What does the Vaillant d.21 fault code mean?

This is not a fault; it simply indicates whether the comfort setting that keeps your tap water ready to heat instantly is currently turned on or off.

How much does it cost to fix Vaillant error code d.21?

Cost varies. Contact a Gas Safe registered engineer for a quote.

Vaillant d.21 Fault Code: What It Means & How to Fix It

What the manual says

Manufacturer manual

Status of the warm start for hot water: off=Function deactivated, on=Function activated and available

Shared across the range

This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.

DIY fix possible

Press the 'i' button on the boiler display to view system statusNavigate to the warm start settings menuSelect 'on' if you want instant hot water, or 'off' if you prefer to save energy

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Related fault codes

d.20View →d.22View →

All 170 fault codes on the ecoTEC Plus 620

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

con d.00 D.000 d.01 d.02 d.04 d.05 d.06 d.07 d.08 d.09 d.10 d.11 d.13 d.14 d.15 d.16 d.17 d.18 d.19 d.20 d.22 d.23 d.24 d.25 d.27 d.28 d.31 d.33 d.34 d.35 d.36 d.39 d.40 d.41 d.43 d.45 d.47 d.50 d.51 d.58 d.60 d.61 d.62 d.64 d.65 d.66 d.67 d.68 d.69 d.70 F.00 F.0 F.01 F.1 F.10 F.11 F.12 F.13 F.20 F.22 F.23 F.24 F.25 F.27 F.28 F.29 F.32 F.33 F.49 F.61 F.62 F.63 F.64 F.65 F.67 F.68 F.70 F.71 F.72 F.73 F.74 F.75 F.76 F.77 F.78 F.83 F.84 F.85 F.86 F.87 F.88 F.89 F.91 F.92 F.97 F22 F70 P.00 P.0 P.01 P.1 P.02 P.2 P.3 P.4 P.5 P.06 P.6 P.07 S.0 S.01 S.1 S.02 S.2 S.03 S.3 S.04 S.4 S.05 S.5 S.06 S.6 S.07 S.7 S.08 S.8 S.10 S.11 S.13 S.14 S.15 S.16 S.17 S.20 S.21 S.22 S.23 S.24 S.25 S.26 S.27 S.28 S.30 S.31 S.32 S.33 S.34 S.36 S.39 S.41 S.42 S.46 S.53 S.54 S.88 S.91 S.96 S.97 S.98 S.99 S.108 S.109 T.02 T.03 T.04 T.05 T.06 T.08

This is not a fault; it simply indicates whether the comfort setting that keeps your tap water ready to heat instantly is currently turned on or off.

What the manual says

DIY fix possible

Avoid the next call-out bill

Related fault codes

All 170 fault codes on the ecoTEC Plus 620

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