BoilerFaultCodesTechnical description
Water to Water Heat Exchanger Giannoni, Ref. PVW 14 E
What causes this fault?
This fault occurs when the boiler's internal sensors detect that heat isn't being transferred effectively to your taps, usually due to a buildup of limescale or heating sludge inside the secondary heat exchanger. The most common reason is 'sludging' from the main heating circuit, which creates a physical blockage that prevents the cold water from heating up properly. In some cases, a failing diverter valve may also be preventing the hot water from flowing into the correct part of the system.
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.
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