Eaton / Cutler-Hammer HKB3125 Molded Case Circuit Breaker
- 125A
- 3 Pole
- Panel Mount
Quantity
Eaton / Cutler-Hammer HKB3125 - 125A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Operating as a critical safety component in industrial power distribution, this 125A Eaton MCCB offers proven thermal-magnetic LI protection. The 3-pole Mark 75 breaker is engineered for 600VAC and 250VDC networks, providing a robust 65kAIC interrupt capacity at 240V. It installs into older switchboards and Series C panelboards that require K-Frame dimensions. For facilities modernizing their infrastructure, this legacy model is officially replaced by the current HKD3125 catalog number.Specifications
| Brand | Eaton / Cutler-Hammer |
|---|---|
| Part Number | HKB3125-R |
| Series | HKB |
| Amperage | 125A |
| Poles | 3 |
| Mounting Style | Panel Mount |
| Voltage | 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 65kA @ 240VAC, 25kA @ 480VAC, 18kA @ 600VAC, 20kA @ 250VDC |
| Terminal Type | Lugs |
|---|---|
| For Use With | Eaton Series C Panelboards, Mark 75 Panelboards, Switchboards |
| Wire Gauge | 3 AWG - 350 kcmil |
| Max Wire | 350 kcmil |
| Min Wire | 3 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, Lug Kits |
|---|---|
| Accessories | Load Side Lugs Included |
| Standards | CSA C22.2 No. 5, NEMA AB-1, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | High Interrupting Capacity, Interchangeable Trip Unit |
Product FAQs
7 answersIs the Eaton HKB3125 interchangeable with older Westinghouse HKB breakers?
Yes. Eaton acquired the Westinghouse distribution equipment division. An Eaton or Cutler-Hammer HKB3125 is a direct, interchangeable replacement for legacy Westinghouse HKB3125 circuit breakers.
What is the modern replacement for the legacy HKB3125 circuit breaker?
The legacy HKB3125 has been officially replaced by the current Eaton Series C HKD3125 catalog number. The HKD3125 shares the same K-Frame dimensions and mounting footprint for retrofitting into existing enclosures.
What does the Mark 75 designation mean on the HKB3125?
Mark 75 is a legacy Westinghouse trade name for their high-interrupting capacity AB De-ion circuit breakers. For the HKB3125, this indicates an upgraded interrupting rating of 65kA at 240VAC compared to standard breakers.
How is the instantaneous magnetic trip adjusted on the HKB3125?
The thermal protection is fixed, but the instantaneous magnetic trip is adjustable via dials on the front of the trip unit. This allows electricians to set the short-circuit pickup to a specific multiple of the 125A continuous rating to achieve proper selective coordination.
Which panelboards are compatible with the HKB3125?
This K-Frame breaker is designed for bolt-on installation in Eaton Series C panelboards, legacy Westinghouse Mark 75 panelboards, and compatible industrial switchboards.
Can the HKB3125 be used in DC power applications?
Yes. The HKB3125 is rated for up to 250VDC with a 20kA interrupting capacity. This makes it suitable for industrial DC control panels, battery backup systems, and specific transit applications.
Does the HKB3125 include ground fault protection?
No. The HKB3125 features a standard thermal-magnetic trip unit for long-time overload and instantaneous short-circuit protection (LI). It does not have built-in ground fault capabilities.
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