"Andy Hall" aka Matt wrote in message
...
On Mon, 22 May 2006 13:50:31 +0100, Doctor Drivel wrote
(in article ews.net):

Buy a Danfoss BEM 5000, that will do
they job for you. I saw one on ebay
that went for £22 brand new plus £5 postage.
~£200 worth of compensator for
buttons. Most don't understand them and
can't see what they can get from
them, thinking a modulating boiler is the answer.
Modulating on a setpoint boiler temp is not
the same as load compensation.

This type of thing is a very poor option
in comparison with a proper weather
compensation on the boiler controller
whereby it knows what the temperature
is.

Matt, it knows what the temperature is as it senses the return temperature
of the heating.

It might be worth £22, but certainly not £200.

Matt, you must have brain damage.

Control of the boiler is on/off which is
the weak part of the whole thing.
While it is able to take outside temperature
into account and be reasonable
if one already has a simple switched boiler,
it has to resort to timed
anticycle to prevent reduction in efficiency
as a result of on/off firing.

The boiler will still modulate. If the flow and return temperature close up
the burner modulates. As the compensator knows roughly what the return temp
should be in relation to the outside temp and the return temp is stable
anyhow, cycling will be minimal. The boiler has anticycle control too.

The better option is undoubtedly an
integrated weather compensator coupled
with room temperature sensing and boiler
and pump output control.

But these cost a hell of a lot, and having one with DHW priority too
(running up the boioer temp to max) is not that common.

A good cheap boiler like the Glow Worm and Danfoss BEM 5000 is highly cost
effective way to go.