On Wed, 3 Dec 2003 00:06:05 +0000, Andrew
wrote:

In article .uk, Ed
Sirett writes

snip

I've yet to see the plume as the boiler is only on when someone's having a
bath (reheating the cylinder) or for odd quater-hours here and there.

So what do you use for space heating ? - just curious. £800 for a Keston
is an expensive way of heating water.

This is fairly typical behaviour with a modulating boiler.

For example, this Keston model drops its power level down to 7kW - I
have a different make which will drop as low as 3-4kW.

During a large part of the year, spring and autumn, and during the day
through he winter, the amount of heat required is much less than the
full output of the boiler. With a conventional boiler, the burner
is turned on and off to reduce the average heat output. In the case
of most types of condensing boiler, the burner power is reduced which
reduces output and water temperature.

It is more efficient to reduce power than to start and stop the
burner. Moreover, reducing the temperature increases the boiler
efficiency as it is pushed further into condensing operation.





..andy

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