BoilerFaultCodesTechnical description
Return temperature too high: check system flow and pump.
What causes this fault?
This fault occurs when the water coming back into the boiler is nearly as hot as the water leaving it, indicating that heat isn't being transferred to your radiators. The most common reason is a pump failure or a blockage in the pipework that prevents the water from circulating through the house. It can also be caused by a build-up of sludge or debris inside the heat exchanger, which traps the heat inside the boiler.
This fault is more frequent in autumn when heating systems are first turned on after a long summer break, as pumps 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.