ZINSCO QB24-3100 U 100A 240V 2-pole Molded Case Circuit Breaker QB243100

Description:

The Zinsco QB24-3100 U is a 100 Amp, 2-pole molded case circuit breaker designed for use in Zinsco / GTE Sylvania panelboards. It operates on 240V systems and features a thermal-magnetic trip mechanism to provide protection against overloads and short circuits. This breaker belongs to the QB24 (QB series) and uses a bolt-on mounting design for a secure connection to the panel bus. While exact suffix variations exist, comparable models in the same QB24 family (e.g., QB243100) are rated at 100A, 240V with bolt-on mounting and standard interrupt capacity around 10 kAIC, and are now discontinued.

Applications:

The Zinsco QB24-3100 breaker is commonly used in residential and commercial electrical systems as a main or feeder breaker for subpanels, HVAC systems, large appliances, and distribution circuits requiring 100A protection. It is installed in Zinsco bolt-on panelboards typically found in older installations and is primarily used today for maintenance or replacement of existing systems.

Technical Specifications:

• Manufacturer: Zinsco / GTE Sylvania / Challenger
• Model / Part Number: QB24-3100 U (QB24 series)
• Product Type: Molded Case Circuit Breaker (Bolt-On)
• Poles: 2-Pole
• Current Rating: 100 Amps
• Voltage Rating: 240 VAC
• Mounting: Bolt-on (QB series)
• Trip Type: Thermal-magnetic (LI – long-time & instantaneous)
• Interrupt Rating: ~10 kAIC @ 240V (typical QB series)
• Function: Overcurrent and short circuit protection
• Status: Obsolete / discontinued

Common Replacements:

• Square D QOB2100 2-Pole 100A Bolt-On Circuit Breaker
• Siemens BQD2100 2-Pole 100A Bolt-On Breaker
• Eaton BAB2100H 2-Pole 100A Bolt-On Breaker