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4.6 Flue Requirements
A natural draught must exist in the boiler when
connected to the flue and this will be checked by the
Commissioning Engineer before the burner is run. If this
is not the case then the customer must take the necessary
measures to ensure a draught like increasing the flue
height or fitting an anti downdraught cowl.
The proper draught conditions in the flue is critical for the efficient working of wood pellet
boilers. TR Engineering Ltd recommend that it’s Therminox range of stainless steel twin-
walled insulated flue pipe is used with its “TR Engineering Ltd” boilers. A draught
stabiliser is fitted as standard to the short section of flue pipe that connects to the boiler.
This will help stabilise draught in average wind conditions. The flue can exit the boiler
house/garage through the roof or through the wall by using a bend on the flue. The
following diagram indicates recommended flue layouts. Installation must comply with the
current Building Regulations and local by-laws and it is the Installers responsibility to
ensure that the flue is installed safely and to the appropriate regulations.
In order to avoid down draught, the chimney or flue must terminate in a position at least
600mm higher than the highest point on a roof, tree or building within a distance of
9 meters (30 ft.). Down draughts will affect the performance of the boiler and may cause
some of the safety features to come into operation.
Down Draught:
If the proper flue height cannot be achieved the commissioning engineer may refuse to
commission the boiler. Whenever possible, the flue should terminate above the apex of the
roof; if this is not possible, use a cowl that is specified as anti-downdraught by the cowl
manufacturer. Use as few bends as possible but when necessary 135º bends are
recommended. In cases where the boiler is commissioned with a lower height flue the
necessary draught conditions are achieved on the day of commissioning, the customer
must sign the Commissioning Report stating that any issues arising from the flue not to the
required height will not be covered under warranty.
NOTE: Read and follow all of the flue pipe manufacturers’ instructions on the
proper installation and support of the flue pipe. Adhere to all clearances.
Reference : BS EN15287-1:2007; Chimneys – Design, installation and
commissioning of chimneys; Part 1: Chimneys for non-room sealed heating
appliances
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