On Mon, 3 Apr 2006 14:59:13 +0100, "Doctor Drivel"
wrote:


"Derek ^" wrote in message


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.


There is no reason that this problem should happen or one of these
devices needed as long as the system is correctly dosed with
inhibitor. It is dealing with the problem in the wrong way.

--

..andy