hTG. and Hot water contrall. Glowarm Space Saver 60 Mk 11?

How can I wire a hot water cylinder stat?. I have pumped central htg. and Gravity hot water. The water get very hot!? and the room stat controls both htg. and the hot water!!?? did I mixed the wiring colour?? I have a Glowarm Space Saver 60 Mk 11 ..looking forward for your reply Regards T. Ellul