Hi. I have a Vokera Excel 80. When we brought the flat (8 years) there was no user guide or anything so I have no paperwork to follow. The boiler has been working fine, until recently. I noticed there was no pressure showing. I ran the hot water and it worked fine. When I turned my central heating dial that worked too. Thought no more of it until this morning when there is not hot water. I turned the central heating on and the pressure bar increased. As soon as I did that, the hot water started working. Obviously I don't want to have to turn my heating on every time I want a bath, but I have no pressure in the boiler. Any ideas on what I need to do?