!
Place the template against the wall. Make sure that the centre of the flue hole is as
shown in figure 2.
!
Pierce the template at the centre of the screw fixing holes and the flue hole and mark
the positions on the wall. Remove the template.
8.4.1
Core drilling.
!
Drill a pilot hole through the wall. Inspect the hole to ensure that it is in the
brickwork and not in mortar. If it is in mortar, it is advisable to reposition the hole
approximately 25mm away - Make sure that the minimum side clearances and height
are complied with. Remember to reposition the screw fixing holes.
!
Drill the flue hole with a 152mm (6in) core drill. Where practical, it is recommended
that the hole is drilled from inside the building to about half the wall depth with the
remainder drilled from outside. This ensures that the edges of the hole are clean on both
sides.
8.4.2
Hammer and chisel cutting.
!
Mark a 152mm (6in) diameter circle for the flue hole. Chisel out the area marked.
!
It may be necessary to make good both the internal and external wall faces. To
achieve a neat finish and to make any future removal of the flue unit easier, it is
recommended that a cardboard cylinder is formed around the flue unit and inserted in
the hole while making good. Remove the cardboard cylinder after making good.
8.4.3
Leaving a hole for a building under construction.
!
It will be convenient to use a non-corrosive metal tube 160mm diameter built into
the wall at the correct position for the flue unit.
8.5 Cutting the flue hole in timber frame buildings.
Drill the pilot hole and hole in outer wall as section 8.4.
!
Since the flue will pass through combustible material in the inner leaf of the wall, a
non-combustible sleeve 203mm (8in.) diameter will be required round the flue (See
figure 10).
!
Cut a hole through the inner leaf to accommodate a non-combustible sleeve 203mm
(8in.) outside diameter. To minimise the effect of breaking through the vapour control
layer (VCL), if possible, cut the hole approximately 10mm undersize so that the sleeve
will be forced through the layer. A recommended technique for cutting the inner leaf is
shown in figure 10.
!
Fit the non-combustible sleeve to the inner leaf. The sleeve must extend to be at least
flush with the breather membrane/timber sheathing but must not protrude more than
10mm into the cavity.
!
The annular gap between the flue unit and the sleeve must be sealed to prevent air
heat and moisture passing along it. The 12.5mm insulating sheet (See section 8.3) can
be used for this. Do not permanently fix the insulating sheet to the wall at this stage
(See section 9.2).
Page 20
INSTALLER GUIDE
©
Baxi Heating U.K. Limited 2007.
