Siemens J3B125 Molded Case Circuit Breaker
- 125A
- 3 Pole
- Bolt-On
Quantity
Siemens J3B125 - 125A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Built to handle heavy commercial loads, this 125A bolt-on breaker utilizes fixed thermal and adjustable magnetic trip functions for precise circuit protection. The device integrates seamlessly into Siemens P4 and P5 panelboards, as well as compatible motor control centers. With a maximum voltage rating of 600VAC and HACR certification, it meets rigorous industrial standards. Facilities looking to transition to newer hardware can substitute this with the FXD63B125 using an adapter kit.Specifications
| Brand | Siemens |
|---|---|
| Part Number | J3B125-R |
| Series | J |
| Amperage | 125A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 240VAC, 480VAC, 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 25kA @ 240VAC, 18kA @ 480VAC, 14kA @ 600VAC, 10kA @ 250VDC |
| Frame Type | J |
|---|---|
| Terminal Type | Lugs |
| For Use With | Siemens P4, P5 Panelboards, Switchboards, Motor Control Centers |
| Wire Gauge | 4 AWG - 300 kcmil (Cu/Al) |
| Max Wire | 300 kcmil |
| Min Wire | 4 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Adjustable Magnetic |
| Available Options | Shunt Trip, Auxiliary Switch, Undervoltage Release, Alarm Switch, Padlock Attachment, Motor Operator, Rotary Handle |
|---|---|
| Accessories | Line and Load Lugs Included |
| Standards | CSA C22.2 No. 5, NEMA AB-1, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | HACR Rated |
Product FAQs
6 answersWhich panelboards and switchboards are compatible with the J3B125 circuit breaker?
This bolt-on breaker is designed for use in Siemens and legacy ITE P4 and P5 panelboards, as well as SB switchboards and motor control centers.
Are ITE J3B125 and Siemens J3B125 the same circuit breaker?
Yes. Siemens acquired ITE, and the J3B125 catalog number was retained. An ITE-branded J3B125 is functionally identical to a Siemens-branded J3B125 and serves as a direct, interchangeable replacement.
What is the purpose of the adjustable magnetic trip on this breaker?
The adjustable magnetic trip allows you to tune the instantaneous short-circuit response. This is particularly useful for coordinating with downstream devices or preventing nuisance tripping from high motor inrush currents.
Does the J3B125 mount onto a standard DIN rail?
No. The J3B125 is a bolt-on molded case circuit breaker. It is designed to be bolted directly to the busbars of compatible panelboard and switchboard chassis, not snapped onto a DIN rail.
Is the J3B125 suitable for direct current (DC) applications?
Yes, this thermal-magnetic breaker is rated for DC systems up to 250V DC with a 10kA interrupting capacity. Thermal-magnetic trip units are well-suited for DC applications, unlike many electronic trip units that require alternating current to operate.
What does the 25kA interrupting capacity (AIC) at 240V mean for installation?
It indicates the maximum fault current the breaker can safely clear at 240V AC without sustaining damage. When installing, you must verify that the system's available short-circuit current at the panel does not exceed this 25kA limit.
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Reviews
Review summary
Customers rate this product 4.0 out of 5 based on 1 review.
- MCMARK C.Verified BuyerReviewingITE/Siemens J20M Control RelayI recommend this productRated 4 out of 5 stars2/4/26it control relay but it was just the coil for the relay. do you have a J20A40 CONTACTS?
it control relay but it was just the coil for the relay. do you have a J20A40 CONTACTS?