Solar Inverter Keeps Shutting Off: Overheating, Grid Issues, and Faults

Understanding Inverter Shutdowns

Your solar inverter is constantly monitoring system performance and safety conditions. When it detects a problem, it automatically shuts down as a protective measure. Understanding what triggers a shutdown helps you diagnose the issue.

Cause 1: Inverter Overheating

Inverters are sophisticated electronic devices that generate heat during operation. If an inverter gets too hot, it will throttle performance or shut down completely to protect itself.

Signs of thermal shutdown:

• Inverter shuts down during the hottest parts of the day (noon to 3 PM)
• Performance returns later in the afternoon when it cools down
• Problem is worse on very hot days (above 90°F)
• Monitoring app may show "temperature" or "thermal" warnings

Common causes of inverter overheating:

• Blocked ventilation: debris, leaves, or insects clogging air vents
• Inadequate airflow: inverter mounted too close to walls or in enclosed spaces
• Dust accumulation on heatsinks (the metal fins inside and outside the inverter)
• Faulty cooling fan (if equipped)
• Extremely high outdoor temperatures combined with heavy solar production
• Inverter rated for lower power than your system is producing

How to fix thermal shutdowns:

• Clear any debris around the inverter's ventilation areas
• Ensure at least 12 inches of clearance around all sides of the inverter
• Don't mount the inverter in direct sun; shade is preferable
• Have a professional clean the inverter's internal heatsinks if dust is visible
• Check that any cooling fans are running (you should hear a slight hum)
• In extreme cases, you may need to reduce the system's load or upgrade the inverter

Cause 2: Grid Faults and Utility Issues

Grid-tied inverters are constantly monitoring utility voltage and frequency. If the grid is unstable, the inverter will shut down to prevent damage or dangerous conditions.

Grid fault indicators:

• Shutdowns happen at different times throughout the day (not just during heat peaks)
• Shutdowns coincide with known utility maintenance or upgrades
• Your utility has recently reported outages or issues in your area
• Monitoring app shows "grid fault" or "frequency fault" error codes

Common grid-related issues:

• Utility performing scheduled maintenance on power lines
• Utility voltage is slightly outside normal operating ranges
• Utility frequency fluctuation (frequency should be exactly 60 Hz in the US)
• High voltage conditions if too many solar systems in your area feed power back simultaneously
• Low voltage conditions during peak demand times

What to do about grid faults:

• Contact your utility company and report the issue with dates and times
• Ask if they've been performing maintenance that might affect power quality
• Document the error codes from your inverter for your installer
• Ask your installer if inverter settings can be adjusted (this requires a licensed electrician)
• Some inverters have configurable voltage/frequency windows; these might need professional adjustment
• If the issue persists, you may need a power conditioning device or inverter replacement

Cause 3: Ground Faults and Isolation Faults

Ground faults occur when unintended electrical current flows to ground (earth). This is a serious safety issue and will cause your inverter to shut down immediately.

Ground fault indicators:

• Monitoring app shows "ground fault" or "isolation fault" error
• Inverter will not restart even when the DC disconnect is cycled
• The system shut down suddenly with no warning

What causes ground faults:

• Water damage to wiring or connectors (rain, snow melt, hose accidents)
• Damaged insulation on DC cables from sun exposure or poor installation
• Corroded connectors that allow water infiltration
• Lightning strike or power surge damage
• Animal chewing through wiring (rodents, birds)
• Manufacturing defect in panels or other equipment

Important: Ground faults require professional repair

• Do not attempt to reset or troubleshoot a ground fault yourself
• Ground faults involve high-voltage DC electricity and are electrocution hazards
• Contact your installer or a licensed solar electrician immediately
• Do not restore the system to operation until the fault is identified and repaired
• Continuing to operate with a ground fault is a fire and safety hazard

Cause 4: Arc Faults

Arc faults occur when there's unintended electrical arcing in the DC wiring. This is both dangerous and will trigger inverter shutdown.

Arc fault indicators:

• Monitoring app shows "arc fault" warning
• Inverter will not restart
• You might smell burning or see burn marks near connectors or wiring

Causes:

• Loose connectors that have developed intermittent contact
• Damaged wiring from pests or weather exposure
• Poor installation where connections weren't properly crimped
• Corrosion at connection points

What to do:

• Do not attempt to troubleshoot arc faults yourself—they're fire hazards
• Contact your installer or a qualified electrician immediately
• Do not operate the system until the fault is resolved
• If you smell burning, turn off the DC disconnect immediately

Cause 5: String Faults or Combiner Box Issues

If one string of panels develops a fault, some systems will shut down completely; others may reduce output.

String fault indicators:

• Monitoring app shows reduced production from one or more strings
• String inverters may display "string 1 fault" or "string 2 fault"
• Output drops by the percentage of your system that the affected string represents
• Issue persists across multiple days

Causes:

• One or more panels in the string failing
• Disconnected or loose wiring in the string circuit
• Faulty string combiner box or breaker
• Degraded solder joints in panels

Troubleshooting steps:

• Check all visible wiring and connectors on the roof for damage or corrosion
• If you have access to the combiner box, check that all breakers are in the ON position
• Document which string is faulting (from monitoring data) and the specific error code
• Contact your installer with this information for diagnosis
• This is usually repairable but requires professional service

When to Call a Professional

Contact your installer or a licensed solar electrician immediately if you see:

• Ground fault or arc fault error codes
• Smoke, burning smells, or visible damage
• Inverter won't restart even after troubleshooting
• Multiple error codes on the display
• Repeated shutdowns despite clear weather and reasonable temperatures
• Water damage or signs of moisture in electrical components