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Siemens B125 Molded Case Circuit Breaker
- 25A
- 1 Pole
- Bolt-On
Siemens
B125
Molded Case Circuit Breaker
Brand
Siemens
SKU
B125
Quantity
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Siemens B125 - 25A 1 Pole Molded Case Circuit Breaker
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Description
Built for commercial and industrial power systems, the Siemens B125 delivers dependable overcurrent protection for 25A branch circuits. This 1-pole molded case circuit breaker features a thermal-magnetic trip unit with long-time and instantaneous functions. It mounts into Siemens P1, P2, P3, P4, and P5 panelboards using a standard bolt-on connection. Rated at 10kAIC at 120/240VAC, it provides essential safety and performance for everyday electrical distribution needs.Specifications
| Brand | Siemens |
|---|---|
| Part Number | B125 |
| Series | BL |
| Amperage | 25A |
| Poles | 1 |
| Mounting Style | Bolt-On |
| Voltage | 120/240VAC |
| Phase | 1 |
| AIC Rating | 10kA @ 120/240VAC |
| Frame Type | B |
|---|---|
| Terminal Type | Lugs |
| For Use With | Siemens P1, P2, P3, P4, P5 Panelboards |
| Wire Gauge | 10-8 AWG (Cu), 10-6 AWG (Al) |
| Max Wire | 8 AWG (Cu), 6 AWG (Al) |
| Min Wire | 10 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Fixed Magnetic |
| Available Options | Shunt Trip, Auxiliary Switch, Alarm Switch, Padlock Attachment, Handle Tie |
|---|---|
| Standards | CSA C22.2 No. 5, UL 489 |
| Approval | CSA, HACR, UL |
| Temp Rating | 40C |
Product FAQs
7 answersWhat commercial panelboards are compatible with the Siemens B125?
This 25-amp bolt-on circuit breaker is engineered for direct installation into Siemens P1, P2, P3, P4, and P5 panelboards.
Can I install this BL series breaker in a standard residential load center?
No. The B125 features a bolt-on mounting style and is designed for commercial panelboards. It is not compatible with standard load centers that require plug-in style breakers.
What wire sizes are supported by the terminal lugs on the B125?
The included load side lugs accept copper conductors ranging from 10 AWG to 8 AWG, or aluminum conductors ranging from 10 AWG to 6 AWG.
How does the thermal magnetic LI trip mechanism function?
The Long-Time (L) function uses a thermal element to protect against gradual overloads, while the Instantaneous (I) magnetic function immediately trips the breaker during a short circuit to prevent equipment damage.
What does the 10kAIC interrupting rating mean for this 1-pole breaker?
The 10kAIC rating indicates the B125 can safely clear a maximum fault current of 10,000 amps on a 120/240V AC system without failing or sustaining internal arc damage.
Can the trip settings on the B125 be adjusted in the field?
No. The Siemens B125 uses fixed thermal and fixed magnetic trip settings. The overcurrent parameters are factory calibrated for 25-amp protection and cannot be modified.
What terminal connection type is standard on the B125 breaker?
This breaker is equipped with mechanical lugs designed to securely clamp branch circuit wiring, ensuring reliable continuity and safe power delivery.
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Reviews
Review summary
Customers rate this product 5.0 out of 5 based on 35 reviews.
Total 5 star reviews: 34 Total 4 star reviews: 1 Total 3 star reviews: 0 Total 2 star reviews: 0 Total 1 star reviews: 0
Reviews Summary
Generated by AI from 66 most recent customer reviews
Last updated 8/15/25
Customers say these circuit breakers meet their specifications and perform as expected. Many reviews highlight the quick delivery times and competitive pricing. Frequent comments address the reliable product quality and ease of installation. The ordering process receives praise for its simplicity, with users noting consistent product availability.
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Rating
35 reviews
- TSTom S.Verified BuyerReviewingSiemens B3100 3 Pole Circuit BreakerI recommend this productRated 5 out of 5 stars8/3/26Superbreakers is our go to!
Great prices, great service and quick delivery.
- MGMaggie G.Verified BuyerReviewingSiemens B250 - 50A 2 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars6/24/26Great Service
Came in great condition and in an incredibly timely manner. Will continue superbreakers for all of my orders in the future!
- DBDonnie B.Verified BuyerReviewingSiemens B115 - 15A 1 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars6/11/26New Breaker
Awesome breaker & Superbreakers is a awesome company!
- BLBrian L.Verified BuyerReviewingSiemens B120 - 20A 1 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars6/4/26Brian
Works great
- JFJoseph F.Verified BuyerReviewingSiemens B120 - 20A 1 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars3/23/26Great value
It was a great value