JohnB
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You'll love this article on condensing boilers 
. I'm glad I don't need one!
. I'm glad I don't need one!
- Thread starter Moo
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Feltwell
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You've sometimes no choice John. We didn't - the boiler here packed up 4 days after we moved in, and it was terminal!
The freezing condensate pipe problem can be avoided with careful routing in most cases - trouble is a lot of plumbers don't seem to bother.
The freezing condensate pipe problem can be avoided with careful routing in most cases - trouble is a lot of plumbers don't seem to bother.
Ditto. Interesting article - thanks.JohnB said:You'll love this article on condensing boilers
Penners
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Moo - sorry I haven't seen this thread until now. We've been away.
What rotten luck for you. But I have to confess that your problem has also rung an alarm bell for us. We moved into this house over two years ago, and it has a condensing boiler (located in the garden!) that was installed a couple of years before we bought the place. So, judging by the apparent 5-year lifespan of these things, it may be on its last winter! Horrors!
Incidentally, regarding your Rayburn question, I don't know whether you'll find a Rayburn with a large enough central heating output for your house. For a rough guide, have a look at this page and enter the number of radiators you have: http://www.rayburn-web.co.uk/choosing-a-rayburn/model-selector.aspx
There is also a range called an Alpha which might do you - although I suspect it may be more expensive than a Rayburn. Have a look here: http://www.waterfordstanley.com/Products/Rangecookers/1186.htm
What rotten luck for you. But I have to confess that your problem has also rung an alarm bell for us. We moved into this house over two years ago, and it has a condensing boiler (located in the garden!) that was installed a couple of years before we bought the place. So, judging by the apparent 5-year lifespan of these things, it may be on its last winter! Horrors!
Incidentally, regarding your Rayburn question, I don't know whether you'll find a Rayburn with a large enough central heating output for your house. For a rough guide, have a look at this page and enter the number of radiators you have: http://www.rayburn-web.co.uk/choosing-a-rayburn/model-selector.aspx
There is also a range called an Alpha which might do you - although I suspect it may be more expensive than a Rayburn. Have a look here: http://www.waterfordstanley.com/Products/Rangecookers/1186.htm
There is (or there was, I'm not sure if it's still in place) a provision to allow a non-condensing boiler to be installed in circumstances where it is impractical or uneconomic to install a condensing boiler. The main application for this was in houses with a conventional flued back boiler, installed in the middle of the building where there was no access to a drain for the condensate, or to a roof or an external wall for the fanned flue terminal. The assessment for this required the totting up of points. The Gas Safe or OFTEC installer should know the details.
Condensing boilers can make use of small diameter plastic flue components and condensate pumps, so it is possible to install them at a distance from the drains and external walls. I'd try to install a condensing boiler unless it proved completely impractical.
The frozen condensate drains of last year were due to the UK's nationwide epidemic of installer negligence. I do not think the winter of 2010/2011 was exceptionally severe; I think the winters of about 2000 to 2010, when most of the condensing boilers affected were installed, were exceptionally mild. Every commercial pipework installation that I know of has required external water pipes to be insulated AND trace heated (or treated with anti-freeze, but that is not applicable to condensate drains). The only customers who would have accepted bare condensate drains were the domestic customers who would not have known they were being sold a lemon.
Every boiler has got a main heat exchanger where the heat transfer from the flue gases to the water takes place. This is where the acidic condensate is produced. These are more reliable than previously, many of the manufacturers use a stainless steel cylindrical heat exchanger made by an Italian company. Some of the 'first generation' condensing boilers had a secondary heat exchanger cobbled on to a standard non-condensing boiler; these mostly didn't last very long and earned all condensing boilers a reputation for short life spans.
Combi boilers have a second heat exchanger where the heat is transferred from the hot boiler water to the domestic hot water. These are usually plate heat exchangers which have very narrow water ways to achieve high rate of heat transfer and a small size. The waterways are liable to get clogged by sludge (on the primary/boiler side) or by limescale in hard water areas (on the secondary/domestic HW side).
Condensing boilers can make use of small diameter plastic flue components and condensate pumps, so it is possible to install them at a distance from the drains and external walls. I'd try to install a condensing boiler unless it proved completely impractical.
The frozen condensate drains of last year were due to the UK's nationwide epidemic of installer negligence. I do not think the winter of 2010/2011 was exceptionally severe; I think the winters of about 2000 to 2010, when most of the condensing boilers affected were installed, were exceptionally mild. Every commercial pipework installation that I know of has required external water pipes to be insulated AND trace heated (or treated with anti-freeze, but that is not applicable to condensate drains). The only customers who would have accepted bare condensate drains were the domestic customers who would not have known they were being sold a lemon.
Every boiler has got a main heat exchanger where the heat transfer from the flue gases to the water takes place. This is where the acidic condensate is produced. These are more reliable than previously, many of the manufacturers use a stainless steel cylindrical heat exchanger made by an Italian company. Some of the 'first generation' condensing boilers had a secondary heat exchanger cobbled on to a standard non-condensing boiler; these mostly didn't last very long and earned all condensing boilers a reputation for short life spans.
Combi boilers have a second heat exchanger where the heat is transferred from the hot boiler water to the domestic hot water. These are usually plate heat exchangers which have very narrow water ways to achieve high rate of heat transfer and a small size. The waterways are liable to get clogged by sludge (on the primary/boiler side) or by limescale in hard water areas (on the secondary/domestic HW side).
Penners
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Onetap - you sound as though you know what you're talking about, and that's a very useful distillation of the facts. Thank you.
Feltwell
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That's useful to know OneTap, thanks.
Whilst fixing my boiler last week I noticed how the condensate drain works - 2 chambers, the first fills up with condensate from the heat exchanger and flue, and allows any crud to settle out, to be drained off via a plug at an annual service. When this chamber is full it trickles condensate into a second chamber, and this is arranged so it waits until it is full before dumping the entire chamber contents down the pipe to the external drain in one go - so there is no constant "drip, drip" of condensate into the drain, there instead is an occasional dose flushed away.
Am I right in thinking the early condensing boilers did drip their condensate constantly down the external drain, and this a reason why there are more prone to that drain freezing?
Whilst fixing my boiler last week I noticed how the condensate drain works - 2 chambers, the first fills up with condensate from the heat exchanger and flue, and allows any crud to settle out, to be drained off via a plug at an annual service. When this chamber is full it trickles condensate into a second chamber, and this is arranged so it waits until it is full before dumping the entire chamber contents down the pipe to the external drain in one go - so there is no constant "drip, drip" of condensate into the drain, there instead is an occasional dose flushed away.
Am I right in thinking the early condensing boilers did drip their condensate constantly down the external drain, and this a reason why there are more prone to that drain freezing?
See Appendix A (p. 69) of this document:
http://www.planningportal.gov.uk/uploads/br/BR_PDF_PTL_DOMHEAT.pdf
Also listed buildings or those in a conservation area may be eligible for an exemption. See paras. 3.6 onwards (p. 8) here:
http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1B_2010.pdf
Fit the boiler in the same position.
Route the boiler condensate pipe to a self contained float operated condensate pumps, used in air con and other heating set ups.
Boiler pipe into pump, flexible plastic pipe to your plastic waste pipe run under the floorboards or outside to a lime chip drain.
Easy peasy
Route the boiler condensate pipe to a self contained float operated condensate pumps, used in air con and other heating set ups.
Boiler pipe into pump, flexible plastic pipe to your plastic waste pipe run under the floorboards or outside to a lime chip drain.
Easy peasy
Penners
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It's a soakaway thingy. Something that you might have a bit of trouble creating, given the lack of rolling fields on your estate.Moo said:
Flyfisher
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The lime chips are there to neutralise the corrosive condensate but, as Penner's says, it still has to drain away to somewhere.
Penners
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Snags invariably have solutions. Yours are (a) to buy, say, a tenth of an acre of prime Naarch land and dig your pit on it, or (b) to drain the condensate into your waste pipe.Moo said:
It's just a matter of how much you want to spend.
I understand that dealing with the condensate can be managed but what about the requirement for venting the flue gas of these contraptions directly outside? Is it possible to use an existing flue going up through the chimney in a period property? My installer says no, so any alternative solutions would be gratefully received.
Thanks,
Chris.
Thanks,
Chris.
Flyfisher
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I understand the key issue is that, even after the condenser stage, the flue gases still contain corrosive compounds and this is further compounded by the gases being much cooler than non-condensing boilers and therefore more likely condense within the chimney flue. I don't know the regulations surrounding all this or whether it's possible to line an existing chimney with a suitable corrosion-resistant liner. That your installer says it can't be done would suggest not, but I'd say you're wise to seek additional opinions. It can be frustrating trying to find a definitive answer.
Historically, of course, chimney degradation because of nasty, corrosive combustion products is not exactly uncommon, yet many are still serviceable after hundreds of years, which is somewhat ironic when we read of modern condensing boilers not everlasting a decade themselves. I also find it hard to believe that a gas boiler can be more destructive to a chimney than a coal fire, which remains perfectly legal - though reality and legality are two very different things.
Historically, of course, chimney degradation because of nasty, corrosive combustion products is not exactly uncommon, yet many are still serviceable after hundreds of years, which is somewhat ironic when we read of modern condensing boilers not everlasting a decade themselves. I also find it hard to believe that a gas boiler can be more destructive to a chimney than a coal fire, which remains perfectly legal - though reality and legality are two very different things.
Flyfisher said:
I think the problem is that coal fires and conventional boilers aren't intended to produce condensation. They will do briefly when starting from cold, until the flue &/or heating system has warmed up, but after that all the parts should be hot enough to evaporate any condensation that has formed. There are also devices like shunt-pumps and 3-port diverting valves that were intended to keep the return temperature on big heating systems above 60 degC or so during start-up. Back-end corrosion could write off a boiler within a few years if the return temperature was allowed to stay low for prolonged periods. Condensing gas boilers should ideally be condensing all the time, so a lot more condensate is produced over the life of the boiler.
They are also fanned flue boilers and usually need a air supply pipe and a flue discharge pipe, commonly combined into a concentric flue terminal. There is a limit to the length of pipe that the fan can shift the air and gas along.