BoilerFaultCodesTechnical description
The display shows alternatively the CH flow temperature and P4. The Syphon-fill programme is active. See service function 4.F
What causes this fault?
This occurs when the boiler enters an automated maintenance mode to ensure the internal condensate trap is filled with water. It is a protective measure that prevents harmful exhaust gases from leaking into your home through the drainage pipe. The boiler temporarily runs at a lower power setting until the cycle is complete, which usually takes around 15 minutes.
This is more common after a period of inactivity, such as the first time you turn the heating on in autumn or after a summer holiday.
DIY fix possible
Wait approximately 15 to 20 minutes for the 'P4' code to disappear automatically.Do not reset the boiler, as this may restart the timed cycle from the beginning.Once the sequence finishes, the boiler will return to its normal temperature display and resume heating.