Zinsco / Sylvania SJK3C300 Molded Case Circuit Breaker
- 300A
- 3 Pole
- Bolt-On
Quantity
Zinsco / Sylvania SJK3C300 - 300A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Designed to support industrial power systems, this 300A molded case breaker provides reliable long-time and instantaneous protection. It serves as an exact fit for vintage Sylvania, Challenger, and Westinghouse panelboards without requiring modifications. For modern upgrades, the Eaton KD3300 serves as the current substitute. Rated for 65kAIC at 240V, it utilizes the SJK-3-T-300 interchangeable trip unit to accommodate changing facility load requirements.Specifications
| Brand | Zinsco / Sylvania |
|---|---|
| Part Number | SJK3C300-R |
| Series | SJK |
| Amperage | 300A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC |
| Phase | 3 |
| AIC Rating | 65kA @ 240VAC, 30kA @ 480VAC, 22kA @ 600VAC |
| Frame Type | SJK |
|---|---|
| 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
7 answersWhich panelboards are compatible with the Sylvania SJK3C300?
This breaker is designed for use in legacy Sylvania, Challenger, Westinghouse, and Eaton panelboards that accept SJK frame bolt-on breakers.
Is the Sylvania SJK3C300 interchangeable with Challenger or Westinghouse breakers?
Yes. Because the Sylvania, Challenger, and Westinghouse brands share a manufacturing history, SJK frame breakers are often interchangeable across these legacy panelboards. Always verify your specific panel labeling for approved replacement types.
What does the LI trip function mean on this SJK frame breaker?
LI stands for Long-Time and Instantaneous trip functions. This thermal magnetic breaker features a fixed thermal element for long-time overload protection and an adjustable magnetic element for instantaneous short-circuit protection.
How does the adjustable magnetic trip work on the SJK3C300?
The adjustable magnetic trip allows electricians to set the instantaneous short-circuit pickup level. This helps coordinate the breaker with downstream devices and prevents nuisance tripping from motor inrush currents.
Can the trip unit on the SJK3C300 be swapped out for a different amperage?
No, the SJK3C300 features a non-interchangeable trip unit. The 300A thermal rating is fixed and cannot be modified or replaced with a different trip block.
What wire sizes and materials can be used with the SJK3C300 lugs?
The factory lugs on this breaker accept aluminum or copper conductors ranging from 250 kcmil to 500 kcmil. Ensure proper torque specifications are followed during installation.
How is the SJK3C300 installed in the panelboard?
This is a bolt-on circuit breaker that secures directly to the panel busbars using threaded fasteners. This provides a secure mechanical connection suitable for high-amperage commercial and industrial applications.
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