What is a Combi Boiler? Detailed Guide and Working Principle
What is a Combi Boiler? Detailed Guide and Working Principle

What is a Combi Boiler? Detailed Guide and Working Principle

When examining the residential solutions produced for home and water heating systems in the world, it draws attention that the most sophisticated and comprehensive among them are combi boilers. While such devices provide hot water flow throughout your home, they also make use of hot water technology to keep the general temperature of the house at the level you demand. Combi boiler products can be called system boilers or regular boilers according to their structures. After briefly reviewing these two types, let's move on to the rest of our content.

  1. System Boilers: This type of boiler device has a more comprehensive and stronger working performance than others. In houses with more than one bathroom, system boilers are really useful for not reducing the flow of hot water and maintaining the flow. Devices that continue to give a strong temperature and flow even when the faucet is opened at the same time in the kitchen, bathroom or other areas have an extremely high durability.
  2. Regular boilers: In some houses, it may be necessary to use hot water at a very high rate at one time due to the population. In this case, regular boilers create powerful results. Regular boilers are often preferred for houses with two or more bathrooms.

Gas Combi Boilers: Which One To Choose?

We understand that there are many gas combi boilres on the market and it takes a bit of research to choose both brands and models. That's exactly why Zara Heating will be your saviour. With years of experience, we know this sector very well, we know the combi boiler model that will be great for you according to different usage styles, family structures and house sizes. You can get our effective gas combi boiler recommendations by contacting us immediately, and you can make an appointment for your quick installation or maintenance requests.

Do you want to learn the details that you should consider when choosing before getting an assistantship? Here are some of them:

Choosing the Gas Combi Boiler in the Right Size

Gas combi boilers of different sizes are available on the market. When choosing among them, you need to consider the following factors:

  1. Hot water you demand
  2. Number of radiators in your home
  3. heat loss factors
  4. Type of fuel used in the boiler
  5. water pressure factor

While making a decision within the framework of the above factors, if your house has 3 or 4 bedrooms, you may think that a gas combi boiler of approximately 20 - 35 kW will be sufficient for you. But if you have a house with 3 4 bedrooms and an en-suite bathroom, the energy requirement will increase up to 30 - 35 kW. When you have such a large house, you can also consider purchasing a system boiler instead of a regular boiler. System boilers suitable for residential use can generally produce energy between 35 - 42 kW.

Additional Technologies Employed by Gas Combi Boilers

While doing a general research in the market, you may have noticed that a certain efficiency ratio is given for each boiler. Brands employ various technologies to increase the efficiency of their models. These technologies can usually be to keep the flow rate constant, to optimize the performance according to the degree of outside air, or to use nofrost technology to prevent the internal parts of the device from freezing. All this is very important to extend the life of the device, increase its current performance and ensure that as much of the energy spent is transferred to heating as much as possible.

If you want to examine the technologies in them while trying to get information about the boiler devices, you can take a look at the detailed review contents of Zara Heating. In these contents you will find information about modern advances.

Condensing technology: What is It and Why is It A Must in the UK?

When you look at the market, you will see that "condensing" technology is used in many devices. There is a reason for this, it is now a legal requirement that all combi boilers in the UK have this technology. The main reason for this necessity is to develop a more environmentally friendly lifestyle by increasing the efficiency of devices.

As you know, in old boiler models, combustion gases usually escaped into the chimney. The loss of these gases meant that almost half of the energy that could be converted into heat was lost. This could result in both very high bills in general and excessive emissions into the environment.

The condensing technology used in new generation boilers provides a great solution. It is now possible to heat the cold water by keeping the heat created by the combustion gases inside the device. This is one of the important secrets of the efficiency of modern combi boiler models.

So what does this have to do with the environment? Consider how much energy is wasted if the combustible gases that cause carbon dioxide emissions do not contribute to the boiler performance. This emission rate is much more than nature can tolerate.

Pre Heat System: Instant Hot Water Technology

Some additional technologies can even make it possible for the water to heat up even faster. In these systems, an additional technology called “pre-heating system” is employed. In this case, an additionally kept water tank is always kept above a certain temperature. In this way, when a user turns on the tap, it can be done in milliseconds to bring the already warm water to the desired temperature and send it to the tap. In this type of models, even if you do not use the water, your boiler continues to work and keep the small tank at a certain temperature. This may result in excessive billing. Therefore, many people do not use this technology in residential buildings.

How Does A Gas Boiler Combi Work?

In this part of the content, we will talk about the working principle of gas combi boiler devices for those who are interested in technology. The sophisticated system that enables the devices to heat both your home and your water is actually based on a simple logic.

A combi boiler takes water directly from the mains. The gas burner is then ignited to heat the water. Immediately after this ignition, the heat exchanger starts to work. This heat exchanger transfers the generated energy to the water. Transferring such a high level of energy to the water enables instantaneous heating of the water, while enabling instant hot water technology.

How Long Does A Combi Boiler Last?

If a combi boiler is an efficient and durable model that you buy by pushing your budget, it can meet your needs for years. That's why we recommend buying high-quality products with long-term performance benefits rather than short-term savings. Usually, a combi gas boiler works effectively for about 15 years. If you regularly maintain the combi models, the warranty coverage of which varies between 7 years and 10 years, through Zara Heating, you can extend the life of the device.

So, what should be done other than regular maintenance to increase the life of a combi boiler? Let's review a few trips together.

  1. Get the radiator key with the help of an expert and open your radiator using the air vent point that your key can enter. When you do this, the air that has somehow gotten into the radiator throughout the year will begin to overflow. You will hear this sound clearly. After the air has been out for a while, it will be the water's turn. You can close the lid as soon as the water starts to gush out. You have completely removed the air that may adversely affect the working performance.


  1. Magnetic filters are great tools for capturing and separating sludge that may be present in the water before it enters the heating system. Cleaning or renewing these devices regularly ensures that the filtering process is more powerful and thus the heating system works more smoothly. Do not forget to consult Zara Heating experts for the maintenance, installation and purchasing processes of magnetic filters.



  1. The inhibitor might work. Depending on the use in your central heating system, scale formation or corrosion may appear over time. The inhibitor works as a true anti-corrosion solution. Inhibitors, which perform many functions such as reducing the accumulated sludge, stronger operation of the central heating system, are also a protective layer against metals.


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