Condensing Boilers [The Ultimate Guide]

Matt Robinson | Updated on March 24, 2021
Condensing Boilers - The Ultimate Guide

In 2008, there was a ‘boiler scrappage’ scheme where people were given some money if they replaced their old boilers with condensing systems. So, the record says, more than 8 million British homes switched to the newer version. This was a move by the government so that people could have a cleaner boiler.

Now, in this article, we shall discuss combi boilers, an ideal choice for residential buildings. Are you worried about rising heating costs? Opting for a combination boiler is the best option. It’s pretty challenging to have an understanding of the world of boilers, there are so many models, so many manufacturers, a lot of sales and installation.

What is a condensing boiler?

A lot of people are interested in purchasing condensing boilers, yes it’s known as condensing because of the way it functions. Condensing systems are compact, these units are easily accessible, the design makes the system far more efficient, and you get more output and can save on energy bills. These days a lot of homes are looking for efficient and greener boilers, therefore condensing boiler is the best choice. Condensing boilers are very efficient; this helps the entire fuel to get utilised to emit sufficient heat to your rooms. The best idea is to replace a G-rated non-condensing boiler with a new condensing system. This way you can improve your heating controls and it would show on your energy bills.

How does a condensing boiler work?

While burning natural gas, condensing boilers produce a mix of water vapour and carbon dioxide. Very different from a traditional system, the heat exchanger of a condensing system is larger and sometimes there is a secondary heat exchanger. It recycles waste gases and puts those back again into the heating system. This is the magical way by which the system maintains about 90% energy efficiency. With these boilers, you get 24 hours even heating for your home. Basically, all modern systems are condensing boilers. In case you are planning to replace the old boiler, do get a condensing boiler. When you have installed a new system, you also need to find out whether it’s working properly. Check whether there is a plastic pipe coming out of the external wall very close to the boiler installation location. This pipe leads to the drain and is called a condensate pipe. The unit proves to be very effective if it has an ERP A rating, you will also be sure then that the boiler is condensing.

Condensing boilers versus non-condensing boilers

Both heat-only boilers and combi ones can be condensing and also non-condensing. The building regulations have stated that all the new boilers that would be installed in homes should be condensing and highly efficient. A boiler that is not condensing takes in air from the room interiors whereas condensing boiler remains entirely sealed and takes air from outside. Condensing boilers are a lot safer than non-condensing boilers. Last but not least, if you measure the efficiency, condensing systems is about 25% more efficient than the non-condensing ones.

Condensing boilers advantages

If you replace a G-rated boiler with a new condensing boiler, you can save about ?350 every year. So, this clearly shows the main benefit of installing this system but there are other advantages as well:

  • Green boiler – When the whole world is going green, homeowners are very concerned about conserving the environment. Condensing boilers are considered green because there are very fewer carbon emissions compared to the traditional ones. So, per year there is a lot of carbon dioxide saving, it’s a big contribution in protecting the environment.
  • Quality metal – Metals that contain ferrous tend to corrode with time and the condensing systems are manufactured devoid of metal thus there is no corrosion as time passes by. You invest in a boiler and it’s really great if it is in proper condition for a long time.
  • Automatic hot water – These boilers do not need a timer for operating effectively, they can automatically produce hot water.
  • Draws air from outside – These boilers draw air directly from outside and this boosts the system’s performance.
  • The size – Condensing boilers are usually very compact and this is why they do not take up much space. You can also install a combi condensing boiler in the kitchen cupboard; space will not be an issue.

Why are condensing boilers more efficient?

Traditional boilers have a hydronic heating loop; this design constantly puts an effort to stop the direct-fired systems from condensing in the heat exchangers. The process of condensation occurs during the time when the water vapour inside the combustion gases of the boiler sinks below the dew point. This is the time when the gas is forced to remain in a liquid state. The change of state happens automatically because approx. 1000 Btu of heat is released for each pound of liquid created. The surface of the heat-exchanger remains cool which plays a major role. But, if normal boilers start performing condensation, it’s harmful to the system. The condensing boilers are crafted using the latest technology and keeping in mind that condensation is a must. The heat-exchangers are engineered using the highest quality material and the design allows draining freely. The new ones can withstand years of condensation without any sign of corrosion. There are some components that can also withstand thermal shock that happens due to fast temperature changes. The engineers can incorporate the condensing equipment directly into the main loop. The hydronic loops are simplified on the condensing boilers, this reduces the maintenance costs.

Type of condensing boilers

Mainly there are two variants: the combi boilers and system boilers. It is good to opt for a system boiler for larger households or for properties that have low water pressure. You can buy system boilers for houses that need on-demand heating. These condensing are available in different shapes and sizes; let’s take a look at the types:

  • Wall mounted systems – mainly known as mounted boilers, these condensing units are extremely convenient. It’s compact, smaller in size and can easily fit in a modular boiler space.
  • Floor boilers – These units are also known as standing boilers or floor mounted. The size is a little larger than the wall-mounted systems and these can also produce more volume of hot water.
  • Single circuit boilers – Single circuit means there is only one main feed via which the water comes in and goes out from the boiler. This type of heating is good but there is one risk, that if the system is not rightly balanced, then the heat is distributed unevenly depending on the circuit developed by the hot water.
  • Double circuit boilers – These boilers have two different pipelines. There is one pipe to take the heated water away from the system and distribute heat to the property. Another pipeline brings water to the boiler for being reheated. These boilers are balanced and heat is distributed evenly throughout the property.

Mechanics of a condensing boiler

Condensing systems have inbuilt fans that are installed close to the heat exchanger and it also works with the speedometer. This is why the condensing systems have a closed combustion chamber which is joined to s coaxial flue from where the combustion gases are evolved. The fan speed can be controlled and this aids to maintain a balanced combustion ratio of gas and air. To reduce the loss of heat arising from flue gas, the heat exchanger must allow water vapour condensation. The condensation process is the highest when the surface of the heat exchanger is equal or just below the dew point temperature. For the boiler to work in the condensing mode, the coolant temperature that’s in the reserve loop must not be more than 57 degrees Celsius. If the coefficient of performance of a boiler is higher, the heating system temperature will be lower. A condensing boiler is more efficient if it is combined with underfloor heating (water-based) with 40 to 45 degrees Celsius temperature. You can improve the comfort level that your heating system gives by installing a condensing boiler, and it also reduces the consumption of gas by 15-20%.

Buy the best boiler

Are you worried about the carbon footprint? Condensing boiler is the solution. There are so many types of boilers; it becomes pretty difficult to decide which one you must buy. It’s wise to weigh the benefits before finally ordering. You get boilers online and there are so many websites that do a comparative study of the best boiler brands. It’s a big investment to buy a condensing boiler but it’s worth it; it helps you to save money on energy bills in the long run. There are boiler and heating consultants who can also help you in case you are not sure which condensing boiler to buy.

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