INSTALLER’S GUIDE
Page 6
Figure 2 Pre-cast Fireplace
Figure 3 Metal Flue Box
2.9.2
To a fireplace that has a precast
concrete or clay flue block system
conforming to BS1289 or BS EN 1806.
The appliance is suitable for
installations conforming to older
versions of BS1289 as well as the
current edition. The flue blocks must
have a minimum width not less than
63mm and a cross-sectional area not
less than 13,000mm
2
.
Older editions of
BS1289 required a cross-sectional area
of 13,000mm
2
. The current revision of
the standard requires 16,500mm
2
. This
appliance is suitable in both cases. The
total depth of the opening measured
from the finished front of the fireplace
(Including plaster, surround etc.) must
be
not less than 118mm.
See figure 2
.
The current versions of BS1289 and
BS EN 1806 recommend that there
should be an air space or insulation
between the flue blocks and the
plaster because heat transfer may
cause cracking on directly plastered
flues. However, generally this
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.
2.9.3
A metal flue box conforming to
BS715 with a minimum internal depth
of 150mm. Incombustible mineral wool insulation of not less than 50mm thickness must
be applied to the top surface of the firebox and it must stand on a non-combustible
hearth. See figure 3.
