BoilerFaultCodesTechnical description
Flow temperature too high, or temperature differential between primary and return too high
What causes this fault?
This fault occurs when the water inside your boiler heats up much faster than the system can carry it away, causing the unit to overheat for safety. The most common reason is a pump failure or a blockage in the pipes, which prevents the hot water from circulating around your radiators. It can also be caused by a build-up of sludge or debris that restricted the flow through the main heat exchanger.
This fault is frequently seen at the start of autumn when heating systems are turned back on after a long summer break, as pumps can often seize up during 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.