Alpha GasSaver Savings Claims

[shadaswell]

I am having my central heating extended into an extension and as part of this work an Alpha CD35 Combi boiler is being fitted.

I see from the Alpha website http://www.alpha-boilers.com that they sell a GasSaver module for this boiler that utilises a second heat exchanger to pre-heat the cold water feed to DHW using the flue gases.

However, I am struggling to understand their claims about the savings it can make - DHW savings of 37% and reducing gas consumption by up to 52% per year.

These figures sound impressive, but do they stack up ? This is a SEDBUK 'A' rated boiler so has an efficiency figure > 90%. I assume this is some form of measure of how much of the calorific value of the gas is converted into hot water. If this is true, then only 10% of the potential heat is disappearing up the flue, and hence recoverable by the GasSaver. So how can it reduce the gas consumption by half ?

Am I being naive with my Maths, or am I unpicking exagerated sales talk ?

Anybody got experience with the Alpha GasSaver ? If it really works as they say, then it could be a winner, despite a high price tag (it nearly doubles the price of the boiler !)

Cheers,

Shadaswell

PS - one more thing - this is a condensing boiler, so isn't it already doing flue heat recovery ?

 

[Agile]

That device stores some heat from the 10% otherwise lost during heating for later hot water use.

However the small print says that saving is between a standard efficiency ( thats not condensing ) and a condensing boiler fitted with the saver.

On a continuous basis the saver might give about 3-4% improvement in efficiency.

ALWAYS read the small print!

Tony

 

[shadaswell]

Thanks Agile - you are absolutely right. I have just downloaded the GasSaver's PDF brochure and it is there in the (very) small print at the end :

Source:Test replacing an Alpha standard efficiency boiler with an Alpha high efficiency boiler and GasSaver.Test conducted by independent scientific test house,TNO. Calculation based on an average household’s consumption of 100 litres of hot water per day.

Most of those savings come from upgrading from SE to HE. I certainly won't be buying the GasSaver now - on principle based on their very misleading PR.

Cheers.

Steve

 

[Gasguru]

I think you will find the gas saver was originally designed at a time when SE boilers were more prevalent and there was a perceived requirement to increase the efficiency of these boilers to improve the SAP rating on new build (that would be necessary when installing large areas of glazing etc) or poor wall U values in "designer" houses.

Having been lumbered with this product Alpha market the device as the next great thing to save the planet (and your wallet) but conveniently forget to explain it only operates in DHW mode and the savings will be negligable. If the boiler was fitted with a larger secondary heat exchanger it would also improve efficiency. Of course the new Giannoni heat exchanger with an extra air to air/gas heat exchanger may well be installed in the next generation Alpha models and will probably offer better savings at minimal extra boiler cost.

It's just another example of the mad boiler world...all competing for that little extra percentage point that ill-informed installers and the public will base their purchase on. Of course the extra money these devices cost if invested in insulation/draught excluders etc would be reap far greater savings (and be a whole lot more reliable).