BoilerFaultCodesWhat the manual says
Manufacturer manualSafety switch-off: Temp. incr. too fast - Temperature increase too fast
What causes this fault?
This fault occurs when the boiler detects that the water inside the unit is getting too hot, too quickly, suggesting the heat isn't being carried away to your radiators. It is usually caused by a pump failure, a blockage caused by sludge buildup, or air trapped within the system preventing proper water flow. Effectively, the boiler is forced to shut down to prevent the internal components from overheating and sustaining damage.
This issue is more frequent in autumn when the heating is turned on for the first time after summer, as pumps can seize and debris often settles while the system is inactive.
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 F.24: no call-out fees, no surprise bills.
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Related fault codes
All 146 fault codes on the ecoTEC Pro 24
Seeing a different code? Every code this model can display, in one place.