Keston HEAT 2 45 Installation & Servicing page 19

TERMINATION OF THE FLUE AND AIR
The flue and air pipes may terminate independently
through any external walls within the same dwelling
except on opposing walls, within the maximum lengths
shown in Fig 3 & 4. (Alternatively a vertical flue pipe
termination is acceptable.)
The air pipe must have an elbow and 150mm length of
pipe directed downwards with a termination grill fitted.
The air pipe can be situated at the side or beneath the
flue pipe to a minimum dimension of 140mm (see diagram
below). It must not be sited above the flue pipe.
The flue and air pipes must extend by at least 40mm from
the wall surface.
Condensing boiler emit a visible plume of water
vapour from the flue terminal, this is normal. It is the
responsibility of the installer to judiciously select a terminal
location that does not cause a nuisance.
If either the flue or air terminal is below a height of 2m
from ground level a terminal guard must be fitted.
MAXIMUM LENGTHS
Due to the resistance presented by extended flue length a slight reduction in maximum boiler output will occur where combined
flue and air lengths in excess of 16.0m (50mm muPVC) are used. In such cases the boiler output will be reduced by 0.8% per
additional metre.
The maximum lengths of both air inlet pipe and flue outlet pipe, when no bends are used, are as detailed in figs 3 & 4.
However, each bend used has an equivalent length that must be deducted from the maximum straight length stated in figs 3 & 4.
Knuckle bends must not be fitted.
A 92.5º swept elbow is equivalent to 1.0m straight length. A 45º bend is equivalent to 0.5m straight length.
It is possible to have variable flue and air lengths as described within the shaded area of Figs 3 & 4.
Keston Heat 2 - 45 &45P - Flue & Air Pipe Length
42
38
34
30
26
22
18
14
10
6
2
2 4 6 8
Flue Pipe Length [m]
SLOPE
'Horizontal' flue outlet pipework MUST slope at least 3.5 degrees (60mm per metre run) downwards towards the boiler. Pipework
can be vertical. Only swept elbows can be used.
Air inlet pipework can be truly horizontal or vertical, or sloping in a downward direction towards the boiler but in each case rain,
etc., must be prevented from entering the pipe. There must be no troughs in any of the pipework, whether it be air inlet or
flue outlet.
Installation & Servicing
SECTION 2 - INSTALLATION
Fig.3
Acceptable Operating Area
10 12 14 16 18 20 22
Fig.2
TERMINAL POSITIONS
Minimum Separation
Flue
140mm
Pipe
Acceptable
range of air
pipe siting
Air Pipe
Terminal
Fig.4
Keston Heat 2 - 55 & 55P - Flue & Air Pipe Length
42
38
34
30
26
22
18
14
10
6
2
2 4 6 8 10
Flue Pipe Length [m]
Elbow
Acceptable operating area
12 14 16 18 20
19