Zinsco QB20 Molded Case Circuit Breaker
- 20A
- 1 Pole
- Bolt-On
Quantity
Zinsco QB20 - 20A 1 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Maintaining legacy commercial electrical systems, this single-pole 20A breaker provides essential overload defense. The SWD designation ensures it can safely handle the repetitive switching of fluorescent lighting circuits. Designed specifically for vintage Zinsco panelboards, the bolt-on configuration establishes a rigid connection to the busbar. This component serves as a direct swap for failing units, often replaced by the UBIZ20B.Specifications
| Brand | Zinsco |
|---|---|
| Part Number | QB20-R |
| Series | QB |
| Amperage | 20A |
| Poles | 1 |
| Mounting Style | Bolt-On |
| Voltage | 120/240VAC |
| Phase | 1 |
| AIC Rating | 10kA @ 120/240VAC |
| Terminal Type | Lugs |
|---|---|
| For Use With | Zinsco Panelboards |
| Wire Gauge | 14-8 AWG (Al/Cu) |
| Max Wire | 8 AWG |
| Min Wire | 14 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed |
| Accessories | Load Side Lugs Included |
|---|---|
| Standards | UL 489 |
| Approval | UL |
| Temp Rating | 40C |
| Construction Features | SWD Rated |
Product FAQs
6 answersWhat panelboards accept the Zinsco QB20 circuit breaker?
The QB20 is designed specifically for legacy Zinsco panelboards that require a bolt-on connection. It will not fit in standard residential Zinsco plug-on load centers or panels from other manufacturers.
What is the modern aftermarket replacement for the obsolete Zinsco QB20?
Because original Zinsco breakers are no longer manufactured, the Connecticut Electric UBIZ20B is commonly used as a direct, newly manufactured substitute for the QB20 in vintage bolt-on systems.
How is the QB20 secured to the panel busbar?
Unlike standard plug-on breakers, the QB series features a bolt-on mounting style. This requires the breaker to be physically bolted to the panelboard busbar, ensuring a rigid and secure electrical connection in aging systems.
Is the QB20 rated for switching lighting circuits?
Yes, this breaker carries an SWD (Switching Duty) designation, meaning it is approved to safely handle the repetitive switching operations of fluorescent lighting circuits without degrading the internal contacts.
Are original Zinsco QB series breakers still in production?
No, the original Zinsco company ceased operations decades ago, making OEM QB20 breakers obsolete. Electricians maintaining these legacy systems must rely on surplus inventory or approved aftermarket substitutes.
How does the thermal-magnetic trip unit function on the QB20?
The breaker uses a fixed trip unit with Long-Time and Instantaneous (LI) functions. The thermal element provides delayed tripping for sustained overloads, while the magnetic element trips immediately to clear short-circuit faults.
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Reviews
Review summary
Customers rate this product 5.0 out of 5 based on 1 review.
- MCMarcos C.Verified BuyerReviewingEaton / Cutler-Hammer QB1030GF - 30A GFCI Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars11/20/25circuit breakers
good product and showed up on time