hi! can anyone help me, i have a eurocombi styx sx20 mffice supplying me with central heating and hot water. my problem is that if the heating is off and i turn on a tap the boiler makes a noise but the boiler does not ignite and heat the water. if i have the central heating on, which all works as normal and then turn on the tap the hot water is fine, it all works. i've looked at the manual for the boiler and i'm thinking diverter valve.