How Does Central Heating Work with a Combi Boiler?

September 1, 2022
Thick, warm socks on a cosy blanket with a hot beverage.

Combi boilers are Britain’s favourite boiler. Not only do they offer a modern, compact design that is easy to install in a kitchen cupboard, but they instantly heat hot water from the mains so you don’t need to find space for a water cylinder.

These compact, efficient boiler models are the perfect choice for homeowners around the UK - particularly those living in smaller properties. But how does central heating work with a Combi boiler? Read on to discover the answer to that very question.

How Does a Combi Boiler Work? 

A Combi boiler operates both your central heating and hot water from one single, tidy unit. Combi boilers have two primary functions: to heat your hot water and to warm up your central heating. 

Inside your Combi boiler are two separate heat exchanges; one functions to provide you with hot water whenever you need it, while the other heats up your radiators on those cold winter nights.

The Primary Heat Exchanger: this heats the water that ends up in your radiators. The primary heat exchanger recycles hot water around your central heating system, warming up your radiators and maintaining a comfortable temperature in your home.

The Secondary Heat Exchanger: Combi boilers don’t require water storage tanks because they draw water directly from the mains. This water is passed through the secondary heat exchanger to provide you with hot water on demand. This means your Combi boiler is always on standby, waiting for you to turn on the hot tap.

The Combi Boiler Shut-off Valve

Although Combi boilers are clever systems, they cannot power your central heating and provide you with hot water at the same time. If they did, you would end up drinking recycled radiator water and nobody wants that! So, to avoid this problem, your Combi boiler has a valve inside that shuts down the pipe to your radiators every time you run the hot tap.

However, this doesn’t mean you have to choose between a warm house or hot water because the valve that shuts down the pipe does so momentarily. Therefore, it is very unlikely you will notice any disruption to the temperature in your home.

Heating Control Apps and Combi Boilers

If you’re wondering whether you can use a heating control app alongside your Combi boiler, the answer is yes. Many new Combi boilers, such as the Ideal Logic Combi IE model, are compatible with heating control apps. This means you can command your boiler to heat the radiators while you’re on your way home from work.

Heating control apps are a popular choice for many people. These apps let you control your heating from wherever you are. This means you can instruct your boiler to fire up the heating while you’re on your way home from work so that it’s warm when you get there. What’s not to like?

Is My Radiator System Compatible with a Combi Boiler?

If you’re considering a Combi boiler for your home, you might be wondering whether your radiator system is compatible. Let’s take a look. 

Replacing a Non-Combi Boiler: if you are replacing your current boiler with a Combi boiler, your central heating pipework may need adjusting to fit your new boiler system. Our specialist boiler engineers can help with this. Rest assured, you won’t need to invest in new radiators unless there is a problem with your current radiator system.

Old Radiator Systems: if you have an old radiator system, it may not be compatible with a Combi boiler. This is because old central heating systems can’t always cope with the high water pressure delivered by Combi boilers. Therefore, you might want to consider upgrading your old radiator system before installing a new Combi boiler.

How Many Radiators Can a Combi Boiler Heat?

Depending on the size of your property and the number of radiators, you might be wondering how many radiators a Combi boiler can heat. The answer to this question varies as it depends on the size of the Combi Boiler. Note, when we talk about boiler size, we’re not referring to the boiler’s physical size but rather the boiler’s output in kilowatts. 

For example, a 24-30kw Combi boiler can typically heat a property with around 10 radiators. Larger properties with more radiators should invest in a 30-42kw Combi boiler to ensure the system can serve their central heating needs. If you’re unsure whether your chosen Combi boiler can serve all the radiators in your home, contact our team. We’d be happy to help! 

Can I Add Radiators onto My Central Heating System? 

If you’re considering adding a radiator or two onto your existing central heating system, this shouldn’t cause any problems with your Combi boiler. However, to be on the safe side we’d recommend you check your boiler’s output or speak with a member of our team to ensure your Combi boiler is powerful enough to handle an extra radiator or two.

Find the Best Combi Boiler for Your Home

At City Warmth, we supply and install a range of Combi boilers from leading manufacturers. If you’re considering a Combi boiler for your home, we would love to advise you on the best boiler for your needs. Browse our fixed price boiler products or give us a call today. We would be happy to answer any questions you may have.

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