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London combi boiler

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Could it be time to update your old boiler? Changing to a more modern, efficient model could make a big difference to your fuel bills. But what are the different types available and which would best suit your needs?


Boiler

Installing a new boiler is a major investment and something many of us dread. Yet, as the cold weather sets in and boiler breakdown season begins, it's something many home owners will have to consider.

But despite the initial expense, the difference a new boiler could make to your energy bills and household carbon emissions is substantial. According to research by the Energy Saving Trust, if you live in an average three-bedroom semi-detached home and are upgrading from an old G-rated gas boiler (the least energy efficient) to a new A-rated boiler (the most efficient), it could save you up to £300 a year on your energy bills and cut your annual household emissions by 1,220 kg.

According to British Gas, modern A-rated boilers are up to 90% efficient compared with old-fashioned G-rated boilers, which can be as low as 70% efficient, meaning that for every £1 you spend on energy, 30P is wasted.

The average cost of replacing a boiler, including installation, is around £2,300, according to the Energy Saving Trust. However, boiler prices can vary from £650 to £1,400 depending on the brand, while installation costs will also fluctuate, depending on the work that will need to be done.

Moving your boiler, from lounge to the kitchen, for example, could add additional costs.

Conventional condensing boilers

Since April 2005 the law has required any new gas-fired boiler — whether a new installation or a replacement — to be a condensing one. The only exceptions are if it is too difficult or expensive to fit, in which rare cases an exception can be made. The same rules have also applied to oil-fired boilers since April 2007. Condensing boilers are so-called because the water vapour which is produced during combustion is condensed into water.

The good news is that condensing gas boilers are more efficient than older models because they release latent energy from burning fuel. They have two internal heat exchangers, one of which extracts heat from exhaust fumes, cutting the amount of heat lost through the flue. What's more, they emit less carbon dioxide into the atmosphere and need less power to run than older boilers.

Conventional condensing boilers that use hot water cylinders are generally more efficient at producing hot water than combination boilers. That means they are a better choice if you have a large household which uses a lot of hot water. However, you will need space in your home to house the hot water cylinder. Plus, condensing boilers need to be positioned carefully because the flue expels droplets of water while the boiler is working.

Combination boiler

Combination or Combi boilers are often installed in flats. This is because, as they don't store water in a hot water cylinder, they require less space.

Unlike conventional boilers, Combi's heat up water on demand rather than keeping it at a constant temperature in a tank, which can be more economical. If you are short for space and you don't want a big hot water cylinder taking up a lot of room, it may be worth opting for a Combi.

Similarly, if yours is a small household and you don't use much hot water, a combination boiler may be the best solution. What's more, because there's less to fit, installing a Combi is often cheaper than installing a regular condensing boiler.

However, if you intend to install solar water heating systems at some point, it may be better to opt for a conventional condensing boiler. Some Combi boilers aren't currently compatible with solar thermal systems. Plus, the temperature of the hot water produced by a Combi can fluctuate if someone in your home flushes the toilet or runs a tap while you are in the shower or running a bath.

Sealed system boiler (closed vent)

Traditionally, most domestic boiler systems are what plumbers call ' open vent'. This means that they use two water tanks in the loft and a hot water cylinder in the airing cupboard. One tank extracts water from the mains to supply the storage cylinder in the airing cupboard which in turn, once the boiler has heated the water, releases it around the home. The second tank — the ' feed and expansion cistern' — supplies water to the central heating system.

A ' closed vent' system boiler differs from this set-up because it heats the central heating system directly, as well as producing hot water for the cylinder. It doesn't need a separate feed and expansion tank in the loft — only a tank in the airing cupboard — and so, like a Combi boiler, requires less space.

It can be more expensive to switch from a traditional open vent system to a closed vent system, but it can free up more space in your home. Installation can also take less time because many of the components are built-in. What's more, unlike a Combi, you can run several taps around the home at once without losing water temperature. Sealed system boilers are ideal for larger families which don't want to lose loft space but use a lot of hot water.