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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.

421

HID range error

Fronius · Symo Advanced Manual

What does 421 mean?

An error has occurred related to the Human Interface Device (HID) range. This typically points to an internal communication or identification issue within the inverter's control system.

Common Causes

  • Internal communication error within the control system
  • Fault related to the device's human interface components

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    If this status code is displayed all the time, notify a Fronius-trained service engineer.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

102AC voltage too high103AC voltage too low105AC frequency too high
Source: Fronius Symo Advanced Manual
Open Manual (Page 43)Search more codes in this manual