How Do Boilers Work?

The Oil 4 Wales Guide to Common Residential Heating Systems

We only notice our running hot water and central heating when it fails — and that happens to a fifth of UK households every year. If you’ve ever had a freezing shower or ice inside you windows on a cold day, you’ve probably wondered, “How do boilers work?” as you try to fix the problem.

Understanding your home heating system is the first step to recognising potential problems or ways to save yourself some money.

Our Oil 4 Wales guide tells you everything you need to know about the common types of residential boiler and heating systems. Keep reading to find out if it’s time to get your boiler checked before it breaks!

Basic Heating Principles of Central Heating Systems

While there are several different types of boiler available for residential homes, the way they work is similar.

A boiler has a heating component — either gas flame or oil — that creates the heat. Water pipes run through the boiler and a heat exchanger. The heat exchanger component allows the heat source to warm up the water without direct contact.

Circulator pumps then push water from the boiler into the central heating system, to a water storage tank, or directly to your hot taps depending on your particular type of boiler.

Heating Fuel Types Explained

The three main types of heating fuel available to UK homes are oil, gas, and electricity. Here’s where you’re likely to find each of them and the boiler types they use.

Gas-Fired Central Heating

Gas is the most common fuel for urban areas as it is easy to connect many houses to one main supply. 

It provides instant heat energy when burned, making it efficient and providing central heating and hot water on demand. Properties with gas can also use it for gas-fired ovens as a cooking source.

However, it’s not used in rural properties located too far from the gas supply pipes. It’s also not always available in blocks of flats due to the logistics of installing gas pipes in high-rises — and the safety issues surrounding potential gas leaks in densely-populated areas.

Oil-Fired Heating Systems

Oil-fired central and hot water heating systems are most commonly found in rural areas far from a mains gas supply. 

An oil tank is located outside of the property and fed into the closed central heating system via the boiler. The tank has to comply with certain oil storage regulations to make sure it’s safe and that the oil doesn’t seep into the ground.

Newer oil-fired boilers are incredibly energy efficient and can heat water on-demand. As you buy the fuel by the tank, you’re also able to budget more easily and have the freedom to switch residential oil supplier whenever you want.

Electric Heating Options

If you’ve just moved in and you’re looking for your boiler but can’t see it anywhere, you’ve probably got storage heaters instead.

These are installed in buildings where gas and oil aren’t safe or accessible to use for central heating or boiler systems — such as in blocks of flats. Instead of having a boiler for your central heating, you’ll have storage heaters that act as radiators on the walls of each room.

These charge up overnight when energy tariffs are lower and heat a central thermal block. This heat is then released throughout the next day.

Different Types of Boiler Explained

You’ll come across three main types of boiler in residential homes: back boilers, conventional, and combination boilers. Here’s how to know which one you have and the basic principles of how it works.

Back Boiler

Back boilers became popular in the 1960s but aren’t included in new builds today. The boiler is installed behind a gas fire frontage in the fireplace, with the chimney acting as a flue.

If you’ve moved into a property that’s been empty for a long time, don’t fire up the back boiler. They’ve been known to explode if left unused for extended periods! Contact your local boiler specialist to assess the system first.

However, back boilers are known to be very reliable which is why they’re still going strong decades after they’ve been installed. They’re not as efficient as modern conventional or combi boilers. If yours needs replacing, it’s likely you’ll need to upgrade to a combi boiler to comply with building regulations.

Conventional Boilers

A conventional gas boiler works with a gravity-fed system to heat water that’s fed around your pipes and radiators — and also provides you with running hot water.

A cold feed pipe comes from a storage tank in the attic down to the boiler. The gravity action draws water down and it then enters the pipes in your central heating system. As water expands when it’s heated, the excess will flow back into the upper storage tank.

Conventional boilers are excellent for large families as you can run a shower and several hot taps at the same time. They’re also very efficient — but do require a lot of space for the water tank (as well as an attic for the gravity-fed system).

Combination (Combi) Boiler

A gas-fired combination — or combi — boiler heats both your central heating system and your hot water from one unit. It saves you space, is incredibly efficient, and will be reliable and cheap to run.

You don’t need a separate hot water tank, which makes them an attractive option for most households. Hot water is on-demand, heated as it runs through the boiler system rather than being stored and heated in the tank.

Cold water enters the boiler and is directly heated by one of two heat exchangers. These are either for the central heating or the hot water — and it’s why your central heating might switch off while you’re running the hot tap. Service resumes quickly once the tap is switched off, however.

Combi boilers are very popular as they conduct two tasks in one small unit. You don’t need a large water storage tank, and you’ll have hot water on demand.

How to Make Sure Your Boiler Runs Efficiently

Stop asking how do boilers work. A clean and well-maintained boiler runs smoothly and saves you money. It’ll use your heating fuel efficiently and you’re less likely to face expensive breakdown costs.

Make sure your home boiler is serviced every year to keep it running smoothly and prevent any frozen mornings without heating in winter!

It’s our job to make sure you’re always warm and toasty. Contact us today to book a service and find out more about our maintenance and breakdown cover plans.