09/10/2025
How to "properly use" circuit breakers to protect your system?🧐
"Proper use" means selecting the most appropriate circuit breaker solution based on your system design and budget, and installing it correctly.
1. Solution Selection: From Basic to Advanced
Basic Safety Solution (Required):
Install a DC circuit breaker of a suitable rating between each string and the inverter.
Purpose: Provides basic manual disconnect and overload protection.
Standard Safety Solution (Recommended):
Basic Safety Solution + DC Arc Fault Circuit Interrupter
Purpose: The DC circuit breaker provides manual disconnection, while the AFCI function actively detects and interrupts DC arcs, preventing fires. Many new string inverters now have built-in AFCI functionality.
Advanced Safety Solution (Optimal):
Solution A (Module-Level Shutdown): Use a power optimizer plus a string inverter with fast shutdown.
Solution B (No DC High Voltage): Use a microinverter system directly.
Purpose: Provides the highest level of safety protection, fully meeting the strictest electrical safety regulations. It is particularly suitable for locations with high safety requirements, such as residences, schools, and shopping malls.
2. Proper Selection and Installation
Voltage and Current Ratings: The rated voltage and current of the circuit breaker must exceed the maximum open-circuit voltage and maximum operating current of the PV array in the location, with a margin (generally recommended to be at least 1.25 times).
Certification: Select products that have passed national mandatory certification (such as CQC) or internationally recognized certifications (such as TÜV, UL) to ensure performance and reliability.
Installation Location:
Mechanical DC switches should be installed in an easily accessible, dry, and corrosive environment, typically near the inverter.
The trigger for the rapid shutdown device (if included in the system) should be installed near the meter box or in a location easily accessible to firefighters.
Professional Installation:
Repair must be performed by a professional PV system installer.
Ensure that all DC connectors (MC4) are fully seated, clicked, and tightened using specialized tools. Loose connections are a major cause of arcing and burnout.
Ensure cable routing is standardized, avoid abrasion, and use high-quality flame-retardant DC cables.
