BoilerFaultCodesWhat the manual says
Manufacturer manualDHW demand: Domestic hot water requirement via impeller sensor
From this model's manual
Verified against the Vaillant Ecotec Exclusive installation & service manual, page 53.
What causes this fault?
This code appears when the flow sensor inside the boiler detects that water is running through the hot water pipe. It is the boiler's way of confirming that it has successfully registered your request for hot water and is firing up the burner to heat it. This is a normal operational signal rather than a malfunction of any internal components.
DIY fix possible
No action required; this is a status code, not a fault code.Simply turn off your hot water tap to see the code change back to its standby state.
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