Solar inverter warning lights and error codes in Perth: what they mean

Most inverter warnings are resolved quickly without a technician visit. The first step is identifying whether the warning is active (currently affecting generation) or historical (cleared but logged). Here's a practical guide for the most common inverter brands used in Perth.

Before anything: check if the system is currently generating

Open your inverter monitoring app. If the app shows active generation (kW output > 0 on a sunny day), the inverter is working — the error may have been a transient fault that cleared automatically.

If the app shows 0W output on a sunny day, or no data for an extended period, the fault is active.

Common inverter warning categories

1. Grid fault / grid code error

What it means: The inverter detected that the grid supply was outside its acceptable voltage or frequency range. Under Australian grid standards (AS/NZS 4777), inverters must disconnect when grid voltage or frequency falls outside defined limits.

Common causes:

• Momentary grid voltage spike or dip (a common event in Perth suburbs with high solar penetration)
• Western Power planned or unplanned outage
• Power quality issues on the local distribution network

What to do: If the fault has cleared (inverter showing generation again), no action needed. Grid faults often self-resolve. If the fault recurs multiple times per week without an obvious outage, contact your electricity distributor (Western Power) — sustained power quality issues may be a network problem Western Power should investigate.

2. Insulation resistance fault (ISO/RCD fault)

What it means: The inverter has detected low insulation resistance on the DC side (between the solar panels and earth). This is a serious safety fault — it may indicate damaged DC wiring, water ingress into a junction box, a damaged panel, or a failing DC isolator.

What to do: Do not attempt to diagnose this yourself. Switch the solar system off at the DC isolator (the red switch, usually near the inverter and also on the roof near the panels). Call your installer or a licensed solar electrician. This fault should not be reset without investigation.

3. Over-temperature warning

What it means: The inverter itself has overheated and reduced output or shut down. This is more common in Perth summers, especially when the inverter is mounted in a poorly ventilated location or in direct afternoon sunlight.

What to do: Check the inverter mounting location — is it in direct sun, particularly afternoon sun? Is there adequate clearance around it for airflow? Many Perth inverters are mounted in garages with poor ventilation. If the warning occurs on hot days and clears in the evening, the installation location may need adjustment (add shade, increase ventilation, or in some cases, relocate the inverter).

If the inverter is well-ventilated and shaded but still over-temperature faulting, the inverter may have a cooling fan fault or internal issue — contact the installer.

4. DC high voltage / string voltage out of range

What it means: The DC voltage from the panels exceeded the inverter's maximum input voltage. This can happen on very cold mornings when panel open-circuit voltage peaks (Voc increases as panel temperature drops).

Common causes in Perth: Less common than in colder climates, but can occur on cold winter mornings (rare). More commonly, it indicates a wiring fault — panels wired in an incorrect string configuration, or too many panels in series.

What to do: If this occurs on warm days or recurs throughout the year, it's a wiring issue — cold-morning voltage spikes are normal, repeated faults are not. Contact your installer — re-stringing may be required.

5. Communication / monitoring disconnected (not a generation fault)

What it means: Your monitoring app shows no data, but the inverter itself may still be generating. Communication failures between the inverter and the monitoring server (via WiFi or Ethernet) are common and don't affect generation.

Signs this is just a communication issue:

• The inverter display (if it has one) shows normal generation numbers
• The physical LED on the inverter is green (not red/fault)
• Neighbours with the same inverter brand also show gaps in their monitoring

What to do: Check whether your home WiFi is working. Try restarting the inverter's WiFi or Ethernet connection (check the inverter manufacturer's app or manual for how to reconnect). If the monitoring gap is longer than 48 hours and WiFi is working, contact your installer to check the inverter's communication module.

6. Arc fault detection (AFCI) trip

What it means: Some newer inverters include Arc Fault Circuit Interrupter (AFCI) technology that detects electrical arcing on DC wiring, which can be a fire risk. An AFCI trip shuts down the system.

What to do: This requires a licensed solar electrician to investigate. Do not reset an AFCI trip without DC wiring inspection. DC arcing faults can cause fires in roof cavities.

Brand-specific guidance

Fronius inverters: Fronius uses a numeric fault code system. Common codes: 301–303 (AC grid fault), 504 (communication), 901–903 (insulation fault). The Fronius Solar.web app shows the fault code and a description. Check the Fronius support portal by entering the specific code.

Sungrow inverters: Error codes appear on the LCD display and in the iSolarCloud app. Common codes: Grid_10min_Volt_Err (grid voltage out of range, transient — usually self-clears), ISO fault (insulation — requires electrician). The iSolarCloud app provides fault descriptions.

Goodwe inverters: Error codes show in the SEMS portal. Battery fault codes (if battery connected) are separate from inverter fault codes. Contact installer for Goodwe fault codes not described in the app.

SMA inverters: Use the SMA Sunny Portal or Sunny Boy Smart Energy app. SMA inverters use a condition/event system — red conditions are faults requiring action; yellow conditions are warnings. Check the SMA event code list on the SMA support website.

When to call your installer vs when to call an electrician

Call your installer first for:

• Any recurring error that resets but comes back
• Over-temperature faults persisting beyond a hot afternoon
• DC high voltage warnings
• System not generating despite no obvious error

Call a licensed solar electrician (CEC-accredited) directly for:

• ISO/insulation fault
• Arc fault (AFCI) trip
• Any fault where the system was switched off for safety and you're not sure if it's safe to restart
• System not generating after storms or significant weather events

If your inverter is showing an active fault and you're unsure what it means, your installer should be your first contact — they have access to the inverter's diagnostic log via their service tools.