On Tue, 18 Nov 2008 16:31:03 -0000, "Roger R"
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> snipped-for-privacy@clara.co.uk> wrote:
> >I want to modify the pipework feeding a radiator on a combi boiler system
> >but I could do with some advice on how to go about it as I am a novice at CH
> >systems.
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> >My idea was to use a couple of freezer kits that go around the pipe
> >isolating the section, avoiding draining down the whole system. I havn't
> >used these kits before, but guess that it is best to release the pressure in
> >the system before starting. If I shut the water off at the house stopcock
> >and open a radiator vent valve, will this be suffiencient to release the
> >pressure in the system? I'm thinking about air stored somewhere - in a
> >closed header tank?
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> >When the pipework changes are done, are there any potential problems
> >about getting any lost corrosion protection fluid / antifreeze back in - and
> >getting any air out of the system to restore normal operation? >
> >Thanks.
The CH system is not pressurised continuously at mains pressure. Mains water is allowed in using a little keyed tap until the pressure gauge registers the correct pressure. You don't need to turn off the stopcock - it won't make any difference.
If it were me I'd drain the whole system before starting - using the drain c*ck not a rad bleed valve. Expect a few buckets full of water. The idea of having a time limit to get everything connected (as the ice melts) is a bit frightening!
Sometimes you add the anti-corrosion stuff into a rad with an upward facing pl;ugged opening on the top, such as a towel rail.
Remember to check for leaks when you pressure it up again. Bleed the air out of each rad. The boiler (in my case) has an automatic bleed valve.
Robert