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Articles > Care and Maintenance of Your Catalytic Convertor

9 Oct 2006


Tech Support:     Catalytic Combustor
                                       Cleaning & Care Guide
Your catalytic combustor is designed to withstand 12,000 hours of continuous use, approximately 5-6 years—depending on your firing practices and severity of your winter. Signs of combustor problems include increased smoke from the chimney, creosote accumulation, sluggish performance, smoking, and high fuel consumption.


Proper maintenance will not only increase the effectiveness of the combustor, but will alert you to problems before they become severe enough to require replacement. Keeping the combustor cells clear increases the amount of surface area available to promote the catalytic reaction, and will prevent sluggish operation. There are three ways your combustor may become clogged.


FLY ASH is the normal accumulation of light grey ash, both from combustion within the catalytic unit and from particles carried up from the stove’s fire bed. It can be removed by gently brushing with a clean, soft brush or with a household vacuum cleaner. Do not use high pressure air to clean fly ash. Ash deposits within the cells of the combustor can be carefully cleaned with a cotton swab or pipe cleaner.


CREOSOTE is a brown tar-like substance which is the product of incomplete combustion of wood smoke. It results from engaging the combustor too soon or trying to operate the unit when the combustor temperature is too low. This material must be burned off the combustor. To burn off the creosote, put the combustor back in the stove and burn the stove at higher than normal temperatures for 30 minutes with the combustor engaged. Repeat as necessary until the material can be removed. REMEMBER: If the combustor is coated with creosote, it is likely that the pipe and chimney are also coated with creosote. Be sure to have the chimney and pipes cleaned before operating at these high temperatures to avoid a chimney fire. Be sure the combustor has cooled completely before attempting to handle it again.

SOOT is a dark granular material which can result from burning off the creosote or from burning foreign materials in the firebox of the stove, such as plastics and colored paper. Clean it as you would the fly ash.

 To Clean Your Combustor -
Tools and Material Required:

Combustor removal instructions found within your "Stoveowners’ Manual"
Distilled water—-2 to 3 gallons, enough to completely cover the combustor by at least ½" its thickness, three separate times. Do not use tap water, it contains minerals which may harm your combustor.
White vinegar—-2 to 3 quarts, or enough to mix a 50/50 solution with the distilled water.
An old pot to heat the cleaning solution in.
A metal wash pan or bucket—big enough to completely submerge the combustor into the vinegar/water cleaning solution.
A plastic coated wire or heavy cord.
Number of handtools (i.e. soft bristle brush, such as an unused paint brush, screwdriver, pliers…) Again, refer to the owners manual of your stove for specifics.
Home vacuum cleaner with standard size hose.
Using the clean, unused paint brush and the vacuum cleaner, remove any fly ash and loose soot from the combustor. If some of the cells are totally blocked use a cotton swab or pipe cleaner. Be careful not to damage any of the cell walls by scraping or scratching them with a hard object.
Pour the water and vinegar in the pot forming a 50/50 mixture of the solution. Heat the solution until it is boiling.

 Take the cord or coated wire and form a handle for your combustor. The cord will act as a handle for dipping the combustor into the boiling cleaning solution.

Slowly dip the combustor into the boiling solution and slightly reduce the heat. There is no need to keep the solution boiling once the combustor is in place. When dipping, do not allow the combustor to bump on the bottom of the pot. Dip the combustor, allowing the vinegar solution to easily flow through the combustor cells. Let it remain in the hot cleaning solution for at least 30 minutes.

 After soaking the combustor in the vinegar solution, dry it with a soft cotton towel. Dump the vinegar solution, rinse the pot and boil half of the remainder of the distilled water. Again, place the combustor in the boiling water to rinse. With the water just below boiling let it simmer for 15 minutes. You will want to rinse the combustor using this procedure at least twice. Use fresh distilled water each time.

 Shake the excess water from the combustor cells and dry it thoroughly. Place the combustor back into your stove according to the instructions in your owners’ manual.

 Allow the combustor to sit for 24 hours before lighting a fire. Steam generated from the dampness of the combustor can damage the catalyst material. If the stove must be put back into operation immediately, place the combustor in an oven and heat at 300ºF for at least 1 hour. Allow the combustor to completely cool before attempting to reinstall it into your stove.

 How to Tell When Your Combustor Needs to be Replaced
When you have removed the combustor, inspect it for signs of degradation. If there is any damage to the ceramic or the catalyst materal, replace the entire combustor before lighting a fire in your stove. The combustor can have several types of damage to the material.


Severe Peeling
You will notice the beige coating, or catalyst, peeling off of the ceramic base.


Thermal Cracking
The ceramic material will be cracked in random lines throughout the combustor. Replace unit if large pieces are missing or falling out.


Substrate Crumbling
Caused by thermal shocking when the combustor has had repeated flame contact or has been cooled too quickly.


Mechanical Cracking
Occurs as a result of the combustor receiving a hard bump or from being dropped. The crack in the ceramic will follow a cell wall or line in the combustor. The breakage will not be as random as it is when the combustor is damaged by thermal cracking. Mechanical cracking of a canned combustor will not affect performance as long as the pieces are held in place by the can.

 It is important to replace the old combustor with a new one of the correct size. If the correct size is not listed in the owners’ manual or on the stove, measure the old combustor. Take note if the combustor has metal around the exterior of it. If so, it is a canned combustor, if not it is uncanned.

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