Growatt Inverter Error Codes: Full UK Fault List and Triage Guide

Key Takeaways

• Growatt fault codes follow a structured series architecture: 200 series for DC array input, 300 series for AC mains grid interaction, and 400 series for internal inverter power electronics.
• The first check during any alarm is identifying whether the trip originated from external grid fluctuations, environmental array dampness, or internal hardware components.
• Never touch exposed DC wiring or open the inverter chassis during active faults; always operate the external AC and DC isolators before performing physical inspections.
• Persistent internal alarms or repeated component failures require escalation to your installer or directly to official technical support at service@growatt.tech.

Why is my Growatt inverter displaying an error code?

When a Growatt solar inverter encounters an electrical condition outside its programmed operational limits, its internal protection relays open, solar power generation halts, and a dedicated alphanumeric fault message appears on the screen. Across British installations—ranging from single-phase residential units to three-phase commercial systems—Growatt inverters monitor both the direct current (DC) photovoltaic array and the alternating current (AC) grid connection in real time.

Understanding the root cause of an alarm prevents unnecessary equipment replacement while protecting both the household electrical installation and the inverter power semiconductors. For broader regulatory standards governing solar electrical equipment across England, Scotland, and Wales, refer to our UK solar electrical installation guide.

Most field alarms do not indicate a catastrophic inverter failure. Instead, they reflect external network conditions, such as transient grid voltage surges, or environmental factors like morning condensation across solar panel connectors. By matching the displayed code against official service documentation, homeowners and qualified electricians can rapidly identify the correct resolution pathway.

Growatt fault code architecture: 200, 300, and 400 series

Growatt arranges system diagnostic events into three clear numeric groups. Recognizing the series prefix immediately narrows down the physical location of the electrical defect:

1. 200 Series (DC Array and Photovoltaic Faults): These codes relate directly to the solar panels, DC isolators, string cables, and array insulation. Events range from DC overvoltage (Error 202) and leakage currents (Error 201) to insulation breakdown (Error 203) and arc fault detection (Error 200).
2. 300 Series (AC Grid and Metering Faults): These codes involve the AC mains connection, utility grid synchronisation, and export control telemetry. Common occurrences include mains voltage boundaries (Error 300), loss of mains connection (Error 302), protective earth anomalies (Error 303), and current transformer sensor orientation issues (Error 306). Compliance with regional grid connection rules is detailed in our micro-generator grid connection guide.
3. 400 Series (Internal Inverter and Hardware Alarms): These codes indicate that the inverter internal control boards, microprocessor routines, temperature sensors, or switching relays have encountered an anomaly. Faults include relay failure (Error 405), heatsink over-temperature (Error 408), bus voltage anomalies (Error 409), and internal communication card errors (Error 411).

Full Growatt error code triage table

The following table provides the complete directory of Growatt diagnostic codes, their underlying technical meaning, and the required corrective action documented by the manufacturer technical center:

Systems configured with paired domestic battery storage also interface with export tariffs and home safety enclosures; see our battery storage fire safety guide and Smart Export Guarantee guide.

Systematic diagnosis: step-by-step troubleshooting protocol

When an alarm condition presents, technicians follow a disciplined five-step diagnostic procedure:

Step 1: Document the active error code and operating state

Note the exact code displayed on the screen and check the status LEDs. A flashing red or steady red fault indicator confirms that power export has stopped. Note the weather conditions, time of day, and whether the alarm coincided with heavy household appliance usage.

Step 2: Perform an external AC grid supply verification

For any 300 series code (such as Error 300, Error 301, or Error 302), verify whether the household consumer unit breaker dedicated to the solar generation circuit has tripped. Check the external rotary AC isolator switch adjacent to the inverter to ensure it remains firmly switched on.

Step 3: Execute a controlled system reboot

Many microprocessor initialization errors (Error 406, Error 407) and bus sampling anomalies (Error 404, Error 409) clear upon a complete power cycle:

1. Turn off the AC circuit breaker in your consumer unit.
2. Turn the external AC rotary isolator to OFF.
3. Turn the inverter integrated rotary DC switch to OFF.
4. If an external battery system is connected, turn off the battery DC breaker.
5. Wait for the screen and all LED indicators to power down completely.
6. Re-energize in reverse order: DC switch first, then battery, then AC isolator, and finally the consumer unit breaker.

Step 4: Inspect solar array and cabling integrity

For 200 series alarms, turn off the system and inspect the visible solar panel cables, junction boxes, and roof penetrations. In the case of Error 203 (PV isolation low), check whether early morning dew on panels is the root cause. If the error clears as the sun warms the array, moisture ingress into an external connector is the likely culprit. For Error 202, string voltages must be tested by a technician before re-energizing.

Step 5: Check sensor and meter telemetry

For systems featuring export limitation or smart meter monitoring, errors such as Error 306 (CT LN Reversed) and Error 307 (M3 did not receive SP-CT) point directly to current sensor wiring. Verify that the RS485 communication cable is seated firmly and that the current transformer arrow points towards the consumer unit load.

Safety: electrical hazard controls and DC isolation rules

Solar installations combine lethal high-voltage direct current from photovoltaic arrays with alternating current mains electricity. Direct current does not possess a natural zero-crossing point, making DC arcs self-sustaining and extremely dangerous.

• Never disconnect DC connectors under load: Opening MC4 connectors or DC isolator plugs while current is flowing will create a continuous electrical arc capable of causing severe burn injuries and equipment fires.
• Safe isolation verification: Before touching any terminal block, an electrician must confirm the absence of voltage using an approved voltage indicator tested against a known proving unit.
• Insulation testing precautions: Testing array insulation resistance requires isolating the solar inverter completely to prevent high test voltages from damaging sensitive internal input circuitry.
• Protective earthing integrity: Never disconnect protective earth conductors (PE) while the installation is energized. An open earth circuit can cause the entire metal mounting frame and inverter chassis to float at hazardous potentials.

When to contact an MCS-certified technician

Homeowners can safely perform visual checks of breakers, rotary isolators, and external cable damage. However, work inside electrical enclosures or involving live circuits must be handed over to a qualified MCS-certified solar installer.

You must escalate immediately to a professional technician under the following conditions:

• Persistent Error 202 (DC input overvoltage): Overvoltage can destroy inverter input capacitors. The array string sizing must be recalculated for cold-weather conditions.
• Repeated Error 203 (PV isolation low): Insulation faults require specialized insulation resistance testing instruments to pinpoint the defective connector or damaged module.
• Internal 400 series hardware failures: If error codes such as Error 405 (Relay error), Error 409 (Invalid bus voltage), or Error 410 persist across multiple system reboots, internal power electronics have failed.

When hardware faults persist despite normal line voltages and correct wiring, contact your installer or the manufacturer European service team at service@growatt.tech with your inverter model number, serial number, and exact error code log.