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Square D QO390-1021 QO3901021 - 90A 3 Pole Miniature Circuit Breaker
- 90A
- 3 Pole
- Plug-On
Square D
QO390-1021
QO3901021 - 90A 3 Pole Miniature Circuit Breaker
Brand
Square D
SKU
QO390-1021
Quantity
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Square D QO3901021 - 90A 3 Pole Miniature Circuit Breaker
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Description
Integrating a 120/208/240VAC shunt trip mechanism, this specialized 90A breaker enables remote tripping capabilities for safety and control systems. The unit requires four panel spaces and installs into compatible Square D QO load centers and NQ panelboards. Along with its remote operation features, it includes the standard Visi-Trip visual indicator and carries a HACR rating, making it highly suitable for demanding commercial HVAC and industrial motor applications.Specifications
| Brand | Square D |
|---|---|
| Part Number | QO390-1021 |
| Series | QO |
| Amperage | 90A |
| Poles | 3 |
| Mounting Style | Plug-On |
| Voltage | 240VAC, 120/240VAC, 48VDC |
| Phase | 3 |
| AIC Rating | 10kA @ 240VAC, 10kA @ 120/240VAC, 5kA @ 48VDC |
| Terminal Type | Box Lugs |
|---|---|
| For Use With | QO Load Centers, NQ 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 Thermal, Fixed Magnetic |
| Available Options | Padlock Attachment |
|---|---|
| Accessories | Shunt Trip |
| Standards | CSA C22.2 No. 5, UL 489, HACR |
| Approval | CSA, HACR, UL |
| Temp Rating | 40C |
| Construction Features | Visual Trip Indicator, HACR Rated |
Product FAQs
8 answersWhat does the 1021 suffix mean on the QO3901021?
The 1021 suffix indicates that this breaker includes a factory-installed 120/208/240VAC shunt trip mechanism. This allows the breaker to be tripped remotely by applying voltage to the shunt trip coil, which is commonly used for emergency stops or safety control systems.
How many panel spaces does the QO3901021 require?
This breaker requires four standard 3/4-inch spaces in a QO load center or NQ panelboard. Three spaces are used for the 3-pole breaker itself, and one additional space is required for the factory-installed shunt trip module.
Can I add a shunt trip to a standard QO390 breaker in the field?
No. Square D shunt trips for QO breakers must be factory-installed. If you need a 90A 3-pole breaker with a 120/240VAC shunt trip, you must purchase the QO3901021 directly rather than attempting to modify a standard QO390.
What wire sizes are accepted by the QO3901021 terminals?
The main box lugs on this 90A breaker accept 4 AWG to 2/0 AWG aluminum or copper wire. The separate shunt trip terminals accept two 14 AWG to 12 AWG copper wires for the control circuit.
What panels are compatible with the QO3901021?
This plug-on breaker is designed exclusively for use in Square D QO load centers and NQ panelboards. It is not compatible with Homeline (HOM) load centers or I-Line panelboards.
Does this breaker feature Visi-Trip indication?
Yes, the QO3901021 includes the Square D Visi-Trip visual indicator. When the breaker trips due to an overcurrent, short circuit, or a remote shunt trip command, the handle moves to a center position and a red indicator appears in the window.
Is the QO3901021 HACR rated?
Yes, this breaker carries a HACR rating. This makes it suitable for group motor applications commonly found in commercial heating, air conditioning, and refrigeration equipment.
What is the bolt-on equivalent to the QO3901021?
The bolt-on equivalent for use in NQ or NQOD panelboards is the QOB390VH1021. Note that the QO3901021 features a plug-on connection and cannot be bolted to the busbar.
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Reviews
Review summary
Customers rate this product 4.9 out of 5 based on 286 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
286 reviews
- RBRobert B.Verified BuyerReviewingSquare D QO120 - 20A 1 Pole Miniature Circuit BreakerI recommend this productRated 5 out of 5 stars10/5/26Square D Q0120-20A circuit breaker
This device was delivered on time as advertised and it was in excellent condition. The installation process was simple and straightforward, and the unit worked perfectly when connected to the electric circuit.
I am completely satisfied and will utilize this component resource for my future electrical needs.
- 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