BoilerFaultCodesYour boiler is getting too hot too quickly, often because there is trapped air in the system or the water isn't moving through the unit properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler operating at higher flow temperature / Air passing through the pump (if shutdown occurs)
What causes this fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature too quickly, triggering a safety shut-off to prevent damage. The most common reason is a blockage or a failing pump that prevents water from circulating away from the heat exchanger, but it can also be caused by pockets of air trapped within the pipework. Essentially, the boiler is generating heat that has nowhere to go.
This issue often surfaces in autumn when the heating is turned back on for the first time, as pump components can seize up after being idle over the summer.
DIY fix possible
Check that your radiator valves are fully openBleed your radiators to remove trapped airCheck your system pressure and top up if it is too lowPress the reset button once the boiler has cooled down
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 2 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Envoy 30 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.
Affiliate links — we may earn a commission at no extra cost to you.