Installation
13
Greenstar 80mm Flexi RF Flue – 6721814542 2019/09
4.8
Extensions and elbows
Connecting flue bends increases the effective flue length and allowance
must be made for the different connectors.
The examples opposite show the dimensions for:
▶ a 90° elbow and the tee piece connected together
▶ two 45° elbows connected together
To calculate the effective flue length:
▶ Identify the number of 90° and 45° elbows required.
▶ Deduct the effective length of each elbow from the maximum
horizontal flue length of 3m.
Table 14 Elbow effective length
Fig. 25 Elbow measurements
To reduce the length of a flue extension:
▶ Mark the flue extension to the required distance, measuring from the
socket end as shown in fig. 26.
▶ Cut the flue extension square, taking care not to damage the tubes.
▶ Remove any burrs and chamfer the outer edges of the tubes to
prevent seal damage.
Only straight flue extensions may be cut.
▶ Do not modify flue elbows or the tee piece.
Fig. 26 Cutting the flue extension
The flue pipe must not be closer than 25mm to any combustible material.
The tee piece has a built-in angle of 3°. All horizontal sections of the flue
must rise by 3° or at least 52mm for each metre away from the appliance
as shown opposite. This is to ensure the condensate flows back into the
appliance.
Fig. 27 Horizontal incline
To install flue extensions:
1. Slide a bracket onto each additional straight flue extension. Working
from the appliance, fit extensions with brackets as required to
support the weight of the flue.
2. Drill two holes (180° apart if possible) through the outer collar of
each flue tube and use screws to secure the connection.
NOTICE:
Appliance fault
Do not drill into the inner flue tube
▶ The appliance might go into lockout due to flue gases mixing with
combustion air
Fig. 28 Assembling extensions and elbow
80/125mm elbow
Effective length (m)
90°
2
45°
1
180m
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