What different types of boilers are there?
Which boiler do I need?
Natural Gas Boilers
Natural Gas is a clean fuel, burning with by-products of steam and carbon dioxide and of all the fossil fuels has the least damaging effect on the environment. It is also the most popular fuel choice for domestic central heating systems.
Natural gas boilers can provide instant hot water and controllable heating to your home. The natural gas is fed from the mains directly into the property and because of this, no storage or ordering of fuel is required, it is also currently the cheapest option in terms of running costs.
Unfortunately however it is not always available to everyone, this is usually down to the location of your property, and you would need to use one of the alternative options (please see below).
It is required by law that gas boilers installations MUST be carried out by a Gas Safe registered engineer (NB. Gas Safe have REPLACED Corgi).
LPG (Liquefied Petroleum Gas) Boilers
For homes that do not have the option of mains fed gas, Liquefied Petroleum Gas (or LPG) is one of the alternatives. Unfortunately it is considerably more expensive to use and requires a storage tank, or alternatively can be provided with replaceable cylinders.
Some natural gas boilers can also be converted to LPG with the appropriate conversion kit, which helps widen the small selection of LPG boilers that is currently on the market at the moment.
It is a legal requirement for installations of all LPG boilers to be fitted by a Gas Safe registered engineer (NB. Gas Safe have REPLACED Corgi).
Oil Boilers
Oil boilers are the more popular alternative to natural gas boilers. They are not the cheapest alternative however they are a competitive option. One of the advantages is the flexibility to change suppliers, helping to keep costs down, however oil is not the cleanest fuel and is regarded as less friendly to the environment.
Oil boilers require a storage tank and should be installed by an OFTEC registered engineer.
Electric Boilers
Although an easily available option to meet your heating needs, electric boilers are ranked as the most expensive for heating, however it is still the second most popular choice after natural gas.
To the end user it is 100% efficient as no heat is lost through the burning of fossil fuel, and because of this there is no need for a flue either, however in contrast, the majority of the country’s electricity is produced by power stations through the burning of fossil fuel, so this is where the environment is affected.
Combination Boilers (Combi Boilers)
The combi boiler is ideal for smaller homes with less than 2 bathrooms, or properties that have a low demand for hot water.
Accounting for over 50% of newcondensing boiler sales, the combi boiler is the most popular choice of boiler in the UK. This type of boiler is a great space saver as it does not require a separate water tank, heating the water directly from the mains through a heat exchanger within the boiler.
These boilers are compact and highly efficient with hot water essentially an endless supply, however the use of several outlets at the same time can reduce the flow rate at each.
Conventional Boilers (Heating Boilers)
Conventional boilers (or Heating boilers) are more suitable in larger homes with higher demands on the hot water, or in an area with low water pressure.
It is the more traditional system and works from the basis of heat only. It requires a hot water cylinder and a cold water storage cistern to feed the cylinder. The flow rate for this type of system tends to be higher, allowing the use of several outlets at the same time without the reducing the pressure. However because of the extra components required, this system uses more space than the others.
System Boilers
The system boiler (or sealed system boiler) is also ideal for homes where there is a high demand for hot water. It has many of the components for the hot water system built in to the boiler, making installation easier.
The system boiler is a pressurised system that is mains fed and normally fitted in conjunction with an unvented hot water cylinder. It also has the capacity to deliver water to several outlets without a reduction in pressure.
Storage Boilers
Storage boilers are ideal for homes with more than one bathroom, it has a compact design for easy installation, however it is less energy efficient than the combi boiler.
The storage boiler is basically a boiler and cylinder rolled in to one unit. It supplies both central heating and hot water in a similar way to the combination boiler, however because it has a built in cylinder it is able to keep a higher flow rate when more than one outlet is in use.
Commercial Boilers
Commercial boilers are ideal for large properties or buildings that require a larger heat output than the standard boiler can provide.
Commercial boilers are usually sealed system boilers, and require an expansion vessel and pressurisation unit to accommodate water expansion.
Flues
Apart from the electric boiler, all indoor boilers require a flue kit to vent waste gases from the property. The waste gases consist mainly of carbon dioxide and steam and can be harmful if not extracted correctly.
Various different flues are available, depending on the type of boiler you have and where it is located in your property. It is strongly recommended that you speak to your plumber or fitter as to which flue you need.
SEDBUK Ratings (Energy Efficiency Bands) & Rating Scale
Seasonal Efficiency of Domestic Boilers in the UK - or SEDBUK - was created under the Government's Energy Efficiency Best Practice Programme. Its purpose is to provide a rating for the efficiency of a boiler, taking into account factors such as climate, type of boiler, fuel type used, and applying them into a scale from A to G.
SEDBUK scale bands A and B are awarded to boilers deemed as highly efficient, while the bands C to G only have a standard efficiency. To install a band C to G boiler you need to apply to your local council for permission.
As from 1 April 2005, the legislation in England and Wales stated that all new gas boiler installations MUST be condensing boilers rated SEDBUK band A or B. As from 1 April 2007 the same legislation was applied for oil-fired boilers.
SEDBUK Rating Scale
- BAND A: 90% - 91.3%
- BAND B: 86% - 90%
- BAND C: 82% - 86%
- BAND D: 78% - 82%
- BAND E: 74% - 78%
- BAND F: 70% - 74%
- BAND G: Below 70%
Which boiler do I need?
1. Traditional open vented boiler with gravity domestic hot water heating and pumped central heating
In a traditional open-vented boiler, the system is fed with water and kept under pressure via gravity-fed water from a tank in the loft. The hot water cylinder is heated via a gravity hot water circuit from the boiler, and central heating via a pumped circuit from the boiler.
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2. Open vented boiler, with fully pumped central heating and domestic hot water
Standard open vented systems have a single pumped circuit for both hot water AND central heating, hence the system is "fully" pumped.
The open vented system has become the preferred option for most installations, be it newbuild or replacement. The control over domestic hot water heating and faster heating has lead to better system performance and efficiency.
3. Sealed system boiler, with fully pumped central heating and domestic hot water
The sealed system is increasing in popularity due to the elimination of the system water feed tank and open vent pipework in the loft. The system is fed and pressurised with water direct from the mains, then sealed. This simplifies installation and reduces maintenance requirements in the loft, and can reduce installation cost.
A conventional tank-fed indirect hot water cylinder can be used, however if a mains pressure unvented domestic hot water cylinder is used then all tanks/pipework are eliminated from the loft.
This eliminates the risk of freezing pipes in the loft. The customer also clearly benefits from the provision of increased flowrate mains pressure domestic hot water to all outlets.
4. Sealed system boiler, with fully pumped central heating and instantaneous domestic hot water, using a combination boiler
As above, this system has increased in popularity due to the elimination of all water tanks in the loft, and also the domestic hot water cylinder. Hot water is heated instantaneously, on demand, by the boiler.
This eliminates the need of a hot water cylinder, allowing for more cupboard space. It also eliminates possibility of freezing pipes in the loft.
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