My air source

[tommy12398]

My ashp keeps cutting out saying there's a flow error but only when the hot water tank needs heat. If its calling for heat,for the ufh or rads upstairs it works fine?

[Conor]

Check the diverter (3 way) valve that splits the flow from the heating system from the hot water cylinder. See if it moves fully when switchimg from heating to hot water.

[ProDave]

Is it a single 3 way valve or multiple 2 way valves.  Either way it sounds like the valve to the hot water tank not opening so there is not enough flow.  that could be a faulty actuator head or it could be a mechanical fault (seized) If you don't know, post a picture of the HW tank and all valves or controls on or near it.

[Kelvin]

As above. I had this problem last year although it was the other way round. We had multiple two way valves and one of the actuator heads had failed which is a common fault.  Easy to replace. 

Edited December 17, 2022 by Kelvin