A5:5 Low

Viessmann A5:5 Fault Code

Also written as A55 — same fault.

The Viessmann A5:5 fault code means: your boiler is currently saving energy by temporarily turning off the central heating pump because the weather outside is warm enough that your home does not need extra heat.. It appears on 6 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: With heating circuit pump logic function (Summer economy)

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 A5:5 fault code

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

Source

Viessmann A5:5 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