INSTALLER GUIDE
Page 10
©
Baxi Heating U.K. Limited 2008.
4.2.1.1
‘Hole-in-the-wall’ Installations
It is recommended that a hearth should be installed as in section 4.9.
If a reduced depth hearth is fitted, the fire must be installed so that the distance
from the base of the fireplace opening in the wall to the finished floor level is at
least 100 mm. It is recommended that the reduced hearth has a depth from the
fixing plane of the fire of 100mm minimum. This is necessary to support the ash
pan casting. Where there is no floor covering or carpet and the floor is of a type
that is likely to be covered in such a way in the future then the distance from the
base of the fireplace opening in the wall to the floor level should be increased to
at least 175mm.
4.2.2
To a fireplace incorporating a metal flue box complying with the constructional
requirements of the current edition of BS 715 and with a flue conforming to BS EN
1856 part 1. The dimensions of the flue box must conform to those shown in figure 2.
Important Note
: Where the flue box has a base sheet that is single wall (i.e. a single
metal sheet) the flue box must be mounted on a non-combustible hearth. The hearth
material must be at least 12mm thick.
4.2.3
To a precast concrete or clay flue block system conforming to BS EN 1858 with
dimensions as in figure 3 (A spacer frame is available for precast flue installations that
are shallower than the 225mm
dimension shown in figure 3 -
See section 2 headed
‘Accessories’). BS 1289 part 1
recommends 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.
4.2.4
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.
Figure 2. Metal flue box dimensions
