Potterton Osprey CF 125, Installation & Service Instructions Manual, Page: 8 / 30

Installation Requirements - Page 8
Fig. 4
1.5 Flue Systems
A flue system (lined throughout its length) must be provided
to evacuate the flue products of combustion from the boiler.
Reference should be made to the building regulations and
BS 5440:1. and the flue system efficiency should be checked
in accordance with BS 5440 and BS 6644.
Ideally a flue should rise vertically and any terminal or
termination point shall be positioned so that combustion
products can disperse safely at all times. Therefore for
practical purposes, the flue should have the shortest
possible run to external atmosphere within the limit of the
minimum length of 1 metre, with as near vertical rise as
possible, 90° bends should be avoided. The terminal must
be at least above roof level and of a type approved by British
Gas.
There should be at least 1000mm of vertical flue from the
boiler flue socket.
Horizontal runs should be avoided, however if a near
horizontal flue run is unavoidable, the total vertical height
necessary should be calculated in accordance with BS
5440:1 and BS 6644.
If an existing chimney is used, ensure that it is thoroughly
swept before lining or connecting the boiler.
Care should be taken to avoid condensation in the flue.
In the case of a pre-lined chimney, it must be connected to
the socket of the boiler flue hood with a length of purpose
made flue.
Where a chimney lined with a vitreous enamelled flue liner is
used, connect and seal a short length of purpose made flue
into the base of the pre-lined flue, to connect to the boiler.
The flue diameter should never be less than the diameter of
the flue spigot on the draft diverter.
Note: A separate 6 - 8" flue adaptor is supplied with the
boiler.