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ErrorLib — Industrial Fault Code Library

Disclaimer: ErrorLib is an independent technical reference tool. While we aim for accuracy, always verify with the manufacturer’s official service manuals before performing maintenance on industrial equipment. ErrorLib is not affiliated with the brands listed.

401

Grid fault

SMA · Sunny Boy Solar Inverter

What does 401 mean?

The inverter has disconnected from the utility grid because it detected a stand-alone grid condition or a very large change in the power frequency. This protects the inverter and grid from unstable power conditions.

Common Causes

  • Detection of a stand-alone grid (island operation).
  • Significant short-term fluctuations in the power frequency of the utility grid.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the grid connection for significant short-term frequency fluctuations.

Browse all codes in this manual (23)
Verified technical data. Last updated: April 2026

Related Faults

101Grid fault10252[Interface]: communication disrupted10253[Interface]: connection speed goes to [100 Mbit / 10 Mbit]
Source: SMA Sunny Boy Solar Inverter
Open Manual (Page 65)Search more codes in this manual