Vaillant 618 system boiler with VR65 controller and V4073 3 position valve. When changing to DHW the valve makes a loud “clonk”. This occurs with the pump running. Change to CH position is quiet as the controller stops the pump during the change. The boiler is set to factory settings (d70=0) so the mid position of the valve is disabled. I assume that this is because the temperature set-points are different for the DHW and the CH.
Is this a fault or a problem with the set-up?
Is this a fault or a problem with the set-up?
