Catalytic or Non-Catalytic: Which is better?We have both catalytic and non-catalytic woodburning stoves in our showroom, and we find that each has its own unique advantages and disadvantages. First, let's go over the process of what a catalytic stove does to burn the smoke and creosote.
CATALYTIC:A catalytic stove uses a catalyst (catalytic converter or catalytic combustor) to reduce the temperature that smoke catches fire at. The catalyst looks like a chunk of honeycomb from a bee's nest, placed in the path of the smoke. Ordinarily, it takes a temperature of approximately 1100 degrees for smoke to catch fire. The catalyst lowers that temperature to approximately 500 - 550 degrees, allowing the smoke to safely catch fire while still inside the stove.
The catalyst then quickly gets hotter and hotter, until 15- 20 minutes after reaching 550 degrees, the temperature in the catalyst will typically be reading around 1400 to 1700 degrees, depending amount of wood in the stove, how dry it is, and the size of the catalyst. Soon, so much heat is being given off by the catalyst that you don't need a big flame to keep warm. You can then choke down the air to produce a smoldering fire, even to the point of putting the flames out, and the extra smoke produced serves as fuel for the catalyst. This greatly reduces the amount of wood needed to produce the desired heat, reduces the amount of creosote buildup in the chimney, and greatly increases the "burn time" for that load of wood.
This photo of the Earth Stove 1003 in our showroom was taken looking up through the door, showing the catalyst glowing red hot at the top of the firebox. The temperature of the catalyst was reading 1700 degrees!
We have used the 1003C by Earth Stove to heat our entire 3000 square foot showroom since 1989. (We have no central heat and use only wood heat. The front is 60' by 10' of single layer glass!) It has the longest "burn time" of any woodstove we have ever seen. After loading up the stove, catching the new wood on fire, and shutting it down to the point of putting the fire out, we can leave the store at 5:30PM and come back 8:00AM the next morning to a bed of coals 8" deep. Ask us for other details about this stove!
NON-CATALYTIC:Non-catalytic stoves use an "air injection" method which literally injects jets of pre-heated air into the fire to ignite the smoke and creosote. The draft pulls hot pre-heated air into several tubes running across the top of the fire-box. Each tube has rows of tiny holes. Heated air squirts through these holes, creating jets which fan the smoke into very active beautiful flames, which look like a gas burner squirting flames down from the top of the firebox.
PROS & CONS:The main drawback to the non-catalytic air injection method is it will not hold a fire as long as the catalytic method. It needs the air flow to burn enough smoke to pass the EPA's clean-burning tests. The wood then burns up faster, which is less convenient and somewhat less efficient. Since the air tubes reach glowing red temperatures, they too will eventually need to be replaced.
We have found that the Lopi Liberty, which is the cleanest burning large EPA certified stove is an exception to the generally short burn time available in most non-catalytic stoves. We installed the model shown in the photo in our showroom in 2000, and found that it would still allow us to stuff the stove full, leave by 5:30 and still have a 3" bed of coals to return to in the morning.
So, the advantages of catalytic stoves are increased efficiency and longer burn time. Among the disadvantages is that learning to how to use the catalyst to get the best efficiency is a bit more tricky that a non-catalytic stove, and many manuals for catalytic stoves are not very helpful. We at Custom Fireplaces & More have written our own "Catalytic Woodstove 101" guide, which explains how to get the best out of the catalyst step by step when breaking in a new stove. We also make ourselves available to answer any questions a new stove owner may have. Eventually, the catalyst will have to be replaced. Average lifespan of a catalyst is about 6-10 years, if a person follows our operation and maintenance guidelines.
You may hear that wet or green wood is bad to use in a catalytic stove because such use may harm the catalyst and greatly shorten its life. It is certainly true that you will not get the best heat out of such wood, but that is also true when using green or wet wood in a non-catalytic stove. It is also true that if one does not understand what to do with a catalyst, it is easy to "glop it up." Using a catalyst for the first tome can be compared to a successful driver used to only an automatic transmission, suddenly switching to a manual without understanding how to use the clutch.
There is no really any rocket science to using a catalytic stove correctly. The catalyst must pre-heat to at least 500 - 550 degrees before closing the damper that forces the smoke through the catalyst. The better stoves will offer a thermometer to show you what the temperature is. Obviously, if wood is wet, this pre-heating will take a lot longer than if the wood were dry. If the damper is closed too soon, and left alone all day or night, and then the same thing happens the next day and the next day, it won't be long before the catalyst will get clogged with the creosote that it never got hot enough to begin to burn off. However, once the catalyst does reach the "light-off" temperature of 500 - 550 degrees, it quickly gets hotter. Within the next few minutes, even if the flame is smothered, it will still keep on burning the smoke & creosote.
The EPA actually has a stricter standard for catalytic stoves and a more relaxed standard for non-catalytic stoves. Depending on your expectations and priorities, one of these methods may stand out as your clear choice. If you have any questions about which method is right for you, feel free to e-mail us.