can any of you central heating experts out there give me a clue about
how to solve this problem i'm having ?

why would CH pressure contantly rise if there are no airlocks and not
too much water ?

the pressure reading on my combi boiler slowly rises until about 3
bar, at which point the relief valve opens and releases some water
until the pressure drops, which all seems 'normal' enough, but the the
cycle immediately begins again (pressure rises, relief valve opens,
pressure drops)....and so on.

this all started after i drained the whole system and refilled it
(along with a quantity of corrosion inhibitor).

I know what you're thinking.......AIR in the system!!. This was my
first thought, and i've been bleeding the rads (or attempting to)
regularly since refilling the system, but for the last couple of
months now, i'm getting no more air, so the system appears to be 'air
free' so what do i do now ?

i've checked the filling loop that doesn't appear to be feeding
anything in, so just where is this pressure coming from ?

i'm not an expert in CH systems so i don't know what other things
could cause pressure rises.....i only know about airlocks and too much
water.