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Since 1969 SFL have been leading the way
Fig 1 A
chimney is an integral part of the heating system, responsible for safely conveying combustion products to the atmosphere. The chimney type is
determined by the application and fuel used, and is designed in accordance with national standards and regulatory documents. The SFL commercial chimney range is designed and manufactured to meet the exhaust gas requirements of specific fuel types in given situations, each flue system is tested up to and beyond their design limits to provide reliable performance statistics upon which project calculations can be based.
In the residential sector, the design and installation of chimneys and flues follow Approved Document J. However, the commercial sector lacks a direct equivalent, prompting the BFCMA to release a Commercial Flue Guide. This guide addresses chimney principles, regulations, design, height considerations, and compliance with the Clean Air Act, aiding in the selection and installation processes for commercial applications. With the introduction of EN1366-13, chimneys now have an official test to assess the fire resistance of both the product and penetration components when passing through a fire rated compartment wall / floor etc. Both SFL products, Europa Plus® and Nova® (100-350) are tested to EN1366-13.
Fig 2
Proper insulation is crucial for optimal chimney performance. The SFL EUROPA® family includes high-pressure, twin-wall systems that can endure continuous temperatures up to 600°C ideal for applications ranging from coffee roasting machines to datacentres. These systems feature a stainless steel inner and outer case, along with high density insulation, ensuring efficient installation across various configurations. Europa Plus is also available in 25mm, 50mm and 100mm insulation thicknesses, where the potential for accidental contact and clearances to combustible materials are critical. Always look for the CE mark and the upcoming UKCA mark, which confirm compliance with stringent product standards. For System Chimneys the product must be CE marked to BS EN 1856-1 and type tested to the products performance classification as detailed under BS EN 1443 – Chimneys – General Requirements.
Fig 3
Chimneys traditionally operate under negative pressure, but many now function under positive pressure conditions. Understanding the chimneys performance designation system to BS EN 1443 helps in selecting the appropriate chimney for condensing and non-condensing appliances. SFL’s NOVA® twin-wall, insulated stainless steel chimney system, is suitable for condensing and positive pressure applications and is specifically designed to meet the demands of the latest high-efficiency heating appliances as well as traditional gas and oil-fired combustion equipment. SUPRA® is SFL’s single wall stainless steel chimney system designed with the commercial installer in mind. Pre-fitted seals make it a go-to product for many commercial condensing and positive pressure applications.
In many installations these two systems can be combined, such as in a recent educational building case study (Fig 3), where the existing chimney system had passed its life expectancy.
14 BUILDING SERVICES & ENVIRONMENTAL ENGINEER NOVEMBER 2024
One of SFL’s premier turnkey solution providers, JRF Chimney Specialists, successfully installed a 250mm Nova® and Supra Plus® chimney products to replace the existing chimney systems. The Nova (100-350) systems is EN1366- 13 tested and SUPRA® is an engineered system capable of meeting the demands for condensing and positive pressure applications, so the perfect combination.
The Supra® chimney system can be used for many varied applications, for example for efficient Spray Booth ventilation (Fig 4). There is no such thing as an off-the-shelf solution –as buildings vary too much in structure. SFL’s technical team can work with you on the most effective solution for Spray Booths in school science and DT laboratories, Colleges or Universities as shown in this recent project where SFL’s premier turnkey solution provider, FBS Flue & Chimneys choose the Supra® 500mm diameter chimney system, complete with roof-mounted galvanised jet cowls for the installation of two state-of-the-art Nukeson Wet Spray Booths. The project was a successful collaboration between King Welsh, FBS Flue & Chimneys, Tarc Solutions, Eco-Nexus and University of Plymouth.
Flue routes should ideally be straight and vertical, minimizing bends that can hinder performance. For natural draft appliances, a vertical rise of 600mm before any change in direction is recommended. Additionally, flues should allow for easy cleaning, particularly at bends, using swept elbows with inspection points. As shown in this recent project, the route taken by the flue can have a significant impact on performance. The straighter and more vertical the chimney the better. In all cases a chimney sizing calculation should be undertaken to EN13384-1/2 to verify the performance of the installation.
Chimneys require proper support throughout their length, maintaining safe distances between chimney and combustible materials is crucial. When entering a masonry chimney, flue pipes should ideally incline upwards at 45°. It is essential to choose a flue diameter that matches the output from the appliance, and this should be further verified by the sizing calculation An adequate air supply is also required for the appliance to operate safely and efficiently.
The purpose of the Clean Air Act and the Environmental Protection Act regulates how flue gases can be dispersed, and the Clean Air Act Memorandum is one solution used to calculate the required height of a chimney. Chimneys must terminate where combustion products can disperse safely without causing harm. Chimney height is one of the main characteristics used, by local authorities, to control the discharge of emissions into the atmosphere.
The required discharge height is calculated to minimise the impact of emissions into the environment and not be prejudicial to public health. The calculations used to determine the chimney height considers the type of fuel, the maximum rated input of the appliance, topography, environment and proximity to other buildings.
A good case study for this can be found in a recent project in Edinburgh (Fig 1). Along with SFL, JRF Chimney Specialist were asked to recommend a solution to improve the existing exhaust system, the current discharge location was causing issues with air quality for the higher surrounding buildings.
Fig 4
By relocating the termination location to ensure it discharged above the higher adjacent buildings, the Flue and Chimney specialists, JRF successfully enhanced the safety and efficiency of the system as a whole, while ensuring compliance with the Clean Air Act requirements.
The discharge velocity of the emissions from a chimney is another important factor in determining how readily emissions are dispersed. The higher the discharge velocity the better the dispersion rate. Adjacent buildings can also have an impact on the required chimney height and must be taken into consideration when calculating the chimney height. The objective is to achieve an effective and safe chimney discharge height, rather than a minimum discharge height.
Condensation can occur even in well- designed flues. Systems should be designed to drain any condensate effectively, following manufacturer guidelines.
Mechanical extract fans can address design challenges in flues and should be controlled by combustion flow switches to ensure safety in case of draught failure. Fan sizing must consider installation specifics.
Twinning boilers into a common chimney manifold requires competent design and installation in accordance with BS EN 13384- 2:2015+A1:2019, and may require local authority notification. Biomass appliances should not be combined with gas or oil flue systems. Concentric chimneys can mitigate downdraught issues and must adhere to specific installation requirements in accordance with the appliance manufacturers installation guidelines.
In summary, selecting and installing flues and chimneys involves careful consideration of materials, design principles, and regulatory compliance. Adequate insulation, proper sizing, and attention to detail in construction and termination are critical for safety and efficiency. SFL are committed to offering industry-leading technical support, throughout the complete process of design, manufacture, and supply of every project. Our experienced team are on hand to assist at every stage of the process. From initial product selection to flue routing and calculations. From complex header configurations to large-diameter stacks, we can accommodate every requirement for any application.
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