Faulty Pressure Release Valve on my combi boiler

[garnet30]

We know we have had a little leak in our system for ages and we have been topping it up every couple of weeks. But I got up on Sunday to find the boiler on "Lock Out" despite the pressure being just under 3 bar (It is a Range Powermax 140) The engineer who came out to me got it working and has ordered a new pressure release valve which is going to be fitted on Thursday but after he left the pressure began to drop rapidly so i topped up to 2 bar (where it has stayed) within a few hours it was locked out again. If the pressure is at 2 bar surely this cannot be the problem, so what else might be causing it to lock out?

[gasman]

you only need to put in 1bar of pressure. Putting 2bar in could make it go over the 3bar threshold when it heats up and the pressure build up with the expznsion of the heated water and cause lock out situations