Osburn MATRIX OB02032, Installation And Operation Manual

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Page 39 Installation and Operation Manual - Matrix
ENGLISH
When it is cold outside, the warm air in the house is buoyant so it tends to rise. This tendency
of warm air to rise creates a slight pressure difference in the house. Called ‘stack effect’, it
produces a slightly negative pressure low in the house (relative to outside) and a slightly positive
pressure zone high in the house. If there is no fire burning in a heater connected to a chimney
that is shorter than the warm space inside the house, the slight negative pressure low in the
house will compete against the desired upward flow in the chimney.
9.5 Supply of Combustion Air
9.5.1 Conventional House
The safest and most reliable supply of combustion air for a wood stove is from the room in
which it is installed. Room air is already preheated so it will not chill the fire, and its availability
is not affected by wind pressures on the house. Contrary to commonly expressed concerns,
almost all tightly sealed new houses have enough natural leakage to provide the small amount
of air needed by the stove. The only case in which the wood stove may not have adequate
access to combustion air is if the operation of a powerful exhaust device (such as a kitchen
range exhaust) causes the pressure in the house to become negative relative to outdoors.
If an air intake is installed through the wall of the house, its pressure can vary during windy
weather. If there are changes in wood stove performance in windy weather, and in particular if
smoke puffs from the stove, the air duct should be disconnected from the stove to determine if
it is the cause of the problem. In some windy conditions, negative pressure at the duct weather
hood outside the house wall may draw hot exhaust gases from the stove backwards through the
duct to outdoors. Check the outdoor air duct for soot deposits when the full system is cleaned
and inspected at least once each year.