BOILERS & BURNERS


PUTTING FLUE AND FLUE TOGETHER By Alan Mason of Keston


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ne of the most common and certainly the most frustrating challenges faced by installers relates to flue termination and the stringent regulations


regarding safety, environmental issues and neighbouring properties.


What are the main problems with flue termination?


A major problem with flue termination occurs when boiler location options are limited, which is often the case in converted premises and listed buildings. In many cases, during an installation, there is no outside wall nearby for flue termination or the boiler must be sited a long distance from the flue outlet for aesthetic reasons. There are also strict regulations concerning pluming proximity to neighbouring properties and if being fitted in a void. Further issues are encountered in applications such as listed buildings where the boiler siting options are limited and the work must comply with strict criteria outlined in the Planning (Listed Buildings and Conservation Areas) Act 1990.


How do you overcome problems with flue termination?


One of the most effective solutions available for problematic installations is a twin flue boiler. Although both twin flue and concentric flue boilers function in the same way insofar as both require an air intake pipe to draw air inside the boiler, and an exhaust pipe to remove the burnt waste gases, a twin flue design allows longer flue runs – with a possible extension of up to 27 metres - thereby expanding the options available for boiler siting. Modern appliances are capable of flue runs up to 21 metres from the boiler from an elevation of 1.5° (or 21 metres and around 3.5° for a heat only model.) Consequently, these boilers can be easily installed in rooms that are not located near an outside wall and in challenging locations such as basement rooms, offering one of the most adaptable solutions for applications where flue termination might prove troublesome, and minimising downtime is a priority. This is great news for installers, who can take advantage of this growing market by


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offering a boiler solution for any type of project, even the trickiest of installations.


What about for commercial and light commercial applications?


For applications that require larger outputs, these Heat 45 and 55 twin flue boilers can be installed on specially designed frame and header kits in cascade. These kits can facilitate up to six boilers in cascade and they not only make installation easier, they also incorporate controls like outdoor sensors for weather compensation, delivering additional energy saving benefits as the flow & return and the low loss header in the kit are pre-insulated which improves efficiency and reduces heat loss, as well as reducing installation time.


What are the differences between domestic and commercial applications?


There are important differences in the legal requirements of flue termination points when comparing domestic, light commercial and commercial installations. These relate to the significantly higher boiler outputs required in commercial applications and are outlined in the Clean Air Act, which contains specific measures designed to minimise air pollution from chimneys and flues. Guidance is contained in BS 6644 or IGEM UP10.


Domestic installations refer to boilers installed in private residences and have relatively low output requirements - In general terms a domestic boiler has a range up to and including an output of 70kW net. Guidance is contained in BS 5440. Commercial installations refer to boilers above 70kW. For example if you had a 70kW net boiler this would be deemed to be a domestic appliance but if you had two 40kW boilers connected to the same system, this would then be classified as a commercial installation because the total net output is greater than 70kW. Similarly, the type of property will also give bearing on whether a domestic or commercial installation irrespective of output. In the boiler industry, the description ‘light commercial’ covers the output requirement for buildings that are used for


ENERGY MANAGER MAGAZINE • MARCH 2016


commercial purposes but are not so large that they can only be served by high output boilers from manufacturer’s commercial ranges. Typical light commercial applications include B&Bs, pubs, restaurants, banks. leisure centres, GP surgeries, schools and smaller office buildings.


Will an installer need extra training?


Although it may be worth installers investing in training in twin flue boiler installation, the good news is that special training is not obligatory; in order to install twin flue boilers, an installer needs just the normal gas safety certification and the ACS CCN1 (Core Gas Safety) and CEN1 (Central Heating Boilers).


To ensure that they are recognised as competent to carry out boiler installations above 70kW, or to install and commission commercial boilers, installers will need to obtain the necessary core commercial qualifications. This includes ACS (COCN1), which covers safety regulations, flueing and ventilation however, appropriate conversion courses are also available.


Regardless of boiler output, some obvious considerations need to be made when designing flue runs. These include ensuring that the flue is not broken or constricted and is adequately suppported at any point in its length so that it can effectively transport products of combustion from the boiler to the building’s exterior. Rules applying to the inspection of concealed flues are also relevant to both domestic and commercial installations. Major changes were outlined in the 2010 Building Regulations to ensure flues can be thoroughly checked to aid the early detection of any areas where flue gases could escape – thereby improving industry safety standards and minimising any risks involving carbon monoxide. In all buildings, inspection hatches are advised to be roughly 300mm x 300mm and, wherever possible, should be positioned within 1.5m of any joint in the flue system.


Further information and guidance can be found in Part J of The Building Regulations.


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