The combustion air filter will prevent plugging of the burner caused by dirt being trapped in
the burners outer mesh. The filter element supplied with the boiler is obtainable from
Keston Boilers or its distributors.
3.4
INSTALLING FLUE AND AIR PIPES
Remember the flue pipe must slope downwards back towards the boiler and this is best
achieved using 92.5
o
bends.
a
From the two connections on the boiler, mark the positions of the two holes for
the flue and air pipes on the wall(s) or ceiling. To allow access to drill the holes it
may be necessary to temporarily remove the boiler. If the boiler stays put then it is
imperative that the front panel and top access plate are replaced and the two
plastic pipes capped off whilst drilling. Under no circumstances must debris from
the wall or cut pipes be allowed to enter the appliance or the plastic pipework.
b
Drill the two holes in the wall/ceiling, preferably using a core drill.
3.4.1
Diameter of holes.
i)
Allowance must be made for socketed lengths if these are to be passed
through the holes :
du =
unsocketted
diameter
= 56 mm
ds
= socketed
diameter
= 65 mm
ii)
For 'horizontal' runs of flue
pipe the holes must either be
oversized or cut at a 5
o
slope
(the latter may be difficult on
long holes).
3.4.2
Oversizing
For every 1m length of run, L, the
minimum diameter of the horizontal
hole, D, must be du + 10 mm or ds +
10 mm respectively, assuming the
pipe touches the wall at points T otherwise D will have to be increased by
clearance from T. See Section 3.4.3 - Examples.
3.4.3
Examples
a.
Wall Depth
L
=
750 mm
Unsocketted pipe
du
=
56 mm
Diameter hole D
=
56+{(
750
/
1000
)x10}
=
56+7.5
=
63.5 mm
b.
Wall depth
L
=
2.3 m
Socketed Pipe
ds
=
65 mm
Diameter Hole
D
=
65+{2.3x10}
=
65+23
WD51/2/1997 Chapter 3 : Installation
The Keston 170 Condensing Boiler
Installation & Servicing Instructions
Page : 17
D
L
du
T
ds
Flue Pipe
