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Square D QO2125-1021 QO21251021 - 125A 2 Pole Miniature Circuit Breaker
- 125A
- 2 Pole
- Plug-On
Square D
QO2125-1021
QO21251021 - 125A 2 Pole Miniature Circuit Breaker
Brand
Square D
SKU
QO2125-1021
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Square D QO21251021 - 125A 2 Pole Miniature Circuit Breaker
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Description
Built for commercial and industrial control applications, this 125-amp miniature breaker includes a factory-installed shunt trip mechanism for remote opening of the circuit. The unit mounts securely into Square D QO load centers, as well as NQ and NQOD panelboards, providing versatile integration for complex electrical systems. Facility managers can rely on the integrated Visi-Trip indicator to quickly identify tripped status, streamlining maintenance and minimizing downtime during power events.Specifications
| Brand | Square D |
|---|---|
| Part Number | QO21251021 |
| Series | QO |
| Amperage | 125A |
| Poles | 2 |
| Mounting Style | Plug-On |
| Voltage | 120/240VAC |
| Phase | 1 |
| AIC Rating | 10kA @ 120/240VAC |
| Terminal Type | Box Lugs |
|---|---|
| For Use With | QO Load Centers, NQ Panelboards, NQOD Panelboards |
| Wire Gauge | 4 AWG-2/0 AWG (Al/Cu) |
| Max Wire | 2/0 AWG |
| Min Wire | 4 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed |
| Available Options | Auxiliary Switch, Alarm Switch, Padlock Attachment |
|---|---|
| Accessories | Shunt Trip |
| Standards | HACR, UL 489, CSA C22.2 No. 5 |
| Approval | CSA, HACR, UL |
| Temp Rating | 40C |
| Construction Features | Visual Trip Indicator, HACR Rated, Common Trip |
Product FAQs
8 answersWhat does the -1021 suffix mean on the QO2125-1021 circuit breaker?
The -1021 suffix indicates that this breaker includes a factory-installed 120/240V AC shunt trip mechanism. This accessory allows the breaker to be opened remotely using an external control signal.
Which electrical panels are compatible with the QO2125-1021?
This plug-on breaker fits Square D QO load centers, as well as NQ and NQOD panelboards. Before installation, verify that your specific panel bus is rated to accept a 125A branch breaker, as some smaller load centers have lower maximum branch limits.
Can I install this QO breaker in a bolt-on panelboard?
No, the QO2125-1021 features a plug-on mounting style. If your panel requires bolt-on connections, you will need to source the equivalent QOB series circuit breaker instead.
How do I identify if the QO2125-1021 has tripped?
Like most Square D QO miniature circuit breakers, this model features a Visi-Trip indicator. When the breaker trips due to an overcurrent or a shunt trip signal, the handle moves to a center position and a bright red flag appears in the indicator window.
What wire sizes are accepted by the terminals on this 125A breaker?
The box lugs accommodate 4 AWG to 2/0 AWG wire. They are rated for both aluminum and copper (Al/Cu) conductors. When using aluminum wire, applying a listed joint compound is recommended to prevent oxidation.
Is the shunt trip on the QO2125-1021 field-installable?
No, the 120/240V AC shunt trip on this specific model is factory-installed. Square D does not offer field-installable shunt trips for standard QO miniature circuit breakers.
How does the thermal-magnetic trip mechanism protect the circuit?
The breaker uses fixed Long-Time and Instantaneous (LI) trip functions. The thermal component provides delayed tripping for prolonged overloads, while the magnetic component trips instantaneously to protect against severe short circuits.
Does the QO2125-1021 require any special mounting hardware?
No special hardware is required for standard installation. It utilizes a standard plug-on mounting design that snaps directly into the bus bar of compatible QO, NQ, or NQOD panels.
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Reviews
Review summary
Customers rate this product 4.9 out of 5 based on 285 reviews.
Reviews Summary
Generated by AI from 100 most recent customer reviews
Last updated 6/13/26
Customers say these circuit breakers arrive quickly and work as described. Fast shipping and competitive pricing are frequently mentioned, with many noting same-day or next-day delivery. Users appreciate the wide inventory, particularly for hard-to-find older-style models unavailable locally. The products function reliably and arrive in good condition. Most customers report straightforward ordering and positive interactions. However, some experienced delivery delays or received incorrect items requiring reordering. A few noted concerns about condition upon arrival or customer service responsiveness.
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Rating
285 reviews
- GCGerard C.Verified BuyerReviewingSquare D QO130GFI - 30A GFCI Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/21/26Great !
I could not find the breaker in hardwood stores. Superbreakers took car of it in a week.
- RHRoy H.Verified BuyerReviewingSquare D QO280 - 80A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/17/26Square D QO280 - 80A 2 Pole Miniature Circuit Breaker
Exactly as described
- KWKevin W.Verified BuyerReviewingSquare D QO120 - 20A 1 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/15/26Great Price
Brand spanking new!
- CEchristopher e.Verified BuyerReviewingSquare D QO115PDF - 15A Dual Function Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/11/26My breakers
Had a hard time locating these breakers locally, when I did find 1 they wanted to charge me triple what superbreakers charged. Items delivered exactly when they said they would, were exactly what I ordered. Appreciated the ease of ordering, definitely my go to from this point on
- JCJerry C.Verified BuyerReviewingSquare D QO250 - 50A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars9/8/26Great quality
No issues