Modern wood stove combustors are designed for 12,000 hours of use. Depending on the length of the heating season in your area and the frequency of stove operation, this offers 2-5 years of combustor use. The combustor should be replaced every 6 years, or once you begin to notice decreased heating efficiency from the stove or darker smoke emitted from the chimney.
We strongly recommend using a thermometer (such as THIS ONE HERE) to monitor catalyst temperatures. The catalyst performs best between 700°F-1400°F; however, temperatures up to 1600°F are common during normal stove operation. Temperatures 1600°F- 1800°F and beyond will shorten the life of the combustor and could cause damage to other parts within the firebox.
Make sure to only burn natural, seasoned firewood. Burning garbage, treated or painted materials, or any other improper fuel could release chemicals or promote creosote, both of which inhibit the combustor from breaking down flue gases efficiently.
Regular Catalyst Inspection
The combustor should be inspected whenever you clean the stove and chimney. Some stove manufacturers recommend inspecting the combustor every 4-6 weeks of use. Keep an eye out for the following 5 things during the inspection:
Ash – Fluffy, light gray ash occurs naturally during normal use. Ash may fill in combustor cells as smoke is burned within the combustor or may be carried out of the firebox by a strong chimney draft.
Soot – Dark and granular soot deposits may accumulate and clog combustor cells after creosote deposits burn away or when materials other than seasoned firewood are burned in the firebox.
Creosote – A brown, tarry substance that builds up when the combustor was engaged before the smoke was hot enough to activate the chemical reaction of the catalyst. Creosote masks the catalytic coating on the combustor surface, preventing the combustor from activating and promoting more
Cracks and Crumbling – Cracks and crumbling pieces are a warning sign that the combustor was heated or cooled too quickly. Many combustors come with a metal band around the ceramic to hold the combustor in place when cracked. A slightly crumbling or cracked combustor may continue to perform properly as long as no large pieces are missing. Take extra care when handling a cracked combustor to avoid losing pieces.
Peeling Catalyst – Areas where the catalytic coating is peeling away from the ceramic may appear “fuzzy” or reveal patches of bright, white steel. You might stretch the combustor for one more season of use by flipping it over; however, severe peeling calls for total replacement.
For more details on combustor care, refer to the stove owner’s manual or this handy guide from Condar HERE.
How to clean a combustor
Use a soft brush and an ash vacuum to gently remove soot and ash from clogged combustor cells without damaging the delicate catalytic coating. Be sure not to scratch the catalytic coating and handle the delicate ceramic catalyst with care. Removing creosote deposits requires a hot fire to burn away the buildup. First, check the chimney and clean any creosote away before attempting to burn the creosote off the combustor. Failure to do so could ignite a dangerous fire in the chimney.
4 Major Mistakes to Avoid:
Operating a wood stove is an art form that varies depending on the needs of your climate, fuel selection, installation specifications and more. Are you sabotaging the efficiency of your stove by making one of these common mistakes?
Burning Improper Fuel
Fuel selection for your wood stove will vary greatly depending on a variety of factors and personal preferences. However, burning anything other than natural, seasoned firewood compromises the effectiveness of your combustor by poisoning and deactivating the special coating that enables the catalytic combustion process and will void the warranty on your combustor. It also allows dangerous deposits of creosote to build up in your chimney which could result in a chimney fire.
Engaging the catalytic technology too soon will increase the likelihood of ash and creosote clogging the cells of the combustor or the air holes of any air tubes or a secondary combustion chamber. Using a stove and/or catalytic thermometer (like these HERE) will help you accurately manage the firebox and catalyst temperatures.
Dramatic or uneven changes in temperature could cause cracks, crumbling, and, in extreme cases, complete destruction of the catalytic combustor. Prevent thermal shock by only using wood that has been allowed to dry for at least 12 months and contains less than 20% moisture content. Protect your wood supply from rain and snow once it has been properly split and dried.
Large loads of wood, or allowing too much air into the firebox, leads to over-firing the stove. Continued operation that exceeds the standards recommended by the manufacturer of your stove can cause serious damage. The most common signs of this abuse are warped air tubes that bend and sag or rapid deterioration of the baffles and blanket. Too strong of a draft could pull the flame into the catalyst causing the coating to peel and accelerating the deterioration of the combustor substrate itself.
Signs the Combustor Should be Replaced:
Decreased Heat Output – This is an early sign of combustor failure. Use a catalytic thermometer to measure whether the combustor is slow to reach catalytic temperatures, and if the combustor heats to the same heat level as it has in the past.
Creosote Accumulation – A healthy catalyst will produce very little creosote buildup on chimney walls.
Sluggish Performance – When engaging the combustor seems to cause the stove to draw air poorly, then the combustor may be failing.
Smoke Emitted from the Chimney – Significant amounts of smoke from the chimney when the combustor is engaged indicates the combustor is no longer breaking down those flue gasses effectively.