BoilerFaultCodesYour boiler has switched itself off because it has detected that a part inside has become too hot to operate safely.
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 Activated (Boiler or Flue)
What causes this fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to kill the power. The most common reasons are a failed pump that isn't moving water away fast enough, or a build-up of limescale and sludge that has blocked the heat exchanger.
This issue often surfaces during the first cold spell of winter when the boiler is suddenly pushed to work at its maximum capacity after sitting idle all summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 25 — no call-out fees, no surprises.
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Potterton Performa 30 HE 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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