BoilerFaultCodesYour boiler has stopped working because air is trapped in the pipes or the water isn't flowing correctly through the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler shut down due to air passing through the pump or system not correctly vented (monitors temperature rise across the heat exchanger).
What causes this fault?
This fault occurs when air bubbles get trapped inside the boiler’s internal pipework or the pump, preventing water from moving heat away from the burner. The most common reasons are a buildup of air after a repair, a leak in the system, or an automatic air vent that has become blocked with debris or limescale over time.
This issue often appears in autumn when the heating is turned back on after summer, as air can settle in the pipes during long periods of inactivity.
DIY fix possible
Check that your radiators are bled and all air is removed from the system.Ensure your system pressure is topped up to between 1 and 1.5 bar.Reset the boiler to see if the air pocket has cleared.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E12 — 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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