"Derek ^" wrote in message
...
On Sun, 02 Apr 2006 19:23:08 +0100, Tim
wrote:

I have this item in my central heating system and want to confirm what
it does. is it a de-aerator?

It is a de-aerator for a vented home central heating system..

I had an identical one. There were others.


Does anybody recognise the manufacturer

It was bought unboxed from a builders merchant. Maybe 25 years ago.The
manufacturer was not indicated.

and which is the inlet/outlet
port, upper or lower.

I'd guess in at the top, out at the bottom so that the flow from the
inlet doesn't sweep the bubbles up and around the outlet such that
some go with the flow. Probably doesn't make a lot of difference
unless air is continually entering the system which cannot be
tolerated anyway.

They seem to have been de-emphasised
now with the advance of sealed
systems and a better understanding
of pumping -over.

Nope. They were not liked as they could accumulate sludge and block up.
Also, many did not understand how they worked which was the main problem.
This 3 port type, as opposed to the 4 port type, is used a lot with combined
vent and feed pipe systems (one 22mm pipe into the bottom of the F&E tank
and no vent pipe over the top). On boilers capable of being sealed systems,
combined feed and vent pipes can be used and I prefer them to two-pipe feed
and vent (no pump over or air being sucked in. Some boilers makers, such as
Baxi and Potterton, stipulate that these air ejectors should be on the
combined feed and vent pipe to expel air. They work very well. With
combined feed and vent a very low head can be obtained, so ideal for loft
fitting of boilers. To alleviate fears of sludge accumulating in the air
ejectors it is best to fit a Maganclean on the boiler return pipe, which
grabs magnetite that causes sludge. The Magnaclean protects the whole system
too.