Boiler Types
Combination Boilers
Combination or popularly known as combi boilers are often confused with condensing boilers. You do NOT have to fit a combi boiler under the Building Regulations, but you DO have to fit a condensing boiler.
Combi boilers heat the hot tap water as it is used. The main difference is that the hot water for the taps is fed directly from the mains rather than from a hot water storage cylinder. In contrast, non-combi boilers heat a tank of hot-tap water and store it ready for use later.
The big advantage with a combination boiler is that it not only delivers continuous hot water, but more importantly delivers it at mains pressure too. So with a combi system you can have a really effective shower without needing an expensive booster pump.
Installers often recommend combi boilers because they are quicker, cheaper and easier to fit than non-combis, mainly because here are no tanks to supply and fit. It is often not mentioned that they are also more complex and prone to breakdown than non-combi boilers.
Combination Storage Boilers
By adding a storage tank to a combi, the problems of flow rate reduction are progressively overcome, depending upon the size of the tank. You can use a couple of taps simultaneously, without an unacceptable drop in performance.
The advantage of this system over a conventional boiler and storage tank is that the hot water never runs out. Hot water is always there as a combi storage boiler doesn't need time to recover before you can use it again.
Boiler Scrappage Scheme: Boiler Types
Condensing Boilers
Condensing boilers are a type of boiler that extract more of the heat energy in the gas (or oil, or any other fuel) than non-condensing boilers and turn it into useable heat to warm your home with. This means they burn less gas for the same amount of heating, leading to slightly lower fuel bills and slightly less carbon dioxide emitted by the boiler into the atmosphere.
It is known as a Condensing boiler because the water from these flue gases 'condenses' in the secondary heat exchanger and drains away at the bottom of the boiler.
Condensing boilers have now been made compulsory by the Building Regulations (with a few limited exceptions) when you replace a domestic central heating boiler. Purchase of A rated for energy efficiency condensing boilers will be eligible for the £400 incentive Boiler Scrappage Scheme incentive payout.
Conventional Boilers
In a conventional boiler gas jets place onto a cast iron heat exchanger through which water passes to be heated. If used to supply taps, hot water cannot be provided on demand but must be stored, usually in a copper cylinder.
This type of boiler has relatively simple controls and tends to be more reliable as less can go wrong. Energy consumption can be high but the cost of this is moderated by the low maintenance costs. They are versatile in that they can be used in almost any type of property and can be pumped or gravity fed.
System Boilers
Like conventional boilers, a system boiler can provide central heating and hot water from a cylinder if required. The key difference with a system boiler is that all the major components are built in to the boiler. For example the pump, normally installed remote from the boiler, in built in; so is the expansion vessel, which replaces the feed/expansion tank often installed in the loft.
With these components built in installation time is reduced significantly, fewer materials are required, costs are reduced and servicing is simplified. System boilers also facilitate a dry loft.
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