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Replacement boiler - condensing?
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ronald.soak
Joined: 29 Apr 2008
Location: London
Posts: 26
 
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Descaling / flushing your existing system seems first choice as the payback period on a new condensing boiler is very long. The claimed efficency improvement is some what of a con as it only applies when the boiler is condensing. This means when the temperature of the return water is below 57 degrees and probably only occurs shortly after startup or in the coldest weather. The efficiencey when heating domestic water will be way down on what is claimed.
Flushing pumps are about £70 a day to hire. Getting somebody in to do it may well cost £400-600. Avoid British Gas as they sub contract to local operators and add a big premium for doing so.
Despite the above if you do go for a new boiler the condensing models really are a no brainer because the marginal cost is nolonger great and the conditions required for exemption from having one really only likely to be meet in ftats.
Reliability of condensing boilers has been poor because many designs just had a secondary heat exchanger cobbled on to an existing non condensing model. Many manufacturers use the same bought in secondary heat exchanger.
These are sand cast alluminium and have very small water ways which clog up very easily causing local hotspots and burnouts.
I am a great fan of Viessmann boilers which have a single stainless steel heat exchanger with a single relatively huge waterway. They are also available with weather compensation. Alternatively the UK made Alpha company also uses stainless steel.
Contary to the good reports posted I am not a fan of Bosch Worcester.
Because they are a very big supplier it is inevitable that there will be lots of both good and bad reports.
I allways think it significant that when Bosch took over the respected Worcester brand the name BOSCH was given prominence and Worcester was an after note. More recently the branding has been reversed along the lines of WORCESTER a Bosch company.
A final point, boiler supply is a corrupt trade with most manufacturers offering goodies to installers for chosing their boiler. Usually these are point based schemes. Install enough boilers and you can go on the holiday or win a motorbike. Not that long ago Bosch were awarding the installers of a single boiler a cordless drill . Guess who pays for this and the other backhanders.
So if you go for a new boiler go condensing, go single heat exchanger, go stainless steel, pick your own brand and remember that your plumbers recommendation may well be conditioned by an inducement that he will not tell you about.
Wishing you a warm winter
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 Tue Oct 07 2008 10:31am |
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Renny
Joined: 30 May 2006
Location: Fife, Scotland
Posts: 80
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ronald.soak wrote:
I am a great fan of Viessmann boilers which have a single stainless steel heat exchanger with a single relatively huge waterway. They are also available with weather compensation. Alternatively the UK made Alpha company also uses stainless steel.
Wishing you a warm winter
Our system is Viessman and integrates with their solar thermal panel on the roof. Installer (who I know as a good engineer) rates them as better than the British boilers. Renny Thomson
aka Scottish Scrutineer
MSA Scrutineer
Scottish Cross Country Motorsport Club
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| Wed Oct 08 2008 6:16pm |
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adam
Joined: 20 Sep 2005
Location: Cheadle Hulme, Cheshire
Posts: 486
 
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Just had a Bosch Greenstar fitted with solar panels - on a sunny day  , can heat water to 60 degrees with enough power from the system to easily power 3 showers with some force
And got £300 back from Bosch
All new rads and fittings - but as TFC pointed out, most of the pipework had to be updated to cope
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| Mon Oct 13 2008 7:38am |
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