Do I have a leak in central heating?

[Day]

My Greenstar 42CDi boiler is 6 month old and was installed together with brand new central heating system and plumbing when the house was redone. At the begining there was one leak in the central heating system and it was fixed. At that time pressure was dropping to 0 within 24h period. After it has been fixed i've been noticing that the highest placed radiator in the bathrooms gets air and every 2 weeks or so had to vent it and refill the system. the pressure was staying on 1 bar and it only dropped after I vented the radiator. The gas inside the radiator was flamable so I assumed that it's due to corosion and added an inhibitor. The air stopped collecting after that. However to test if there is still a leak somewhere I refilled the system to over 1.5 bars and within a week or two the pressure dropped to 1 bar (or sometimes very slightly lower depending on water temp) and hasn't decreased further for over 2-3 month. I'm wondering where has that water gone and why isn't the pressure steadily decreasing further? Does the boiler automatically reduces the pressure to 1bar if the pressure is above that?
Do you think that there is a leak in the central heating system or maybe there is problem with the boiler itself?

 

[45yearsagasman]

If your system pressure has been steady at 1 bar for 2-3 months then you have no problems. The slight fall you had may have been air being vented by auto air vent. A rise and fall of pressure is normal. Always recharge a system when the water is cold. Make sure that your expansion vessel still has a precharge. Consult your MI's or get someone to check it for you. As said your boiler now seems to have settled down.
Boilers will only vent when the system pressure approaches the PRV limit, which is normally 3bar.

 

[bengasman]

Bring the pressure up to about 1.7 bar, and see what happens.