BoilerFaultCodesYour boiler has detected that the water returning from your radiators is too hot, causing the system to shut down to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Central heating (CH) return sensor overheating
What causes this fault?
This fault occurs when the internal sensors detect that the water flowing back from your radiators is at a dangerously high temperature, suggesting the heat isn't being dissipated correctly. The most common reasons are a blockage in the system, a failing pump that isn't circulating water fast enough, or a faulty sensor sending incorrect readings to the boiler.
This issue often comes to light during the first cold spell of autumn when the heating is turned on for the first time after summer, often due to a pump that has seized while sitting idle.
DIY fix possible
Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barSwitch the boiler off and on again to see if the fault clears after the system cools down
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A boiler cover plan would cover faults like E21 — no call-out fees, no surprises.
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Ravenheat CS 80/90, WH System, WH 80/90 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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