5
FGi.FPi.FXi
Issue
12 10/17
Where the chimney is believed to have previously served an open fire installation, it is possible
that the higher flue gas temperature from the stove may loosen deposits that were previously
firmly adhered, with the consequent risk of flue blockage. It is therefore recommended that the
chimney be swept a second time within a month of regular use after installation.
If you have any doubts about the suitability of your chimney, consult your local dealer or
chimney specialist. If there is no existing chimney then either a solid fuel compatible
prefabricated block chimney or a twin-walled insulated stainless steel flue to BS 4543 can be
used. These chimneys must be fitted in accordance with the manufacturer’s instructions and
Building Regulations.
4.2.
Ventilation
Document J of the Building Regulations states that (except in recently built properties) purpose
provided ventilation is not required in England and Wales unless the appliance nominal rated
output is greater than 5kW. Over 5kW 5.5 cm
2
of ventilation (550mm
2
) is required for every kW
output above 5. For example 6.5 kW requires 8.25 cm
2
and 8 kW needs 16.5cm
2
. In any case, if
difficulty in starting the fire or any excessive fuming is experienced, ventilation must be put in
place as required to eliminate these flue problems. If a flue draught stabiliser is fitted then extra
ventilation is required. See Document J of the Building Regulations for detailed guidance
especially in new build properties where purpose provided ventilation may be required.
4.3.
Flue Draught
Typically a flue draught at the flue collar of 2.2mm to a maximum 3.5mm water gauge (22 to 35
Pascals) is required for satisfactory appliance performance. This relates to 12-25 Pascals at the
higher tapping on EN13240/13229 test rigs. The flue draught should be checked under fire at
high output and, if it exceeds the recommended maximum, a draught stabiliser must be fitted
so that the rate of burning can be controlled to prevent over-firing.
4.4.
Connection to the Chimney
This appliance is not suitable for use in a shared flue.
Whilst 6” 150mm diameter flue or liner is recommended wherever possible, a suitable 5”
125mm flexible flue liner is permitted be used on these stoves providing that they only burn
smokeless fuel or seasoned wood logs with the air limiter fitted in in full accordance with the
wood burning instructions.
An existing fireplace opening can be bricked up or sealed with a register plate. A short length of
suitable quality rigid flue pipe of a minimum 125mm internal diameter may then be used to
connect the stove to the chimney. This flue pipe should conform to Building Regulations. The
stove must be insulated and properly fitted into the fireplace opening by back filling with 6:1
ratio vermiculite & cement mixture using minimal water through the top of the fireplace or flue
spigot opening. The surface should be finished using 1:1:8 mix of cement, lime and sand. The
connecting pipe is fitted with the spigot pushed up from inside the stove and rotated onto its
keyhole slots to join to the pipe. If the connecting flue pipe enters the vertical flue way at any
other angle except vertically, ensure that the pipe end is no closer (along the axis direction of
the pipe) than 76mm to the side or rear chimney walls.
If necessary a hole must be opened up into the flue way above the fireplace in order to fit the
appliance to the flue correctly. Please consult HETAS for recommended fitting methods if in
doubt. It is essential that all connections between the stove and chimney-flue are sealed and
