Low
S.8 on Vaillant ecoTEC System

Your boiler is taking a short, normal break to prevent the system from switching on and off too frequently after it has finished heating your home.

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

Anti cycling mode (after heating operation)

From this model's manual
Verified against the Vaillant Ecotec installation & service manual, page 43.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This status occurs when the boiler has reached its required temperature and shuts the burner off to prevent wasting energy. It then enters a timed waiting period to stop the system from rapidly switching on and off, which protects the internal components from unnecessary wear and tear. You will usually see this once your radiators are up to temperature or the thermostat has been satisfied.

This is more frequently observed during spring and autumn when the weather is milder and the boiler doesn't need to run constantly to keep the home warm.

DIY fix possible

Wait approximately 5 to 15 minutes for the countdown to endCheck that your room thermostat is set to your desired temperatureEnsure at least one or two radiators have their valves fully open to allow heat to dissipate

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