BoilerFaultCodesYour boiler has detected that the water leaving the unit is getting too hot too quickly, causing it 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: Higher flow temperature
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, often due to a blockage or a pump failure. It is essentially a safety mechanism that trips when the unit detects that the heat isn't being circulated properly into your radiators or hot water tank. Common culprits include a seized internal pump or a buildup of debris that has restricted the flow of water through the main heat exchanger.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after sitting idle all summer, which can cause the pump to stick.
DIY fix possible
Check that all radiator valves are fully open to allow water to circulate.Ensure the central heating bypass valve (if visible) is not closed.Check that the system pressure gauge is between 1 and 1.5 bar.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like C1 — no call-out fees, no surprises.
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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.
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