Hi guys/gals, my Baxi runs fine if cold set pressure is no more than 0.5bar, pressure increase when hot 1.5bar. If I try to increase the cold pressure to 0.7bar then the hot pressure reaches 3bar and the pressure relief valve drips the excess pressure away. When this happens and the boiler returns to cold the cold pressure is back to 0.5 bar and the boiler runs perfectly well. So, I guess it's either the expansion vessel pressure needs topping up (boiler is approx 13yrs old) or the vessel has failed and needs changing. Any guesses as to which I'll find tomorrow when I press the shraeder valve? Thanks for your help/comments. Ps. Does a replacement vessel come pre-charged?