BoilerFaultCodesTechnical description
Return temperature too high flow sensor temperature).
What causes this fault?
This fault occurs when the water coming back into the boiler is nearly as hot as the water going out, which prevents the heat exchanger from cooling down. The most common reason is a blockage in the system or a failing pump that isn't pushing the water through your radiators quickly enough. It can also be caused by a build-up of sludge or debris trapped in the boiler's internal filter.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after months of inactivity, which can cause the pump to seize.
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.
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