page no. 17 of 36
OUH Range Users, Installation & Servicing Instructions Doc Ref M105 issue 5.8 Apr 2020.
The minimum distance between surfaces of the flue pipe
and any surfaces made from combustible materials is
300mm. If it is necessary for the flue pipe to pass through
a structure made from combustible materials a metal
sleeve must be used so that the minimum clearance of
300mm is maintained.
All models are supplied with a rear flue outlet.
The flue system connects directly into the flue socket on
the top (OUH20) or rear (OUH30 - 60) of the heater. The
socket is sized to accept standard sheet metal flue that is
secured in place using suitable fasteners.
The flue system must be fabricated with sockets facing
upwards and sound joints must be achieved by either:
(a) a close tolerance mechanical fit between sections, or
(b) the use of a suitable caulking string and cold caulking
compound.
In all cases the flue outlet socket must be connected via
an approved flue system to outside air.
The minimum flue length (end of flue terminal to top of
heater) shall not be less than 2.0m.
All flue ducts must be supported independently of the air
heater.
A closed chimney system that conforms to the
requirements of EN1856-1 and has a designation
appropriate to the application must be connected to the
outlet of this tee. The cross sectional area of the chimney
serving the appliance must be not less than the area of
the flue outlet of the air heater.
The chimney must have a minimum height, from the
heater to the flue terminal, of 2m.
Horizontal runs of flue must be minimised but where they
are unavoidable the ratio of vertical to horizontal flue
should be not less than 3:1.
If necessary a single offset using two 45° bends can be
included to avoid obstructions. The minimum equivalent
resistance of the flue system should not be less than
0.0mb, the maximum not greater than 0.5mb.
In order to minimise condensation the use of twin wall
chimney is recommended. With high efficiency heaters
some condensation in the chimney, particularly at the
terminal, is unavoidable and in addition there can also be
rain water ingress.
Facilities should be made for disconnecting the chimney
pipe(s) from the air heater(s) for inspection and servicing
purposes.
The chimney outlet must be fitted with a terminal and
where the heater chimney is less than 200mm (8") in
diameter an approved terminal must be used.
The chimney must be supported independently of the air
heater.
The chimney must terminate in a freely exposed position
and must be situated so as to prevent the products of
combustion entering any opening in a building in such
concentration as to be prejudicial to health or a nuisance.
Note: For flue positioning and minimum
clearances of flue, please refer to current
IGE/UP/10, BS5440-1 and BS5440-2
standards.
The design of the flue system should minimise the
formation of condensation and long external runs
should be completed in twin wall insulated flue. Where
condensate and/or rain water ingress is envisaged to be a
problem a flue drain length or condensate drain tee must
be fitted. The condensation pipe from the collection tray
to the disposal point should be of non-corrodible material
of not less than 22mm (3/4") size.
