What Is A Combi Boiler?

What Is A Combi Boiler

If you want to know what is a combi boiler, this guide will explain it you in easy to understand manner.

A combi boiler is a type of heating and hot water system that can be installed in homes and businesses. It’s a smart choice for those who want to save on their energy bills and also have the convenience of instant hot water. Combination boilers are more efficient than other types because they heat both cold water and the air before the same time, which saves on your energy costs!

You know that a boiler is an important part of your home, but you don’t know what it does or how it works. A combi boiler is the perfect solution for homeowners who want to save money on their heating bills and reduce their carbon footprint.

Combination boilers are more efficient than traditional boilers because they have both gas and electric elements. The best thing about this type of boiler is that when the electricity goes out, you can still heat your home with natural gas! This means lower energy bills all year round.

What’s the difference between a combi boiler and a normal boiler?

A combi boiler is a type of boiler which combines the heating and hot water elements in one machine. The combi boiler can provide instant hot water, and provides high-efficiency heating which enables you to save money on your energy bills.

Combi boilers produce far less carbon monoxide than the older ‘Constant Pressure’ system. They also make use of an internal expansion vessel, which is necessary to protect against water hammer and ensure safety in the event of a high pressure release.

Many combi boilers will provide consistent hot water for washing machines and dishwashers with minimal loss of pressure.

If you’re thinking about investing in a new combi boiler, prices vary dramatically depending on the size and type of your home. A small one or two bedroomed flat is likely to require a system that costs no more than £350 – whereas a large household with five or six bathroom facilities could pay out as much as £4000.

What is a combi boiler and what are its benefits

The combi boiler is a kind of boiler that has two heat source: gas and hot water. These boilers are known for their more efficient usage of resources, as they make the most use of these resources by transferring heat from the gas to the hot water before it enters the pipes. This type of boiler can also be used with radiators.

These boilers are also known to be safer, as there is no need for lagging pipe work to prevent condensation. They’re more cost-effective than boilers that only use gas and have much easier installation requirements because there is no pipework needed in order to connect them.

One of the most important things to know about combi boilers is that they’re incredibly efficient, which means that it could be a good idea to look into them before getting a heat-only boiler. The installation cost of combi boilers is lower than the average price for putting in a whole new heating system and can cut down on further costs, such as fuel or gas bills.

Their simple mechanism makes repairs and replacements much less complicated and much cheaper. The average lifespan of a combi boiler is higher than the life of other, more basic models and they’re also safer because there’s no risk of gas leaks.

Combi boilers really only have one drawback: they don’t work as well if you live in an older home that has poor insulation or windows. They can increase your heating bills in these cases.

How does A Combi Boiler Work?

Combi boilers are a type of boiler that is used for central heating. They work by using water to heat up the liquid in pipes, radiators, or under floor heating. The liquid is heated to boiling point so it can warm up your whole house.

There are two different types of combi boilers – one which has a gas-fired primary circuit and an electric secondary circuit, and one which has a water-fired primary circuit and an electric secondary circuit.


Combi boilers that have a gas-fired primary circuit and an electric secondary circuit use a Combined Cycle Gas Turbine (CCGT). The water is heated to boiling point in the boiler’s heat exchanger.

There is also glycol solution, which is used to prevent the system from freezing up when there is not enough hot water in the system. This solution also allows the air to be blown out of the system when it is time to drain it down for servicing.

The hot liquid then goes into a coil, located in the top part of the boiler casing, where there are water pipes inside it. These coils get cold because they use cold water from your mains supply, and this cold water is used to cool the gas turbine.

After the gas has been through the turbine it enters a economiser, which is like an air-preheater. It warms up as it passes over hot flue gases from the boiler’s combustion process, therefore saving fuel.

The cooling water for this process is taken from a heat exchanger in the gas boiler. Next, the gas goes to a super heater ahead of a turbo-generator.

There are two circuits for this system – one which sends flue gases to a stack and another which sends them through an air pollution control (APC) equipment. This APC equipment removes any harmful emissions from the gas before it is released into the atmosphere.

The combi boiler that uses a water-fired primary and an electric secondary circuit (the one we will be focusing on) also has two circuits – one which sends flue gases to a stack and another which sends them through APC equipment similar to above. However, this system uses water-fired boilers instead for the primary circuit, and electric secondary circuit.


The combi boiler that has a water-fired primary and an electric secondary circuit is known more commonly as a ‘wetback’ system… This means it works similarly to most household appliances which heat up using electricity. The heat exchanger is located in the hot-water cylinder, and so as well as heating up your water it also heats up the surrounding casing. Next, a pump sends this warm water into a coil inside the boiler’s heat exchanger.

The system then works in reverse – instead of cold water passing over a hot surface to cool it down, now hot water passes over a cold surface (inside your radiators or under floor heating) to warm it up.

The water used for this system is taken from the hot-water cylinder, and heated directly inside the heat exchanger – there aren’t any pipes involved during this process. It then goes into another heat exchanger known as an air-to-air heat exchanger, where it is preheated before going into a second pump. This time the water goes into a coil inside the boiler casing.

One of the benefits of this system is that because there isn’t a pump involved in heating up the water after it leaves the boiler, you will only have to run your hot water for a couple of seconds. Therefore it uses less electricity, saving you money on your electricity bills!

A boiler with both a gas and an electric secondary circuit would cost between £900 and £1,000. This is around the same price as a combi boiler that has an electric primary and gas secondary – so they cost roughly the same to run per year.

The advantages of a wetback system are that it is cheaper to run and they have low servicing costs, which means you can save money in the long term by avoiding repair bills. The only downside is that this type of combi boiler will cost more to install… But if you are already replacing an electric boiler with a gas one, it makes sense to spend a bit more and also install a wetback system.

Because this is such an efficient system (87% compared with 70% for the other options), they will save you money on your gas bills too! And if you use solar panels, there’s even more good news – combi boilers that have water-fired heat exchangers can be used with solar panels, so you could combine the two and save even more money.

The savings will vary depending on how much hot water your family uses and what time of year you’re in. But if you use an average amount of gas and electricity, a wetback system will save around £220 per year. And it will pay for itself after 7 years.

This could be a combi boiler with an electric primary and gas secondary, or one with water-fired heat exchangers…

You need to choose between three different options – A) Combi boilers that use an electric primary and gas secondary circuit B) Combi boilers that have water-fired heat exchangers C) Combi boilers that have both an electric primary and gas secondary circuit.

Why are combi boilers bad?

There are three reasons combi boilers can cause problems which boil down to their high maintenance requirements. Firstly, the design is so intricate that a problem with any part of it can have an adverse effect on the whole thing – imagine a carburetor in a car and you get the idea.

Secondly, they require periodic servicing by a specialist technician – who not many people around these parts seem to know what those initials RT mean!

Thirdly, even if you do find someone knowledgeable enough about them to try and fix one for you.

What Is A Combi Boiler

Which is best combi or conventional boiler?

A combi boiler is a device that provides both heating and hot water to a house. It’s called “combi” because it can provide hot water to the home either from a storage tank or from the boilers’ heat exchanger – it does both.

Combi boilers are really popular because they provide significant cost savings over conventional systems because you don’t have to have two tanks.

In addition, a combi boiler will typically allow for more hot water at any given time, meaning that your family will always have enough water to take showers and wash dishes at the same time.

However, combi boilers are more complicated than conventional systems and need to be installed by a professional. As such, they tend to cost more. If you’re looking for real savings in your next heating bill, though, then it may well be worth the extra expense.

Reference : How does my boiler work and how to use it efficiently?

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