6 nn Low

Keston 6 nn Fault Code

Also written as 6NN — same fault.

The Keston 6 nn fault code means: your boiler has successfully heated your home and hot water to the requested temperature and is now resting until more heat is needed.. It appears on 1 Keston model 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: Burner off because required temperature has been reached

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Keston models that show the 6 nn fault code

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

Source

Keston 6 nn fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

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