fresh air to the intakes. If the fresh air arrival is minimised or restricted, an air pressure drop
can develop at the air intakes and a blowback of fumes could be created.
Convection Air Outlets:
These must have a minimum cross-sectional area of 500cm².
They must never be less than 30cm from the ceiling and must not be restricted.
In the upper part of the convection chamber a false ceiling of incombustible material can be
installed. This will act as a deflector. It should be covered with insulation material and be at
least 30cm below the ceiling proper. This thermal damper will avoid unnecessary
temperature rises of the ceiling and will maximise the recuperation of hot air which may be
vented through diffusers at this level.
Two decompression grilles, with a minimum cross-sectional area of 20cm² each, should be
installed diagonally opposite each other at the lower and upper ends of the convection
chamber (both above the insert itself) to provide for a constant airflow within the chamber
and normalisation of the air pressure.
In the case of an insert installed in a corner one of these decompression grilles could be
installed on the front façade of the convection chamber.
Allowing for Fresh Air in the Room:
Air extractors in the same room can cause problems as this can result in insufficient fresh air
supply for the insert. A supplementary air supply must be allowed for.
An air intake should preferably be directly from the outside or otherwise from an adjacent
well-ventilated room.
The air discharge point should preferably be directly into the chimney or as close as possible
to the actual insert. The cross-section of the air intake should at least be equivalent to ¼ of
the cross-sectional area of the flue conduit or a minimum of 200cm².
The Flue Conduit
The conduit must be resistant to chimney fires.
The conduit must be metallic e.g. double-skin stainless steel tubing.
There should not be more than 2 bends and any bends must not be in excess of 45⁰ from the
vertical.
The connection between the insert and the conduit must be airtight – particularly if there is
an additional extraction system of hot air from within the convection chamber.
Where flexible conduit is joined to rigid pipe the joins should overlap by at least 40mm.
If there is too much draw a damper can be installed in the conduit where the connection to
the insert is made. This damper must be easily accessible.
USE OF THE HEATER
The minimum internal diameter of the flue must be 150mm. As soon as possible, this
diameter, should be increased to 180mm.
There may be NO reduction in the flue diameter – UNDER NO CIRCUMSTANCES. This could
result in the “blowback” of fumes into the room as soon as the heater door is opened, and a
reduction in the evacuation of fumes.
The chimney must originate in the same room where the heater is installed.
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