INSTALLER’S GUIDE
Page 8
appliance is suitable for
installations under all
circumstances unless there is a
history of cracking problems.
Remember that faults such as
cracking may be caused by
poorly built and restrictive flues,
e.g. mortar extrusions, too many
bends, flue heights below three
metres, restrictive terminations
etc.
2.2.3
If the fireplace opening is
greater than the acceptable
dimensions given in this guide,
do not use the back of a fire
surround or marble to reduce the
opening. This may cause
cracking of the surround back or
marble.
2.4
Suitable flues and
minimum flue sizes are as
follows: -
It should be noted that, as with
many appliances, sharp bends or
horizontal runs in metal flues at
the top of the system can be a
cause of problems in these types
of installation.
•
225mm x 225mm
conventional brick flue.
•
175mm diameter lined brick or stone flue.
•
200mm diameter factory made insulated flue manufactured to BS4543.
•
175mm diameter flue pipe. See BS6461 Part 1 for suitable materials.
•
Single wall, twin wall or flexible flue liner with a minimum diameter of 125mm. The
materials to be used are stainless steel or aluminium as specified in BS715. The liner
must be sealed to the surrounding area above the fireplace opening and to the top of the
chimney. An approved terminal must be fitted.
•
A properly constructed precast concrete or clay flue system conforming to BS1289 or
BS EN 1806. This system is only suitable if the conditions stated in section 2.2.2 are met.
Figure 3. Precast or clay flue block system
