Question about air in the radiators.....

[KingboyD]

How does air get into a system that appears to be sealed and is pressurised to 1.3 bar approx.

I`m just wondering why in my combi heating system my towel dryer needs bleeding often, its the highest point in the system so naturally any air will collect there, but how does this air get into the system in the first place??

 

[TicklyT]

A variety of reasons.

Some air will nearly always be trapped in the system when it is filled initially. it may take some time before all of it moves into a rad where it can be released.

Some gases are disolved in the fill water, and come out of solution when the water is heated in the system.

Some gases (usually hydrogen) are formed by corrosion in the system. Corrosion inhibitors added to the fill water usually limit any damage, but some oxidation is almost inevitable.
(a small amount of oxidation actually improves the corrosion resistance of some metals by forming an impervious skin. Aluminium is a good example. The tough oxide layer that spontaneously forms on exposed surfaces is what makes it such a difficult metal to solder.)

Some plastic pipework can actually absorb gases from the atmosphere. It is usual to use barrier pipe, which has an additional layer built in to stop that happening.

 

[twgas]

are you sure it's air and not 'gas'

 

[KingboyD]

TicklyT - Thanks for that detailed answer


twgas - I hope not! Next time I bleed my rad I`ll have a sniff/hold a match over the bleed screw lol

Can gas enter the system?? What would cause that? My Boiler is a Worcester 28 cdi.





Ps - I won`t do the match test, honest!