BoilerFaultCodesTechnical description
1 With boiler off & system cold, fill system to 1.0bar. 2 Bleed radiators, refill system to 1.0bar. 3 If fault persists, contact installer.
What causes this fault?
This fault occurs when the boiler detects a lack of water or poor circulation, which prevents the pump from moving heat away from the heat exchanger safely. The most common reason is low system pressure caused by a leak or air trapped in the pipework, but it can also happen if the pump itself has seized or a valve is accidentally closed. To protect internal components from overheating or burning out, the boiler shuts down until the water levels are restored.
This fault is frequently seen in autumn when heating systems are switched back on after being idle all summer, as air pockets or minor leaks may have developed during the warmer months.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.