Wednesday, September 21, 2016

Downdraft Wood Stoves: Consumers Beware

The simplicity of the non-catalytic stove makes it the most popular type of stove in North America by far.  With most non-cats, the consumer only needs to worry about a single lever to regulate the amount of air in the firebox.  But some consumers unwittingly buy a very unique kind of non-cat, a  downdraft stove, and often regret it.  

June 2021 update: The number of new downdraft models are dwindling but they still appear on the second hard market.  We are not aware of any on the market now.  Please let us know if you know of one. AGH has applied for DOE funding to design and build a new type of fan-assisted downdrafted stove that would overcome the issues of older, manual designs.)

There used to be a handful of downdraft stoves on the market but were gradually been pushed aside by non-cat stoves with air tubes that reburn smoke as it exits the firebox.  The downdraft stove works with a second lever that engages a by-pass damper which forces the smoke down into a chamber where heat can reburn it before it goes back up the chimney. 

Almost all stoves on the market today do not try to get smoke to go down, but rather try to reburn it on its journey upward with secondary air introduced through holes in tubes or in upper wall of stove – or with a catalyst. Hybrids use both tubes to inject for secondary air and a catalyst.  (Click here for more on cat, non-cat and hybrid stoves.)

Downdraft stoves tend to be finicky, need to be very hot to work properly and are more prone to leaking smoke into the house.  Most consumers should not consider them unless they know what they are getting into and are prepared to be much more engaged with their stove.  The same can be said about catalytic stoves.  Consumers should understand that they need to know how to use the second lever that engages the by-pass damper and occasionally check the catalyst, and replace it when it needs replacing.

Stove change out programs, that switch out old stoves with new, EPA certified models may want to exclude downdraft stoves from eligible replacements as they may be the hardest class of stove to run consistently without visible smoke. 

The downdraft stove became popular in the 1980s when Vermont Castings used it to extract more heat from a stove and to help pass the emission testing required by the state of Oregon, and later by the EPA.  The by-pass damper helped slow down the fire, create turbulence, and extract more heat from the hot gases before they went up the stack. The Resolute Acclaim, one of the most popular wood stoves of the last century, was a downdraft stove.  It clocked in at 3.4 grams per hour and continued selling through the 2000s, but has since been taken out of production.

The Harman TL300 is a downdrafter but now discontinued and Vermont Castings may have discontinued theirs.  The Lopi Leyden and the Avalon Arbor (same stove) went off the market in 2012. There may be better designs of downdraft stoves that are easier to operate in other countries.

The original Frankin stove
was a downdraft with no
front door and often
made for a smoky house.
Downdraft stoves have existed for centuries in various designs. The original stove invented by Ben Franklin also had a downdraft incorporated into the design, and it is one of the reasons that the stove was so finicky and disfavored by the majority of consumers. Franklin himself admitted that the stove was difficult to operate and took lots of attention and wasn’t something that “could be left to the servants.”  Later iterations of the Franklin stove added a door and most got rid of the downdraft.

Consumer feedback

Hearth.com is a premier chat room for wood stove experts and rookies alike. It contains a lot of good feedback on downdraft stoves:

- “The creosote smell when closing the bypass is not an uncommon issue with the downdrafting stoves. I've seen Harman stove owners complain with it as well. I will sometimes get it. Sometimes not. It's not noxious, just a faint odor that I can do without. CO monitor pays it no mind.”

- “I wish a group of downdrafters could get their heads together on this one and figure out what is going on. It's a common problem to different stoves. Maybe that box full of smoke is letting some escape at the joints.”

- “I've smelled it when the draft was strong, but typically it comes when the flue has begun to cool down a little. Loading lid was a prime suspect, but I regasketed it and sat a cast iron pot on there.”

- “Downdraft stoves are notoriously fussy and demanding of a strong draft.”

- “The Leyden has undergone a few changes of the years. There are some ports that need thorough cleaning "Monthly" as well and they are not easy to reach. Make sure these ports are cleaned regularly. Your manual shows how to do this correctly.”

- “These stoves have to be seriously hot to work.”

- “I sometimes get a bit of smoke when loading. Mostly because I'm too lazy to do it right. Again, operate the stove as designed and if it doesn't work, get a look at the flue, check for ash buildup, etc.. ... your flue design is gonna be a tough one.”

- “I don't want to melt your stove down, but my hunch is that you're not getting it hot enough on a 3-4" coal bed.”

- “Is the wood very well seasoned? That is very important with this stove as is a good draft.”

- “I would try running your stove top temperature a little higher (650-700) before you go to secondary burn, typically you get some drop in stovetop temperature when you close the damper.”

- “The Lopi Leyden is a very problematic stove. You don't want it, believe me!”

- “I also suggest to take off the Vermont Castings Resolute and Lopi Leyden. Both use a different mechanism to achieve a clean burn than the other non-catalytic stoves. Both stoves usually have a steeper learning curve, can be prone to costly repairs and are better suited for full-time burners which does not seem to be your intention.”

- “As others have mentioned, the Oakwood (and other downdrafts like Lopi Leyden and certain Vermont Castings models) can be a bit fussy about dry wood and good draft, requires a bit more babysitting and longer learning curve, and is not well suited to slower/lower burns in months like November and April.”

- “You want a stove with tubes in the top or a catalyst. Avoid stoves that draw smoke down into the back of the stove. For example: Vermont Castings, some Harman's and Lopi Leyden.”



12 comments:

  1. In the Canterbury district of New Zealand a tough new emissions test has been written called Canterbury Test Method 1. This new test uses wood as delivered by a merchant that includes knots and bark. The measure measure start up emissions, plus additional test runs to the normal softwood fuel using wet wood of 25-30% MC, and a hardwood load. Typically this stoves have to achieve less than 1g of emissions for the 1kg start up load. To date only 8 models of stove have passed this test, they are all downdraft. Downdraft fires are the fires of the future.

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  2. Thanks for this post. We should probably add a line in blog saying its based on existing downdraft stoves on the US market. Do all the ones you mention have lever to close a by-pass damper? If so, they may be more consistently clean in the lab than with average consumer. John A.

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  3. Leyden and Arbor have been off dealer's sales floors since 2012. So readers beware, author has not done full research on today's market.

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    1. I agree, as I have been using my Temp Wood stove for over 25 years and never had a smokey house. It has no damper,no gaskets, just a tube on both sides of the stove. Air is regulated by the round metal discs that can cover the tubes and regulate the air intake.

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  4. We have used wood as our primary heat source for over 40 years. Our firewood, personally cut from our own land is a combination of fir and alder that is cut, split and dried for a year before burning. We used a Vermont castings Resolute with little or no problems and routine maintenance from the early 1980's until 2004 when we decided to upgrade for better EPA rating. We purchased a Lopi Leyden. The combustion chamber of the first Leyden literally fell a apart within 18 months. After sending out a technician to inspect our stove, wood and burning habits, Lopi replaced the stove for free. The second Leyden has repeatedly had the same problem and I just finished the 4th total rebuild of the entire combustion chamber. This stove is a total "POS". Stay far, far away from it. We will be replacing the Leyden this next Spring. Not sure yet what to purchase but we do like a top loader.

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  5. Cook stoves are downdrafters as well. It's necessary to heat up the oven.

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  6. we got an Avalon Arbor back in 2010 . It's our only source of heat. I had no idea until just now 2019 in this article that it is a downdraft stove . I was always trying to figre out where the airpipes were. It always worked okay. I never thought of woodstoves as being a "set it and forget it" kind of thing. We burn seasoned eucalypts exclusively, locally obtained. Dry! This year this stove acts like it's choked all the time. I went on the website to see if there is anybody's experience with that; like, they experienced that and maybe cleaned it somehow and it got less chokey. Tell you one thing -- those six littleholes in the back firebrick make a big difference. Poike those little guys with an awl or something similar on a reglar basis (hint -- the "outside" holes are at crazy angles !)

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  7. My Dad had a stove years ago that was hydronic. It had a large chamber at the bottom for wood, and about the same size for the top for the water, and tubes for the smoke exhaust ran through the water chamber and out the stack. It was amazing for warmth and we never had a problem heating the house via the radiators. Is there anything like that on the market today? Thanks

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  8. Are there any tempwood ll out there in good condition for sale?
    Pictures of all sides pls

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    1. I have had a Tempwood 2 since 1976 and would never sell it... Its a gem , puts out 55,000 btu s easy to light and stay lit..Best stove out there no matter who says what

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  9. so what about the Sedore? It is downdraft-ish.

    https://transnorth.ca/product/sedore-canadian-2000-multi-fuel-biomass-stove/

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  10. Can anyone tell me what is the magic temperature for using the reburn on my VC resolute and is it OK not to use it? Thanks!

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