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Multi-site HVAC: ‘You put it where?’

Buderus technical liaison officer Pete Mills looks at boiler siting issues for the larger home
Multi-site HVAC: ‘You put it where?’
DURING the last 15-20 years we have seen considerable change in the demographic profile of the nation. A rise in the number of single parent families, the growth in demand for single occupancy accommodation, and the continual rise in property prices has meant a increase in popularity for smaller one- and two-bedroom homes or apartments. At the other end of the scale we have seen rising wealth in the family, and an increase in the number of millionaires which has spawned an increase in five- and six-bedroom family homes and luxury “designer” properties for today’s wealthy footballers and the like.

For these larger homes in particular, money is readily available for all mod cons and luxury features – from swimming pools to home gyms and snooker rooms for example.

Of course all these extra facilities mean an increased demand on central heating and domestic hot water provision, and many such homes require larger output boilers which would be equally at home in commercial buildings.

Boilers, such as the wall hung Buderus 800 or GB162, are more than capable of meeting this level of heat demand with outputs of 43kW and 60kW for the 800 and from 80kW to 100kW for the GB162 range.

Although of a higher output, the larger boilers are still relatively compact and designed to look more like their purely domestic counterparts than large industrial boilers which, in Buderus’ case, can have outputs up to 19,200kW.

Nevertheless with larger domestic boilers, location can be an issue.

While suitable in looks and operational requirements for wall mounting in a utility room, they would not generally be considered for kitchen siting, even though the 800 and GB162 are extremely quiet in operation.

In fact fluing is a key determinator of larger boiler siting. The higher the output of the boiler, the more pluming there will be, as the condensing boiler extracts the latent heat from the flue gases and the exhaust gases reach the dew point and condense on contact with the atmosphere. No longer are these large properties necessarily set in acres of countryside, but many can be in close proximity to each other (such as large town houses in major cities) and in these situations, fluing can exhaust into restricted spaces.

This can cause condensation to fall on neighbouring properties which brings problems to other residents. In addition the products of combustion in the flue gases will stay around longer in a confined area - making things worse. And with more fan power on larger boilers, the flue gases tend to be projected over a wider area, potentially making the problem with the neighbours even worse.

While horizontal fluing tends to be the norm in the UK for domestic housing, generally in Europe this is not the case and vertical fluing has been preferred for many years – perhaps this is because Europe has generally used condensing boilers for around 25 years and has therefore found vertical fluing to be a sensible way of avoiding difficulties with pluming.

Certainly Buderus recommends vertical fluing for larger installations where properties are quite close to each other and consider this as best practice wherever practical.

Flue outlet positions are of course covered in Building Regulations Part J, which also covers considerations of the building, and BS5440 Part 1. However vertical fluing overcomes many these issues and should ideally be planned at the design stage. Locating the boiler in the garage or separately designated boiler room is the ideal solution as vertical fluing is then a relatively simple matter, eliminating complex routing. Of course the terminal position must comply with regulations – and best practice – to discharge away from neighbours.

Another issue which can affect boiler siting is the length of run required from the gas main to the boiler. Although this is not usually a problem with the average home, lengthy runs create difficulties in larger houses as the gas supply has to be sufficient to meet the maximum demands of the boiler.

This problem has been recognised and alleviated somewhat as recent changes now allow 35mm gas supply pipework (compared to the previous 28mm) to be used in domestic properties. Where the installation volume does not exceed 0.035m2 and the meter is no larger than a U16/G10, IGE/UP/1B Ed 2 can be used by domestic installers, as the testing and purging standard.

Domestic ACS qualifications permit installers to install boilers up to 70kW input before having to gain commercial ACS qualifications. This will often give the domestic installer sufficient scope to meet the requirements of larger domestic homes in preference to complex installations of say two or three separate smaller, principally domestic, boilers, where space is limited.

Boilers ideally suited to these larger domestic properties are available – and with the new regulations, installers previously limited to smaller installations can now consider larger homes as a normal part of their target market.

Buderus T:01905 752936
1 July 2007

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