BoilerFaultCodesYour boiler has noticed that water is not circulating correctly or the temperature sensors are giving conflicting readings.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow return sensor temperature test
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the heat exchanger as quickly as it should, leading to a rapid heat build-up. The most common reasons are a failing circulation pump that can't push the water around or a blockage in the system, such as a build-up of sludge. It can also be triggered if the temperature sensors themselves have become faulty and are sending incorrect data to the control board.
This issue often comes to light during the first cold snap of autumn when the heating is turned back on after being idle all summer, which can cause internal pump parts to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like E154 — no call-out fees, no surprises.
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