How much does it cost to fix Viessmann error code 72:1?

Typical repair cost for the Viessmann 72:1 fault is £140-£260 including labour.

72:1 Medium

Viessmann 72:1 Fault Code

Q: What does the Viessmann 72:1 fault code mean?

Your boiler is struggling to accurately measure the temperature of the water being heated for your taps, causing it to shut down while filling your hot water cylinder.

Also written as 721 — same fault.

The Viessmann 72:1 fault code means: your boiler is struggling to accurately measure the temperature of the water being heated for your taps, causing it to shut down while filling your hot water cylinder.. It appears on 5 Viessmann models in our database.

Technical description: OFF during DHW loading to set value 2

What causes the Viessmann 72:1 fault?

This fault occurs when the temperature sensor inside your hot water cylinder sends an incorrect or interrupted signal to the boiler's control board. The boiler shuts down as a safety precaution because it can no longer accurately monitor how hot the water is getting inside the tank. The most common reason is a failing sensor or a loose connection in the wiring leading from the cylinder to the boiler.

Typical repair cost £140-£260 (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 72:1 fault code

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

Source

Viessmann 72:1 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