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System Design
OUTLET SITING
Flue terminations for solid fuel & oil are subject to EN15287-1 2007. Figures A and B illustrate
recommendations for the most commonly encountered outlet terminations. Flue terminations
for gas in domestic situations are governed by the BS5440-1 2008 Section 4.2. Figure C
illustrates recommendations for the most common siting situations encountered. Adjacent
taller structures may require increased height. The minimum flue projection through the roof is
600mm to the underside of the terminal.
FLUE ROUTING
The chimney should remain as straight as possible through its vertical run to assist flow. Should
it be necessary to offset a chimney run the following guidelines should be adhered to:
It is recommended that a vertical rise of 600mm should be allowed immediately above the
appliance before any change of direction.
Within a system, on all fuels, there should be no more than 4 changes of direction of maximum
45°.
90° Factory made bends or tees within the system may be treated as being equal to two 45°
bends (see Document J of the Building Regulations issued October 1st 2010).
TERMINAL TYPES
On solid fuel appliances, an open termination is normally recommended. However in certain
conditions, rain caps or anti-downdraught terminals may be used.
Rain caps and anti-downdraught terminals are available in two versions, with mesh/spark guard
and without mesh. Where a terminal with mesh is used, there is a risk of soot build up, and
therefore regular cleaning is required to avoid blockage, particularly when using oil or solid fuel.
PROVISION FOR SWEEPING, CLEANING AND MAINTENANCE
Provision should be made for inspecting and cleaning the chimney. To aid cleaning, sufficient
distance should be left between changes of direction to permit the safe passage of cleaning
brushes within the system. This is particularly important on solid fuel applications. It is
recommended that chimneys serving solid fuel appliances be swept as frequently as necessary
but at least twice a year. Choose an access component suitable for your installation unless
cleaning/inspection can be done through the appliance.
