I was having an overpressure problem on my heatline c28 boiler, The presuure would go above 3 bar and water would dribble from the overflow whilst the boiler was in central heating mode, then once the central heating was switched off the pressure would drop to below 1 bar, I would have to use the filling loop to get the pressure back up to the working range, Having had a few cowboys around I thought I would get the boiler repaired by british gas and take out a service contract afterwards. The british gas engineer fixed the problem the expansion chamber needed topping up. However he cancelled the contract because he could not find GC number for our boiler on his system and there was no gc number on the id plate inside the boiler. The plate states that the boiler is a C28 model however he said it was a condense C28 surely they are the same? Heatline have been no help at all and there help line is 60p a minute