How to make HW have priority over CH

[buncers]

I have a problem with my system when both CH and HW are on. The CH seems to take priority and the HW hardly warms up.

To get the HW to heat I usually need to turn down the heating on the thermostat or turn it off on the programmer.

Is there a way to make the system give priority to the HW over the CH.

 

[RBG]

What boiler is it?

 

[ShaunCorbs]

You can do it with relays but normally just stagger the times eg hot water comes on an hour before heating etc