BoilerFaultCodesWhat the manual says
Manufacturer manualR Safety Thermostat Operated (pump fault) followed by 20, 28, 40, 160 or 321 indicates possible faulty components.
What causes this fault?
This fault occurs when the water inside your boiler becomes too hot, causing a safety sensor to trip and shut the system down to prevent damage. The most common reason is that the water cannot move around the system properly, often due to an airlock in the pipework or a pump that has failed. It can also happen if your radiator valves are all closed or if there is a physical blockage restricting the flow.
This fault is frequently seen in autumn when heating systems are turned back on after a long summer break, as pump components can seize up from lack of use.
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 110: no call-out fees, no surprise bills.
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