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8390-975
Vermont Castings • Defiant® Model 1975-CAT-C Installation Manual_R8 • 02/21
. The Catalytic Element
This wood heater contains a catalytic combustor, which needs
periodic inspection and replacement for proper operation. In
the United States it is against the law to operate this wood
heater in a manner inconsistent with the operating instructions
in this manual.
Under normal operating conditions, the catalytic combustor
should remain active for two to six years (depending on the
amount of wood burned). However, it is important to monitor
the combustor periodically to ensure that it is functioning
properly, as well as to determine when it needs to be replaced.
A non-functioning combustor will result in a loss of heating
efficiency, and an increase in creosote and emissions.
Inspection and Cleaning
Inspect the combustor for fly ash accumulation and physical
damage two to three times per year. Clean the combustor
as needed.
The refractory package that houses the catalytic combustor
should be inspected for a buildup of fly ash and cleaned
if necessary. This may be done when you examine the
combustor.
When to Suspect a Combustor Problem
The best way to evaluate the performance of your appliance’s
combustor is to observe the amount of smoke leaving the
chimney — both when the combustor has “lighted-off” and
when it has not. Follow these steps:
• With a fire going and the combustor properly activated, with
the damper closed to route smoke through it as described
in the Operation Section, go outside and observe the
smoke leaving the chimney.
• Then, open the stove damper and once again check the
smoke leaving the chimney.
You should see significantly more smoke when the stove
damper is open and exhaust does not pass through the
combustor. However, be careful not to confuse smoke with
steam from wet wood. Steam dissipates in the air quickly;
smoke does not.
If this test indicates a problem, consider other possible factors
as well, such as the weather or a change in the quality of
your fuel. In warm weather, draft is weaker than it is in colder
winter weather, and fires can burn sluggishly. Small, hot fires
are a good solution under these conditions.
Burning “green” (insufficiently seasoned) wood will result in
poorer performance than burning properly seasoned fuel.
Reloading with green wood can also thermal shock the
catalyst, resulting in cracking, or the eventual fallout, of the
ceramic honeycomb substrate. You may have to run your
stove hotter (more air) to achieve acceptable performance
using green or wet wood.
Also, consider any changes in your operating routine.
Once you have ruled out any other possible causes for a
decline in performance, inspect and clean the combustor if
necessary. Be sure to protect any surface you use for setting
the stove parts aside.
Figure 6.7
- Inspect the catalytic combustor.
To assure a long life for the combustor, it is recommended
to service the combustor on a regular basis based on the
amount of use. This procedure takes about five (5) minutes
and requires no tools except for a vacuum if cleaning is
necessary.
Cleaning the Combustor
1. Check the combustors honeycomb-like element for a
buildup of fly ash. If any is evident, take the combustor
outside and clean it by blowing air gently through it. Do
not push anything through the honeycomb; do not use
compressed air to clear the passages. Such abrasion can
scrape the thin coating of platinum (the catalyst) off the
ceramic base, shortening the catalyst’s life and reducing
its effectiveness.
2. Inspect the element for damage or degradation. Although
small hairline cracks will not affect performance, the
element should be essentially intact. If the element is
broken in pieces or has sections missing, it should be
replaced. Call your local Vermont Castings Authorized
Dealer for a replacement element.
3. If the element is in good condition and clean, re-install it
in the stove and replace the refractory inner fireback and
access door.
Inspecting the Combustor
Remove access door and inner fireback. Remove the catalytic
combustor by lifting and sliding it towards you, Figure 6.7.
ST1180
catalyst access
Catalyst
Access Door
Inner Fireback
