does the "AB" suffix in the FC24040AB catalog number indicate?
The "AB" suffix specifies the phase connection. It indicates that this 2-pole breaker connects directly to the A and B phases on the panelboard bus.
What type of panelboard accepts the FC24040AB circuit breaker?
This legacy F-frame breaker is designed exclusively for use in Square D I-Line panelboards and switchboards. It utilizes a specialized plug-on bus connection.
Is the FC24040AB still manufactured, or is there a modern replacement?
The FC series is a legacy F-frame breaker. For modern upgrades or replacements, Square D recommends the PowerPacT H-frame series. The direct modern equivalent is the HJA26040, which fits the same I-Line panelboards.
What does the 65kAIC rating at 480V mean for system coordination?
The 65kAIC rating indicates that this breaker can safely interrupt up to 65,000 amps of fault current at 480VAC. This extra-high interrupting capacity makes it suitable for commercial and industrial systems with high available fault currents.
How does the I-Line mounting system work for this breaker?
The breaker features a plug-on design with blow-on joint technology. The breaker jaws clamp directly onto the I-Line bus assembly, and a single mounting screw secures the unit to the panel backpan.
What safety precautions are required before installing this I-Line breaker?
Always de-energize the panelboard or switchboard before installation. Verify the power is completely off using a properly rated voltage sensing device, and wear appropriate personal protective equipment (PPE) in accordance with NFPA 70E guidelines.
Why is this 2-pole breaker housed in a 3-pole frame?
Square D I-Line 2-pole breakers like the FC24040AB are built into a standard 3-pole housing. This design maintains uniform spacing, phase isolation, and alignment on the panelboard bus structure.
Can the FC24040AB be used in DC electrical systems?
Yes, this thermal magnetic breaker is rated for use in DC applications up to 250VDC, where it provides an interrupting capacity of 10kA.
What type of trip unit is installed in the FC24040AB?
This breaker features a fixed thermal magnetic trip unit. It provides non-adjustable long-time (thermal) protection for overloads and instantaneous (magnetic) protection for short circuits.
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Review summary
Customers rate this product 5.0 out of 5 based on 2 reviews.