BoilerFaultCodesYour boiler has detected that water is the wrong temperature as it enters and leaves the unit, essentially indicating that the water is not circulating through your radiators properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature difference between flow and return too large
What causes this fault?
This fault occurs when water is unable to move through the boiler fast enough to carry heat away, causing a dangerous temperature buildup. The most common reasons are a failed internal pump that has stopped spinning or a heavy buildup of sludge and debris that is physically blocking the pipework. It can also be caused by air trapped in the system or sensors that are sending incorrect readings to the control board.
This issue often appears when you first turn the heating back on in autumn, as moving parts can seize and debris can settle during the summer months of inactivity.
DIY fix possible
Check that all radiator valves and boiler isolation valves are fully openEnsure your central heating pump is running and hasn't seizedBleed all radiators to remove trapped air that might be blocking water flow
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E10 — no call-out fees, no surprises.
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Remeha Quinta 115 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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