BoilerFaultCodesWhat the manual says
Manufacturer manualSafety temperature limiter by NTC activated
What causes this fault?
This fault occurs when the boiler's internal temperature rises too quickly or exceeds a safe limit, causing the system to shut down to prevent damage. The most common reasons are a lack of water flow caused by a faulty pump, a blockage in the central heating pipes, or air trapped within the heat exchanger.
This issue is frequently seen when the heating is first turned back on in autumn, as pump components can seize up after being idle throughout the 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 F.20: no call-out fees, no surprise bills.
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