worcester bosch 26/32 oil boiler + solar?

I have fitted thermal solar system to my oil combi heatslave 26/32. I have used a combi valve that directs any water from the solar cylinder that is not to temperature to the combi to top up the heat however even with the hot water control on minimum the water is coming out frm the boiler super heated. Can you recommend any alteration wither internally or externally so that the heat exchanger will only top up the hot water .