Growatt Error 303: Neutral-to-PE Voltage Too High
Error 303 means the voltage the Growatt measures between neutral and earth (PE) is too high, typically above about 30 volts. On a healthy installation that voltage should be very low. A high reading points to a wiring or earthing problem, so this is mostly an electrician's job rather than a quick reset.
What usually causes Error 303
- An earthing (PE) issue at the inverter or distribution board.
- A neutral problem on the supply, sometimes a wider grid wiring issue.
- Incorrect neutral-to-earth bonding, especially after recent wiring work.
What to do
- Note any recent changes. Did Error 303 start after new wiring or an install change? That points straight to the earthing or neutral connection.
- Power-cycle once. AC breaker off, then DC isolator, wait 5 minutes, restart, in case it was transient.
- If it returns, have an electrician check it. They measure the neutral-to-earth voltage and inspect the earthing and neutral connections. A genuinely high N-PE voltage should not be ignored.
When to bring in a professional
A high neutral-to-earth voltage is an electrical wiring and safety matter. If Error 303 persists, have a licensed electrician inspect the earthing and neutral, rather than continuing to reset it.
Related Growatt codes
Sources
- Growatt inverter user manual and error-code reference (Error 303 = neutral-to-PE voltage above 30V; check AC wiring and earthing).
- Growatt installer documentation.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off". This guide covers noting recent changes and a single safe power cycle only. Earthing, neutral and voltage measurements must be done by a licensed electrician.