BoilerFaultCodesTechnical description
Maximum flow temperature value exceeded or insufficient circulation – temporary fault.
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, causing it to reach a dangerous temperature in seconds. This is usually caused by a pump failure, a blockage in the pipes, or trapped air, all of which prevent the water from circulating properly. Essentially, the boiler is producing heat but has nowhere to send it, so it shuts down to prevent internal damage.
This fault is more frequent in autumn when heating systems are switched back on after being idle, as pumps can seize up or debris can settle during the summer 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.