What is a heat exchanger in a boiler?

So what exactly is a heat exchanger

and how does it work in your boiler?

A heat exchanger does precisely what its name describes – it allows heat to be exchanged between two fluids or substances, usually water or gas, without letting the substances mix together. You may take it for granted that your boiler is able to heat water up and then deliver it around your home, either through your radiators or to your taps. You might not, however, have thought about how it achieves this. The heat exchanger is the key. Without this device, your boiler wouldn’t be able to warm up your water.

What is the purpose of a Heat Exchanger?

Heat exchangers can be found in all sorts of appliances and industries. They’re used to recycle heat in the waste gases at power plants and to heat swimming pools. They can also work in the opposite way and cool something down. Refrigerators and air-conditioners contain heat exchangers which draw the heat away from the room or compartment to keep it cool.

Heat exchangers are most commonly found in boilers. They allow your boiler to heat the water that is then pumped through your radiators to warm your home. The heat exchanger is a long, coiled pipe. This cooler pipe or heat exchanger surrounds the combustion chamber, where gas is burned to release its energy. The water in the heat exchanger is warmed by the hot combustion gas and then pumped round your home thereby transferring the energy from the gas to the rooms where it is needed. 


Condensing gas boilers

Condensing gas combi boilers used to have two heat exchangers, as it was thought that this was more efficient. To begin with, the water was heated in the primary exchanger. As hot waste gases were produced, the water that returned from its circuit around the radiators was pushed into the secondary heat exchanger, which only used waste gas to heat the water. This second heat exchanger recovered the “latent heat of vaporisation” which adds almost 10 % to the boiler efficiency.

What boilers have stainless steel heat exchangers?

Without a heat exchanger, your boiler wouldn’t be able to heat the water that moves around your radiators and comes out of your taps. This makes a heat exchanger a really important part of your boiler. If it breaks, you won’t have any heating or hot water. Therefore, it’s imperative that it’s made out of a strong material that is long-lasting. Stainless steel is one of the best materials for this purpose. There are many benefits of using stainless steel for the heat exchanger. First, stainless steel offers impressive resistance against corrosion.

Viessmann boilers only contain one heat exchanger. The patented stainless steel design means that it is able to capture the heat from combustion and the latent heat of vaporisation in one pass of the single heatexchanger. This is due to the exchanger’s larger surface area and the position of the burner, which sits centrally within the cylindrical heat exchanger and the patented design. As the water moves through your radiators, it’ll slowly begins to cool down. Your boiler is able to detect the temperature of the water and modulates the gas burning rate to deliver the correct amount of heat.

gas boilers by Viessmann
Combi Boilers

Combi Boilers

System Boilers

System Boilers

Open Vent Boilers

Open Vent Boilers