BoilerFaultCodesYour boiler is shutting down because the water is not circulating properly through the system, causing the heat to build up too quickly in one area.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Delta T (Flow - 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 gap between the outgoing and incoming pipes. The most common reasons are a failing internal pump, a build-up of sludge blocking the pipework, or air trapped within the heat exchanger. Essentially, the boiler is producing heat but has nowhere to send it, so it shuts down to prevent internal damage.
This fault is more frequent in autumn when the heating is first turned on after summer, as the pump can seize or 'stick' during the months of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure there is enough water pressure in the system (typically 1.0 to 1.5 bar)Bleed all radiators to remove trapped air that might be blocking circulation
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E07 — no call-out fees, no surprises.
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Remeha Avanta 18V 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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