BENSON 30 - Flue System Specifications

Doc No. 20-45-159 Page 11 of 60
and 2, are used as consultative documents when considering
ue requirements.
Care should be taken to ensure that the ue terminal is not
situated in a high-pressure area, the proximity of buildings
and other obstacles which will inuence this must be taken
into account, preferably at the design stage. See pages 15 & 16
Provision must be made for the disconnection of the ue for
inspection and service requirements, and it is strongly advised
that where bends are tted inspection covers are included.
The materials from which the ue is constructed must be
non-combustible, resistant to internal and external corrosion,
and be capable of withstanding the stresses and loadings
associated with normal use.
When designing the ue system the prevention of the
formation and entrapment of condensation must be a key
consideration.
Twin wall or insulated systems are recommended, as they tend
to inhibit the formation of condensates.
Where condensation is unavoidable traps should be included
to encourage the condensates to ow freely to a point from
which they may be released, preferably into a gully.
The condensate pipe from the ue to the disposal point must
be made from corrosion resistant pipe of not less than the
internal diameter of the drain pipe.
If the ue passes through a wall, ceiling, or roof made from
combustible material then it has to be sleeved so as to provide
a minimum of a 25mm void between the exterior of the ue
and the internal wall of the sleeve. The maximum permitted
temperature of any adjacent combustible material is 65°C.
The position of the ue and its terminal should be such that it
does not impair the combustion process.
It should terminate in an exposed position so as to allow the
escape and dissipation of ue gases without risk of their
re-entering the property through windows, ventilation ports,
etc. The ue should extend to at least 1m above the height of
any object within 3.5m of the terminal.
Flue terminals should be tted on all ues, the terminal must
be of the approved type, and have outlet grilles on all sides
giving a total free area of at least double that of the ue.
Caution
It is imperative that the ue should be properly sealed where
it passes through the roof, this can best be achieved by using
the approved method of roof ashing plate and cravat.
Note:
It should be noted that claims made under warranty and
attributed to the ingress of water may not be considered
especially if an approved method of sealing has not been
used, or if the design of the ue has not made provision for
possible condensation problems.