BoilerFaultCodesWhat the manual says
Manufacturer manualSafety 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like 25: no call-out fees, no surprise bills.
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