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10.
The Venting System
10.1 General
The venting system, made of the chimney and the liner inside the chimney, acts as the engine
that drives the wood heating system. Even the best insert will not function safely and efficiently
as intended if it is not connected to a suitable chimney and liner system.
The heat in the flue gases that pass from the insert into the chimney is not waste heat. This heat
is what the chimney uses to make the draft that draws in combustion air, keeps smoke inside
the insert and safely vents exhaust to outside. The heat in the flue gas can be seen as the fuel
the chimney uses to create draft.
10.2 Block-off Plate
To reduce the possibility of a cold air back draft from the masonry chimney into the room, the
installation of a sheet metal block-off plate (A) is recommended. When fabricating the block-off
plate, cut the pipe hole slightly larger than the liner diameter and pass the liner through the hole.
Install the block-off plate and secure it with masonry nails. Seal the joints between the plate and
the chimney with high temperature silicone and use stove cement to seal between the pipe and
the plate.
In Canada, the CSA B365 Standard permits «Roxul» type wool to be stuffed around the liner as
it passes through the throat area as an alternative to a sheet metal block-off plate. However, this
method is less efficient than using a plate.
A
Figure 17: Block-off Plate
Figure 18: Block-off Plate
10.3 Suitable Chimneys
This wood insert will provide optimum efficiency and performance when connected to a 6"
(150 mm) diameter chimney liner. The connection to a chimney having a diameter of at least 5"
(130 mm,Canada only) is permitted if it allows the proper venting of combustion gases and that
such application is verified and authorized by a qualified installer. Otherwise, the diameter of the
flue should be 6" (150 mm). The reduction of the liner diameter to less than 6" (150 mm) should
only be done if the total height of the masonry chimney is greater than 20' (6,1 m).
Installation and Operation Manual - Matrix 2700 Insert
Page 33
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