Morso 5660 Instructions For Installation And Use Manual page 23

Mounting
Remove or fix any existing damper in the chimney in the open position.
It is important that there are a few millimetres between the insert box and the surrounding masonry.
Otherwise, the thermal expansion of the insert box may cause cracking of the masonry.
As an initial estimate, the dimensions of the insert opening in the masonry are 75 mm x 55
mm x 5 mm (width x height x depth).
The insert must be levelled with the levelling screws. Note that the insert box must be even
(flush) with the masonry.
It may be advantageous to insulate with 5-50 mm Rockwool or similar heat-resistant material
around the insert box.
The insert is connected to the chimney by a 150 mm in diameter flue pipe that is fastened to
the flue collar with the supplied self-drilling screws (pre-drill to diameter .00 mm) and sealed
with the sealing cord supplied.
Seal between the flue pipe and the masonry chimney with refractory mortar. A thermal expansion
of the flue pipe may cause cracking of the refractory mortar. Therefore, it is important to use a
wall bushing and sealing cord.
If there is no cleaning door as shown in the drawings, it may be advantageous to install one.
This will make the installation of the flue pipe easier, and in some cases, the chimney sweep
may require one.