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Growatt Error 405: Relay Failure

Updated June 2026 · Reviewed for technical accuracy · ~3 min read

Error 405 (relay error, sometimes also shown as Error 117) means the Growatt detected a problem in the relay that connects it to the grid. The relay is the switch that physically links the inverter to your AC supply, so the inverter checks it on every start. A one-off Error 405 often clears with a restart, but a persistent one needs a look, partly because it can be triggered by the AC wiring around the inverter.

What usually causes Error 405

  • A grid or wiring condition the relay self-check did not like, especially the neutral-to-ground relationship.
  • A genuine fault in the relay or its circuit on the inverter's board.
  • A transient glitch that a restart clears.

How to handle it safely

Switches only The restart is external. Any voltage measurement or board work is for a qualified electrician or installer.
  1. Power-cycle the inverter. Turn off the AC breaker, then the DC isolator, wait 5 minutes, then restart. A transient Error 405 often clears here.
  2. Have the AC voltages checked. A known cause is a high neutral-to-ground voltage. An electrician can verify it: the voltage between neutral and ground should typically be low (under about 5 volts). A high reading points to a wiring or earthing issue feeding the relay fault.
  3. If Error 405 keeps returning after a clean restart and good AC wiring, the relay or the inverter's power board likely needs service. Contact your installer or Growatt.

Quick decision flowchart

Error 405 appears
↓ power-cycle once
✅ Clears and stays gone → likely a transient. Keep an eye on it.
❌ Returns → check neutral-to-ground voltage; if fine, the relay/board needs service.
When to bring in a professional A returning Error 405 means either an AC wiring/earthing issue or a faulty relay on the board, both of which need a qualified person. Do not keep resetting it indefinitely.

Related Growatt codes

Error 303, N-PE voltage Error 404, DC bus sampling Error 300, AC voltage

FAQ

Is Error 405 the same as Error 117?

They both describe a relay fault on Growatt inverters and are handled the same way: restart, check the AC neutral-to-ground voltage, and if it persists, have the relay or board serviced.

Can I keep using the inverter with Error 405?

The relay is a safety-critical connection to the grid, so a persistent relay fault should be resolved rather than ignored. A single restart to clear a glitch is fine; repeated faults need a professional.

Sources

  • Growatt inverter user manual and error-code reference (Error 405 / 117 = relay failure; check AC supply and neutral-to-ground voltage).
  • Growatt installer documentation.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off". This guide covers a safe power cycle only. Voltage measurements and board or relay work must be done by a licensed installer or electrician.