Zinsco / Sylvania SJK-3C-300 Molded Case Circuit Breaker
- 300A
- 3 Pole
- Bolt-On
Quantity
Zinsco / Sylvania SJK-3C-300 - 300A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Manufactured for heavy-duty industrial environments, the 300A SJK-frame breaker provides reliable overcurrent protection for 600VAC systems. It utilizes a thermal-magnetic trip mechanism to handle demanding commercial loads. This bolt-on unit serves as an exact fit for discontinued Sylvania, Challenger, and Westinghouse panelboards. For modern upgrades, the Eaton KD3300 acts as the current substitute. Rated to interrupt 30kA faults at 480VAC, it delivers robust performance.Specifications
| Brand | Zinsco / Sylvania |
|---|---|
| Part Number | SJK-3C-300-R |
| Series | SJK |
| Amperage | 300A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC |
| Phase | 3 |
| AIC Rating | 65kA @ 240VAC, 30kA @ 480VAC, 22kA @ 600VAC |
| Terminal Type | Lugs |
|---|---|
| For Use With | Sylvania Panelboards, Challenger Panelboards, Westinghouse Panelboards, Eaton Panelboards |
| Wire Gauge | 250-500 kcmil (Al/Cu) |
| Max Wire | 500 kcmil |
| Min Wire | 250 kcmil |
| 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 |
|---|---|
| Accessories | Trip Unit (SJK-3-T-300) |
| Standards | UL 489, NEMA AB 1 |
| Approval | UL |
| Temp Rating | 40°C |
| Construction Features | Interchangeable Trip Unit, HACR Rated |
Product FAQs
5 answersWhich panelboards accept the SJK-3C-300 circuit breaker?
This bolt-on breaker is designed for legacy Sylvania and Challenger panelboards. Due to historical manufacturer acquisitions, it is also compatible with specific Westinghouse and Eaton distribution panels designed to accept the SJK frame.
How does the adjustable magnetic trip function on the SJK-3C-300?
The breaker features a thermal-magnetic trip unit with Long-Time and Instantaneous (LI) functions. While the thermal overload protection is fixed, the magnetic instantaneous trip is adjustable. This allows panel builders to fine-tune the short-circuit response for proper selective coordination with downstream devices.
Can the trip unit on the SJK-3C-300 be swapped or upgraded?
No, this specific breaker model features a non-interchangeable thermal-magnetic trip unit. The Long-Time and Instantaneous (LI) protection components are integrated directly into the breaker frame and cannot be removed or replaced.
Is the Sylvania SJK series still actively manufactured?
No, the Zinsco and Sylvania SJK series are obsolete. The product line was historically acquired by Challenger, then Westinghouse, and is currently owned by Eaton. We supply these legacy breakers to help facilities maintain existing infrastructure without the expense of a full panel retrofit.
What are the lug and conductor requirements for this breaker?
The SJK-3C-300 includes factory-installed lugs rated for both aluminum and copper conductors. The terminals accept wire sizes ranging from 250 to 500 kcmil. Always verify the required torque specifications based on the conductor material during installation.
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