"Tony Bryer" wrote in message
...
On Wed, 29 Mar 2006 18:23:53 +0100 Jeff wrote :
Can anyone explain how boiler modulation works, its benefits etc
and the same for weather compensation

In brief (as I'm just going home) modulation means that the boiler
includes a facility for varying the fuel being burnt (and thus the
output) - for example my Glow-worm 24Cxi combi will modulate between
5 and 18kW. When the temperature of the water coming back to the
boiler starts to rise (because the radiators cannot get rid of all
the heat being produced) the burn rate is reduced accordingly.

Think of it as driving a car: if you only had an on/off switch for
the engine you'd have to fire up, then switch off and coast for a
bit, start up again .... instead you ease off the throttle until the
engine is producing just enough power to maintain the desired speed.
Likewise a modulating boiler.

Weather compensation adjusts the boiler's output temperature to suit
the current outside temperature, so the rads will be hotter on cold
days, less hot on milder ones. This makes for greater comfort and
also enhances the boiler efficiency.


So in the above analogy... weather comp varies the 'desired speed' in effect
turning up or down the boiler temp knob ?

The control for the modulation must work on a fixed differential from flow
to return ?

Tony you said 'in brief' - i would love the long and detailed version as i
am trying to get my head around this for a future project.

Regards Jeff



--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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