The new UK Annex to BS EN 15287-1, the European installation standard for flues and chimneys, has introduced the most radical changes to the guidance on flue installations for biomass applications, for many years. The UK Annex outlines a number of alternative installation methods. Dennis Milligan explains the changes
One of the most significant alternative installation methods in the Annex increases the length of the horizontal flue that can be installed through a wall from 150mm to 450mm. This will simplify the connection through the wall to an external flue. However before the installation can be used certain conditions have to be fulfilled:
- An appliance that is Defra exempt or alternatively one that is limited to burning authorised smokeless fuel must be installed.
- A flue flow calculation in accordance with BS EN 13384-1 must be carried out. This should confirm the safe operation of the proposed installation configuration. The results of the calculation should be left with householder along with appliance installation instructions.
- The total length of the single wall connecting flue pipe must not exceed 1.5 metres.
- The appropriate distances to combustible materials from both the appliance and the connecting flue pipe must be maintained at all times.
Other significant changes in the annex include widening the use of stainless steel twin wall flues. They can now be used to reline an existing chimney shaft and be used as a connecting flue pipe; connecting directly to the appliance. The use of a twin wall flue to connect directly to the appliance will significantly reduce the required distance to combustible materials. The minimum distance from the appliance before any change in flue direction is allowed has been set at 600mm. When a single wall connecting flue pipe it is now recommended that the lower end of the twin wall chimney should extend a minimum of 425mm below the ceiling of the room. The flue connection to the twin wall chimney must be made in the same room as the appliance. To be certified as a CE approved system all the chimney the components used with a flexible liner must have been tested with the flexible liner and also be CE approved. Failure to use CE approved components will invalidate the manufacturer’s guarantees. In Document J, the recommended operational temperature range for a flue is between 150°C and 450°C. The upper temperature has been reduced to 400°C in the new UK Annex. It also explains the purpose of the new corrosion resistance category for burning wood under dry conditions.
The new UK Annex also suggests alternative ways to facilitate the visual inspection of enclosed stainless steel flues in voids, as required by Document J. Where practical, the length of the chimney may be inspected by the removal of the firestop or register plate or by looking down from above in the roof space, possibly with the use of a camera. Where impractical a 100mm square access door should be created to allow the inspection using a torch and mirror. When the installation of the connecting flue pipe is completed, an inspection should be carried out to ensure that all joints have been properly made and that all supports and clips are properly located and secured.
The latest version of Document J was published before the new UK Annex was written so it was not able to incorporate the new alternative installation methods in the document. However through the Frequently Asked Questions section of Document J the advisory document now recognises the new alternative installation methods introduced in the latest edition of the European Standard for the Installation of Flues and Chimneys. This removes any grey issues in working to this standard.
The British Flue and Chimney Manufacturers Association (BFCMA) has produced a new guide, entitled General Guidance on the Selection and Installation of Flues and Chimneys for Wood Burning and Multi Fuel Appliances in Residential Properties. This document gives clear guidance on how to install a flue in accordance with the new installation standard. It also clearly shows how the new guidance differs from Document J. The guide also provides straightforward guidance on the types of flue required for different appliances and fuels.
The guide can be viewed and downloaded from the BFCMA website, www.bfcma.co.uk
The new UK Annex to BS EN 15287-1 was published in the autumn of 2013 and the Frequently Asked Question in Document J was published at the start of 2014.
The BFCMA is the UK’s only trade association representing manufacturers and sole distributors of factory made chimney and flue products. It was established to promote the advantages of chimneys and encourage continued improvements in standards, efficiency and service.
// The author is the vice president of the British Flue & Chimney Manufacturers Association //