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WD51/2/1997 Chapter 2 - Boiler Connections
2.8
FLUE SYSTEM
2.8.1
2.8.2
Installation & Servicing Instructions
system and a pump selected that is capable of meeting the flow rate required at
the total pressure loss generated by the boiler and the rest of the system. The
selected pump must comply with BS 1394. It is important to note that the
minimum flow rate must be maintained whenever the boiler is firing. Systems
using zone valves must be specifically designed to only fire the boiler when the
pump is running and the minimum flow rate can be achieved.
Design
Individual air supply and flue outlet pipes are used. The material used for flue
outlet &/or air inlet must be muPVC to BS 5255 an of an internal diameter of 51
mm.
O56
80
Flue Outlet Terminal
Both flue outlet terminal and air inlet terminal are supplied and are illustrated in
Figure 2.8.1 above.
Maximum Lengths
The maximum lengths of both air inlet pipe and flue outlet pipe, when no bends
are used, are as detailed below.
Maximum Air Inlet Length
Maximum Flue Outlet Length
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.
o
A 92.5
sweep elbow is equivalent to 1.0m straight length.
Example:
Air inlet uses two one 92.5
(ie a+b in figure 2.8.2) = 15.0m - 1.0m - 1.0m = 13.0m
Flue outlet uses one 92.5
c+d in figure 2.8.2) = 15.0m - 1.0 m = 14.0m
The Keston 170 Condensing Boiler
40
Figure 2.8.1 : Terminals
:
:
o
sweep elbows. Hence, maximum length permissible
o
sweep elbow. Hence, maximum length permissible (ie
211
O83
O56
Air Intake Terminal
15.0 m
15.0 m
Page : 11
87
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