On Fri, 30 Jun 2006 14:12:57 +0100, TheScullster wrote
(in article ):


"Andy Hall" wrote


I've installed and worked on both and migrated from a vented to a sealed
system.

............snip

Many thanks once again for such an informative response Andy.
Can I prevail on your time/kindness and ask you to look at the schematic
http://www.thesculls.freeuk.com/CHScheme.jpg please?
This shows the flow from the boiler to the vent and the relative position of
the make up feed.
It looks like I do indeed have the worst case when the hot water motorised
valve is shut. With the valve shut, both the pump and the boiler are
"between" the fill and vent connections. ie fill to pump suction, vent after
pump and boiler.
To get around this, can you see any problem with moving the fill to the
point where the water tees from the flow/vent to the h/w cylinder?
This looks like it would create an arrangement close to a combined fill/vent
but not quite.
(The schematic shows system items at approx the right relative elevations).

Thanks again

Phil



I had a similar arrangement to what you are describing when the system was
open vented except that the pump was on the flow side after the vent tee and
before the motorised valves.

If you're going to do this feed repositioning, I would use an air separator
like the Myson Aerjec. www.bes.ltd.uk part no. 11334.

Mine was set up like the third diagram, although any will work.
The fittings are copper tails which will go into any solder fitting.

The other advantage of these is that it makes initial filling/venting of the
system much easier since the small bubbles of air that initially tend to
circulate with the water can escape easily through the vent and tend to end
up less in the radiators.