42
WinterWarm Fireplace Insert or System
2000941
Appendix: Catalytic Combustor
In any chemical reaction, including the combustion
process, there are certain conditions which must be
met before the reaction can take place. For example, a
reaction may require a certain temperature, or a certain
concentration of the reactants (the combustion gases
and oxygen), or a certain amount of time. Catalysts,
though not changed themselves during the reaction,
have the ability to act at a molecular level to change
these requirements. In the secondary combustion
chamber of the WinterWarm, the catalyst reduces the
temperature at which secondary combustion can start
from the 1000 - 1200
°
F (540 - 650
°
C) range to the 500
- 600
°
F (260 - 315
°
C) range, increasing efficiency, and
reducing creosote and emissions.
The catalytic reaction, though advantageous, does
have some limitations of its own. Primary among these
is that the reactants (the gases) come into close
physical contact with the catalyst itself.
To ensure the necessary contact, the catalytic element
in your WinterWarm is composed of a ceramic base in
the shape of a honeycomb. On each of the
honeycomb’s many surfaces a coating of the catalyst
(usually a noble metal such as platinum or palladium) is
applied. The large surface area exposed in this configu-
ration ensures the combustion gases have the greatest
opportunity to come in contact with the catalyst.
Loss of catalytic activity will be apparent in several
ways. First you may notice an increase in fuel con-
sumption. Second, there will be a visible increase in
the rate at which creosote builds up in your chimney
connector system. You may also notice a heavy
discharge of smoke from the chimney. There are a
number of catalytic problems which can cause loss of
activity:
Blockage
While the honeycomb pattern ensures good contact, it
also increases the resistance to flow of the combustion
gases, and, because of the many surfaces, provides
more places for creosote and fly ash to deposit. It is
important to follow the operating instructions in order to
minimize these deposits, and to periodically inspect
your catalyst for signs of blockage.
Masking and Poisoning
While the catalyst itself does not enter into the combus-
tion process, it is possible for certain elements, such as
lead and sulfur, to attach to the active sites on the
surface of the honeycomb. Though the catalyst is still
there, it is covered, or masked, by the contaminant, and
cannot function. To avoid this situation, it is important
not to burn anything in your WinterWarm that is a
source of these contaminants. Particularly avoid
painted or treated wood, coal, household trash, colored
papers, metal foils, or plastics. Chemical chimney
cleaners may also contain harmful elements. The
safest approach is to burn only untreated, natural wood.
Flame Impingement
The catalytic element is not designed for exposure to
direct flame. If you continually overfire your Winter-
Warm, the chemistry of the catalyst coating may be
altered, inhibiting the combustion process.
Thermal degradation of the ceramic base may also
occur, causing the element to disintegrate. Stay within
the recommended guidelines of the Operation section.
Mechanical Damage
If the element is mishandled, damage may occur.
Always treat the element carefully. Remember the
catalyst is made of a ceramic material; treat it as you
would fine china. Hairline cracks will not affect the
performance of the catalyst, as long as the steel sleeve
holds the element in the proper position.
Peeling
Peeling of the surface coat may occur if the catalytic
element is frequently subjected to excessive tempera-
tures. Follow the operating instructions carefully to
avoid this type of damage.
Every Vermont Castings' product is equipped with
either a Corning “Long-Life”
®
or a Technical Glass
Products “Honeycomb”
®
. The products are equivalent.
If for any reason you must ship your catalytic element,
remember its fragile nature. Place the element in a
plastic bag, and package it with a generous amount of
shock absorbing material.
