Paralleling two circuit breakers for higher capacity is generally not recommended due to various safety and functional concerns. Circuit breakers are designed to operate within specific parameters to ensure the safety of the electrical system and its components. Let’s delve into the reasons why paralleling circuit breakers is discouraged:
1. Coordinated Protection:
- Sequential Operation: Circuit breakers are often installed in a power distribution system with a coordinated protection scheme.
- Selective Tripping: Each breaker in the system is designed to trip in a specific sequence to isolate the faulty part of the system while maintaining power in other areas. Paralleling breakers can disrupt this coordinated protection.
2. Current Sharing Issues:
- Imbalance in Current Sharing: Paralleling breakers may not share the current evenly.
- Unequal Load Distribution: One breaker might carry more load than the other, leading to imbalance and potential overheating in one of the breakers.
3. Overcurrent Coordination:
- Overcurrent Protection Coordination: Paralleling breakers can interfere with the overcurrent coordination settings.
- Compromised Safety: This interference can compromise the safety of the system by allowing higher fault currents to flow than what the breakers are individually designed to handle.
4. Manufacturing Tolerances:
- Manufacturing Variations: Despite efforts to maintain consistent manufacturing tolerances, there can be variations between individual circuit breakers.
- Current Sharing Discrepancies: These manufacturing differences can result in discrepancies in how the breakers share the load current, leading to potential issues.
5. Mechanical and Electrical Stress:
- Mechanical Stress: Paralleling breakers can lead to mechanical stress on the bus bars and other components due to the increased current flow.
- Electrical Stress: Higher current levels can also lead to increased electrical stress on the contacts and other internal components.
6. Certification and Standards:
- Certification Requirements: Circuit breakers are certified to specific standards that may not permit paralleling.
- Compliance with Standards: Paralleling breakers might violate certification requirements, making it essential to adhere to manufacturer and industry standards.
7. Maintenance and Testing Challenges:
- Complex Testing: Paralleling breakers require more complex testing and maintenance procedures.
- Increased Downtime: This complexity can result in increased downtime during maintenance activities, affecting the overall reliability of the electrical system.
8. Cost Considerations:
- Expense: Paralleling breakers can incur additional expenses due to the need for specialized equipment, testing, and maintenance procedures.
- Cost vs. Benefit: The potential benefits of higher capacity should be carefully weighed against the increased costs and potential risks associated with paralleling breakers.
9. System Integration Challenges:
- Integration with Other Devices: Paralleling breakers might pose challenges when integrated with other protective devices and control systems.
- Compatibility Issues: Ensuring compatibility with existing systems becomes crucial and may require additional engineering considerations.
10. Safety Risks:
- Arc Flash Hazards: Paralleling breakers can increase the risk of arc flash incidents, posing significant safety hazards to personnel.
- Fire Hazards: Overloading one breaker while the other carries less load can lead to overheating and potential fire hazards.
In conclusion, paralleling two circuit breakers for higher capacity is generally discouraged due to the complexities and risks involved. It is crucial to consult with electrical engineers, adhere to manufacturer specifications and industry standards, and consider alternative solutions such as higher-rated single breakers or other protective devices. Any modifications to an electrical system should be performed with careful consideration of safety, reliability, and adherence to relevant regulations and standards.