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Boiler Systems - System Boilers 

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 What is a System Boiler?

 In a system boiler, cold water enters the boiler directly from the mains supply.
The water is heated via a heat exchanger, which transfers energy from the gas jets to the water.
Once heated, the water is pumped to the hot water cylinder, where it is stored until required. 

worcester bosch range of boilers

What is a system boiler UK?
A system boiler is a closed system that only requires a boiler and a cylinder, whilst a regular boiler requires header tanks in the loft to feed the hot water cylinder and to maintain the water level in the radiators.

Is a system boiler the same as a regular boiler?
Because of the separate hot water storage cylinder, it is easy to mistake a system boiler and a regular boiler (also commonly known as a conventional or traditional boiler). There are, however, some fundamental differences.
A system boiler is a closed system that only requires a boiler and a cylinder, whilst a regular boiler requires header tanks in the loft to feed the hot water cylinder and to maintain the water level in the radiators. For this reason, system boilers are often the preferred choice unless there are specific reasons why a regular boiler may be more suitable, such as in areas with low water pressure or homes with older radiator systems that would be unsuitable for the higher pressure of a system boiler.

How much space does a system boiler need?
One of the most important considerations when considering a system boiler is whether you have sufficient space. If your house has been built with an airing cupboard, this can be the ideal place to house the hot water cylinder - but be aware that you will lose the use of this space as a storage space. Remember, you will also need to account for the additional space required by the cladding. As system boilers do not require header tanks to be fitted in the attic, they are suitable for homes with no loft space or where a loft conversion has been done or is planned.

How efficient are system boilers?
With condensing technology, the boiler itself is extremely efficient, with many models achieving up to 90% efficiency in optimum conditions. A very important consideration with a system boiler is the potential for heat loss from the hot water cylinder. To combat this, it is important that your cylinder is properly insulated for maximum efficiency. Because all taps and showers will receive near instant hot water at the same pressure, a system boiler can also help optimise your home's water consumption.

Can a system boiler run out of hot water?
The only limitation to the amount of hot water a system boiler can supply is the capacity of the hot water cylinder. If all the hot water is used, you will have to wait for more to be heated. This is usually on a set timer. To guarantee sufficient water, it is recommended that you consider how much water is likely to be used at any given time for things like showers, baths and taps when sizing your cylinder. Be aware, however, that in many cases the size of cylinder you choose will ultimately be dictated by the space available.

Are System Boilers any good?
System boilers are more expensive to buy initially than combi boilers, however they have better reliability. Less efficient when heating the hot water tank as water is not heated and used at the point of demand.

What cylinder do I need for a system boiler?
As part of a system boiler installation, you should however turn to an unvented cylinder. Unvented cylinders take their water supply directly from the mains, rather than a tank, which allows for stronger flow rates and a much lower risk of water contamination.

How many radiators will a 30kW system boiler do?
How Many Radiators Can a 30kW Boiler Run? For combi boilers, sizes from 28 to 32kW can keep between 10 and 15 radiators nice and toasty. On the other hand, 30kW heat only and system boilers can heat 15 to 20 radiators, making them the ideal choice for running larger properties.

What happens if a boiler is oversized?
Oversized boilers 'cycle' on and off excessively, i.e.,
they heat up too quickly, run for short blasts and then turn off because they are too hot. Each fire up is something close to full capacity which dumps a huge amount of heat into the system and overheats the radiators.

should i turn my radiators off?
Should I turn radiators off in unused rooms?
You will almost certainly be able to save money by turning your radiators off in individual rooms that are not in use. It is a waste of money and energy to be heating unused spaces. Also, close the doors to any unheated rooms to help stop the warm air from the heated rooms or spaces escaping into the colder ones.
The only problem if you turn off the heat in an unused room it can cause damp. Photographs, bedding and other items in the room can start to mould.

worcester system boiler 

ask dave tells you what a system boiler is
When costing out your new boiler  you will need to know what brand and size of System Boiler. Gathering in several quotes from Gas Safe Engineers is good finding an Engineer you can work with is very important.