This is only a little less saving than a 'careful' [1] customer who I installed a Keston25 for earlier in the year. In his case the upgrade was from a conventional flued Ideal Concord and very simple timer + plain copper cylinder with (ragged jacket). Finished with Grade 3 Part L cylinder (same size but with a fast coil). All TRV (except bathroom as bypass). Programmable Thermostat.
I think this finally put to rest the speculation about the maximum savings acheivable by installing a condensing boiler.
Yes it does, by the bucketful. Not that it empties into a bucket I should add, but through 22mm plastic and a trap to the waste.
I wonder whether modulating the pump as well as the burner has an impact. The Keston, AIUI, does it by switching a Grundfos pump to one of its three settings.
The MAN has a means of analogue or perhaps quasi-analogue control of the pump (also Grundfos) from 35% minimum up to 100%. From the display on the PC screen when the diagnostic software is run, the pump rate adjusts to the firing rate, but they are not directly linked. I've seen dT between flow and return on occasions of around 25 degrees, so even if the flow is approaching 80 degrees when it's really cold or in HW mode, condensate is produced. There is realtively little visible pluming, even on a cold day. I wonder whether this has something to do with the cylindrical heat exchanger and burner design.....
As I figure it, provided that the change from gaseous to liquid state of the water happens either in the boiler or the part of the flue within the building, the efficiency improvement should be achieved since it is from the heat released by the latent heat of condensation due to the change of phase. The visible "steam" is of course water vapour and already in liquid phase from the latent heat perspective.
Having it condense as water inside the boiler would appear to be more of a convenience in that sense. Most installation guides that I have seen talk about installing the flue such that it is at a slight angle, sloping towards the boiler. I am told that this is mainly to avoid acidic concentrate dripping down walls etc.
Perhaps this explains the "nuisance plume" aspect. If the heat exchanger is rather too warm but nevertheless reasonably efficient and the flue is cool enough, I would expect pluming to occur until the water vapour re-evaporates. This would imply the best efficiencies not being achieved, I think.
There's no point in a 25% energy saving, if you have to replace it every
5-10 years. The replacement cost for a non diyer is probably >> £1000. There seems to be a total lack of 10 year warranties!! Where are the projected reliability figures? We know that Ideal Concords have a working life span of
Where do you get this notion that boilers have to be replaced every 5-10 years?
Lots of 3 and 5 though.
Don't you know as you are so confident on the lifespan of boilers.
The same for any boiler. Look at a Concord. There is sweet nothing inside. All the kit is outside the case and that is what fails. So this inefficient cast-iron lump just sit there, while the rest does the work.
That depends on your motivation. If it is purely economic and that really were the motivation then that may be the case. However, if you are also concerned about CO2 and NOx emissions and fossil fuel consumption then it may be a factor.
There is no reason to assume that a well designed and made (and I emphasise well designed and made) condensing boiler would be any less reliable than a simplistic one with mechanical parts.
For example, the flame failure thermocouple used in most "simple" boilers is an item that fails regularly. Granted they only cost £2 as a part, but if professional labour is used to fit then that goes up to at least £50 if not more. Bimetallic thermostats aren't that brilliant either. Other components such as gas valves are of similar technology and used in both cases.
That only leaves a fan, some thermal sensors, a microprocessor board and the condensate drain arrangement. Provided the electronics are of good design, using good quality components and not situated in a hot part of the case, reliability should be high. There is very little in a condensate drain.
Condensing technology is only relatively new in the UK, and it is well known that several manufacturers made a pig's ear of their early designs.
However, in most of the rest of Europe, notably Holland and Germany, condensing technology has been commonplace for 15 years. German consumers are noted for their expectation of reliability and good engineering so had condensing products been flakey for any length of time, it would not have survived.
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you will note that there is a lot of emphasis on quality
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