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Square D QOB2451021 Miniature Circuit Breaker
- 45A
- 2 Pole
- Bolt-On
Square D
QOB2451021
Miniature Circuit Breaker
Brand
Square D
SKU
QOB2451021
Quantity
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Square D QOB2451021 - 45A 2 Pole Miniature Circuit Breaker
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Description
Providing remote disconnect capabilities, the Square D QOB2451021 is a 45-amp, 2-pole miniature circuit breaker. It is an excellent choice for commercial and industrial facilities requiring automated or emergency power shutoffs. This unit fastens securely into Square D NQ and NQOD panelboards using a standard bolt-on connection. The box lugs accept 8-2 AWG copper or aluminum wiring. It features a 120/208/240VAC shunt trip, a 10 kAIC rating, and a Visi-Trip visual indicator.Specifications
| Brand | Square D |
|---|---|
| Series | QOB |
| Amperage | 45A |
| Poles | 2 |
| Mounting Style | Bolt-On |
| Voltage | 120VAC, 120/240VAC, 48VDC |
| Phase | 1 |
| AIC Rating | 10kA @ 120VAC, 10kA @ 120/240VAC, 5kA @ 48VDC |
| Frame Type | QOB |
|---|---|
| Terminal Type | Box Lugs |
| For Use With | Square D NQ Panelboards, Square D NQOD Panelboards |
| Wire Gauge | 8-2 AWG (Al/Cu) |
| Max Wire | 2 AWG |
| Min Wire | 8 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 (120/208/240VAC) |
| Standards | CSA C22.2 No. 5, UL 489, HACR |
| Approval | CSA, HACR, UL |
| Temp Rating | 40C |
| Construction Features | HACR Rated, Common Trip, Visual Trip Indicator |
Product FAQs
9 answersWhat does the 1021 suffix mean on the QOB2451021 breaker?
The 1021 suffix indicates that this breaker includes a factory-installed 120/208/240 VAC shunt trip. This accessory allows the breaker to be opened remotely via an external control signal.
How many panel spaces does the QOB2451021 require?
Although it is a 2-pole breaker, the factory-installed shunt trip requires an additional pole space. It will occupy a total of three spaces in your panelboard.
Which panelboards are compatible with the QOB2451021?
This bolt-on miniature circuit breaker is designed exclusively for use in Square D NQ and NQOD panelboards. It will not fit in standard QO load centers, which require plug-on breakers.
How is the QOB2451021 installed in a panelboard?
It features a bolt-on connection type, which provides a secure, vibration-resistant installation directly to the panelboard bus. This mounting style is standard for commercial and industrial NQ and NQOD panels.
What size wire is required for the shunt trip terminals?
The shunt trip terminals on this breaker accept two 14 AWG to 12 AWG copper wires. The hot and neutral control wires can be connected to either terminal.
What wire sizes are accepted by the main breaker lugs?
The primary box lugs on the QOB2451021 accept 8 AWG to 2 AWG copper or aluminum conductors.
Can the QOB2451021 be used in DC applications?
Yes. In addition to its standard AC ratings, this breaker is rated for 48VDC applications with an interrupting capacity of 5 kAIC.
What type of trip mechanism does the QOB2451021 use?
It utilizes a fixed thermal-magnetic trip mechanism. The thermal element provides long-time overload protection, while the magnetic element provides instantaneous short-circuit protection.
Does this breaker include a tripped status indicator?
Yes, it features the Square D Visi-Trip indicator. When the breaker trips due to an overcurrent event or a shunt trip command, a highly visible red indicator appears to help quickly identify the tripped circuit.
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Reviews
Review summary
Customers rate this product 4.9 out of 5 based on 205 reviews.
Reviews Summary
Generated by AI from 100 most recent customer reviews
Last updated 3/11/26
Customers say these electrical breakers arrive exactly as ordered and work perfectly for their intended applications. They consistently praise the competitive pricing, which many report is significantly lower than local suppliers. Fast shipping and prompt delivery are frequently highlighted, with many receiving orders within days or even next-day delivery for urgent needs. The breakers arrive well-packaged and in excellent condition. Many reviews emphasize the company's extensive inventory availability, particularly for hard-to-find breakers. One customer experienced difficulty with order cancellation and was charged a restocking fee, which caused dissatisfaction.
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Rating
205 reviews
- BLBOOSTIX L.Verified BuyerReviewingSquare D QOB220 - 20A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars8/17/26QOB220
That's nice breakers!
- PHPaul H.Verified BuyerReviewingSquare D QOB330 - 30A 3 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars8/5/26Quick shipping and delivery
Shipped and delivered on time for installation at one of our projects. Thank you!
- RMRick M.Verified BuyerReviewingSquare D QOB220 - 20A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars8/3/26Project Mgr
Just what I needed.
- DHDoug H.Verified BuyerReviewingSquare D QOB220 - 20A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars8/3/26Square D QOB breakers
As always, our order arrived timely, and accurate. You can’t beat their prices that’s why we have used this company for years.
- RKRyan K.Verified BuyerReviewingSquare D QOB230VH - 30A 2 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars7/1/26Awesome
Worked great