Catalytic Combustor FAQ
WHAT IS A CATALYTIC COMBUSTOR?
Our catalytic combustors consist of a durable, temperature-resistant ceramic composition which is extruded into a specific cell density, creating a honeycomb configuration. It is then cut to manufacturer's specified sizes and fired. We then wash coat the unit with alumina oxide for high surface area coating and precious metal support. Later a noble-metal catalyst, like Palladium is applied.
ORIGIN OF THE WOOD STOVE COMBUSTOR
Hundreds of new stove companies began to spring up. Many of them building stoves with efficiency between 50 and 70%. This was as good as or better than gas furnaces and oil burners. However, the advantages of burning wood for heating was also accompanied with some disadvantages.
Much wasted energy was lost in the smoke (30% in some stoves). The smoke from wood-burning fires produced harmful air pollution Airtight stoves burning slow produced heavy amounts of Creosote.

HOW DOES A CATALYTIC COMBUSTOR WORK?
By definition, a catalyst is not consumed or used up. The nature of a catalytic reaction is often defined as:
Normally, smoke will burn, or oxidize, at a temperature of 1,000°F or higher. Burning a stove this hot would require continuous intense fire and would require a higher wood consumption. The answer to eliminate this is the catalytic combustor.
Wood smoke gases coming in contact with the catalyst causes chemical changes to take place. This will then allow the smoke to ignite at temperatures around 500°F (or 260°C). This temperature is easily achieved in the firebox of a wood burning stove. As the gases ignite and burn within the catalytic combustor, clean by-products of water vapor (H20) and carbon dioxide (C0²) are emitted.

WHAT ARE CATALYTIC COMBUSTORS MADE OF?

WHAT DOES A CATALYTIC COMBUSTOR DO IN A WOOD BURNING STOVE?
WHAT ADVANTAGES ARE PROVIDED BY USING A CATALYTIC COMBUSTOR?
90% LESS CREOSOTE* - Condensation of smoke in chimneys and flues creates creosote build up which is the primary cause of chimney fires. The combustor reduces this danger because it burns most of the smoke and reduces creosote accumulation as much as 90%. However, you should continue to inspect your chimney regularly for safety.
HOW DO I MAINTAIN THE COMBUSTOR'S OPERATING CONDITION?
Combustor temperatures can become extremely hot during operation. Temperatures above 1600°F will damage the catalyst. Temperatures between 1400°F — 1600°F are normal, but temperatures 1200°F — 1400°F are recommended.
HOW AND WHERE SHOULD I MONITOR THE COMBUSTOR'S TEMPERATURE?
HOW WILL I KNOW THE COMBUSTOR IS WORKING?
Some stoves are equipped with a combustor view port. It should be noted that the combustor glows during the first 20 — 30% of the burn cycle, when the catalyst is receiving the most smoke and burning at a high temperature. The combustor can reach 1000°F and produce a glow. The combustor does not have to glow to be working. As less smoke is present to burn, the combustor temperature drops and the glow will cease. It is suggested that visual checking NOT be a method of determining combustor functionality.
Another method is to visually observe the exhaust coming from the chimney. When the bypass is in the closed position, and the catalytic combustor is in good operating condition, there should be no dark smoke coming from the chimney.
If the catalytic combustor is not working properly, the stove's operator will notice an increase in fuel usage and a build-up of creosote in the system.
IS IT ALRIGHT TO "HOT FIRE" MY CATALYTIC STOVE?
DOES THE COMBUSTOR HAVE TO "GLOW" BEFORE IT IS WORKING?
WHY DOES THE CATALYTIC COMBUSTOR STOP WORKING?
WHY DO COMBUSTORS NEED TO BE REPLACED?
Thermal Shock Occurs when refueling with wood containing moisture. Moist smoke is sent to the combustor when the by-pass is closed and the results are thermal shock and cracking of the substrate. Continual practice of this will cause the combustor to deteriorate. Fatigue The catalytic combustor has a six year life expectancy when used according to recommend manufacturer's guidelines. Although some combustors have operated with efficiency for as long as ten years, the combustor's life is based on the stove operator, maintenance, fuels used, and the stove manufacturer's design. Mishandling Dropping the combustor. Using abrasive tools while cleaning it. Using high pressure air to blow the cell free of debris. Using cleaning solvents to clean the combustor. Beating the combustor to remove it from its holding device. Direct Flame Impingement Flames burning for long periods of time directly into the combustor with the by-pass, or damper, closed will damage the combustor. Allowing this to happen will change the make up of the catalyst and reduce efficiency. Flame impingement will cause the substrate to break down. Poisoning This happens by burning materials other than seasoned, dried wood. Foreign matter such as garbage, painted wood, large amounts of colored paper, cardboard, rubber, plastic, paneling, oily products and so on, will eventually reduce the efficiency of the catalyst.
WHY IS "FLAME IMPINGEMENT" BAD FOR THE CATALYST?
WHY COMBUSTORS MAY STRUGGLE TO WORK PROPERLY
Light-Off Light-off was not achieved before the stove's by-pass was closed. This means the catalyst was not at the temperature necessary to receive and burn the inlet gases. This will result in the combustor cells plugging with fly-ash and creosote. When starting a fire in a cold stove, the catalyst needs 500°F of temperature focused on it for 20 — 30 minutes to allow proper light-off. Refueling Wet Wet or unseasoned wood will shut the catalytic combustor down at once. This will result in the combustor's cell plugging with fly-ash and creosote. This will also cause thermal shock to the combustor's substrate and hair line cracks will occur in the cell walls. Masking Masking blankets the combustor with a substance that prevents catalytic activity. This can occur when burning materials other than seasoned, dry wood. Plugging Plugging is a build-up of soot, creosote and/or fly-ash in the combustor's cells. This occurs when the combustor is operated or positioned improperly. Inlet gas temperature must be maintained around 500°F to keep the catalytic reaction active. This will also occur when burning material that produce large flakes of char, I.E. wrapping paper and cardboard.
WHAT CAUSES "THERMAL SHOCK" TO THE COMBUSTOR?
WHAT CAUSES MY STOVE TO BACK PUFF?
WHAT CAUSES THE COMBUSTOR TO BECOME PLUGGED?
WHAT ARE OTHER REASONS THE CATALYST MIGHT LOSE EFFICIENCY OVER A PERIOD OF TIME?
WHAT DOES A HEALTHY COMBUSTOR LOOK LIKE?
HOW LONG SHOULD THE COMBUSTOR LAST BEFORE IT IS NECESSARY TO REPLACE IT?
WHAT ASSURANCE DO I HAVE THE CATALYTIC COMBUSTOR WILL LAST IN MY E.P.A. CERTIFIED STOVE?
Applied Ceramics also offers special prorated prices on the converter for the 4th, 5th and 6th years of the stove's life if ever needed. We couldn't make this offer, if we had doubts about the longevity of the unit.
Combustors bought from Applied Ceramics for existing stoves have a separate 5 year prorated warranty in place.
TIPS FOR INSTALLING A CATALYTIC WOODSTOVE
DO insulate your existing masonry chimney, especially if it's located on an outside wall. Why? Because insulation helps create a proper draft and prevents icing, which can block your chimney.
DO insulate the space between the existing masonry chimney and the flue, but do not use loose pack insulation. Why? Because loose pack insulation can enter the flue and block the flue gases.
DO use the manufacturer's recommended flue diameter. For woodstoves vented through an existing masonry fireplace chimney, use solid pack insulated lining to fit the stove flue into the chimney Why? Because an improperly sized flue will not provide the draft needed to operate the stove. Also, smoke may leak into your house through the air inlets without proper draft.
DO make certain that all seals connecting the stove to the flue, and within the flue, are as airtight as possible. Why? Because tight seals will prevent smoke from leaking into your house and contribute to good draft.
DO determine the correct amount of draft for your stove. Draft is the force that moves hot gases up through the flue. Draft depends on the length of the flue, local geography, nearby obstructions, and other factors. Consult certified installers and chimney sweeps (they may have draft gauges to measure draft). Why? Because too much draft produces an uncontrolled burn and may cause the stove parts to overheat. This can damage the stove. Too little draft will cause "backpuffing" of smoke into the room, or will accelerate the deposit of soot in the stove or flue.
TIPS FOR OPERATING A CATALYTIC WOOD STOVE
-
DO burn only dry, well seasoned wood, not wet or fresh cut wood. Season wood at least twelve months; store outdoors, loosely covered, to allow air to circulate freely through the pile. Wood with snow or rain on it should not be used when refueling. Why? Because "green" or wet wood releases less heat because energy from the fire must evaporate the moisture before producing useful heat.
Why? Because refueling with wet wood will cause moist smoke and cause the combustor to receive a thermal shock which can crack the unit.
-
DO operate your stove in the bypass mode initially as stated above. Wait until stove temperature is hot enough before engaging the catalyst. Why? Because to some extent, the catalyst may reduce the draft. With poor draft, the fire will take longer to develop and the catalyst will take longer to light-off.
Why? Because by closing the bypass too soon, the catalyst may not have reached it's light-off point and a masking of fly-ash and creosote could blanket the unit or clog the cells. Light off could be sluggish and draft could be restricted.
-
DO build and maintain hot fires quickly after initial wood loading. Why? Because a hot fire will help your catalyst light off faster. However, once lit, the catalyst will stay lit even if the fire burns lower. Catalyst temperatures of 1000°F or more are typical in normal operation. Once the catalyst lights-off, it will stay lit at inlet temperatures around 500°F.
-
DO operate the stove's internal fans/blowers (if your stove has them) in accordance with the operating instructions. Some manufacturers recommend leaving the fans turned off for 30 minutes after start up and refueling, and setting them on low for small fires. Why? Because when the catalyst lights-off, you'll notice a sudden increase in the temperature as the catalyst temperature climes to above 1000°F. Also, the catalyst may glow (though not always) and there will be a sudden decrease in visible pollution from the chimney.
-
DO burn moderately sized loads of wood that will provide several hours of uninterrupted burning and minimize door openings. Why? Because minimizing door openings keeps the temperature high, which reduces pollution. Frequent door openings increases pollution.
-
DO NOT burn trash, treated wood, particle board, plywood, plastic, petroleum products or any other foreign matter. Seasoned dried wood only. Why? Trash produces fly-ash. Treated wood, particle board, and plywood contain chemicals that, when burned and inhaled, are hazardous. Other fuels may overheat and damage your stove. Cardboard, foil and plastic may block exhaust flow through the catalyst, causing smoke to spill into your room. Burning foreign matter can also poison the catalyst and cut back on it's efficiency.
-
DO NOT operate your stove in the catalyst bypass mode after the catalyst has reached the recommended temperature (500°F focused on the combustor for 20-30 minutes). Why? Because at this point, your catalyst should be working for you (to produce more heat using less firewood) and for the environment (destroying smoke and the cancer-causing pollution in the smoke).
-
DO NOT over fire your stove, especially when the catalyst is in place. Avoid catalyst temperatures near or above 1800°F. This is another reason to use a catalytic temperature monitor. Why? Because catalytic combustors can be damaged or destroyed by prolonged high heat. If temperatures are above 1800°F, switch to the bypass mode and allow the catalyst to cool down to about 1000°F before resuming normal catalytic operation.
-
DO NOT open the ash pan while the catalyst combustor is engaged. Why? Because this will lead to overheating.
HOW TO PROPERLY MAINTAIN A CATALYTIC WOOD STOVE
-
DO check the catalytic combustor when the stove is cool by shining a bright flashlight (where possible) onto the catalyst's surface from above and viewing from inside the stove; look for large gaps between the catalyst and the sealing gasket. Why? Because the amount of light you can see coming through the cells in the catalyst is a good indication of how clean the catalyst is. Creosote and fly-ash will block much of the light if the catalyst is clogged. Large gaps around the catalyst would indicate the gasket material is missing and gases could be allowed to bypass the catalyst.
-
DO check the catalytic combustor for signs of physical damage (large pieces of the honeycomb missing) or buildup of ash, soot, or tatty materials that might plug up the catalyst. Normal appearance will be a light gray powdery look. Why? Because if pieces are missing the unit will have less catalytic surface area and less efficiency and increase pollution. If buildup occurs on the catalyst and interferes with its proper operation, this will diminish the catalyst's efficiency and also increase pollution.
-
DO NOT burn the a catalytic stove without the catalytic combustor in it. Why? Because the stove's designed efficiency depends on the catalyst. Why? Because the stove will run hotter and damage could occur. Why? Because this will increase pollution. (It's against Federal Law) Why? Because you will burn more wood and get less heat.
-
DO check all gasket material, the bypass damper, and the seams on cast iron stoves, once a year; replace frayed or worn materials. Re-cement the seams if necessary. Check the catalyst gaskets and the gasket that seals the bypass mechanism. Why? Because gaskets in good condition will provide a seal. A poor seal around a catalyst bypass allows smoke to pass through unburned, thereby increasing pollution. Like gaskets, the bypass damper and seams are areas where leaks can develop.
-
DO check the wood-loading door and ash drawer for tightness. Why? Because these areas are subject to warp or worn gaskets. Poor fit may result in overheating or may allow smoke to escape into the room.
-
DO make sure the thermostat (if your stove is equipped with one) is working properly; replace as necessary. Refer to parts list in your owner's manual. Why? Because a broken thermostat can prevent air inlets and dampers from opening and closing properly.
-
DO check the flue twice a month and have it cleaned at least once a year. After cleaning, check the seals and re-tighten joints in the flue and to the stove. Why? Because clean flues reduce the risk of chimney fires; tight seals and joints prevent leaks.
-
DO replace firebrick and other insulating materials when you see cracking or buildup. Why? Because these insulating materials are critical to your stove's heating efficiency and pollution reduction properties.
-
DO NOT remove or tamper with the preset operating or temperature controls. Why? Because it is against the law, it will void your stove's warranty, and will create a safety hazard. The stove will be less efficient and more expensive to operate.
-
DO take advantage of the technical assistance provided to you by your dealer, the stove manufacturer and the manufacturer's of the catalytic combustor. Why? Because this service was paid for when you purchased your catalytic wood burning appliance new.
TROUBLESHOOTING - PROBLEMS, CAUSES, AND SOLUTIONS
|
|
|
---|---|---|
(See Photo #1) |
|
|
|
|
|
(See Photo #5) |
|
|
(See Photo #6) |
|
|
(See Photo #7) |
Burning wet, pitchy woods or burning large loads of small diameter wood with the combustor in the operating position without light-off ever occurring. |
|
(See Photo #8) |
|
|
Examples of Combustor Conditions








HOW AND WHEN TO CLEAN THE CATALYTIC COMBUSTOR
Should the combustor's cells become masked with fly-ash, use a soft bristled brush or paint brush to dust the combustor gently.
NEVER USE ANYTHING ABRASIVE to clean the combustor. A vacuum cleaner may be used, but NEVER USE HIGH PRESSURE AIR to blow the cells of any build-up. Any cell blockage can be removed with the use of a pipe cleaner or cotton swab.
Should the combustor become masked with soot or creosote, it is possible to burn the accumulation off by opening the bypass and building a hot fire. Once the hot fire is created, close the bypass halfway and burn for 30 — 60 minutes with the bypass in this position.
Midwest Hearth strongly recommends that it would be wise to check and clean the combustor before each burning season and inspect all flues for creosote build-up. Cleaning the flue helps prevent chimney flu fires.
HELPFUL HINTS ON SELECTING FIREWOOD
However, if you are a serious wood burner using a catalytic wood burning stove, hardwoods are your best choice. Hardwoods such as Oak and Birch provide a longer lasting fire with a shorter flame.
Never put chemicals of any kind in your stove. They can stop the combustor from working.
Never burn rubbish, chemically treated wood such as discarded railroad ties, utility poles and old yard fences. All will emit poisonous fumes and could add to those materials that collect in the chimney, thus increasing the possibility of a chimney fire.
HOW TO PREPARE YOUR FIREWOOD
Splitting and Stacking
Splitting logs hastens drying. The key to seasoned wood is that it has been split. Splitting exposes the wet interior and increases the surface area of each piece that is to be air dried or seasoned.
Stack split wood or small round logs to allow air circulation and leave it under cover for 10 to 12 months, if possible. This will provide the best heat yield from the wood when ready to use.
REMEMBER:
Re-fueling with wood that has moisture in or on it will create a damp smoke that shuts the combustor down once the bypass has been closed.
Storage
A woodshed is best. The idea is to keep the moisture off the wood while drying to allow proper ventilation. Store the wood away from the house as it can become a home for insects.
SELECTING THE RIGHT FIREWOOD
|
|
|
|
|
---|---|---|---|---|
HOW TO BUY FIREWOOD
A "truckload" is not a standard measure and depends on the size of the dealer's truck. A standard pickup holds only about 1/3 — 1/2 of a full cord. If you have purchased a cord of wood that you feel is not a full cord or not the species you ordered, contact you State Bureau of Weights and Measures.