BoilerFaultCodesYour boiler has likely overheated, causing it to shut down automatically as a safety precaution.
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
What causes this fault?
This fault occurs when the water inside your boiler reaches a temperature that is too high, triggering a safety switch to cut the power. The most common reasons are a pump failure preventing water from circulating or a buildup of sludge and limescale that blocks the heat exchanger. It acts as a vital safety feature to prevent the internal components from being damaged by extreme heat.
This issue often surfaces when the heating is first turned on after summer, as the pump can seize up from months of inactivity.
DIY fix possible
Wait for the boiler to cool down for at least 30 minutesRotate the selector switch to the 'R' (Reset) position for 5 seconds, then releaseCheck that all radiator valves are open and the system pressure is between 1 and 1.5 bar
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 24 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Performa 24 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.