21:0 Low

Viessmann 21:0 Fault Code

Also written as 210 — same fault.

The Viessmann 21:0 fault code means: your boiler is simply notifying you that a routine service is due based on its operating hours.. It appears on 5 Viessmann models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: No maintenance indication for the burner
Typical repair cost £100-£180 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Viessmann models that show the 21:0 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Viessmann 21:0 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026