BoilerFaultCodesWhat the manual says
Manufacturer manualOverheat fault
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit, triggering a safety shutdown. The most common reasons are a failed pump that isn't moving water around the system or a build-up of sludge and debris that has blocked the flow within the narrow pipes of the heat exchanger.
This issue is more frequent in autumn or winter when the heating is first turned on after a long summer break, as internal pump parts can seize from inactivity.
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 F20: no call-out fees, no surprise bills.
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Related fault codes
All 70 fault codes on the Ultracom 35 Store
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