Low
D.0 on Vaillant ecoTEC Regular

Your boiler is currently restricted to a lower power setting for heating, meaning your radiators might take longer to warm up or may not get as hot as they should.

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

Heating part load error

From this model's manual
Verified against the Vaillant Ecotec installation & service manual.
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 occurs when the boiler's software has been manually adjusted to limit how much gas it uses for the heating system. It is usually set by an engineer during installation to match the size of your home, or it may have been limited accidentally during a service. Because of this limit, the boiler cannot use its full power to heat your radiators even if the house feels cold.

This issue is most noticeable during the first cold snap of winter when the boiler's restricted power output struggles to keep up with the dropping outside temperatures.

DIY fix possible

Check if any radiator valves are turned off or restrictedMonitor if the home reaches the desired temperature over a longer periodNo immediate action is required if your home remains comfortable

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