Century FW2600 Installation and Operation Manual
Good System Design
Inside chimneys are preferred because
even when no fire is burning, there is
normally upward flow in the system.
8.4.2 Why the chimney should penetrate the highest heated space
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 di
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 sh
negative pressure low in the house will compete against the desired upward flow in the
chimney.
There are two reasons why the
chimney in the house at right will
cold backdraft when it is cold
outside and there is no fire
burning in the stove. First, the
chimney runs up the outside of
the house, so the air in it is colder
and denser than the warm air in
the house. And second, the
chimney is shorter than the
heated space of the house,
meaning the negative pressure
low in the house will pull outside
air down the chimney, through the
stove and into the room. Even the
finest stove will not work well
when connected to this chimney.
Installation and Operation Manual
Good System Design
Inside chimneys are preferred because
even when no fire is burning, there is
normally upward flow in the system.
Inferior System Design
Outside chimneys are a problem because
when no fire burns they will go into cold
backdraft if the stove is installed low in the
house.
Why the chimney should penetrate the highest heated space
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
There are two reasons why the
chimney in the house at right will
cold backdraft when it is cold
nd there is no fire
burning in the stove. First, the
chimney runs up the outside of
the house, so the air in it is colder
and denser than the warm air in
the house. And second, the
chimney is shorter than the
heated space of the house,
pressure
low in the house will pull outside
air down the chimney, through the
stove and into the room. Even the
finest stove will not work well
this chimney.
37
Inferior System Design
Outside chimneys are a problem because
when no fire burns they will go into cold
ckdraft if the stove is installed low in the
When it is cold outside, the warm air in the house is buoyant so it tends to rise. This
fference 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
orter than the warm space inside the house, the slight
negative pressure low in the house will compete against the desired upward flow in the
