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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.

ALARM 15

Hardware mismatch

Danfoss · VLT HVAC Drive High Power

What does ALARM 15 mean?

A fitted option card is not operational with the current control board hardware or software version. This indicates an incompatibility preventing proper functioning of the option.

Common Causes

  • Option card firmware version is incompatible with the frequency converter's main control board firmware version.
  • Option card hardware revision is not supported by the frequency converter's main control board hardware.
  • Incorrect option card type installed (e.g., I/O card for a fieldbus slot).
  • Option card not properly seated in its slot on the control board.
  • Damaged option card or control board slot preventing correct communication.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Verify the part number and firmware version of the installed option card against the frequency converter's compatibility matrix in the manufacturer's manual.

  2. 2

    Check the frequency converter's control board firmware version (e.g., parameter 15-00 FC Type) and compare it with the option card's requirements.

  3. 3

    Remove the option card and reseat it firmly into its designated slot on the control board, ensuring connectors are fully engaged.

  4. 4

    If available, try installing a known good, compatible option card into the slot to rule out a faulty slot on the main control board.

  5. 5

    Consult the frequency converter manual for specific instructions on option card installation and potential firmware upgrade procedures.

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

Related Faults

0Internal fault (Serial port cannot be initialized)17Control word timeout22Hoist mechanical brake
Source: Danfoss VLT HVAC Drive High Power
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