Talk:Condensing boiler/Archive 1

Archive 1

Confusing

The final exhaust from a condensing boiler is, obviously, at a lower temperature than from a conventional boiler. As a result a fan is usually required to expel it, and it produces a visible "plume" of condensing water vapour.

If the water is already condensed, why would we see a plume? This sounds like two different designs getting confused. --njh 01:08, 15 March 2006 (UTC)

The final heat exchanger cools the exhaust to approximately room temperature. This causes some water to condense out of the exhaust. When the remaining exhaust is vented to the cold exterior, more water condenses. Each decrease in temperature results in additional condensation. —Ryanrs 15:31, 13 May 2006 (UTC)

Globalize

I think this topic can be moved to the global catagory... as it now includes content from north america (206.116.24.2 02:02, 5 March 2007 (UTC))

Reversions

Someone (I haven't tracked back to find out who, but there have been a lot of anon edits on this page) had removed all the wiki links and US-ised the spelling. I have reverted a lot of these changes; if you object, please comment here. No big deal, but just for information if you're a newcomer (a) that sort of wholesale change to a page shouldn't usually be done without first proposing it on the Talk page to check there aren't good reasons not to do it and (b) to stop time-wasting edit wars over spelling conventions, wikipedia works on the rule that whichever spelling variant the page is started in, it stays in (unless its subject matter makes US spelling obviously more appropriate than international, or vice versa). Also, (c) if you revert someone's edits it is polite to explain why on the Talk page, which is why I am adding this note. seglea 21:07, 17 June 2007 (UTC)

Vapor/Vapour was spelled both ways in the very first edit, so there is no established spelling based on a starting variant. In any case, if you want to change the spelling to "vapour", then please do so for the entire article per WP:ENGVAR. If you make the article's spelling consistent, I will not revert it. --VMS Mosaic 22:31, 17 June 2007 (UTC)

Ah yes, I'd missed one, sorry. I'm not greatly bothered about this issue (I'm happy to write with either set of conventions), but as it happens the initial edit was wholly in international spelling (I wrote it, in March 2006 - note that "vaporize" has no "u" in any spelling variant, though that ise/ize thing still lurks). There is a (slightly) more cogent case for using international spelling since these things are more in use in Europe than in North America. So I have put it back to "vapour", throughout now, I hope.

BTW, the table layout that someone introduced looks nice but behaves oddly if you change the page width, does anyone know how to fix that?

seglea 18:21, 18 June 2007 (UTC)

Safety

Does anyone have any knowledge of safety issues with condensing boilers? I am interested in a fatal accident involving one which may be relevant to this type of boiler; can this issue be addressed? Peter 07:21, 27 March 2008 (UTC)~

A properly designed and installed condensing boiler should not have any significant safety issues beyond those of other types of boilers. Because they are direct vented, they are safer than non-power vented boilers because carbon monoxide is much less of an issue (assuming the venting is properly installed). VMS Mosaic (talk) 17:24, 27 March 2008 (UTC)

Need much more development

This article is pretty weak, very little information about the operating modes of these boilers, the problems they cause ignorant installers and householder, the need for weather compensators, information about idea flow and return temperatures, etc etc. Can any heating engineers help? —Preceding unsigned comment added by 82.41.227.59 (talk) 20:49, 7 November 2008 (UTC)

Update and perhaps clarify

I design appliances and condensing heat exchangers and noticed this article is a little old and IMO could be clearer.

My work is in the UK so I will UK terminology. I haven't bothered at this stage to link keywords.

For example the opening sections, my suggestion:

"A condensing boiler or heater utilises the latent heat of water produced from the burning of the hydro-carbon fuel, in addition to its sensible heat. This is achieved by increasing the heat exchanger surface area, either by addition or enlarging. A typical increase of efficiency can be as much as 10-12% but is temperature dependant, reducing as the water side temperatures increase. However it is always more efficient at any temperature than a non-condensing heat exchanger.

The condensate produced is slightly acid 3-5 pH, so the choice of materials used in the wetted areas have to be suitable. At high temperature most commonly used are Aluminiuum Alloy and Stainless Steel, in the low temperature areas plastics, for example polypropelyene. The production of condensate also requires the installation of a heat exchanger drainage system."

Peterbel (talk) 20:17, 17 February 2010 (UTC)

Go for it. UK/US English is barely a consideration — if you have expert knowledge to contribute. It is helpful, however, to cite reliable references, where there might be some difference of opinion? In some ways, I think those are the most valuable contributions that experts have to make in Wikipedia. Regards, Piano non troppo (talk) 03:31, 18 February 2010 (UTC)

Replacement cycle

Is expected boiler lifespan taken into account when considering "efficiency" and green-ness? I think it should be. I ask because I have just had one of these installed, and looking inside at all the additonal parts - over and above those of the old boiler which came out (which only very few parts, none of them moving) - the potential for failure and early demise seems greatly increased. I will be very surprised (and indeed pleased) if this boiler lasts half the lifetime of the one it replaced, which had been in place for about 30 years. 81.147.171.172 (talk) 11:06, 24 September 2010 (UTC)

Condensing boilers have fans, motors, printed circuit boards and plastic parts. By contrast, old boilers use a cast iron jacket coupled with a few very basic, standard and easily replaceable components. For normal domestic use, with a £1200 per year spend on gas (with a cast iron conventional flue boiler), you would likely still come out financially better off even with a 3 year replacement cycle with a newer boiler. Many new boilers come with a 5 year manufacturer's warranty, and will probably last 10 - 15 years. Far short of a cast iron boiler life expectancy, but financially and environmentally much better as the amount of gas saved is huge, and newer boilers tend to be lighter on materials and therefore have a lower manufacturing carbon footprint..Nick Hill (talk) 11:08, 19 December 2011 (UTC)

Efficiency of condensing vs cast iron

An often overlooked factor when comparing condensing boilers with old boilers is to consider the question of open flue vs fan assisted balanced flue. As far as I know, all efficient condensing boilers have a fan assisted balanced flue. The fan assisted balanced flue itself produces a series of system-wide heat savings. 1) When the flames go out on an open flue cast iron boiler, the chimney continues to convect, and air continues to convect through the cast iron heat exchanger carrying the valuable heat with it. When a fan assisted flue boiler extinguishes, almost no air convects past the heat exchanger to the outside. 2) Open flue systems need adequate in-room ventilation. This ventilation must always be in place and not be user controllable. This causes direct heat loss from the premises and indirectly adds to the inefficiency of conventional boilers. By comparison, fan balanced flue condensing boilers don't need special ventilation. They draw exactly the air they need from the outside. 3) Not a boiler but certainly a system issue; older cast iron systems often use gravity to heat hot water in a cylinder. If the head between the boiler and cylinder isn't substantial, or the pipe run is long and/or not of a large bore, water will move slowly, resulting in the boiler taking longer than a fully pumped system to heat the tank of water, Given such systems tend to be of a cast iron open flue design, the result is a huge waste of heat. The boiler may take one or two hours to heat the tank of water in a typical gravity fed domestic system. All that time, heat is being lost up the open flue chimney. 5.2Kwh of heat is necessary to heat a typical 100l DHW tank from 15c to 60c.. The heat input to a cast iron gravity fed system may be several times that. Because condensing boilers will be pumped, as the heat exchangers have too greater resistance to flow for a gravity fed system, and heat is not lost when flames are extinguished, a condensing boiler will be far more efficient compared to an open flue cast iron boiler for hot water heating, I have access to a typical system and will meter the actual values. Nick Hill (talk) 20:31, 13 December 2011 (UTC)

I conducted an experiment using Baxi Bermuda 401 cast iron open flue back boiler + water tank with 69L usable capacity, Used 1.226 cubic metres of natural gas to heat water through 40 centigrade (11 to 51c), but experiment failed as gravity fed water also heated upstairs radiators. In all, 3.2Kwh of heat got into the hot water tank through using 13.5Kwh of gas. I'll re-run the experiment when the system has cooled down, with rad valves shut.Nick Hill (talk) 23:46, 13 December 2011 (UTC)

Since installation, the system had leaked heat into upstairs rads. I took steps most householders wouldn't take to prevent it for the purposes of the experiment, Some may therefore consider the previous result of 23.7% efficiency more indicative. With a carefully controlled installed system, I achieved 30% efficiency from gas to tank. I'll write up system parameters and test conditions more fully then link from here. Nick Hill (talk) 01:01, 17 December 2011 (UTC)

I have written up the experimental results here: http://www.nickhill.co.uk/cast_iron_boilers/cast_iron_boiler_efficiency.html Nick Hill (talk) 19:56, 19 December 2011 (UTC)

How Condensing Boilers Work

"the water vapour produced by the burning fuel in the boiler is condensed back into liquid water. Provided the returning water is sufficiently cool, the steam condenses to liquid water"

could be worded better, I think. 86.173.180.188 (talk) 00:56, 12 December 2009 (UTC)

Agree. Also, we need to convey that condensing boilers are more efficient not just because they DO condense, but because they MAY condense. Looking at it another way, conventional boilers need to be designed so that they DON'T condense, as there is no method to handle the condensation, and such condensation may damage the heat exchanger as well as appear to the householder user as a leak. Therefore, the efficiency of conventional boilers is limited to design criteria which require condensation to be unlikely. These design criteria require a heat exchanger with a high thermal resistance so that area in contact with the flue gases doesn't stay cold for long. This limits the efficiency of non-condensing types to well below the theoretical level. Nick Hill (talk) 13:08, 16 December 2011 (UTC)

I think the following sentence confuses cause and effect:

"A condensing boiler extracts additional heat from the waste gases by condensing this water vapour to liquid water, thus recovering its latent heat of vaporization."

Condensing steam in the exhaust is a side effect of extracting more heat - not a process in itself. The more correct statement should be something like:

A condensing boiler extracts additional heat from combustion waste gases, compared to traditional systems, resulting in a much cooler exhaust gas. A side effect of such cooling is that water produced by combustion, that formerly would have remained in vapor state until being exhausted, now condenses to liquid in the boiler heat exchanger.

Or something like that... --Jrm03063 (talk) 18:47, 16 February 2014 (UTC)

Extra Requirements

They have a reputation for being less reliable and require professional installational and regular service and may suffer for the lack of familiarity with them among installers and plumbers. In reality, gas condensing boilers have only one extra element to be installed - the drain pipe for the condensate collected during operation.

Is this really true? I believe they also require a second pump to be installed at the top of the system (ie near the hot water cylinder) - which involves laying a new electrical cable through most of your house. See point 6 here: http://www.miketheboilerman.com/newboilercost.htm —Preceding unsigned comment added by Wogone (talk • contribs) 16:08, 24 March 2008 (UTC)

I have a Weil-McLain gas condensing boiler. Yes, it keeps the boiler circulator pump (mounted just a few inches above and wired directly into the boiler) running for a short time. It does require an extra pump because the boiler circulator pump is separate from the system circulator pump(s). VMS Mosaic (talk) 17:39, 24 March 2008 (UTC)

No, this is not true. The central heating system in my house (which includes a condensing boiler and which also provides the hot water) does not even have a hot water cylinder. Furthermore, the only significant difference between a condensing boiler and a non-condensing boiler is the fact that the condensing boiler extracts more heat from the exhaust gases than a non-condensing-one does; it does not otherwise influence the design of the heating system. JanCeuleers (talk) 12:14, 9 October 2014 (UTC)

Sorry, I meant to say "Yes, this is really true". In other words, the mere fact that the boiler is of the condensing variety does not make it necessary to add a pump in one place or another.

Neutrality (as in: lack of)

This article relies too heaviliy on sources whose vested interests lie in promoting these boilers and denying many of the drawbacks that they have (branding them as myths). For example, I know of several people who have been forced to have condensing boilers fitted once their existing boilers failed. In each case, the installation costs have far outstripped the cost of the boiler (typically a two full day job needing two people for a substantial part of that time). In each case it has been worked out that if the boiler lasts 12 years (a typical boiler life), they will never recover the installation cost through the relatively modest energy saving. Problems with installation include: the usual need for a different flue design and problems with installing the condensate drain which (here at least) must lead to the outside of the building (existing boilers are rarely mounted on an outside wall).

It should also be noted: that these sources claim a normal boiler life, if the boilers are regularly serviced. As the engineer who recently serviced my (conventional) boiler observed, it is impossible to service a condensing boiler properly as the inner part of the boiler (the parts that the air and combustion gasespass through) is sealed and cannot be opened by anyone other than the manufacturer (any warranty is void otherwise). The only servicing that he can carry out is restricted to checking the flue and condensate drain are free of obstruction and that the thing actually lights. 86.159.159.194 (talk) 17:55, 24 October 2012 (UTC)

" I know of ". Please see WP:OR

Your installation cost analogy doesn't really stand up. A failed boiler needs to be replaced, whether it's condensing or not. There is no requirement to install a condensing boiler instead of a still-functional boiler. In fact, it may be possible to install a new non-condensing boiler if there's a real problem, like visible pluming. The only real difference in installation is the condensate drain, and that's a sorted problem these days, if you're paying attention.

Whilst there might be a point that throwing good boilers away to install new ones isn't going to give an overall saving, against the cost of an entire new install, no-one is ever suggesting such a thing. Andy Dingley (talk) 21:09, 24 October 2012 (UTC)

The analogy does stand up if you are in the wrong jurisdiction. In most of Europe, if a failed boiler does require to be replaced, it must be replaced with a condensing boiler. It has been illegal to install a non condensing boiler for some years now. The condensate drain is one of the major issues over installation costs, because not all existing boilers are placed conveniently on an outside wall. It is illegal here to run the condensate drain into the waste plumbing, it has to lead to the outside world, not via the drains. When my boiler had to be replaced last year, it required a new flue installation - £1,500 (because the old one was not compatible with condensing boilers), the condensate drain had to be routed half way across the flat necessitating ripping up floor boards and boring a hole in the outside wall - another £1000 odd, but worst of all, the erection and removal of scafolding on the outside of the building because of the presence of a glass conservatory below the point where the condensate drain had to emerge (cost ~£7000). And all this on top of the boiler and its installation cost. Had I been allowed to have a conventional boiler installed, the total bill would have been unlikely to exceed £1000. I estimate that I will never recoup the ~£10,000 extra costs before this new boiler gives up the ghost. By the time that happens, the environmentalists will have thought of some new requirements to bolster the replacement costs next time round. I B Wright (talk) 15:15, 30 October 2012 (UTC)

I'm already in the "wrong jurisdiction", the UK.

My point is firstly that there is no requirement for existing, functioning non-condensing boilers to be replaced by new boilers, or by new condensing boilers. There are constraints on replacement boilers, but no involvement with ongoing use or maintenance.

It's not "illegal to install a non condensing boiler" in the UK. In most cases a condensing boiler is required, but there are exceptions and it is recognised (through a surprisingly well-implemented scoring system) that there are some cases when a condensing boiler is inappropriate. In those cases, a new non-condensing boiler can be installed. Most likely situations reaching this score will be replacements, not new installs.

I presume that your flue is long, probably fan-blown, and would thus be a high score for non-condensing to be acceptable.

Also your prices are excessive. Who did this work? British Gas?! Long-haul condensate drains were a problem ten years ago, but it's a well-sorted issue these days, even if you have to pump them, and it doesn't (need to) cost £1000. If you let some cowboy charge you "~£10,000 extra costs", then you have my sympathies, but it's not a WP:RS for blaming condensing boilers. Andy Dingley (talk) 21:08, 30 October 2012 (UTC)

In addition to the comments made previously, there are stipulations for draining condensate into a waste drain line. BS 6644 states that ideally condensate should route to the sewer drain complying with local and national regulations. Alternatively, the condensate can be discharged into the rainwater system or a purpose-made soak-away. In some municipalities, they do not allow for the condensate to be routed into the sewer drain unless the condensate has been neutralized. This is, simply, a very small PVC tank filled with limestone gravel that the condensate floods before entering the drain. Several manufacturers offer this as an accessory kit for MUCH less than the price you have mentioned. This would also have taken away the need for all of the scaffolding and additional charges for routing. It sounds as if you had an inexperienced contractor working on this or they were just trying to fleece you.

The Second is that if you have an existing flue, there should not have been a need for a new one to be completely built. The reason for certain sizing of non-condensing flues is because they rely on natural convection for venting. This natural convection in all cases would require a larger flue and limit itself to shorter flue lengths that a power vented flue. The power vented flue and the fact that a portion of the mass flow of the boiler flue gasses is condensed requires a smaller flue than a non-condensing boiler of the same input. Installers can and have routed PVC and polypropylene flues through the inside of an existing flue and simply attach a power vented fan to the system. This should be only a fraction of the cost you were charged. 64.132.236.254 (talk) 19:48, 2 April 2013 (UTC)

There has been no further discussion for 18 months, so I submit that it is time to remove the "biased" tag from the article. JanCeuleers (talk) 12:34, 9 October 2014 (UTC)

Myths: yet more propaganda

Without statistical data in reports cited in references that people can get hold of, the Myths section is pure and unadulterated political propaganda. It should be removed or proper citations for research and hard data from BRE given. — Preceding unsigned comment added by EngineersNeeded (talk • contribs) 18:39, 10 February 2015 (UTC)