BoilerFaultCodesThe 6 most common faults
01
8.15 High DIY-safe
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
What to try first
Locate the filling loop (a silver flexi-hose) connected to the underside of the boiler.Open the valves on the filling loop to allow cold mains water into the heating system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone, typically between 1.0 and 1.5 bar.Close the valves firmly and ensure the filling loop is disconnected if it is a removable type.
02
8.4 High Engineer
Your boiler is failing to keep its small pilot flame lit, which prevents the main burner from igniting and stops your heating and hot water from working.
Full guide for 8.403
8.14 High Engineer
Your boiler's air-moving fan is struggling or rattling, which could lead to your heating or hot water cutting out.
Full guide for 8.1404
LOW WATER TEMPERATURE High Engineer
Your boiler is not heating the water effectively because it is having trouble regulating the flow of gas or detecting the water movement required to trigger the heating process.
Full guide for LOW WATER TEMPERATURE05
BUBNEB STAYS ON High Engineer
Your boiler is failing to ignite properly because debris or trapped air is interfering with the gas or water flow, meaning your heating and hot water will not work.
Full guide for BUBNEB STAYS ON06
HEATING BODY NOISE High Engineer
Your boiler is making loud banging or kettling noises because of internal debris buildup, incorrect gas settings, or restricted water circulation.
Full guide for HEATING BODY NOISEon the Chaffoteaux Britony Duo 55
Pressure gaugeFilling loop valvePressure relief valveThermocouplePilot assemblyGas valve
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Chaffoteaux shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue