pressure can be as high as 2.50 bar and still work your prv(pressure relief valve) will relieve any excessive pressure after that,the problems you could have is-1 pressure passing through the bypass valve into the heating side of the boiler,-2a faulty prv and not letting the excessive pressure escaping-3 and finally a faulty expansion vessel letting the water expand when heating up thus showing high pressure on the guage.
hugopop, October 2008
