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How are modern boilers more efficient than older boilers?

Started by Zarostulus, December 02, 2015, 06:52:38 PM

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Obviously the technology is newer, but which technology specifically makes them so much more efficient than boilers 20 or 30 years ago? When my mother replaced her 25 year old boiler she almost cut her bill in half. How? What were the old boilers doing so terribly wrong?


Well for one, the older boilers were poorly insulted and heated up the room significantly, more than the hot water itself. However this room is the room I mainly heat anyway so the difference is not as bad as it would be otherwise.


[quote author=LucidEnergy link=topic=195.msg488#msg488 date=1449082938]
Well for one, the older boilers were poorly insulted and heated up the room significantly, more than the hot water itself. However this room is the room I mainly heat anyway so the difference is not as bad as it would be otherwise.
Is it new technology/materials that make this better in newer boilers, or do we just put more in and spend more money on it?


A bit late to reply, but..

The main inefficiency of old boilers is the heat contained in the water vapour they vent (you see it as clouds of vapour coming from the flu on a cold day).

Modern boilers are supposed to pass this vapour over a series of condensing fins, so that the water condenses inside the boiler and the heat it contains can then be used in the boiler, rather than being pushed out as clouds of "steam". That's why they're referred to as condensing boilers. All new boilers installed since about 2007 have to be condensing.

Unfortunately for the condensing to work the boiler needs to have an output temperature or less than 60 degrees, otherwise the condensing plates get too hot to allow condensation.

The problem is that most people run their boilers at over 65 degrees, so that their radiators can put out enough heat to keep them warm.

This is because there's a big temperature difference between the pop of a radiator and its base (typically 15 plus degrees) - warm water rises, the same as warm air.

The solution is to place a system between the boiler and radiators that alters boiler output and manages the radiator heat output centrally. It's a brilliant system and typically saves between 30-50% on your bill, because it stops 80% of the eat from the radiator going straight up to heat the top of the room!

If you want to know more, please pm me - otherwise this post'll turn into a novel!



I just looked at the original post, and thought I should address the point that the new boiler halved your mum's bill. Firstly, that's fantastic news.

Just a couple of points. Some people use the word boiler to mean the hot water cylinder, which is heated by a coil from the boiler or an electric immersion heater. If it was this unit that was changed, the saving would be explained by the new cylinder being so much better insulated.

However I assume from your post that you mean the boiler that runs both the radiators and heats the hot water cylinder.

So what would make it so much cheaper.

1) Energy prices may have dropped just as the new boiler went in. You could have got a 10% saving in cost right there (prices are set to go back up and beyond as we go forward).

2) When the new boiler was installed, it's likely that the radiator system was flushed. Radiators should be flushed about every three years since they build up sludge internally, which among other things makes them inefficient.

3) On the same lines the radiators may have been bled for the first time in ages, again increasing their efficiency.

4) The older boiler probably needed replacing because spares were getting hard to find and could easily have been running at 75% efficiency through no fault of it's design.

5) The new boiler probably is slightly more efficient.

It's when you combine many or all these effects that you get such a large saving. So it's quite possible that very little of the saving was down to the new boiler itself.

Whatever the reason, it's a great saving!


There is a very slight difference regarding the efficiency of boilers as compared to the old generation. It is a bit efficient because of the new materials and technology.
Oliver Masson
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