Common Sense Flue Systems.

Common Sense Flue Systems.

Flexible flue options are essential for many non-domestic applications, particularly those with little or no choice regarding boiler siting. Here we take a look at some of the legislative requirements to be considered when designing flue systems for light commercial applications.

Although many good practice guidelines apply to flue system design regardless of whether a building is domestic or commercial, there are some key differences in the legislative requirements for commercial applications.

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 at any point in its length so 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 300mm3300mm and, wherever possible, should be positioned within 1.5m of any joint in the flue system.

Importantly, there are major differences in the legal requirements of flue termination points when comparing domestic and commercial installations, which is mainly a result of the significantly higher boiler outputs required. These are outlined in the Clean Air Act, which contains specific measures designed to minimise air pollution from chimneys and flues.

First passed in 1956 and regularly updated throughout the years to reflect changes in technology, the Clean Air Act covers boilers and furnaces with an input greater than 366.4kW. This is because the levels of airborne pollutants expelled by these larger boiler installations are considered to be dangerous to the health of those in the nearby area if not dispersed at ‘high level’ – i.e. above the roofline of the building.

IGEM’s IGE/UP/10 standard, which covers the Installation of flued gas appliances in industrial and commercial premises for both room-sealed and open flued installations, outlines the restrictions on the position of flue terminations below 366.4kW and a simple risk assessment form in the standard makes it clear where these types of flue installations can be positioned.

The form contains guidance around aspects that may differ depending on the type of building and its location – such as if the building is situated close to an area where the public may gather or whether the flue is likely to cause a nuisance to adjoining properties. Another aspect to consider when designing a commercial boiler flue system is the pluming. This is certainly an issue for domestic installations as well but which can be particularly problematic with multiple boiler installations due to the higher quantities of waste gases being produced.

The increased use of condensing boilers also exacerbates this issue, because the cooler temperatures of condensing boiler flue gases make the plume more visible as steam and the gases even more likely to be blown out horizontally from the flue (or drift further below) instead of travelling up and dispersing as a result of thermal convection.

To avoid complaints from building occupants or pedestrians passing near the flue terminals, these aspects must also be considered in relation to the flue termination point.

In order to meet the various legislative requirements and recommendations regarding flue termination points (in

addition to other possible restrictions that can arise such as those relating to listed buildings), installers need to be able to offer flexible solutions. Boiler manufacturers have long been aware of the issues installers face with problematic flue runs and have developed a variety of solutions to ensure both legislation and customer requirements can be met.

One of the most flexible and reliable solutions on the market for installations requiring a complex flue run are twin flue, boiler models. Twin flues offer one of the most adaptable solutions for buildings with limited possibilities for boiler siting or flue termination. In addition, a solution that avoids drastic changes – such as the boiler having to be sited in a new location – can greatly reduce downtime, which is another important consideration for owners of commercial buildings who may risk losing revenue during a refurbishment project.

Flues for these types of boilers can be run horizontally from an elevation starting at around just 1.5°, making them ideal for use within restricted spaces, which is often the case for refurbishment projects. These types of flues can also be extended up to 21 metres from the boiler, solving numerous issues for installers whose only viable option for a termination point is located quite a distance from the boiler.

Twin flue boilers are available that can meet the higher outputs required by commercial buildings but that are also very similar in design to combi, heat-only or system domestic boilers, minimising the need for any additional training.

To simplify installation even further, installers can opt to install multiple boilers on manufacturers’ specially-designed frame and header kits, which are delivered to site with the boiler and the flow and return flexible connections pre-assembled to the header – in addition to connection pipe assembly, non-return valves and pipework connector. This means that installation can be quick, despite a more complex flue run being required.

With so many innovations now on the market, there is a boiler solution available for nearly any type of commercial building. Boiler manufacturers with expertise in twin flue boilers are well placed to assist installers in finding solutions that not only meet the requirements of non-domestic building legislation such as the Clean Air Act, but will also reduce the building’s environmental impact, increase customer satisfaction and maximise user comfort.