50mm
75mm
Maximum Air Inlet Length
:
39.0m
117.0m
Maximum Flue Outlet Length:
20.0m
60m
Maximum Total Flue and Air Intake Length :
40.0m
120.0m
Example (assuming 50mm muPVC flue and
air pipework)
Air inlet uses two one 92.5
o
sweep elbows.
Hence, maximum length permissible
(i.e. a+b in figure 3.8.2) = 39.0m - 1.0m - 1.0m
= 37.0m
Flue outlet uses one 92.5
o
sweep elbow.
Hence, maximum length permissible (i.e. c+d
in figure 3.8.2 = 20.0m - 1.0 m = 19.0m
3.8.3
Slope
‘Horizontal' flue outlet pipework MUST slope at
least 2 degrees (32 mm 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 this 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.
Due the low temperature of the flue gases
further condensate will form within the flue
system. Drain points, with suitable traps, must
therefore be incorporated within the flue system
at the base of vertical flue sections in excess of
6m, for 50mm muPVC pipe flue systems. These
additional condensate drains must be run to
discharge as detailed in section 3.11. Such drain
points can be formed using standard muPVC
fittings. Refer to the example in Figure 3.8.3.
3.8.4
Terminations
Air inlet terminals must be facing horizontally or downwards to prevent entry of rain into
the terminal and positioned to ensure only fresh air is drawn into the boiler. The air
terminal must be located outside of the building.
Flue and air terminals must be positioned so that flue products are not drawn into the air
inlet. Site specific wind conditions should be considered to achieve this.
Drawing of combustion air directly from a ventilated boiler room invalidates the heat
exchanger warranty.
The flue outlet terminal is designed to face outwards but can, if desired, be adapted to
face in any direction BUT must not be directed in the region of the air inlet. The flue
terminal and air inlet terminal can be located on different, but not opposing wall faces.
The two terminals are subject to the requirements of BS 5440 Pt 1 for clearances from
features of the building although some can be decreased to the values indicated.
WD440/3/2007 Chapter 3 - Boiler Location
The Keston Qudos 28h & Qudos 28hP Boilers
Installation & Servicing Instructions
Page : 18
Figure 3.8.2 : Flue & Air Maximum Length Example
FLUE
c
d
AIR
a
b
KESTON Qudos 28h
6 in min.
Figure 2.8.3 :
Flue Condensate Drain
Point Example
Tee Fitting
To Boiler
To
T
er
m
in
al
