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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.

21

Low Temperature (Adv. Code 0)

Vacon · X4

What does 21 mean?

This fault is triggered when the heatsink temperature drops below -10.0 degrees Celsius. Operating the drive outside its specified low-temperature limits can affect the performance and reliability of internal components, particularly electrolytic capacitors and LCD displays. This prevents safe operation and could cause damage.

Common Causes

  • Drive operating in an unheated environment with ambient temperature falling below the specified minimum operating temperature (e.g., -10°C).
  • Heatsink temperature sensor (thermistor) fault, causing it to report an artificially low temperature.
  • Ventilation system drawing in extremely cold air directly onto the drive's heatsink.
  • Drive enclosure not adequately insulated for cold environments or experiencing localized cold spots.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Measure the ambient temperature inside the control panel enclosure and directly around the drive's heatsink using a calibrated thermometer.

  2. 2

    2. Ensure the operating environment temperature is consistently within the drive's specified range (typically 0°C to 50°C for industrial drives).

  3. 3

    3. If the ambient temperature is genuinely low, consider installing a panel heater with a thermostat to maintain the minimum operating temperature inside the enclosure.

  4. 4

    4. Power down. Visually inspect the heatsink thermistor and its connections for damage or looseness.

  5. 5

    5. If the ambient temperature is above -10°C and the fault persists, the heatsink thermistor or its measurement circuit may be faulty.

Browse all codes in this manual (33)
Verified technical data. Last updated: April 2026

Related Faults

1System Fault10Restart Lockout (Adv. Code 0)11Ground Fault (Adv. Code 0)
Source: Vacon X4
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