Medium
d.77 on Vaillant ecoFIT Pure 418

Your boiler is struggling to bring your hot water cylinder up to the required temperature within the expected time limit.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Max. cylinder reheating

From this model's manual
Verified against the Vaillant/Vaillant Ecofit Pure 412 installation & service manual, page 31.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check that the thermostat on your hot water cylinder is not set to an unusually high temperature.Ensure the valves on the pipes leading to your hot water cylinder are fully open.Verify that your heating and hot water controls/timer are calling for heat correctly.

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Related fault codes

F.20View →F.24View →

All 129 fault codes on the ecoFIT Pure 418

Seeing a different code? Every code this model can display, in one place.

cond.00d.01d.02d.04d.05d.07d.08d.09d.10d.11d.13d.16d.17d.18d.20d.23d.24d.25d.27d.28d.31d.33d.34d.40d.41d.43d.45d.47d.50d.51d.58d.60d.61d.62d.64d.65d.66d.67d.68d.69d.71d.75d.80d.81d.82d.83d.84d.85d.90d.93d.94D.094d.95d.96D.096F.00F.01F.10F.11F.13F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.83F.85F.87F.88F.89P.00P.01P.02P.03P.06S.01S.02S.03S.04S.05S.06S.07S.08S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.39S.42S.46S.53S.54S.88S.91S.96S.98S.99S.108S.109

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