Low
S.21 on Vaillant Turbomax Plus 824/828E

Your boiler is simply performing a routine check of its internal fan before starting to provide hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Fan running (warm start)

From this model's manual
Verified against the Vaillant/Vaillant Turbomax Plus 824 828e installation & service manual, page 38.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

S.20View →

All 92 fault codes on the Turbomax Plus 824/828E

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

d.00d.01d.02d.05d.07d.08d.10d.11d.21D.22d.23D.24d.25d.30d.33d.34d.35d.37d.40d.41d.50d.60d.61d.64d.65d.67d.68d.69d.71d.72d.73d.75d.76d.80d.81d.82d.83F 22F.00F.01F.10F.11F.20F.22F.23F.24F.27F.28F.29F.32F.33F.37F.41F.42F.43F.60F.61F.62F.63F.64F.65F.66F.67S.00S.01S.02S.03S.04S.05S.07S.08S.10S.11S.13S.14S.16S.17S.20S.23S.24S.27S.28S.30S.31S.32S.33S.34S.36S.39S.53S.54

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