Electrical draft inducer

I installed a draft inducer on an Ideal Steel stove recently and was asked for some photos of what it looks like. As the inducer does not really apply to any one stove, I thought I would just start a new thread specifically about the inducer. First, the photos:

From the front (note, the eye does not really see any red color although the camera picked it up):


From about 45 degrees, showing the actual fan, the motor and the control box where the switch / rheostat is mounted:


Finally a view from the side and a little from the rear- this view is where you would see the back of the stove from:


When first installed, it leaked so badly that it was unusable in my opinion; it filled the stove room with smoke escaping from the gaps in the housing as well as where the inducer itself was mounted to the smoke pipe. I did a very 'quick and dirty' thing about the housing gap and simply wrapped electrical tape around it. Before anyone (or everyone) asks: no, that is NOT a great idea and NO, electrical tape is not a great method to seal the exhaust of a woodstove. That said, I do monitor and record my exhaust temperatures and they never, ever exceed 600F so it is not likely that the tape will melt either. In actual practice, the tape shrunk a bit and got somewhat shiny but seems to be stable; I plan on removing it and using silicone sealant on the seams next year. As to the rest of the leaks, I filled them with extreme temp. silicone sealant rated at 700F and just dusted a coat of black stove paint over it to hide the red color. Finally, there is a large hole in the side of the housing where the motor shaft connects to the fan itself; that had to go and I used quite a few folded layers of aluminum foil to basically block the hole off. It is not airtight but as there is always a vacuum present at that point in the housing, whether the draft inducer is running or not, it is sufficient for now and again will be replaced next year.

And I only run the inducer when opening the stove door and never, ever at any other time or for any other reason (such as starting a fire, a fuel re-loading, etc.). There was one last problem in that the stove pipe joints, including all the joints in the elbow above the draft inducer, are subjected to internal pressure when it runs on 'high', there was a bit of leakage at those joints for a time. Nothing near the amount that would leak out the stove door when it was open before the draft inducer was installed though so I would call this an improvement. And please understand that a bit of smoke and some very fine fly- ash would sneak out of those seams only- it was not as if it was shooting out flaming bits of wood or coals . Lately though, those leaks seem to be diminishing or stopping entirely; I suspect the very small gaps are being clogged with very fine ash and the situation is 'fixing itself'.... sorta', kinda'.

Now, how does it work: It works great! I do not run the inducer with the door closed, ever, as it sucks up a lot of ash so first thing is I open the bypass, then open the door maybe 3" or so. Then flip on the inducer and open the door as much as I want, including fully open. No smoke or ash spills into the house and I can take my time reloading the stove, scraping coals around, dumping ashes and cleaning the window. Then I push the door to w/in 3" of closed or so, turn off the inducer (and wait 5 seconds for it to wind down) and close the door. It absolutely solves the problem of smoke spillage as well as fly- ash getting into the room where the stove is (and sooner or later, everywhere else too).

I am not really suggesting everyone run out and get one, and if anyone's stove is working for them without the inducer I would say that is the best possible way because it is less complicated, requires no electricity and less expensive to use a wood stove without the inducer but if smoke and / or dust is a problem, it might be worth considering.

By the way, this is a Tjernlund AD-1 model and is made for use on wood and coal stoves. It comes with a rotary switch / speed controller and only requires a regular household AC cord to plug the unit in. They are meant to be used continuously when the wood / coal stove is running so should be up to that task. I point this out because there are a lot of in- line draft inducers that are absolutely not meant to go into the flue of any wood or coal stove; they are usually galvanized and do not have a switch / speed control. This model is flat black and does have the control already.

Brian

 

Thanks for the write-up and pictures Brian. I'm really contemplating one of these sorts of fans for my Daka that resides downstairs with 25' of chimney outside. It has a decent draft once fired up but reloading can be a smokey affair, even after I re-installed the door flapper thing that hangs down inside the firebox.

 

Glad to help if I can- these forums have contributed a great deal to my own knowledge of burning wood, wood stoves, chimney, etc., etc.. The collective knowledge shared freely is a hugely powerful tool IMO.

And you bring up a good point that I kind of forgot: my use of a draft inducer really has nothing to do with a Woodstock stove; I believe any and all stoves with modern, large doors suffer the same thing. I watched a Jotul 500 chug an impressive amount of smoke into the room as a friend of mine showed me that he could open the door without smoke spillage . I certainly did not mean to imply in any way that draft inducers are needed or more useful on Woodstock stoves than any other brand or type: opening up a 180 square inch hole in the front of a stove and expecting all that air, along with the smoke from an active fire to race up a 6" diameter (28 square inches of exhaust) is really pretty silly IMO. Natural draft is more of a 'suggestion', induced draft by mechanical means is more like insistence.

Brian

 

Most draft inducer work OK, but some are better than others. One important principle is that the flue gas system should be under negative pressure for safety reasons. Only chimney top inducers can accomplish this. Rotating paddle type inducers push flue gases up the chimney and leakage is possible. Paddles can also foul with creosote if stove is not clean burning (no secondary air). These are the reasons we at Heat-Booster developed a chimney top venturi type Draft-Booster. It keeps entire system under slight negative pressure and there are no fan blades or paddles in contact with flue gases. A clean air flow creates the draft. See picture of our first prototype being tested. There is no visible smoke because the Durango Stove (a very interesting but temperamental unit) is clean burning. The inducer drops into chimney opening and it is fastened with a couple of metal straps that are attached to chimney with a hose clamp. A countdown timer is used to operate the blower in the unit.
We believe the design to be perfected at this time. Unit is all 316 SS for parts in contact with flue gases.


The Draft-Booster is part of our other system, the Heat-Booster. See below pictures. Thermal efficiency of the system is in the 90% range when burning good dry wood. The Durango stove loads North-South and burning starts from door end. A fully loaded stove will burn clean for many hours. It is good that all the wood is not burning at same time. This type of stove needs very good draft to operate properly.
Heat-Booster reclaimers create pressure drops that must be compensated for using Draft-Boosters. This is because the tubes in the unit and low flue gas temperature after the unit. See picture of our first test unit. Design of the Heat-Booster has also been perfected after many years of development. The system that I have described typically uses half the wood compared with a standard EPA type stove. Durango stove, as shown in picture, has no problem keeping a 2,400 ft2 house warm (>75°F) during the coldest days in winter. Complete combustion with excess air, and efficient heat recovery makes it possible to get 90% thermal efficiency. Catalyst drawer shown is not required as the stove burns clean. In fact, the catalyst never "lights up".

 

Ok so you are pulling heat off the flue pipe by adding a third chamber in the case of a double wall flue or by using the double wall and pulling heat off the single wall flue pipe- there by reducing the flue gas temp which then needs additional help to exhaust and may or may not in this imperfect world cause creosote build up in the flue due to the lower temp of the exhaust gases. I do not see anything new or exciting about the expanded triple/double chamber with forced air flowing though it to reclaim flue heat at that point all been done before with the aforementioned possiblities. On the other hand the off set induction unit I see as a step forward being that it creates a neg. pressure at the flue exit and is not in the exhaust flow directly nor pumping cold air into the flue there by cooling things down with the possibility of increased condensation of undesirables and the resultant accumalation of same. I am ignoring the cat at present as you stated that it was not firing. If the cat was firing I would guess that the temps indicated in picture would be considerably higher. Thus would change my outlook on portions of the flue beyond your reclaimer installation.
I could see the external cat/ heat exchanger portion as being possible to retrofit or as a inclusion to meet new epa requirements as to particulate emmisions .

 

The Heat-Booster is not just a double wall stove pipe, but an actual heat exchanger with many internal steel tubes. Double wall stove pipes are not very good reclaimers as surface area is not increased. Picture shows a prototype used for testing. Design has been much improved over the years. New design has fewer but larger tubes plus an internal by-pass tube for use when loading wood. Thermal efficiency is amazing.
The catalyst was found to increase temperatures only slightly when it was working. Just the right amount of excess air must be supplied for the catalyst to function.

 

Interesting, Are you experiencing any build up of creosote on the vertical tubes in the exhaust flow? In the early 2000's there was a stove out of MN. that the top third was a heat exchanger in the exhaust flow , cross wise ( kind of like a Magic Heat on extreme steroids) as it was located just above the burn chamber( stove had secondary tubes as well) it did not have a problem with creosote build up at that point- but was equipped with a movable plate that exchange tubes were mounted through. This to clean any possible build off. It was a interesting design - likely killed by the testing requirements of our EPA as it was just a fledgling startup at the time as I have not been able to find anything on it anymore.( Epa requirements killed a lot of interesting designs back then) To the best of my recollection it did not have any bypass for startup/reload at the time. No cat used in it.

 

"Creosote" is a catch-all for anything solid or semi-solid from flue gases. A clean burning stove operated at medium to high firing rates will not produce "creosote". It will however leave a buildup of particulate ash that needs to be removed periodically. "Creosote" of the organic kind is a result of incomplete combustion due to low firing rates with lack of oxygen. I do not recommend use of reclaimers in these situations. My preference is to clean the tubes (a wire brush on a rod) periodically, rather than using twice the wood. Cleaning time is less than 10 min.