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Zinsco Q40 Miniature Circuit Breaker
- 40A
- 1 Pole
- Plug-On
Zinsco
Q40
Miniature Circuit Breaker
Brand
Zinsco
SKU
Q40
Quantity
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Zinsco Q40 - 40A 1 Pole Miniature Circuit Breaker
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Description
Providing essential overcurrent protection for residential circuits, the Zinsco Q40 is a 40-amp, single-pole breaker rated for 120/240VAC. It delivers reliable long-time and instantaneous trip functions to keep household wiring safe. Engineered to fit original Zinsco load centers, this plug-on unit restores functionality to aging electrical infrastructure. It serves as an exact hardware match for discontinued panels.Specifications
| Brand | Zinsco |
|---|---|
| Part Number | Q40-R |
| Series | Q |
| Amperage | 40A |
| Poles | 1 |
| Mounting Style | Plug-On |
| Voltage | 120/240VAC |
| Phase | 1 |
| AIC Rating | 10kA @ 120/240VAC |
| Frame Type | QC |
|---|---|
| Terminal Type | Lugs |
| For Use With | Zinsco Load Centers |
| Wire Gauge | 8-4 AWG (Cu/Al) |
| Max Wire | 4 AWG |
| Min Wire | 8 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Fixed Magnetic |
| Accessories | Lugs Not Included |
|---|---|
| Standards | UL 489, HACR Rated |
| Approval | UL |
| Temp Rating | 40C |
| Construction Features | HACR Rated |
Product FAQs
5 answersWhat is the modern replacement for the Zinsco Q40 circuit breaker?
The Connecticut Electric UBIZ40 is a direct, modern replacement for the original Zinsco Q40. It is an ETL-listed 40A, 1-pole breaker designed specifically to fit legacy Zinsco load centers.
Can I use the Zinsco Q40 in a Sylvania electrical panel?
Yes. Sylvania purchased Zinsco in the 1970s and continued manufacturing the same panel designs. The Q40 is compatible with both Zinsco and Sylvania load centers that accept Q-series or QC-frame breakers.
How does the Q40 breaker mount into the panel?
The Q40 utilizes a plug-on connection type. It snaps directly onto the aluminum busbars found in Zinsco load centers without requiring bolt-on hardware.
Are Zinsco panels and breakers safe to continue using?
Zinsco load centers have a documented history of busbar connection failures and breakers failing to trip during overcurrent events. While replacement breakers can restore functionality to an existing panel, many electricians recommend a complete panel upgrade for long-term safety.
What does the LI trip function mean on the Zinsco Q40?
The LI designation indicates that the thermal-magnetic breaker includes both Long-Time and Instantaneous trip functions. The long-time function protects against sustained overloads, while the instantaneous function trips immediately during a short circuit.
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Reviews
Review summary
Customers rate this product 5.0 out of 5 based on 47 reviews.
Reviews Summary
Generated by AI from 91 most recent customer reviews
Last updated 8/1/25
Customers say these circuit breakers arrive quickly and match their specifications perfectly. Many reviews mention success finding hard-to-locate specialty breakers through this supplier. Common feedback includes praise for the accurate product descriptions, reliable shipping, and competitive pricing. While some note occasional stock limitations, users consistently report the breakers fit and function as intended.
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Rating
47 reviews
- CGCrocefissa G.Verified BuyerReviewingSiemens Q115 - 15A 1 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/18/26Quick delivery and great price.
The circuit breakers are at a great cost.
- JBJason B.Verified BuyerReviewingSiemens Q2150B - 150A 2 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars9/18/26Great experience
The product was exactly what I needed and it arrived on time.
- DQDon Q.Verified BuyerReviewingSiemens Q3100 - 100A 3 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars9/14/26Siemens breaker
Great customer experience, great prices and fast shipping... Definitely will be buying her again.
- CSChristopher S.Verified BuyerRated 5 out of 5 stars8/12/26Siemens 60
Perfect new condition
- GSGeorge S.Verified BuyerReviewingSiemens Q2150B - 150A 2 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars3/4/26Great service
Every time I call or go online you have the parts I'm looking for.