Square D A1B140 Molded Case Circuit Breaker
- 40A
- 1 Pole
- Bolt-On
Quantity
Square D A1B140 - 40A 1 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Part of the classic A1B series, this 40A single-pole molded case circuit breaker delivers thermal-magnetic protection for commercial and industrial environments. It operates at 120VAC with a 10kAIC interrupt rating. Designed specifically for bolt-on applications, it mounts into vintage Square D NA1B panelboards. When panel upgrades are required, this unit is replaced by the QOB140 using a specialized retrofit kit.Specifications
| Brand | Square D |
|---|---|
| Part Number | A1B140-R |
| Series | A1B |
| Amperage | 40A |
| Poles | 1 |
| Mounting Style | Bolt-On |
| Voltage | 120VAC, 48VDC |
| Phase | 1 |
| AIC Rating | 10kA @ 120VAC |
| Frame Type | A1B |
|---|---|
| Terminal Type | Lugs |
| For Use With | Square D NA1B Panelboards |
| 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 |
| Available Options | Shunt Trip |
|---|---|
| Accessories | Load Side Lugs Included |
| Standards | CSA C22.2 No. 5, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | Visual Trip Indicator |
Product FAQs
7 answersWhat type of equipment uses the A1B140 circuit breaker?
This breaker is engineered specifically for legacy Square D NA1B panelboards. It is primarily used by electricians to maintain and service older commercial and industrial distribution systems rather than new installations.
What is the modern replacement for the A1B140 breaker?
If you are upgrading your panelboard, the A1B140 is typically replaced by the QOB140 circuit breaker. Note that installing a QOB breaker in an older NA1B panel requires a specialized retrofit kit.
What is the 277V equivalent to the A1B circuit breaker?
While the A1B140 is rated for 120VAC, Square D manufactured the Y1B series as the 277V equivalent for use in similar vintage commercial panelboards.
How is the A1B140 secured during installation?
It mounts directly to the bus of an NA1B panelboard using a bolt-on connection. Ensure the panel bus is de-energized before bolting the breaker in place. The load lugs accept 8 to 4 AWG copper or aluminum wire.
Can the A1B140 be used in DC electrical systems?
Yes, while primarily used for 120VAC applications, this breaker is also rated for 48VDC systems, making it suitable for specific control or battery applications.
Will the A1B140 fit into a standard Square D QO load center?
No. The A1B140 features a legacy A1B frame designed exclusively for NA1B panelboards. It is not physically compatible with modern QO or Homeline residential load centers.
How does the A1B140 respond to different types of electrical faults?
The breaker uses a thermal-magnetic mechanism. The thermal element provides a delayed trip for sustained overloads, while the magnetic element trips instantaneously to clear severe short circuits, protecting the panel and downstream wiring.
SuperClub
Join free. Get 500 SuperPoints.
Earn points on eligible purchases and redeem them at checkout.
100 SuperPoints = $1 off.
Warranties
Add an extra year of protection
60-Day Warranty
Your purchase includes 60 days of SuperBreakers warranty coverage.
Add a 1-year warranty extension in your cart.
Get a Quote
Don’t see what you’re looking for?
We source obsolete and hard-to-find parts every day.
Shipping
Free Shipping Policy
Parcel shipments with item value over $99 qualify for free economy shipping within the continental US. Please call to confirm special handling instructions. We do not charge a handling fee or require a minimum amount on any order. SuperBreakers does not ship on customer accounts.
Same Day Shipping
We strive to ship out your items the same day the order is placed. In rare circumstances SuperBreakers may reserve up to 5 business days to consolidate orders for complete shipment.
Expedited Shipments
Orders being shipped via Next Day Air, 2 Day Shipping or 3 Day Shipping must be received by 3 PM EST to guarantee same-day shipments. Expedited orders only ship on normal business days. Shipments will NOT be sent out on Saturdays and Sundays.
International Shipping
All International orders require a $1,000 minimum order threshold. Due to the special nature of these shipments, we require that these be placed with a SuperBreakers representative. Additional shipping and instructions will apply. All International Orders are Non-Cancel and Non-Refundable.
Reviews
Review summary
Customers rate this product 5.0 out of 5 based on 2 reviews.
- NLNoble L.ReviewingSquare D A1B115 - 15A 1 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars7/19/21Great Service, On Time Delivery, Great Price
SuperBreakers is my a dependable source to meet my customer's requirements at a good value and with on time delivery. When you throw in great customer service, you can't beat that combination.
- CHCobe H.ReviewingSquare D A1B120 - 20A 1 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars2/11/19Repeat customer
Although these breakers are refurbished they work great. It beats having to change the whole panel because of one breaker.