BoilerFaultCodesYour boiler has shut down because it has detected it is getting too hot, usually caused by poor water flow or a lack of water in 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: Safety thermostat (STB) active: check the flow/content (low-water protection).
What causes this fault?
This fault occurs when the internal temperature sensor detects that the water inside the boiler is getting dangerously hot, triggering an emergency shutdown to prevent damage. The most common reason is a restriction in water flow, often caused by a failing pump or a build-up of sludge and debris blocking the heat exchanger. It can also happen if there is an air lock in the system or if the radiators are turned off, leaving the hot water with nowhere to go.
This fault is more common in autumn when heating systems are turned back on after a long summer break, as internal pump components can seize up from lack of use.
DIY fix possible
Check the pressure gauge and top up the water if it is below 1.0 barEnsure all radiator valves and boiler isolation valves are fully openBleed your radiators to remove any trapped airPress the reset button once the boiler has cooled down
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E02 — no call-out fees, no surprises.
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Remeha Quinta 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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