The Classic Combi has been discontinued but keeps on being resurrected for housing associations and other big users but is generally considered to be old technology these days. Its narrow but VERY high by comparison with other units.
I'd heard somewhere that this regulation is coming in. Is that April 2005?
Yep. All bar an earthquake it will be introduced. I have spoken to a few boiler manufacturers about the nuisance plume, which will create problems in flats. Two said they have a way of getting around that, but no info at all. Could be BS.
What is the nuisance plume?
It's a plume of visible water vapour that may come from the flue under some conditions of operation of a condensing boiler.
The amount of the plume will depend on how hard the boiler is working, the temperature and the design of the boiler. Some boilers generate more than others, and in general, the newer designs emit rather less, being able to collect more inside to be delivered to the drain.
Whether it is a nuisance or not depends on the smount, circumstances, location of flue and your point of view.
My own boiler has very little pluming and is certainly not a nuisance.
.andy
To email, substitute .nospam with .gl
Sorry for a stupid question but would this plume occur outside, i.e. after the flue exits from the flat, or does it occur at the interface between the boiler and the flue?
No it's not stupid.
The plume, where it happens, would appear from the flue exit outside.
With a non-condensing boiler, the temperature of the heat exchanger is arranged to be at a high temperature (70-80 degrees Celsius). The combustion products, which are basically water and carbon dioxide plus a few other things at much lower concentrations, exit from the flue at a fairly high temperature, and unless the air outside is very cold, are invisible. You may have noticed visible water vapour from the flues of conventional boilers on very cold days.
A condensing boiler is more efficient partly because it has a larger and better heat exchanger, but also because it is designed so that it can operate at lower temperatures. At a temperature of below 54 degrees, water, which has been in the form of steam condenses to water or water vapour. This change of state (or phase as described in physics), releases what is known as latent heat. This heat is "free" and is added to that produced by the burning of the gas, thus improving boiler efficiency. THe mechanism is similar to that used in a fridge or the reverse of sweating - you feel cooler with sweating because heat is required to evaporate water.
Depending on the boiler design and temperature of operation, more or less of the water vapour is collected inside the boiler and is delivered to a drain. Any that is left as visible water vapour is delivered out of the flue into the air along with the flue gases. There may be some amount of water deposited from the vapour to the inside of the flue and so it is normal to arrange that this is sloped back towards the boiler slightly so that any water runs into the boiler's drain arrangement and does not drip from the flue exit. The water is slightly acidic and would mark brick and stonework.
The condensing boiler has a drain arrangement which is normally done with small plastic pipe like overflow pipe to a suitable drain inside or outside the house.
Air for the boiler is drawn in from outside via the flue, which is normally a concentric tube arrangement, so there is nothing to and from the inside of the house.
.andy
To email, substitute .nospam with .gl
That's crystal clear. Yes, I've seen vapour from the flue but wasn't sure if this was something different. I don't see the vapour as a problem myself but I guess I'll check with the freeholders to be on the safe side.
Thanks very much for the explanation.
It is not free. You have paid for it in your oil and gas bills.
That is why I put the comment in inverted commas.
(I know that you have difficulty with spelling and punctuation, of course)
The energy is obtained as a result of the change of state of the water from gaseous to liquid phase as it cools. It is energy that is not directly derived from the burning of the natural gas and heat transfer to the heat exchanger, and is as a result of the latent heat phenomenon. In that sense it is "free" energy that you would not otherwise have and is in addition to what is measured by the simple examination of energy input vs. energy output.
Latent heat is also exploited for air conditioning and heat pumps, where the heat delivered to and from a space is greater than the energy input required to do so.
In the case of air conditioning the latent heat of condensation and evaporation is used to transport the heat energy. In the case of a condensing boiler, the latent heat is added to the heat resulting from combustion at the heat exchanger.
When I went to school, latent heat was a first form grammar school physics experiment. Perhaps you missed class that day.....
.andy
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You should have written what I did instead.
< snip tripe by Andy >
I rather thought that it would be too difficult for you to comprehend. Presumably you don't know how your time machine works either...
.andy
To email, substitute .nospam with .gl
< snip tripe by Andy >
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