Square D KC34125 Molded Case Circuit Breaker

This K-frame circuit breaker is designed exclusively for Square D I-Line panelboards and switchboards. It utilizes a specialized plug-in mounting system that connects directly to the I-Line bus stack, eliminating the need for separate line-side wire terminations.

No. The KC34125 is engineered specifically for I-Line architectures. It is completely incompatible with NQ, NQOD, or NF panelboards, which require entirely different breaker frames and bus connections.

The KC34125 features a thermal-magnetic trip unit with a fixed thermal element for overload protection and an adjustable magnetic element for short-circuit protection. The adjustable setting allows electricians to coordinate the instantaneous trip point with downstream devices to isolate faults more efficiently.

Installation involves pushing the molded line-side jaws onto the I-Line bus stack and tightening a captive retaining screw with a screwdriver. This ratchets the breaker firmly onto the bus, ensuring a secure and maintenance-free line connection.

The factory-installed mechanical lugs on the load side will accept either aluminum or copper conductors ranging from 4 AWG to 350 kcmil. It is recommended to apply an approved oxide-inhibiting compound when terminating aluminum conductors.

The KC series is part of the legacy K-frame molded case circuit breaker family. While newer installations typically utilize the PowerPact H-frame or J-frame series, this K-frame breaker remains fully supported as a direct replacement component for existing I-Line panelboards.

The plug-on design inherently reduces exposure to live line-side wiring. By connecting directly to the insulated bus stack, it eliminates the risk of loose line-side cable terminations that can lead to hazardous thermal hot spots or arcing over time.