Keep The Home Fires Burning In The Fireplace:
For the past bunch of years as many as 100,000
American homes burn after accidents involving
heating with wood. The single biggest reason for
so many fires is this: People do not understand
the nature of creosote or how quickly it builds
up within chimneys. Creosote is a combustible
deposit that can catch fire and is the fuel that
burns when there is a chimney fire.
fire combine to condense out the unburned gases
and tars onto cooler chimney sections. The
weaker the draft and the cooler the flue, the
greater the buildup of creosote. Also the cooler
the chimney, the more likely that third degree
or "glazed" creosote will form. This is much
denser and more difficult to remove than the
so-called "flake" creosote.
The traditional wood stove inserted into a
fireplace is a breeder of creosote, particularly
if the original masonry fireplace is on an
outside wall. NOTE: Inside chimneys tend to
reflect the temperature of the surrounding
living space.
Fireplaces have large flues built to accommodate
an open wood fire. The fire temperature is very
high and the draft up the flue is very strong.
This type of flue is actually too big, and if on
an outside wall, will be too cold to properly
accommodate a wood stove. There will never be
enough temperature to heat the flue and never
enough combustion to force a strong draft.
Creosote will precipitate rapidly. The same
thing happens when an insert is coupled to a
triple-lined, prefabricated metal fireplace
chimney. These chimneys have space between the
linings to keep them cool. Creosote formation
will be very rapid whether the chimney is on the
outside or the inside of the house. Either
modify these chimneys or plan on removing the
stove and cleaning the chimney every two months
of operation. (The standard is to clean when
one-fourth of an inch of creosote is deposited
on the walls.) In any case, check after the
first two months of operation to give yourself a
gauge. Remember, the colder the weather the more
rapid the creosote buildup.
Modifying fireplace chimneys:
You can modify a masonry or triple-lined flue to
better accommodate a fireplace-insert wood
stove. The most practical thing to do is to drop
a stainless steel "Z-Flex" liner down the
existing flue. This should be connected through
a blocking shield at the bottom of the chimney
throat to the flue of the wood stove. It is then
pulled taut and held from the chimney top.
Vermiculite insulation is then poured around the
new liner and the pipe is sealed at the top with
a combination cap screen. This is best done by
an experienced chimney sweep. The flexible liner
costs about $10 per foot and the vermiculite
cost will vary depending on the space between
the liner and the original flue. The entire job
should cost around $500. It can cost more than
this to remove the tar-like "third-degree"
creosote, which can easily form in cold flues.
The lined and insulated flue will now be smaller
and warmer. This will yield a stronger draft and
far less creosote precipitation. It provides an
extra measure of containment in the event of a
chimney fire and is removable should you wish to
return to fireplace use.
Woodstove operation:
Woodstoves can be burned hot (a full load of
wood with air inlets wide open) for a short
period (about five minutes to 30 minutes) at
least once a day. This procedure is called
pyrolizing dries third-degree creosote, shrinks
it, and causes it to drop down the flue or be
expelled upward with the stronger draft.
A few caveats:
Pyrolize from day one and you should be okay,
but if the flue already has a good deal of
creosote in it, this may actually ignite a
chimney fire. Beware of "back-puffing." Never
open the door to an airtight stove that has been
smoldering for a long time. The inrushing air
may cause the smoldering smoke to flame up and
shoot right out the door. Flames can shoot more
than five feet. Always open the air ports so the
fire can get going again before opening the
door. Open the air ports and then get the wood
burning more quickly to add to the fire.
Warning signals:
If your stove has always worked well and then
begins to smoke around the doors or ports, it
may mean that the chimney is restricted with
creosote. Let the fire die, wait a day or two,
remove the stove and check. If you haven't
cleaned the chimney in the last year, you can
bet you need a clean sweep. Do not ignore a
darkening of your chimney top or brown liquid
running down metal flue pipes. Both indicate
considerable creosote buildups and merit a
relatively immediate check.
A LIST OF NEVERS:
Never hook a wood stove to a flue pipe that is
used to service a gas appliance. These have
aluminum linings and soon will corrode or burn
out.
Never flue a wood stove via an old brick chimney
without a terra cotta liner.
Never use anything but Underwriters Laboratory
approved equipment.
Never use a screen over a wood stove flue. It
will block-closed quickly. (Animals tend to
avoid wood stove flues, presumably because of
the creosote.)
Never rely on chemicals to keep your flue clean.
There are many products on the market that claim
to be effective at eliminating or reducing the
buildup of creosote in the chimneys. Most of
them contain a lot of salt. Take their claims
with a grain of salt as well. There is no
substitute for the chimney sweep.
Catalytic combustors: Most newer were fitted
with catalytic combustors. This is a device that
fits over the stove flue. It causes escaping
gases to burn, and will greatly reduce creosote
buildup. It must first be brought up to a
relatively high temperature. If it isn't, it
acts as a trap for escaping creosote and
contributes to the problem. There are a number
of retrofit kits available for various existing
stoves. Contact the manufacturer of your stove
or even a competent chimney sweep.
The stoves may be cheaper energy sources, but
care and discipline are required to maintain
their most effective and safe use.