1.3. Description of the appliance.
The Franco Belge 921 series boilers are designed to burn
solid fuel, wood and peat.
The heat exchanger is manufactured from high quality
plate steel. Its specific design provides a large surface
area for efficient use of the heat generated. The large top
loading plates enable large pieces of fuel to be burnt whilst
facilitating easy access for cleaning.
Regulation of the fire is by a water-sensing thermostat
which controls the primary air flow rate. Primary air is
introduced at the bottom of the heat exchanger. Fixed
secondary air outlets at the top of the fire box introduce a
constant supply of additional air to assist combustion of the
flue gases.
The appliance is fitted with externaly controlled riddling
grate.
1.4. Sizing the boiler
All models are rated in BTU/hr output and should be sized
to the heat loss of the building.
If appliance is undersized, it will not be capable of produ-
cing sufficient heat for the system. Oversizing will result in
excessive hot water production and expansion and serious
chimney congestion problems could occur especially when
burning wood.
2. Assembly and installation
Please read through completely before commencing
installation
.
The installation should be carried out by a qualified heating
engineer who is experienced in solid fuel heating.
The installation must be in accordance with the current
codes of practice relating to the installation of solid fuel
appliances.
2.1. Positioning the appliance
The room in which the appliance is to be installed must
satisfy Current Building Regulations.
These will stipulate an adequate fresh air inlet of at least
350 cm
2
. This must be installed in such a way, that in
adverse wind conditions the air flow cannot be reversed as
this may suck air out of the room in which the unit is
installed.
The position of the boiler will be determined by the best
position for the chimney, whilst ensuring that a safe dis-
tance is left between the boiler and combustible surfaces.
2.2. The chimney
The chimney is the key to a successful installation and the
following key areas should be checked.
Height
The minimum height should be 5 metres with the terminal
at least 1 metre from the roof surface and in a clear area
away from possible downdraft. If in doubt always increase
the chimney height. This will help to ensure an adequate
draft and clearance of the flue gases from the area of the
building.
Insulation
The chimney needs to be warm from bottom to top and
should be adequately insulated. Cold chimney and cool
flue gas temperature will result in tar formation and smoke
emission into the room.
Resistance
If the chimney has a horizontal section at the appliance
outlet, this should not exceed 30 cm. Any changes in
direction should be gradual (15 degrees maximum) and
the chimney system must not incorporate more than two
bends. The straighter the chimney, the less resistance.
Any resistance will slow down the flue gases and help to
create a build up of tar deposits.
Draft
The appliance requires a draft of between 04" and 07"
W.G. to burn effectively. This is the up draft of air through
the appliance. It is the result of the height of the chimney
and heating of the column of air within the chimney. An
inadequate draft will cause soot and tar formation in the
chimney.
The appliance requires a class 1 chimney. Existing unlined
chimneys should be lined with a liner suitable for use with
solid fuel burning appliances. If there is no existing chim-
ney, there are a variety of prefabricated systems available
and it is recommended to discuss your particular applica-
tion with a chimney specialist.
1
2
3
5
4
2
Figure 2 - Side cross section
1 - Secondary air inlet.
2 - Water circulation.
3 - Water return.
4 - Primary air inlet.
5 - Water flow.
Document n° 343-4EN ~ 10/11/1998
Solid fuel boilers 921 series
Grillon - Buchère
20
Technical manual