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Siemens / ITE CJ3B300 Molded Case Circuit Breaker
- 300A
- 3 Pole
- Bolt-On
Siemens / ITE
CJ3B300
Molded Case Circuit Breaker
Brand
Siemens / ITE
SKU
CJ3B300
Quantity
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Siemens / ITE CJ3B300 - 300A 3 Pole Molded Case Circuit Breaker
Re-Certified
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Description
Rated at 100kAIC, this 300A current-limiting molded case circuit breaker protects commercial distribution systems. The 3-pole, 600VAC Siemens CJ3B300 severely restricts let-through fault current to safeguard downstream equipment. This bolt-on MCCB fits legacy ITE motor control centers and CDP panelboards. It provides a direct replacement solution, avoiding the need for a CJD63B300 retrofit kit. It features reliable thermal-magnetic trip technology and integrally fused Amp-Trap limiters.Specifications
| Brand | Siemens / ITE |
|---|---|
| Part Number | CJ3B300-R |
| Series | CJ |
| Amperage | 300A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 100kA @ 240VAC, 100kA @ 480VAC, 100kA @ 600VAC, 100kA @ 250VDC |
| Frame Type | CJ |
|---|---|
| Terminal Type | Lugs |
| For Use With | ITE / Siemens Switchboards, Motor Control Centers, CDP Panelboards |
| Wire Gauge | 250 kcmil - 500 kcmil (Cu), 350 kcmil - 500 kcmil (Al) |
| 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, Alarm Switch |
|---|---|
| Accessories | Amp-Trap Current Limiters |
| Standards | UL 489, NEMA AB 1 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | Current Limiting, Interchangeable Trip Unit, High Interrupting Capacity |
| Special Features | Current Limiting (Integrally Fused) |
Product FAQs
7 answersWhat equipment is compatible with the CJ3B300 circuit breaker?
The CJ3B300 is designed for use in legacy ITE and Siemens switchboards, motor control centers, and CDP panelboards. It requires a bolt-on connection and fits standard C-frame mounting spaces.
What wire sizes and materials are supported by the lugs on this breaker?
The standard lugs accept 250 to 500 kcmil copper wire or 350 to 500 kcmil aluminum wire. Ensure proper torque specifications are followed during installation to prevent thermal issues at the terminals.
How does the trip unit operate on the CJ3B300?
This breaker features a thermal-magnetic trip unit with fixed thermal protection for long-time overloads and an adjustable magnetic trip for instantaneous short-circuit protection. The adjustable magnetic setting allows you to fine-tune the instantaneous trip point to coordinate with downstream devices.
Is the CJ3B300 a current-limiting breaker?
Yes, the CJ3B300 is a current-limiting circuit breaker. It is designed to clear high-level fault currents quickly, reducing the let-through energy and peak let-through current to protect downstream equipment. It provides a 100kA interrupting rating across 240V, 480V, and 600V AC systems.
Can the CJ3B300 be used to replace older ITE C-frame breakers?
Yes, the CJ3B300 serves as a direct replacement for legacy ITE and Siemens 300A C-frame circuit breakers in existing switchboards and motor control centers. Using this exact match avoids the need for complex retrofit kits.
Can the CJ3B300 be used in DC applications?
Yes, the CJ3B300 is rated for use in DC systems up to 250VDC, where it provides a 100kA interrupting rating. When applying a 3-pole breaker in DC circuits, follow the manufacturer wiring guidelines to ensure voltage is properly distributed across the poles.
What safety precautions should be taken before installing the CJ3B300?
Installation should only be performed by a qualified electrical professional. Ensure all power sources to the switchboard or motor control center are completely de-energized and locked out before mounting the breaker or terminating the conductors.
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