Warning What does this mean?

Your system is down or running degraded, but this is not an immediate safety danger. Work through the safe steps below.

Growatt Inverter 405 — Is a Relay Fault Serious?

Error 405 means your Growatt inverter's internal grid relay has failed — the relay is the switch that connects the inverter to your home's AC supply, and the inverter halted rather than operate with a faulty one. Restart the inverter once; a persistent 405 is a hardware problem that needs Growatt service or your installer.

What should I do first?

Two quick questions — we'll point you to the right starting point.

Is this code still showing on your inverter's display?

What this code means

Every grid-tied inverter contains relays — electrically operated switches that connect and disconnect it from the AC grid. They are safety-critical components: they isolate the inverter during faults, during shutdown, and during the self-tests the inverter runs every time it starts up. Before feeding a single watt, the inverter verifies that its relays open and close correctly.

Growatt's official fault table lists "Error 405 — Relay fault" for the case where that verification fails. When it does, the inverter takes the only safe option: it halts with the fault LED lit and refuses to operate. A relay that cannot be trusted cannot be allowed to connect the inverter to the grid — a stuck or welded relay could, for instance, fail to isolate the inverter when it should.

So yes, Error 405 is serious in the sense that the inverter is out of action until it is resolved. But it is the inverter failing safe, not failing dangerously. The manual's guidance is a two-step: restart the inverter, and if the problem still exists, contact Growatt. A 405 that clears with a restart was likely a self-test upset from a grid transient. A 405 that returns is a hardware fault — a worn, stuck, or damaged relay, or a fault in the relay's control circuit — and relay work is internal, high-voltage, and strictly for qualified service personnel.

What is this downtime costing you?

Rough estimate while your system isn't producing. Adjust the numbers to match your setup.

System size (kW) Peak sun hours / day Electricity rate ($/kWh)

–per day

–per week

–per 30 days

≈ – kWh of lost production per day.

Estimate only — assumes ~80% real-world output vs. nameplate. Actual losses depend on weather, shading, panel direction, and your tariff.

Common causes

['A relay that has worn or stuck after years of daily switching cycles — mechanical parts have finite lives.', 'A failed relay self-test during startup, possibly triggered by a grid transient at exactly the wrong moment.', 'An internal control-circuit fault causing a healthy relay to be reported as faulty (or masking a real failure).', 'Voltage transients or surges damaging the relay coil or welding its contacts.', 'A relay that was already marginal finally failing its verification after a power cut or restart.']

Safe steps to try

Work top to bottom, ticking off each step as you complete it. 0 of 1 done.

['Note the code — Error 405 with the fault LED lit — and when it appeared, including anything happening on the grid at the time.', 'Power-cycle the inverter: switch off the external AC disconnect, then the DC isolator, wait about ten minutes, then switch the DC isolator and AC disconnect back on.', 'Observe whether the inverter completes its startup self-test and resumes feeding power — a clean restart clearing 405 points to a transient upset.', 'If 405 returns, stop cycling the inverter — log the recurrence and leave the unit off if your installer advises it.', 'Never open the inverter — relay diagnosis and replacement is internal high-voltage work for qualified service only.']

Is your inverter still under warranty?

Before paying for a repair, check — your installer may fix this free.

Brand Year installed

Based on typical standard warranty terms — always confirm with your warranty card or installer paperwork, as terms vary by model, region, and purchase date.

When to call an electrician

Contact Growatt service or your installer if Error 405 persists after a restart or keeps coming back. The manual's own guidance is 'restart the inverter, if problem still exist, contact Growatt' — there is deliberately no homeowner step beyond that. Relay faults are internal hardware issues: diagnosis, let alone replacement, must be done by qualified service personnel. Opening the inverter risks electric shock and voids the warranty, so this one belongs to the professionals from the moment a restart fails to clear it.

Frequently asked questions

What is the relay in my inverter, exactly?

An electrically operated switch that connects and disconnects the inverter from the AC grid. It provides safety isolation, so the inverter refuses to run if the relay cannot be verified as working.

Is Error 405 dangerous?

The inverter fails safe — it stops rather than operate with a suspect relay. The danger would come from ignoring the fault or opening the unit, not from the code itself.

Can I replace the relay myself?

No. It is internal, high-voltage, warranty-voiding work. Error 405 belongs to Growatt service or a qualified technician from the start.

Error 405 appeared right after a power cut — coincidence?

Possibly not. Grid disturbances can stress the relay or trip its self-test at startup. One restart will tell you whether it was transient or a genuine failure.

Need a professional?

This fault may need professional diagnosis. Contact a qualified solar electrician in your area.

Sources: meaning and troubleshooting verified against the manufacturer's documentation — Growatt MIN 2.5-6K TL-X2 User Manual (GR-UM-293-A-01), section 11.4 Inverter fault — Error 405 'Relay fault' (hg.growatt.com)