Zinsco Q2430-40DU Molded Case Circuit Breaker

The Zinsco Q2430-40DU Molded Case Circuit Breaker is a 3-pole, 40-amp unit designed for 240 V systems and compatible with Zinsco/GTE Sylvania panelboards. It uses a thermal-magnetic Magnatrip trip mechanism to provide overload and short-circuit protection, with an interrupt rating of approximately 10 kAIC at 240 V, and is built for plug-in mounting in the Q24 frame with load-side lug terminals. The “D” designation indicates suitability for delta 3-phase configurations, making it suitable for industrial and commercial delta power systems that require 40 A protection for motors, compressors, pumps, or distribution feeders. This model is now obsolete and typically available only as surplus or refurbished units, reflecting its legacy role in older installations. Common replacements in modern layouts include Square D QOB340 3-Pole 40A Bolt-On, Siemens BQD340 3-Pole 40A Bolt-On, and Eaton BAB3040H 3-Pole 40A Bolt-On breakers.