How Does A Condensing Boiler Work?

How Does A Condensing Boiler Work

In this guide, We will explain how does a condensing boiler work.

A large part of the energy that is used in our homes for heating water comes from burning natural gas or using electricity. With a condensing boiler, heat from the flue gases is used again to heat the water. This means that there is less need for an external energy source and this in turn leads to lower operating costs. In addition, burning natural gas or using electricity to power a hot water tank can add up to 15% of carbon emissions from heating which can be reduced by using a condensing boiler.

In terms of how it works, the heat from the flue gases heats water in a heat exchanger and this hot water is then stored in an insulated hot water tank. In order to make sure that there isn’t too much pressure on the system, a safety valve opens before any excess pressure can build up in the tank.

What is a condensing boiler?

A condensing boiler is a type of boiler where the heat exchanger in it turns water to steam and this steam is used to heat the home. Unlike a conventional boiler, a condensing boiler collects the latent heat from the flue gases that are emitted when water or gas is burned.

This means that when it produces hot water, that hot water has been heated twice-once by burning fuel and once by extracting energy from flue gases. In many cases, this means that operating costs for a condensing boiler are lower than those for other types of boilers.

How Does A Condensing Boiler Work?

In this section, we will explain how does a condensing boiler work:

A condensing boiler works differently to a traditional boiler. Rather than just burning fuel and creating hot water, it also draws heat from the gases that come out of the chimney.

Condensing boilers are quite efficient as they produce hot water twice: first by burning fuel, and secondly by extracting energy from flue gases. This means that operating costs for a condensing boiler can be lower than those for other types of boilers.

The key aspects of how a condensing boiler works include:


this is an enclosure with coils inside which captures or ‘condenses’ water vapour so it returns as liquid and runs through the coil -boiler: where diesel, gas or oil burn to create steam


hot gases from the combustion chamber of a boiler enrich the air before it enters the house and feeds air to the fire at its optimum temperature -flue: collects combustible gases and fumes, and takes waste products (carbon dioxide, carbon monoxide) up through chimney.

A condensing boiler works by having water vapour condense on the coil inside a condenser. This liquid runs through another coil and heats up water which is then pumped around the house for hot water. A flue captures the gases from a boiler before they go up a chimney stack.

Benefits of using a condensing boiler

The benefits of condensing boilers can be described as follows:

  • First, they produce hot water at lower operating costs. This is because there is no requirement for an external heat source to raise the temperature of the water produced by the boiler. Instead, the condensing boiler extracts additional energy from flue gases that are emitted during burning of fuel.
  • The second benefit is that it offers greater efficiency in usage of natural gas and this means lower operating costs. This is because there will be no wastage of heat energy which again means lower operating costs.
  • Thirdly, condensing boilers are more efficient than conventional boilers because there is less unwanted heat loss through flue gases leaving the stack.
  • Fourth, the units can offer savings on installation costs because there is no need for an additional heat exchanger which would otherwise be required in the case of a conventional boiler.
  • Finally, condensing boilers are said to provide more controllable heating than other types of boilers. This means that the whole house can be heated to a preset temperature rather than just one room or one area.

Disadvantages to using a condensing boiler

The main disadvantage is that they are not very popular in the UK. This is because of the high initial purchase price. Due to high prices, not many people use condensing boilers.

Another disadvantage of using a condensing boiler is that they need to be installed by a qualified gas engineer. This means that an installation of the boiler will cost more than one that can be easily installed by somebody without any training or experience.

Condensing boilers are effective in homes where people space heating is needed over large areas, but not intensively. A condensing boiler works very well for this purpose because of their high efficiency.

Key points to consider when purchasing one for your home’s heating system

The first thing that you need to consider when buying a condensing boiler is what size you’ll need. This is because there are many different sizes of condensing boilers available on the market, and they’re also priced differently.

A larger condensing boiler will heat your home faster than a smaller one. You should also think about how often your home goes without heating in winters, as this will affect how much hot water you’ll need at any given time.

If you have a combi boiler, you’ll need to check if the condensing boiler can be fitted with it. This is because some condensing boilers only suit certain types of home heating systems, depending on their construction or other factors.

You should also consider safety factors when buying your condensing boiler. It’s vital that you purchase a condensing boiler that gives you peace of mind, as condensing boilers are only separated from the flue gas by a very thin metal sheet.

It’s important to know whether your boiler has been fitted with anti-corrosion protection and other safety features, especially if it’s going to be installed in a damp or humid environment.

To find out how much it’ll cost to install a condensing boiler, you need to calculate the costs of buying and installing one into your home’s heating system. You can then compare them to the annual operating costs that your boiler will give off. If you’re going to be relying on government assistance such as the Renewable Heat Incentive (RHI), you should also factor in the costs of getting it installed.

When looking at different condensing boilers, you should visit independent review websites to find out which ones are praised for their hot water generation. Customer reviews may not always be factually correct-even if they’re negative-so it’s best to look for fully independent reviews from other customers that praise or complain about certain condensing boilers.

If you want to cut down on heating your home and don’t mind waiting a while for hot water, you can always look into purchasing a combi boiler instead. It’s much cheaper than buying a separate hot water tank and condensing boiler, and the two devices can work in tandem.

Alternatives to the use of a condensing boiler in your home’s heating system

If you are looking for an alternative to a condensing boiler, one option is an air-source heat pump. This machine works by using refrigerant to transfer heat between the air and water within the machine. This process uses very little energy, because it can work with ambient heat in the environment.

Another option that is gaining popularity amongst homeowners who are looking for an alternative to a condensing boiler is a biomass boiler . Similar to a wood burning stove, this boiler uses wood pellets to generate thermal energy. This is similar to how a condensing boiler operates, but this type of boiler also doesn’t require the use of oil or gas for burning fuel.

A third option that can be used as an alternative to a condensing boiler is ground source heat pumps . The process through which they operate is essentially the same as air-source heat pumps, but they are ground-based. These types of boilers require the use of an electric pump for water and a gas or oil heating unit in order to operate.

One thing to consider when choosing an alternative to using a condensing boiler in your home is that there may be zoning laws in place that will require you to use certain types of heating systems. You will want to contact your local municipality before choosing a replacement for a condensing boiler, in order to make sure the system you choose is allowed where you live.

What is the difference between combi boiler and condensing boiler?

Combi boiler is a type of boiler that heats your home using hot water by turning the water to steam. Condensing boilers are similar to combi boilers in that they use hot water to heat the home. The difference between them is that condensing boilers have an extra step that allows it to extract latent heat from flue gases emitted when burning fuel.

This means that the heated water coming out of a condensing boiler has been heated not just by fuel but also by extracting energy from flue gas in addition to burning fuel. This can mean lower operating costs in many cases, since this heat extraction is free in most homes.

You also need to understand that condensing boilers are not all the same. Some condensing boilers require electricity to operate while others use natural gas or fuel oil as the primary source of energy.

These types of condensing boilers work by transferring some or most of the heat from flue gases to a secondary fluid- either water, oil, or antifreeze- that turns to steam.

This means that there are two steps in heat transfer- heating the secondary fluid and then heating the water with the hot fluid.

Do you need a water tank with a condensing boiler?

If you have a condensing boiler, you will need a tank for the water to flow through the boiler. Without the tank, water would get into the flue gases and leave droplets of moisture inside your home. This has been shown to cause problems with efficiency and increase operating costs.

How Does A Condensing Boiler Work


Condensing boilers are a type of boiler where the heat exchanger in it turns water to steam and this steam is used to heat the home.

The downside may come with zoning laws which prevent you from using certain heating systems in your area; however if you live in an area where you are allowed to install a condensing boiler, this may be the most efficient option for your home.

References : Domestic Renewable Heat Incentive (Domestic RHI)

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