Cooling fan
Common VFD, drive, UPS, and cabinet overheating failure point.
Danfoss FC 51 Fault Codes - What They Mean
The Danfoss VLT Micro Drive FC 51 is a compact VFD used on small fans, pumps, conveyors, and OEM equipment. Danfoss lists the FC 51 as a limited lifecycle product, so troubleshooting often comes down to deciding whether the fault is an external wiring/load problem or a replacement-drive event.
Common FC 51 Alarms And Warnings
| Code | Meaning | First Check |
|---|---|---|
| Alarm 13 | Overcurrent | Motor cable, acceleration ramp, jammed load |
| Alarm 14 | Earth fault | Motor insulation and cable damage |
| Alarm 16 | Short circuit | Output terminals and motor leads |
| Alarm 27 | Brake chopper fault | Braking resistor and wiring |
| Alarm 29 | Heatsink temperature | Cooling path and ambient temperature |
| Alarm 30 / 31 / 32 | Motor phase U/V/W missing | Motor cable continuity |
| Alarm 38 | Internal fault | Power cycle once, then replace or repair if it returns |
| Alarm 46 | Power card supply | Internal supply or power card issue |
| Alarm 47 | 24 V supply low | Control wiring load or internal supply |
| Alarm 51 | AMA check failed | Motor data and motor connection |
Step-by-Step Fix
- Write down the alarm number. FC 51 alarms can look similar on a small display. Confirm the number before troubleshooting.
- Check the load. For Alarm 13, inspect the fan, pump, or conveyor before changing parameters. A small FC 51 has little overload margin.
- Test the motor and cable. For Alarm 14, 16, or 30-32, power down, wait for discharge, disconnect the motor leads, and test cable insulation and motor winding continuity.
- Review ramp times. Increase acceleration time for overcurrent on startup. Increase deceleration time or inspect the brake circuit when trips happen while stopping.
- Clean the cooling path. Alarm 29 often comes from cabinet dust, blocked side clearance, or a failed fan in a hot enclosure.
- Verify motor setup. Wrong motor current, voltage, or AMA setup can create nuisance overloads.
- Retest under real load. Run the machine through the same step that caused the trip.
Parts Often Needed
| Part | Notes |
|---|---|
| Replacement FC 51 drive | Common when Alarm 38 or Alarm 46 returns |
| Motor cable | Replace after failed insulation test |
| Braking resistor | Check when stop-time faults appear |
| Cabinet fan and filters | Cheap fix for repeated temperature trips |
Need Replacement Parts?
Before ordering, match the drive part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
Call a qualified technician for any Alarm 14, Alarm 16, or Alarm 38 that repeats after the motor cable is disconnected. Those faults can involve dangerous stored DC voltage and failed power electronics.
Source Notes
- Danfoss VLT Micro Drive FC 51 Operating Instructions.
- Danfoss FC 51 lifecycle information.