Saturday
Jan012011
by 
Bishop Hill
Bishop Hill Condensing boilers
North has an interesting piece (H/T Autonomous Mind) about the widespread failure of condensing boilers in the UK this winter and last. The problems have been caused by the condensate pipes freezing up in cold weather. Unfortunately condensing boilers seem to have been pushed hard by the government in one of their fits of eco-madness.
A few years back I discussed condensing boilers with a local plumber - an Englishman - who couldn't understand the Scottish fixation on combi boilers. Now I wonder if perhaps the Scots didn't just know something he didn't.
Reader Comments (32)
Ah yes, all lost in the fog of war. Con.....dense
The other big problem with condensing boilers is they typically don't last very long. All that condensation causes rust. From my knowledge of commercial property, 7-8 years for a condensing boiler is considered a good life time. 25 years for a combination boiler on the other hand.
So while a condensing boiler might save energy in terms of heating, does it save energy in terms of the total lifetime of the device when you consider manufacturing and replacement costs?
40% fail rate, you would not accept that with a new car would you? Too much stuff inside them to go wrong that's the reason they wont last 10 years with medium use, the old ones were nice and simple to build and repair and as such relaible.
AND, to make matters worse as the price of metals have ballooned, they are now fitting polymer plastics parts instead.
Another New Labour Scam
Yes condensing boilers - they have not just been pushed hard by the government, they are the only ones you can get now due to building regulations. A Combi heats water on the hoof instead of storing it, but I think I am right in saying that Combi boilers are also condensing these days.
I currently have a condensing boiler (7 years old now). It is supposedly more efficient than the 30 year old boiler I had in my last house, but I have not detected much improvement. The rises in the cost of gas will have long since overtaken any savings so it is difficult to judge on that score.
The main problem has been when the pipe freezes the condensate slowly backs up the pipe and floods the boiler and electronics.
I survived last last winter, but have had mine freeze, despite lagging, this year. I have sawn off the pipe (still lagged) inside my garage and lead the condensate into a bucket, so that it doesn't go outside at all. My next door neighbour had his condensate overflow freeze twice last winter and British Gas, who serviced it, lagged the pipe inside and outside the property to stop it happening again. It has frozen twice over the recent spell and I have now helped him saw off the pipe inside his garage to discharge into a bucket. We will have to put matters back to normal when winter is over. The bucket takes two to three weeks to fill so it isn't too bad.
There is no doubt it is a design fault. A British gas engineer has told me that the latest models have a much wider pipe of 40mm or so instead of the usual 15mm overflow pipe used. This should be less likely to block even if freezing occurs.
Is not the root cause having a wrong design for the installation? Not unlike a lot of external pipes in the UK?
Copnor
As I said in my comment Combi's are condensing now anyway.
You are right about the short life of the average condensing boiler but modern combi's are no better. My mother-in-law had two new ones fitted in 10 years.
Rob Schneider
Well you could be right - but my condensate overflow is the only external pipe in the whole house. It is a bit of a myth that modern UK homes are worse in that regard. It took too many years to get to where we are but those built now have incoming and outgoing water internal and modern WC's with no external overflow.
The way forward for condensing boilers must be to lead the overflow pipe internally to a nearby drain, say in the utility room or the like. I am thinking of doing this myself when things warm up.
Problem is - we were told we would not have winters like this, BUT now we are told they are due to climate change. You couldn't make it up.
Now you add electrical resistance heat tracing to the condensate drains so they won't freeze and any energy savings are lost forever. Engineering by politicians seems so dodgy, if that's the right word.
@ Retired Dave,
Re the "myth", well comparing my UK house with previously owned houses in other countries where there also was possibility of outside temperatures below freezing, my relatively new UK house has many more external water pipes which are sadly prone to freezing.
Wikipedia, "Condensing boiler" has:
Condensing boilers, are up to 50% more expensive to buy and install than conventional types in the UK and the US. However, as of 2006[update], at UK prices the extra cost of installing a condensing instead of conventional boiler should be recovered in around 2–3 years[citation needed] through lower fuel use, and 2–5 years[citation needed] at US prices.
Are there any updated figures available?
I have seen comments in blogs saying it takes 10 years to repay the extra cost compared to a non-condensing bolier, but that the average life of a condensing boiler is a lot less than that. However, I haven't yet seen something worth citing.
Well, I have a new barratts home ( which seem to be universally hated by lots and lots and lots of people) and it has no external water pipes and we have had no issues with the boiler...yet! :)
Mailman
condensng boilers are a big hit in Holland for many years, and last at least 15 years on average.
It makes perfectly sense that by lowering the exhaust fumes' temperature one saves (considerable) energy.
there are however two important features
- each boiler should come with a special exhaust pipe which prevents water included in the fumes from freaazing. exhaust pipes should be tested for the specific boiler.
- needs maintenance every two years; mainly. by cleaning the condensing water overflow from fungis buld up.
The reliance can vary by manafacturerr and type, so independent test results are a must.
I have no experience of condensing boilers and this info comes from something I read in the web version of the Daily Mail yesterday, but.......condensing boilers rarely achieve their theoretical efficiency (and therefore "5 year" payback time) in typical UK installations because the return water (which I assume is used in the condenser) is not cold enough. To get cool enough water, one needs to run the whole system at a lower temperature but use much larger radiators (or underfloor heating loops).
Condensing boilers do more than save heat, they save jobs for British tradesman. Here is the typical repair cost HERE and these do not include call out charges and such. They are the part costs when delivered to your frozen house in the middle of a storm. Labour is extra, should you want it installed.
I am so happy with me Irish TURF FIRE
re: Robert Christopher
From the same article:
did you see the Daily Mail?
specifically linking this to John Prescott, the kyoto protocal and 'climate change'
In 2005, the then-deputy PM John Prescott drew up a masterplan to help Britain meet its CO2 emissions targets, as dictated by the 1997 Kyoto Protocol. This involved a new law ordering that all new and replacement boilers fitted to British homes - some 1.4m annually - must from that date be of the condensing type.
Read more: http://www.dailymail.co.uk/sciencetech/article-1342357/Central-heating-break-big-freeze-Heres-.html#ixzz19nVT4eqT
Many thanks for the name check. Most grateful!
I installed Kidd condensing boilers at work. I left about 4 years later but they were still working well and saving about 30% annually on the previous gas consumption. This saving was correctly calculated using degree days from the local weather station.
The Kidd boilers are for large houses, hotels, offices and the like and had an expected lifespan of 20+ years. This is vastly better than the current mass market offerings, which typically fail on corrosion and electronics in as little as 5 years. I have no vested interest in Kidd.
In my own home I have retained my 40 year old Glow-worm (non-condensing).
Budgie
This is vastly better than the current mass market offerings, which typically fail on corrosion and electronics in as little as 5 years.
Whilst it is generally considered a third rate source, the Wikipedia article pointed to by Robert Christopher above, but with a direct link HERE does explain what a chemical cesspool the inter workings of a condensing boiler really is. The condensate not only freezes, but it is acidic as all hell as well. The use of cheaper materials is the issue in the units you refer to. And the use of aluminum at all is a big mistake. You want stainless steel or ceramic, not aluminum anywhere near the condensate.
Save a few quid on one and replace it in a few years.
The problems are worse in houses like ours, which have a back boiler in the fireplace. For years we had a Baxi Bermuda back boiler, and a Valour gas fire in the hearth. Fine. In the event of a power cut, we could use the gas fire to keep the main room warm.
When the Baxi needed replacing, we had to have a condensing boiler. That required a flue liner which closed off the chimney, and we were told we could no longer have a gas fire in the hearth. So now we have an electric fire. In the event of a power cut, our house could freeze up. We had to buy a calor gas pot bellied stove as an emergency backup.
I am expecting problems with the condensate pipe which emerges from the east facing wall of the house, where it will be exposed to the most bitterly cold winds we ever get. I will probably have to investigate lagging, and perhaps a heating element, to keep that pipe above freezing.
All because of stupid, meddling, pontificating, ignorant greenies and their political poodles.
Don Pablo, I think you have slightly missed my point. It is a fact that condensing boilers can work well, be reliable, and save fuel, and I gave the example, from personal experience, of Kidd boilers. You can check on the internet that other people think highly of them too.
So the reality is that the many and frequent failures of current domestic condensing boilers are down to poor design, poor materials, poor manufacture and over complication (often the electronics), rather than a failure of the principle.
As for the acidity of the exhaust that is dependent on the fuel burnt and is no different whether condensing or non-condensing. The difference is that in a condensing boiler impurities are trapped in the condensate internally, rather than 'safely' exhausted to atmosphere.
Perhaps the government that imposed condensing boilers on us should also force the manufacturers to quote MTTF and MTBF. Then we would really know which boilers were rubbish.
OK, finally a post that I am an expert on! So talking from authority :)
Condensing boilers, like most other newer technologies have gone through a rapid learning curve. Unfortunately, most of the products are initialy tested in perfect conditions, then we homeowners get to be the real guinea pigs.
I have had installations that have saved my clients, year to year, approx. 45% in gas usage from their old cast iron models. But, and this is the big one, as stated above, this is from a system that can operate at low temps, below 140*F (60*C). Once you get the return water coming back at 60* or higher, you loose the condensing feature and the boilers are now only about 10-15% more effecient. Here on the left coast of Canada, about 80% of our initial installs are under slab floor heating, and with this style of system, these boilers really shine.
Onto life expectancy. As all boiler manufactures state, the boiler, whether standard or condensing are to be serviced at least once a year. You all probably know from experience, that standard boilers are way more lenient, so the servicing in reality is usually closer to every 3 years. But with the condensing technology, and the heat exchangers of most boilers being in the horizontal plain, these boilers must be cleaned and serviced every year! I actually have some clients, whose use on their boilers is extremely high, heating, making hot water through a stand alone tank, pool, hot tub, even extra heat for their air systems that I have to service their systems twice a year. I find that most of the fuel savings that these boilers achieve, right now with nat. gas prices being historically low at the moment, are easily eaten up by the servicing requirements. But if the gas prices rise in the near future, then yes, there will be a payback on investment.
end part one
Most manufactures will give about 15 years warranty for their heat exchangers if they are stainless steel. The aluminum style, are typically 30-40% cheaper and are meant to have their heat exchangers changed out every 5-7 years. Hopefully this is done in time, that a leak does not occur and eat through the electronics. Most of the heat exchangers of the SS type are manufactured with a lower grade of stainless and we have had some problems with them rotting out in 2-5 years. What is not realized by most people, including the installers, is that low grade stainless is very susceptible to two types of attack, chlorides and rust. Working in Vancouver, there is really no way of avoiding chlorides, as the sea outgasses them constantly, so they are incorporated into the combustion air side of the equation.. But avoiding rust can be accomplished by using more expensive brass/stainless circs, flanges, copper or pex tubing and fittings, etc. plus adding some good chemical conditioners and O2 scavengers can mitigate this problem.
My oldest install with this lesser SS exchanger is now going into its' eigth year. For about the last 4 years I have only been installing the higher grade SS which is found in the Viessmann boilers or a local company. This local company has also turned the heat exchanger to the vertical position, and forces the exhaust downward, so cleaning of this unit is almost a non issue.
Now the biggy. Installation of these boilers is critical! They are not your fathers boiler. I have taken training with more then half a dozen different manufactures. They all have their little quirks as to their installs. Unfortunately, most of the companies out there don't take the time to learn the right ways, so the homeowners get left with a ticking time bomb of costs and problems, which in the long run is good for me! Another bitch that I have is that all of the old standard style boilers basically used the same simple parts, so stock was kept to a minimum, and servicing/diagnostic was actually quite simple. Well no more. Now you basically have to use the OEM of each manufacture, so stock has multiplied (extra cost) you need to buy extra analytic equipment now (extra cost) and now that heat exchangers, condensate traps, etc must be annually cleaned, we spend more time per call (extra cost).
Condensate,
As The Don, Pablo has mentioned, this condensate can be as low as 4 on the base/acid scale, so if installing one of these boilers into an older home, it must be passed through a nuetralizing system, for if the old underground piping is cast iron or copper, these pipes will be eaten away in no time. So far here in Vancouver, we have no directives that all condensing systems must be nuetralized, so most installers, if in a new home just pipe directly into a drain as the piping to the muni will be plastic. I take it that a lot of homes in Old Blighty, do not have an internal floor drain, as most older homes here do not, so again more cost to either pipe the effluent to a sink drain, usually by mechanical means, or just allowing the condensate to be piped to the outside so that it can pour into the ground. Of course if the piping to the great outdoors is used, then yes, you can bet that eventually you will have a frozen, clogged drain. But hey, it saved a cost on the install and maybe beat the competitors price by not including a condensate pump, so you got the job.
Anywho, these like all other devices can be a good investment, so long as the customer educates themselves a bit, and really checks the installing companies history and work ethic. But in the long run, are you going to get your money in 2-5 years? Very doubtful IMO. If the average life span is 15 years, will there be a net CO2 decline? Maybe just a bit. For not only do you have to factor in the service vans' exhaust, but if the old standards can last twice as long, and contain less parts, then we reduce all of that evil CO2 used in the mining, smelting, manufacturing, transporting, etc. But truth be told, according to one of our Gas company guys here, in an unguarded moment, he stated to me, that the main reason they were promoting/subsidizing these new boilers/furnaces (yes we are still at about 80-85% forced air here in the colonies) was that they were approaching max capacity on the main trunk gas pipeline, and did not want to spend the dough to install a new one yet. Also, they get a better price shipping the gas to California, so the more that they can save here, the better their profits! Realize that I have no problems with this thinking, I am all for big profits, just don't dress it up in the AGW meme!
Months before the legal deadline, I had my old but perfectly functional noncondensing oil CH boiler ripped out and replaced by a new noncondensing boiler. At a cost of several thousand pounds. Why? Well, if the old boiler had failed after the deadline, then I would have had to replace it with a condensing boiler. And my boiler is centrally located (no access to external walls) above a concrete floor. So there's nowhere for the condensate to go. A condensing boiler would have had to be installed in a different part of the house and would have entailed rerouting all the relevant plumbing. As a subsequent owner will discover, in due course ..
So condensing boilers are great if:
They are built to a very high standard, much higher than required by law, using expensive high quality materials, and costing several times (and with a much higher carbon footprint in manufacture) than the offering any plumber is likely to suggest for a domestic installation. The law was never going to enforce such standards because the costs would have been visible and very high.
They are correctly installed with no corner cutting at all, which might be very expensive in an existing installation. The extra expense will have its carbon footprint.
They are run sympathetically.
They are maintained to a much higher standard than conventional boilers (again with added costs and carbon footprint).
In practical terms they turn out to be much like wind turbines and CFLs. A solution imposed by politicians who don't have anything but the shallowest understnding of what they are doing and probably have motivations which are not obvious or honourable. They create at least as many problems as they solve, especially when inflicted as a blanket requirement. Very many people could put forward clear and convincing arguments for not wanting them based on economics, carbon footprints, energy security and so on.
My old style Potterton Prima is nearly 20 years old. It is serviced annually and still runs OK. My central heating engineer (old style, seen it all before, and actually has the same boiler himself) is happy to keep maintaining it but has warned that at some stage we will have to replace it. He will only recommend Vaillant boilers because he says they are built better and don't have plastic internal parts etc. Seems to confirm some of the comments above.
DeNihilist and Budgie
First of all, I fully understood you Budgie, but I was simply pointing out that it is far too easy to obtain a product made with inferior materials what will not last. And as DeNihilist points out, there are many grades of stainless steel. This is but a simple list of Stainless Steel types. And it goes well beyond the inner workings of a furnace. A stainless steel sink can be made of 304 SS or of 316 SS. You want the 316. It is often touted as "marine grade" stainless steel.
And there are grades of "stainless steel" what will rust, believe it or not. I had a utility room sink that rusted. It is now a 316 grade. The same applies to the boiler, condensing or not. Quality costs more, but it really worth it because it will last.
I built my house about 6 years ago, my moto, keep it simple, oil fired standard boiler, (Irish, what they dont know about oil fired boilers doesn`t exist), runs on clean 28 sec oil, neeeds no servicing, will last a lifetime.
I hope you don't regret your smugness, Robuk. Over the weekend, I met a couple who have a house in Northern Ireland, also with oil-fired heating. They've just had to call out their local, friendly, neighbourhood plumber to repair bursts in their radiators and pipework, after the heating failed due to a frozen fuel oil feed pipe. The Irish may all there is to know about oil-fired boilers, but not, perhaps, about keeping them running in exceptionally cold weather. This is the same experience UK owners of condensing boilers are having to live with, and learn to manage.
And another thing, Robuk, if I'm not mistaken, you can buy an awful lot of service for the extra cost of oil over gas, even after recent gas price hikes.
In order to capture that heat energy, a condensing boiler uses extra heat exchangers to extract heat from the waste gases. The latent heat from the gases is then used to help heat up the water in the boiler.