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WD388/0/2004
3.8
FLUE SYSTEM
NB:
When installing a replacement boiler a new flue system must be used. Do
not re-use the existing boiler flue installation.
3.8.1
Design
Individual air supply and flue outlet pipes are used.
The material used for the flue outlet and the air intake
systems, must be muPVC to BS 5255. In addition the
flue outlet and air intake pipe work, must be marked
BSEN 1566-1 and the fittings must be marked BSEN
1329. Marley muPVC Solvent Weld Waste System
(50mm) and Polypipe System 2000 muPVC Solvent
Weld Waste System (50mm) are recommended. DO
NOT USE ABS PIPE OR FITTINGS.
Alternatively, where flue or air intake lengths of up to
60m are require, Keston Composite 75mm flue and air
pipe can be used (contact your KESTON Heating stockist for details). Keston Composite
75mm pipe MUST be painted where exposed to UV light.
Both 50mm flue outlet terminal and 50mm air inlet terminal are supplied and are illustrated
in Figure 3.8.1. Both terminals are identical. If 75mm terminals are required these can be
obtained from your KESTON Heating stockist. Request part numbers C.17.2.26.00.0
(terminals) and C.17.2.00.60.0 (50 to 75 adapters).
3.8.2
Maximum Lengths
The maximum lengths of both air inlet pipe and flue outlet pipe, when no bends are used,
are as detailed below.
However, each bend used has an equivalent length that must be deducted from the
maximum straight length stated above. Knuckle bends must not be used.
A 92.5
o
sweep elbow is equivalent to 1.0m straight length. A 45
0.5m straight length
Maximum Air Inlet Length
Maximum Flue Outlet Length:
Maximum Total Flue and Air Intake
Length :40.0m
* A flue length of between 16 and 20m in
50mm pipe will reduce the DHW output
by 1%
** A flue length of between 48 and 60m in
75mm pipe will reduce the DHW output
by 1%
Example (assuming 50mm muPVC flue
and air pipework)
Air inlet uses two 92.5
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
Hence, maximum length permissible (i.e. c+d in figure 3.8.2 = 20.0m - 1.0 m = 19.0m
NB:
The air and flue pipes can be passed outside the buiding through only one
wall or through two different walls.
Installation & Servicing Instructions
Chapter 3 - Boiler Location The Keston C36 Combi & C36P Combi Boilers
:
120.0m
o
sweep elbows.
o
sweep elbow.
Flue Outlet/Air Inlet Terminals
Figure 3.8.1 : Terminals
o
bend is equivalent to
50mm
75mm
39.0m
117.0m
20.0m*
60m**
FLUE
d
c
KESTON COMBI
(COMBI P)
Figure 3.8.2 : Flue Air Maximum Length Example
AIR
b
a
Page : 16
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