Solar PV

Inverter tripping or fault

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

The inverter display is blank, showing a red light, or displaying a specific error code (e.g., “AL01”, “Grid Fault”, “Isolation Fault”). You may also notice your generation has stopped.

What’s normal vs not normal

Normal:

  • The inverter shutting down at night when there is no sun (often showing “Waiting” or “Low Power”).
  • A brief “reconnecting” message if there’s a minor flicker in the local grid.

Not normal:

  • The inverter tripping the RCD in your fuse box (consumer unit).
  • A persistent “Isolation Fault” or “Earth Fault” message.
  • The inverter making a loud buzzing or clicking sound.

Likely causes (ranked)

  1. Grid voltage too high: Your local grid may be reaching its upper voltage limit, causing the inverter to disconnect for safety.
  2. Moisture ingress: Water getting into DC connectors or rooftop isolators (common after heavy rain).
  3. Overheating: The inverter is in a poorly ventilated area (like a hot loft) and is shutting down to cool.
  4. Internal component failure: Capacitors or relays reaching the end of their life.
  5. Faulty RCD: The safety switch in your consumer unit may be too sensitive for the “leakage” naturally produced by inverters.

Quick checks you can do safely

  • Check your fuse box—has the “Solar PV” circuit breaker or RCD tripped?
  • Ensure the area around the inverter is clear of clutter to allow for cooling.
  • Note down the exact error code shown on the screen.

When to call an installer

  • If the RCD trips immediately every time you try to reset it.
  • If the screen shows “Isolation Fault” (this indicates a potential electrical leak).
  • If the inverter is hot to the touch or smells of burning.

Questions to ask your installer

  • “Is the grid voltage in my area consistently high? Do I need a voltage logger?”
  • “Do I need a ‘Type B’ RCD to prevent nuisance tripping?”
  • “Is there any sign of water damage in the rooftop isolator?”

Related NetZeroNow tools & guides

FAQs

Can I restart the inverter? You can try a “Power Cycle” (AC off, DC off, wait 1 minute, DC on, AC on), but if it trips again immediately, stop and call a professional.

What is an ‘Isolation Fault’? It means the system has detected that electricity is “leaking” where it shouldn’t—often due to a damaged cable or water in a connector. It is a safety feature.

Why does it trip when it’s sunny? This is often due to “Grid Overvoltage.” When many houses on your street are exporting solar at once, the local grid voltage rises, and your inverter must shut down if it exceeds 253V.

Where should the inverter be? Ideally in a cool, dry place like a garage or utility room. Lofts are common but can get too hot in summer, reducing the inverter’s lifespan.

Does it have a fuse? Yes, there are usually fuses or circuit breakers on both the AC (mains) side and sometimes the DC (solar) side.

Written by NetZeroNow | Last updated on 2026-03-02