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FLUE SYSTEMS
WIND
HIGH LOW HIGH LOW HIGH LOW
ROOF PITCH OVER 30° ROOF PITCH OVER 30° FLAT ROOF
5. WIND EFFECTS ON BUILDINGS
6. IMPORTANT NOTES
The following drawing shows the general high and low
pressure areas on buildings.
Flues should not be terminated in a high pressure area.
Do’s
6.1 Ensure that when an appliance is fitted to any chimney
system, that it is inspected and tested for soundness so that
any defects are rectified or a new flue system provided if the
soundness is in doubt.
6.2 Ensure that the flue system is always installed and supported
strictly in accordance with the manufacturers instructions.
6.3 Ensure that all joints are properly, securely and efficiently
made in accordance with the manufacturers instructions.
6.4 Ensure that the flue pipe connections from the appliance rise
vertically for at least 600 mm (24'')before any change of
direction is contemplated. The reason for this is that the
initial draught is crucial nearer the appliance because of the
higher flue gas temperature. Any horizontal or angled runs at
the bottom of the flue will create severe restriction to the gas
movement and affect appliance operation.
6.5 Try to construct the chimney vertically all the way to the
terminal.
6.6 Ensure that no part of the flue is installed at an angle more
than 45°/135°
6.7 Ensure that the flue diameter is not less than the
appliance outlet.
6.8 Ensure that the effective vertical height of any chimney with
bends is at least twice that of the horizontal distance between
appliance and terminal.
6.9 Try to position the chimney inside the building to avoid
excessive cooling and risk of condensation.
6.10 Ensure that the chimney is installed and located in
accordance with building regulations and Building regulations
and British standards, particularly the distances from
combustible materials are required.
6.11 Remind the householder that a chimney and an appliance
must breath, which is why a permanent supply of combustion
air must be provided and kept clear of obstructions.
6.12 Advise the householder to have the gas appliance regularly
and expertly serviced.
6.13 Ensure that if a gas flue block or mixed system consisting of
gas flue blocks and prefabricated gas vent is constructed to
avoid constructional faults.
6.14 Ensure that the flue is terminated in accordance with
Building regulations.
Don'ts
6.15 Use single walled galvanised ducting as a flue system for any
domestic gas installation.
6.16 Use non insulated flue systems externally.
6.17 Allow clothes, furnishings or any combustible material to
come into contact with any flue pipe.
6.18 Use bends if they can be avoided.
6.19 Run horizontal flue anywhere in the system.
6.20 Position the chimney externally if it can be avoided.
6.21 Be tempted to use inferior materials for the flue system; they
may only last a short time and replacement would be costly.