Low
d.40 on Vaillant Ecomax Condensing 600/800 series

This code is simply a status message from your boiler showing you the current temperature of the water flowing through your heating system, rather than an error or a fault.

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

Actual flow temperature

From this model's manual
Verified against the Vaillant Ecomax Condensing 600 800 Series installation & service manual, page 47.
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 your display to see if the system is currently heatingObserve if the fault code disappears when the heating or hot water demand stopsMonitor the boiler for any actual error codes appearing instead of the status number

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