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Siemens FJ63B125 Molded Case Circuit Breaker
- 125A
- 3 Pole
- Bolt-On
Siemens
FJ63B125
Molded Case Circuit Breaker
Brand
Siemens
SKU
FJ63B125
Quantity
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Siemens FJ63B125 - 125A 3 Pole Molded Case Circuit Breaker
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Description
Engineered for commercial and industrial applications, the Siemens FJ63B125 is a 3-pole, 125A molded case circuit breaker from the legacy FJ6 frame family. It delivers dependable thermal-magnetic overcurrent protection for demanding electrical systems. This bolt-on MCCB installs into Siemens P1, P2, and P3 panelboards, as well as SB switchboards and older I-T-E F-Frame enclosures. For modern upgrades, this unit is officially replaced by the FXD63B125 model.Specifications
| Brand | Siemens |
|---|---|
| Part Number | FJ63B125-R |
| Series | FJ6 |
| Amperage | 125A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 240VAC, 480VAC, 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 25kA @ 240VAC, 22kA @ 480VAC, 18kA @ 600VAC, 10kA @ 250VDC |
| Frame Type | FJ63 |
|---|---|
| Terminal Type | Lugs |
| For Use With | Siemens P1, P2, P3 Panelboards, SB Switchboards, I-T-E F-Frame Panelboards |
| Wire Gauge | 6 AWG - 350 kcmil (Cu/Al) |
| Max Wire | 350 kcmil |
| Min Wire | 6 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 |
|---|---|
| Accessories | Load Side Lugs Included |
| Standards | CSA C22.2 No. 5, NEMA AB-1, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | Non-Interchangeable Trip |
Product FAQs
5 answersWhich enclosures and panelboards accept the FJ63B125?
This bolt-on MCCB is designed for Siemens P1, P2, and P3 panelboards, SB switchboards, and legacy I-T-E F-frame enclosures.
What is the modern replacement for the FJ63B125?
The Siemens FXD63B125 serves as the direct modern replacement for this legacy FJ6 frame breaker, maintaining the same physical footprint and electrical specifications.
How does the adjustable magnetic trip work on the FJ63B125?
The breaker features a fixed thermal element for standard overload protection and an adjustable magnetic element. This allows electricians to fine-tune the instantaneous short-circuit trip point for better coordination with downstream devices.
What wire sizes and materials are supported by the standard lugs?
The included load-side lugs accommodate either copper or aluminum conductors ranging from 6 AWG to 350 kcmil.
Is mounting hardware included for panelboard installation?
No, installing this breaker into a Siemens P1, P2, or P3 panelboard requires a separate F-frame mounting strap kit specific to the panelboard type.
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