Siemens JJ63B300 Molded Case Circuit Breaker
- 300A
- 3 Pole
- Bolt-On
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Siemens JJ63B300 - 300A 3 Pole Molded Case Circuit Breaker
Re-Certified
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Description
Built for demanding industrial applications, the Siemens JJ63B300 is a 3-pole, 300A circuit breaker rated for 600VAC systems. It utilizes a rugged J-Frame construction to handle commercial power distribution. The breaker mounts into Siemens P4 and P5 panelboards using a secure bolt-on connection. For facilities maintaining legacy equipment, it provides an exact fit and cross-references with the newer JXD63B300 replacement.Specifications
| Brand | Siemens |
|---|---|
| Part Number | JJ63B300-R |
| Series | JJ |
| Amperage | 300A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 65kA @ 240VAC, 25kA @ 480VAC, 10kA @ 600VAC, 25kA @ 250VDC |
| Terminal Type | Lugs |
|---|---|
| For Use With | Siemens P4, P5 Panelboards, Switchboards |
| Wire Gauge | 3/0 AWG - 500 kcmil (Al/Cu) |
| Max Wire | 500 kcmil |
| Min Wire | 3/0 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, Padlock Attachment |
|---|---|
| Accessories | Line and Load Lugs Included |
| Standards | NEMA AB-1, UL 489, CSA C22.2 No. 5 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | HACR Rated, Interchangeable Trip Unit |
Product FAQs
8 answersWhat panelboards are compatible with the JJ63B300 breaker?
This bolt-on breaker is designed for use in Siemens P4 and P5 panelboards, as well as compatible Siemens switchboards. It mounts directly to the bus using bolted connections.
Does this breaker include lugs on both the line and load sides?
No, the JJ63B300 is a bolt-on breaker. It includes load side lug terminals for your outgoing wire connections, but the line side bolts directly to the panelboard bus.
What wire sizes are accepted by the load side lugs?
The factory installed load lugs accept aluminum or copper wire ranging from 3/0 AWG to 500 kcmil. Ensure you use the proper torque specifications listed on the breaker faceplate during installation.
How does the adjustable magnetic trip function work on this breaker?
While the thermal overload protection is fixed at 300A, the magnetic trip is adjustable. This allows electricians to tune the instantaneous short circuit response to coordinate with other breakers in the system and prevent nuisance tripping.
Can I use this to replace an older ITE JJ63B300?
Yes, Siemens acquired ITE and continued manufacturing the JJ frame under the Siemens brand. A Siemens JJ63B300 is a direct replacement for an ITE JJ63B300.
Can the JJ63B300 be used in DC applications?
Yes, this breaker is rated for use in direct current systems up to 250VDC, where it provides a 25kA interrupting capacity.
Is the JJ63B300 interchangeable with Sentron JXD6 breakers?
The JJ frame is a legacy design. While Sentron JXD6 breakers occupy the same 400A frame class, you must verify your specific panelboard or mounting hardware accepts the legacy JJ footprint before attempting a substitution.
What does the 25kA at 480V interrupting rating mean for my installation?
The 25kA rating indicates the maximum fault current the breaker can safely clear at 480V without sustaining damage. Your system's available fault current must be calculated by a qualified engineer to ensure it does not exceed this value.
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