15 Low

Main 15 Fault Code

The Main 15 fault code means: your boiler has detected a minor internal communication hiccup and requires a simple manual reset to get back up and running.. It appears on 4 Main 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: resettable error

DIY fix possible

Locate the reset button on the front control panelPress and hold the button for 3 to 5 secondsWait for the boiler to restart and the fault code to clear from the display

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Main models that show the 15 fault code

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

Source

Main 15 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026