BoilerFaultCodesTechnical description
Permanent fault. Critical flue gas temperature value reached, no circulation or sensor fault.
What causes this fault?
This fault occurs when the boiler's internal components reach a dangerously high temperature, triggering a safety shutdown to prevent damage. The most common reason is that water isn't moving through the system quickly enough to carry heat away, often due to a pump failure or a blockage. It can also be caused by a faulty sensor sending an incorrect temperature reading to the boiler's computer.
This fault is more common in autumn when heating systems are first turned back on after summer, as circulation pumps can seize up during long periods of inactivity.
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.