IndustrialDriveDataDrive Board & Diagnostic Database
Diagnostic workflow

Danfoss VLT Alarm 29 Heatsink Temperature Workflow

Entry symptom: Danfoss VLT reports alarm 29 during operation or immediately after power-up.

Safety controls before proceeding
  • Do not bypass thermal protection.
  • Fans may start unexpectedly.
  • Hot heatsinks can burn.

Investigation sequence

1

Classify cold or hot trip

Cold-start alarm suggests sensor/feedback; hot-load alarm points to cooling, ambient or overload.

2

Check airflow

Inspect fans, filters, heatsink dust and cabinet ventilation.

3

Compare load

Record output current, duty cycle, ambient and derating condition.

4

Inspect sensor path

If alarm occurs cold, escalate to temperature feedback or control electronics after safe isolation.

Stop conditions

  • Fan failure confirmed
  • Cabinet temperature is unsafe
  • Alarm occurs cold with no thermal cause

Linked records

Alarm 29
Heatsink Temperature Fault

The drive heatsink temperature has exceeded the allowed limit or the temperature feedback/cooling path is not credible.

Open →Circuit
Danfoss VLT Cooling and Heatsink Temperature Path

Routes alarm 29 through cooling fans, heatsink contamination, airflow, cabinet ventilation, ambient temperature, load current and temperature feedback.

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