Pressure drop firebird boiler

[Braddi]

We have a firebird combi boiler. The pressure has been steady ish at around .8 to 1 for a while. But on Friday it was serviced and the engineer put the pressure up to 1.5 - yesterday it dropped right down below 0.5 and it started making a really horrid noise.

We topped it up to 1 and it was sort of OK but now it's cold it's at about 0.6 to 0.7

The engineer is coming back but he doesn't think there is anything wrong with the boiler.

So we are wondering about the dreaded leaks and if to get someone in to help find it- we are a bungalow so no water patches on the ceilings.

Anybody got any experience with this kind of thing?

 

[MANDATE]

The water expands when heated, the extra water goes into the expansion vessel. The air inside the vessel gets compressed and you get a rise in pressure of around 1bar (unless the vessel has lost some of its air charge)
So starting with 1bar and going up to 2bar when heating on, or 1.5bar up to 2.5bar is about right.
There is a pressure relief valve which opens at 3bar although it should never get to that.
However if vessel has been neglected or there is a blockage in the connecting pipe and PRV does open the pressure will drop quickly.
Problem is that sometimes the PRV does not seal again correctly so you get left a very small leak. This type of leak is more gradual and takes a lot longer to drop a bar.
I would keep with the 1bar setting and see what pressure you get when heating is on and if you get anywhere near the 3bar.
If you have a gradual pressure loss say overnight when heating was not on then suspect the PRV. You have the option of cleaning the PRV or fitting a new one. Of course cleaning it may not solve the problem whereas a new one will.