BoilerFaultCodesWhat the manual says
Manufacturer manualDifference between warm start and hot-water outlet target value
What causes this fault?
This fault occurs when the boiler struggles to keep its internal store of hot water at the correct temperature for the 'warm start' feature. The most common reasons are a buildup of limescale in the heat exchanger or a failing sensor that is giving the control board inaccurate temperature readings.
This issue is more noticeable in winter when the incoming mains water is much colder, forcing the boiler to work harder to maintain its pre-heat temperature.
Engineer required
This fault requires 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 d.73: no call-out fees, no surprise bills.
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