Yet another Boiler thread (sorry)

Sorry about this guys and gals. I know there is a lot of boiler talk going on here at the moment and I'm trying to keep up with the diverse and sometimes opposing points of view.
My question is regarding combi versus condensing combi. Is it worth trying to beat the April deadline for having a normal combi fitted or are the benefits of the condensing combi worth the extra cost? Is there a difference on longevity between the two types in general?
Thanks,
--
Paul Giverin

British Jet Engine Website http://www.britjet.co.uk
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Wait until after April to see if prices drop, as 90% plus of all boilers will be condensers then, so makers costs will drop. If you need to replace a boiler then go condenser. The myths abouth them being unreliable are well ...just myths. Replacing an old cast iron job, you may save up to 40% of your gas bill.
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Almost a myth.
If the CI boiler has an efficiency of 54% then the condensing replacement would need to operate at 90% efficiency. To do that it would have to be an efficient boiler to start with and operate in condensing mode almost constantly. Not totally impossible but not in the real world either.
Some relatively efficient fan flue boilers have CI heat exchangers and over them a more typical saving would be 10-15%.
I wonder if dIMM has a job in the procurement dept of the Ministry of Defence. :-)
--
Roger

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contains these words:

of
< snip ill-informed drivel >
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Roger wrote:

He did say "may" and "up to" ;-)

Given the modulating burner and the more sophisticated control system, you will probably get it operating in condensing mode for the vast majority of the time.

As you say 40% is pretty unlikely, but 25% is not unreasonable.
--
Cheers,

John.

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You need to check that this is completely accurate, but, I believe a lot of the cheaper models of condensing combi's only operate in condensing mode for heating and not hot water. I know Worcester-Bosch Greenstar models operate in condensing mode for both heating and hot water but I don't know which others do/don't.
It should be said that our new condensing combi boiler over our old model makes a huge difference in gas comsumption (this winters compared to last winters gas readings). I'm unsure how much of this is down to the fact that the new boiler doesn't have a pilot light running 24x7 and how much is due to increased efficiency.
I know this doesn't directly answer the original question but hopefully it's of some use.
Seri
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That is true, but only for combi's

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Seri wrote:

That may well be the case, although as has been mentioned before in other threads, there is no massive gain in efficiency when a condenser starts condensing. Its extra efficiency is down to a who package of design features.
--
Cheers,

John.

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25% is about as bad as it is likely to get. 23% was the example quoted in another thread for an upgrade from a back boiler and back boilers are not exactly renowned for their efficiency.
Assuming a replacement efficiency of about 85% a 15% upgrade is from about 74%, 25% from 64%.Where would you place a 'relatively efficient fan flue boiler with CI heat exchanger"?
--
Roger

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Trouble is many who ask for advice may actually believe this and budget for the replacement accordingly. However, actual savings of 40% in cash terms on gas use are most unlikely. Half that would be nearer a norm.
--
*Rehab is for quitters

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

< snip drivel >
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Note the 'may'. That's the important word. The other important word that should come after it is 'not'.
Hope for 20%. That's far more likely.
--
*I'm planning to be spontaneous tomorrow *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

< snip drivel >
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Paul Giverin Wrote:

If I were changing my boiler at home right now I would definately fit condensing boiler without question. I would fit one of the bette purpose built versions like those which use the Vaillant syste (Vaillant, Hastead, other people may use it) the Buderus, Worcester all of wich have the necessary protection against the acidic water tha is hanging around in the exhaust gases.
The grafted on extra heat exchanger style is OK, but they are bes operated in Sedbuk band B. Baxi for instance told me during a trainin day that they don't want their 105he condensing too much, that's wh they've limited it to band B. This and others like it have an excellen Class D boiler as their basis, but they pass return water through preheat extra heat exchanger which sucks the last heat out of th exhauset on it's way outside. They do not want the primary hea exchanger to start condensing as the burner which is in the olde position beneath, would quickly corode.
Therefore fit a good one.
I certainly wouldn't fit a Band D boiler for myself
-- Paul Barker
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Paul Barker snipped-for-privacy@news.diybanter.com typed:
<snip>. Baxi for instance told me during a training

I thought (but could be mistaken) that the burner on these are ceramic.
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