On Thu, 02 Feb 2006 03:55:55 -0800, Honeymonster wrote:

My open vented central heating system suffered from air ingress so I
had it converted to a sealed system. However, this has not cured the
problem, air still collects in one of the upstairs radiators. I've
done the hydrogen test and it really is air. Any idea how it can be
getting in? The at cold system pressure is constant, so I presume
there are no leaks. As the air collects the pressure doesn't rise but
when I bleed it out I then have to replenish the system via the filling
loop to restore the normal "at cold" pressure. It makes no sense to
me!

plenty of background info in the FAQ below.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html