32
OPERATING
&
INSTALLATION
INSTRUCTIONS
FOR
PEDESTAL
WOOD
HEATERS
when
there
is
no
fire
burning.
This
means
that
when
you
light
a
fire,
the
initial
smoke
goes
up
the
flue
system
and
strong
draft
builds
quickly
as
the
flue
system
warms
up.
Flue
systems
that
exit
a
house
wall
and
run
up
outside
can
cause
problems.
Good
System
Design
Inside
flue
systems
are
preferred
because
even
when
no
fire
is
burning,
there
is
normally
upward
flow
in
the
system.
Inferior
System
Design
Outside
flue
systems
are
a
problem
because
when
no
fire
burns
they
will
go
into
cold
downdraught
if
the
wood
fire is
installed
low
in
the
house.
8.4.2
WHY
THE
FLUE
SYSTEM
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
flue
system
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
flue
system.
There
are
two
reasons
why
the
flue
system
in
the
house
at
right
will
cold
downdraught
when
it
is
cold
outside
and
there
is
no
fire
burning
in
the
wood
fire.
First,
the
flue
system
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
flue
system
is
shorter
than
the
heated
space
of
the
house,
meaning
the
negative
pressure
low
in
the
house
will
pull
outside
air
down
the
flue
system,
through
the
wood
fire
and
into
the
room.
Even
the
finest
wood
fire
will
not
work
well
when
connected
to
this
flue
system.
