Notes on Choosing DC Circuit Breakers for Solar Power Systems

Importance of Correct Circuit Breakers

• Choose the right type of circuit breaker for each component:
  • PV solar feed
  • Charge controller
  • Inverter
• Understanding specifications is crucial for reliability.

Market Options and Research

• Numerous DC 12V, 24V, and solar PV circuit breakers available.
• Research and read reviews to avoid poor-quality products.
• Be cautious of sellers mislabeling AC breakers as DC PV rated.

Testing Circuit Breakers

• Use an ohmmeter to check for high resistance.
  • Ideal resistance is very low.
  • High resistance can indicate a faulty breaker.
• Breakers should be kept cool to maintain efficiency.
• If a circuit breaker overheats, its resistance can increase, reducing efficiency.

Choosing Between Circuit Breakers and Fuses

• Fuses (e.g., ANL fuses) often have less resistance than circuit breakers.
• Both should be kept cool to function correctly under load.
• Overheating can cause premature tripping or failure to trip.

Quality Considerations

• Quality breakers should have detailed specifications available.
• Avoid cheap breakers with misleading claims - they may not protect your system.
• Ensure the breaker is rated correctly for the application.
  • Too low = tripping under normal conditions (e.g., surge draws).
  • Too high = failing to trip during short circuits.

Understanding Breaker Ratings and Symbols

• Learn to read labels on circuit breakers:
  • DC Marking: Straight line over dashed line (up to 500 volts DC).
  • AC Marking: Wavy line - not suitable for DC.
• Be aware of double pole ratings - each side can handle 250 volts.

Trip Sensitivity and Types of Breakers

• Types of circuit breakers:
  • Fast trip: Sensitive to overcurrent.
  • Delay trip: Resists tripping for a brief period under surge.
• Some breakers are polarized (positive and negative).
  • Incorrect installation can cause failure to protect the circuit.

Installation Tips

• Torque terminals properly to prevent loose connections.
• Secure wires near the breaker to avoid movement.
• Avoid the cheapest breakers to ensure safety and reliability.
• Saving money on breakers can lead to major issues (e.g., fire).

Testing Circuit Breakers

• Test breakers for functionality only if safely possible.
• Double pole DC breakers can switch both positive and negative sides of the circuit.
• Understand that circuit breakers are riveted at the factory and cannot be serviced.

Conclusion

• Invest in quality components to protect your solar power system effectively.
• Take time to understand specifications and ensure proper installation.