Condenser Boilers - advice please!

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alzheimer | 12:05 Fri 08th Jan 2010 | Home & Garden
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I have been told that the new Condenser Boilers that we are all being recommended to install - do not function well- or at least are inefficient in the very cold conditions that we are currently experiencing.
Has anybody else heard this or has anybody experienced this. For obvious reasons I don't want to install something that is not up to the job - and would be grateful for any words of wisdom!!


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There's some generic stuff here that may be of help.
There's a difference between 'less efficient' and 'inefficient' - it's called a matter of degree!
Virtually all condensing boilers are A rated - which means they convert 90% or more of the input gas/oil into heat - the rest disappearing up the flue. Compare this to the worst G-rated boilers that are the subject of the recent Government-inspired scheme to spend taxpayers' money which are around 60% efficient. It takes a lot of non-optimised working of a condensing boiler for it to fall anywhere near the old G rated boilers.
It is true that boilers are designed for an input temperature rnage and in these exceptional conditions, any boiler will be slightly less efficient. That is not a reason to ignore them.
Your comment about not functioning well is well-made. It was certainly true that when these things first came in about 6 years ago, the early ones had more failures - but it isn't that true of virtually all new technology? Don't be an early adopter is a good rule. But that was 6 years ago, and I think if you ask a few more questions of heating engineers you will find that the early bugs are a thing of the past. They are more complex in design than non-condensing boilers.
Hi Builders Mate, while on this subject, which is best? combination boiler or condensing boiler? or are they the same thing?
Hi - hope this helps, but the problem is due to the pipe that comes out of the boiler and out of the house - it can't cope with this weather as over a prolonged cold spell it gradually freezes up and this causes the boiler to stop working.
A combination boiler combines the function of an instantaneous water heater with domestic central heating. It doesn't therefore have a hot water storage tank, heating up the hot water as and when it is needed for a bath/shower.
A condensing boiler refers to the type of combustion chamber used to burn the gas or oil with air to produce heat. With the older conventional type of chamber, burning produces (mainly) carbon dioxide and water vapour that both disappear out of the flue as hot gases. This means that some of the input heat is being lost - the maximum efficiency of such boiler is perhaps around 80%. A condensing boiler takes these hot waste gases and passes them over part of the heat exchanger such that they are cooled to a lower temperature BEFORE being shoved up the flue. The temperature of the flue gases are perhaps as low as 70 degrees C - and in particular the water vapour is cooled to such an extent that it is no longer steam but hot water droplets. The effect of all this is that more of the heat gets transferred to the water in the house - not wasted up the flue - and hence the higher efficiencies of the low 90s percent.
A new combination boiler will invariably now be a condensing boiler as well - because of the Government initiative to minimise domestic dwellings wasting as much energy as we did previously.
Hi Buildersmate,

Our Potterton combination boiler has a small tank that produces hot water instantly for most uses but if you want to fill a bath you need to have the hot tap turned down a bit so the water says hot.
Fair enough - it must have been found more efficient to do it that way. The combi principle is as I describe, but I'm not saying there aren't variants.
Question Author
MANY thanks everybody - I really appreciate ALL your input and suspect that your comment Sherrardrk - about the freezing up of the outlet pipe may be the most likely answer to the cold weather problems - if our neighbour's pipe is anything to go by.
Actually, not sure how legal it is, it's about 2m from our bedroom
window, and when on we feel we are next to the top of a power
station cooling tower!!!
That energy-saving website you gave me is full of good basic info too - so I have learned a lot - and thank you all.
Just to add to this post i had a combination boiler fitted 2 years ago, a worcester 37cdi
and must say its been great for heating and hot water and up to now no problems, also i have seen a big reduction in my gas bill. I have also just fitted a shower direct from the boiler again giving great performance, what i would advise to anyone having a new boiler is try to go for one thats as simple as possible (ie) if you have a choice of a manual timer or a digital that i had, go for a manual, in my mind they have gone to far
with technology these days were it is not really needed, i know its called progress but they don't seem to iron out the problems they already have before introducing further
Question Author
I couldn't agree more willwonker - I think modern technology is progressing too fast at the moment. However your idea re the shower is well worth noting - thanks.
Incidentally - there was a piece in the humble Sunday Post yesterday - telling a story about a couple who had a six months old condenser boiler that went AWOL in the recent freezing conditions - and had to be thawed out!! Exactly the point you made sherrardk. So - now armed with all your invaluable help folks...I know how to have mine installed..... How would we all manage without Answerbank!!!
If the installation of the boiler is internal there is no way in my mind it will freez, the problems most people are having are with the condensate pipe freezing and this is mainly due to sloppy workmanship, they can;t be bothered to route this pipe internaly
has far as possible to leave as little as possible expossed to the elements (ie) frost,
when leading it to the outside down pipe, i've seen many of these condensate pipps three and four meters long on outside walls without lagging, the minimum size is 22mm dia this must be lagged, some installers use 38/40 mm then they say it don't need lagging, in this weather i would question that, again i made sure with mine that only about one foot leads into my outside down pipe and it is well lagged, it was more trouble to install (ie)lifting more floorboards but well worth it.

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