requirements of the current edition of
BS EN 1856 Part 1 or BS715. The
dimensions of the flue box must
conform to those shown in figure 2.
4.2.3
A precast concrete or clay flue
block system conforming to BS1289
or BS EN 1806 with dimensions as in
figure 3 or using a 05654K1 spacer
kit. (Installation Instructions part
number 3003095). BS EN 1806 and
BS1289 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 (See figure3).
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.
4.3
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 BS EN 1856 Part 1 or
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
Page 10
INSTALLER GUIDE
©
Baxi Heating U.K. Limited 2007.
Figure 3. Precast or clay flue block system
dimensions
