How Modern Boilers Work

Central heating is the most popular from of heating homes. The boiler heats the water which is circulated through the pipework and radiators by a pump, before returning to the boiler. The 3 most common types of boilers found in British homes are the combination boiler, system boilers and heat only boilers. The combi boiler is two appliances in one, a pressurised central heating boiler and an instant water heater. You don’t require a hot water cylinder as they heat water on demand when a tap is turned on. A system or regular condensing boiler, also known as a sealed system, provides central heating and hot water with the use of a storage cylinder. Heat only boilers work in conjunction with a hot water storage cylinder and cold water top up tanks to provide both central heating and hot water.

Since April 2005 the building regulations state that any new boilers installed must be condensing. Condensing boilers are cleverly designed to give higher efficiency compared to standard boilers. With ordinary boilers, gas goes through the heat exchanger, burns, heats the water and is then dispelled into the atmosphere through a flu which is like a chimney. With a condensing boiler, there is a second heat exchanger. After going through the first one, gas fumes are formed. Those fumes then go through the second exchange and are recycled to produce more heat. In other words, one is getting twice the amount of energy from the incoming source that would be possible with a standard boiler. Because of this feature modern condensing boilers have a lower workload so a lot less effort is needed to produce heat and hot water.

Condensing boilers have various features, sizes and are available in models that use gas, LPG and oil for fuel. By their ability to reclaim heat, that would otherwise be lost to the environment, they add to the over-all concept of a 'green planet' by reducing carbon dioxide emissions going into the atmosphere.

Combi boilers

The condensing combination boiler is by far the simplest form of central heating and is the most popular type of boiler in the UK, now found in around 70% of homes. Combi boilers provide central heating and hot water without the need for a separate tank to store water; hence you can easily tuck them away under the stairs or in kitchen cabinets.

They are most suited to homes with one bathroom, households with single people, couples, families with one child. Benefits are that you get instant hot water combined with heating your radiators and they are very compact which make storage easier if space is limied. The disadvantages are that you can't run mulpiple showers or baths at the same time. Usually available in following outputs: kw 24 30 35

System boilers

A system boiler which is also known as a 'sealed system' provides central heating and hot water via a storage cylinder housed in an airing cupboard. These are the best choice for homes with more than 2 bathrooms or if your mains pressure is low.

Benefits are that you get a high flow rate for domestic hot water. There is no need for water tanks in the loft, as with an open vent boiler. You can use more than one hot tap or shower at same time. The disadvantages are that the water is not instant as the full water cylinder needs to be heated first. Once the water in the storage cylinder runs out you have to wait for it to reheat and you need to have space for the cylinder. Usually available in following outputs: kw 12 15 18 24 30 38.

Open Vent Boilers

Open vent boilers are also known as heat only systems. They provide provide central heating and hot water via a boiler, a storage cylinder housed in the airing cupboard and water tanks in your loft. They are suited for larger homes with an existing open vent boiler system.

Advantagtes of open vent boilers are that you have a high flow rate for domestic hot water. You can run two showers or run two taps at the same time. On the down side once the water in the storage cylinder runs out you have to wait for it to reheat and as well as space for the cylinder there needs to be room for the bulk feed and expansion tanks. These are normally placed in the loft. Usually available in following outputs: kw 12 15 18 24 30 38

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