Zinsco QB24-100NU Molded Case Circuit Breaker

The Zinsco QB24-100NU is a 2-pole, 100 Amp molded‑case circuit breaker designed for Zinsco / GTE Sylvania panelboards, rated for 240 VAC with a thermal‑magnetic trip that protects circuits from overloads and short circuits. It uses bolt‑on mounting to secure a solid electrical and mechanical connection to the panel bus and belongs to the QB series. This single‑phase device is intended as a main or feeder breaker in residential and commercial distribution systems, suitable for subpanels, large appliances, HVAC equipment, and other high‑load loads requiring 100 A protection. It offers an interrupt rating of approximately 10 kAIC at 240 V. The QB24‑100NU is discontinued/obsolete, with common replacements including Square D QOB2100 2-Pole 100A Bolt-On Circuit Breaker, Siemens Q2100 / BQD2100 2-Pole 100A Circuit Breaker, and Eaton BAB2100H 2-Pole 100A Bolt-On Breaker.