On Tue, 4 Jan 2005 13:21:27 -0000, "Jim Alexander"
wrote:
"Andy Hall" wrote in message
.. .
Yes. There isn't a sudden condensing efficiency orgasm that happens
at the dew point. Efficiency increases with falling return
temperature and exhibits a greater *rate* of this below the dew point.
Hmmm. Preparing for "compulsory" replacement condensing boilers in May 2005
(two jags bombshell No2) had a holiday project trying to find some hard data
on this. Failed miserably. Any links to actual data over the full
operating temperature ranges?
Ergo, the objective is to get the temperature as low as possible for
as much of the time as possible.
Yep, unfortunately my radiator system is designed for 70deg mean water
temperature. Works well but has little margin for condensing operation.
Jim A
Several things here.
1) There are to be some exemptions which will basically operate if
replacement of an existing conventional boiler with a condensing one
will be too disruptive. This will be cases related to flue
arrangements, condensate drain etc., and a points scoring system is
used. Thus if you have a backboiler with conventional flue in the
middle of the house, then you may score sufficient points not to need
to replace with a condensing model. However, if it's a wall mount in
the kitchen, you would be pretty unlikely to meet exemption criteria.
Details are at
www.2jags.com (
www.odpm.gov.uk)
2) There are some typical curves for condensing boilers on the Keston
web site.
3) It doesn't matter if you have an existing radiator design for the
more typical 82/70 boiler arrangement. When the weather is really
cold, the boiler will wind up to these temperatures. When it's
warmer, less heat will be needed and it will modulate down and try to
operate at as low a temperature as possible. So for much of the year,
you would still be operating in the more efficient range below the dew
point. Obviously if you take the situation over the whole year it
won't be *as* good, but still worthwhile.
--
..andy
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