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So, why are we so sold on Viessmann?

August 16, 2019

Although we are happy to install any brand of boiler, and actively do so to keep an awareness of what is available on the market. There are many reasons Viessman are THE leaders in the commercial and domestic heating and renewable industry. Firstly they spent much,  much more than any competitor on research and development at 5 million Euros per week. Much of this informations then sold across the industry to their competitors at a later date to fund further advancements. Dispute the main UK competition also being German (Worcester Bosch and Vaillant) they have won Germanies heating manufacturer of the year 28 years running due to the repeated innovations. They have now just started to be recognized since winning which? Most reliable boiler brand 2017 

So why haven't I heard of Viessmann? 

Although they have been around for over 100 years largely in the commercial and renewable sectors the domestic range have only been available in the UK  merchants since 2005. Their typical German route to market is also not one sales based, and as such their marketing budget is very small compared to the likes of Worcester.  

So what makes Viessmann better?   

Stainless steel heat exchanger- stainless steel is the most corrosion resistant material available. And above that there are different grades. 316 is known as marine grade' its titanium infused and the most corrosion resistant of all the grades. This is what Viessmann heat exchangers are made of. 

The other material widely used is aluminium, this has the advantage of better heat transfer per co2, so for the same heat transfer a stainless steel heat exchanger had to be slightly larger.  Its also lighter and cheaper to manufacture. However we see these as things that benefit manufactures and installers not customers.  

The down sides of Aluminium are that it has a very small PH range before it corroded, and that PH range is generally doesnt suit your radiators, so essentially you have to pick between radiator decay or heat exchanger decay.  

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The other issue with the low PH tolerance is that the condensate that modern boilers create is a PH or around 4. This slowly but surely erodes the heat exchanger, creating dirt to clean out and damaging the heat exchanger. 

This erosion of the hex, in the best case scenario, t causes a thickening of what's known as a passive layer. This actually protects the heat exchanger, however lowers the 'heat transfer coefficient' read as efficiency. 

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Modulation ratio 

When we say modulation ratio  we mean the boilers minimum output to its maximum out put. Say for example a boilers maximum output is 30kW, and it has a 5 to 1 ratio, the minimum output would be 6kW.  

The wider we can get this the more your boiler can run smoothly without cycling (turning on and off) and this is what gives us efficiency, think of a car starting and stopping, as well as longevity. It also means your boiler can run much cooler which gives even more efficiency by promoting condensing. A process where by so much heat is given up  to the heating water in the heat exchanger that the gas products cool and create water before exiting out of the flue at a much cooler temperature. 

Worcester Bosch modulation is typically around 4/6 to 1 

Vaillant isntypuaclly around c to 1 

Viessmann 100 range is 6 to 1 the 200 range an amazing 20 to 1! 


Lastly, the most efficient controls available. 

Viessmann pride them selves in their industry leading advancements in condensing technology. By capturing latent heat in the flue gases that would otherwise leave the building and be disperses in to the atmosphere we can gain up to an extra 10% of efficiency. What's more by matching the load of a property rather than undershooting and over shooting we can make the boiler un smoothly and more gently for longer amounts of time at lower outputs. Fortunately these two things come hand in hand with Viessmann's top of the range weather compensation control, which other manufacturers are begging to offer entry level versions of but pale in comparison in our humble opinions. 


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