Square D KI36250 Molded Case Circuit Breaker

This breaker is designed specifically for Square D I-Line panelboards and switchboards. Its I-Line style plug-in connection allows the breaker to connect directly onto the interior bus structure, eliminating the need for separate cable connections on the line side.

As a current-limiting circuit breaker, it is engineered to trip exceptionally fast during a severe short circuit. This rapid action minimizes the peak let-through current and arc energy, offering enhanced protection for sensitive downstream electrical equipment.

The KI36250 features a thermal-magnetic trip unit with fixed thermal and adjustable magnetic settings. The 250-amp continuous overload rating cannot be changed, but you can dial in the instantaneous magnetic trip point to match specific motor startup or inrush current needs without nuisance tripping.

The standard mechanical lugs on this breaker are rated for dual-rated use with both aluminum and copper conductors (Al/Cu). They accept wire gauges ranging from 4 AWG up to 350 kcmil.

The LI designation indicates that the breaker provides Long-Time and Instantaneous protection. The Long-Time function protects against gradual heat build-up from continuous overloads, while the Instantaneous function clears the circuit immediately when a massive short circuit is detected.

The KI36250 belongs to the legacy K-Frame series, which is no longer in active production for new distribution builds. It remains highly sought after as a direct footprint replacement to avoid expensive panel retrofits. New electrical designs generally specify the modern PowerPact series instead.