Guide 3 – An Encyclopedia of Boilers

How much do you know about boilers? Unless you work in a gas related industry, chances are your knowledge is a little sketchy.

Fact is that however well you treat your boiler age catches up with all of us, and the day will eventually come when it wishes to retire. Buying a new one can be a minefield.

The more you know, the easier it will be to make an informed decision. The right boiler for you is going to be compatible with your lifestyle/household and able to deliver what you want, when you want, efficiently and economically.

Types of Boilers

Question number one is what kind of boiler do you want? There are three main types: combi, conventional and system. Let’s explore the pros and cons:

Combi Boilers

Combi Boilers are the most popular in the UK and can be fuelled by either gas or electricity.

Thumbs up: 

  • Heat and hot water when you need it without all the palaver of hot water tanks, cylinders or pumps.
  • Compact, so doesn’t take up as much space as other types
  • Suitable for homes where several people want hot water at the same time
  • Economical to run

Thumbs down:

  • Your water pressure might not be so strong if you use hot water from more than one tap at the same time
Conventional Boilers

Conventional Boilers need both a cylinder and a tank and are also known as ‘open vent’ or ‘regular’ boilers. If your home is an old property and your heating system hasn’t been upgraded for ages, chances are this is the boiler you are currently using.

Thumbs up:

  • Hot water available from multiple taps at the same time
  • Cheaper to replace or upgrade if the individual components already exist

Thumbs down:

  • When your hot water runs out, you have to wait for it to heat up again
  • The cylinder and tank are not small – you will need the space for them
System Boilers

System Boilers are good for homes which need to have hot water in more than once place at the same time. You don’t need a water tank but they do operate with a water cylinder which is usually stored in an airing cupboard.

Thumbs up: 

  • You don’t need to have the space for a tank
  • Hot water available from multiple taps at the same time

Thumbs down:

  • You will need enough space to store the cylinder
  • When your hot water runs out, you have to wait for it to heat up again
  • Hot water is not instant

Fascinating Boiler Facts

Like their owners, boilers come in different shapes and sizes. The right one for you will depend on how many people there are needing to be kept toasty and showered in your home and how many radiators your boiler needs to service.

The UK’s Most Common Boiler Sizes
  • 12-24kw – best for flats/houses with up to 3 bedrooms and 10 radiators
  • 24-30kw – yes if your home has 3 or 4 bedrooms and 15 radiators
  • 30-35 kw – suitable for 5 bedrooms plus with up to 20 radiators
  • 40 kw – the right one for you if your gaff is a mansion
Boiler Law

Since 2010 it has been a requirement that all new boilers are A rated for energy efficiency or at least 88% efficient. The system used to rate boilers for energy savings is called SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK). It sounds terribly complex but simply means that all new boilers are given a thorough once over before being rated. This allows you to choose a healthy, green, environmentally friendly boiler that doesn’t pump out any nasties.

Boiler Location

Where will your boiler be happiest? Generally speaking, the answer is where the old one lived. All the necessary pipework will already be there and you’ll have a gaping big space staring at you every day if you decide to situate it elsewhere. However, depending on the type of boiler you choose, remember that you might need room to accommodate a cylinder and possibly a tank too.  

Boiler Controls

If you’ve ever wondered what those dials on you boiler actually do, we can help you unravel the mystery. They allow you to manage when it’s hot, how hot it gets and how much energy you consume. All at the flick of one or two or possibly even three little switches:


Room thermostat   

This one can usually be found in your hall or upstairs landing. It contains a built-in air temperature sensor which regulates the level of heat throughout your home. As a guide, a setting of between 18-20 degrees C is enough to keep most warm blooded folk comfortable without wasting valuable and costly energy.

When your home reaches the desired level of warmth, this little gadget messages the boiler to tell it to have a rest until the temperature goes down. The grateful boiler can then put its’ feet up until you start feeling nippy.


Boiler thermostat

This controls the temperature of the water running through your taps, radiators and heating system.  Again, you can adjust it to suit your personal preferences.

The LOW or MIN setting of around 50 degrees C is appropriate for spring and summer. When things get colder in autumn and winter, the HIGH or MAX setting of around 80 degrees C allows your radiators to get toasty quickly.

But be aware that you will be chewing up more energy and be careful not to scald yourself when running a bath or washing up as the water will be HOT!


Timer Switch

Yes, it is fairly self-explanatory but we’d hate to omit a detail you might be dying to know.

Your timer consists of a built in clock display which allows you to control when your heating and hot water start work and when they down tools.

The more upmarket models give you the option of changing your preferences according to the day of the week so your boiler and radiators can have a lie-in on Saturdays and Sundays too!

Boiler Safety

A happy boiler is one that is loved and cared for. There are several things you can do to ensure that yours lives a long, healthy and productive life, delivering heating and hot water for you all year round:

Book A Service Every Year

A thorough MOT carried out by a Gas Safe registered engineer is vital. For your own peace of mind, you need to know that your boiler complies with the necessary safety regulations, has been tested and any faults repaired and is squeaky clean rather than clogged up with gunk. A dirty, slow, unpredictable or unusually noisy boiler is crying out for attention. Listen to what it is telling you.

Beware Carbon Monoxide

Put simply, you can’t see or smell it but it can kill you. Protect yourself and your nearest and dearest by installing an audible alarm that complies with British or European Standards. The dangers of carbon monoxide poisoning can’t be underestimated. Familiarise yourself with the symptoms and seek medical help immediately if you have reason to believe there has been a leak.

Treat Your Boiler To A Monthly Fire-Up

To ensure your boiler stays in tip top condition, give it a regular toning session. Fire it up for ten minutes every four weeks to check all the components are doing what they should be doing and that the pump is pulling its’ weight. Doing so will minimise your chances of a breakdown and keep your boiler on its’ toes.

What To Do If You Suspect A Gas Leak

Don’t procrastinate. Don’t ignore it. Call the National Gas Emergency Service pronto on 0800.111.999. It’s always better to be safe than sorry.