Air in central heating.

[carrust]

Can somebody please tell me how air gets into my central heating ? I've got combi boiler, & it is pressurised to 1 bar, that's about 15lbs / sq in. So, if the system is up to pressure & there are no leaks, how on earth can air get in ! I must be told !

[ELVIS68]

If it`s been drained and re-filled it can get air- locks, and to get rid of them you have to bleed one of the rads

[buildersmate]

It probably isn't air - its hydrogen, the gaseous product of corrosion caused by the water in the system attacking the inside steel surfaces of radiators. The other byproduct is black sludge - iron magnetite, that collects at the bottom of the rads, impeding wtaer flow (eventually). Over a number of years (15 perhaps) , the rads all eventually corrode through from the inside.
Have you got corrosion inhibitor in the system, to the right concentration? If the answer is no and you want to know how to install the stuff, post again.

[gasman]

Spot on buildersmate :o). You know your stuff.

[carrust]

Thank you buildersmate, that's cleared it up for me. I can get some sleep now.