New member and new to wood burning. I purchased a harman tl300 this last fall and have a few months of burning under my belt. I cannot get this stove kick into the after burn mode. After reading the endless threads on this stove I feel I am doing everything right. The stove has 20+ft of chimney, the wood is oak and ash,standing dead with little to no bark remaining on the tree, I get a giant bed of coals, and engage the afterburn once the stove top hit s 500 to 550 which other members say is the sweet spot. Temps drop gradually and no jet engine sound. I will have some hot coals in the morning but thought these stoves gained heat once engaged and would sweat you out of a room. .any thoughts would be greatly appreciated!
Harman tl300 afterburn issues
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mellow
Resident Stove Connoisseur
Welcome to the forums..., there can be quite a learning curve here, until you get a feel for the stove in your particular set up. Very commonly, the problem is shutting the bypass too soon, or the primary air too far/too fast.
First... when was that wood cut/split/stacked? Standing dead may or may not be dry enough, and the Harman stoves do like it very dry for the AB to run. Also, is that 20' a 6" flue?
I found that stove top temp was not always a good indicator for getting the AB to fire. A deep coal bed is a good start, but make sure the coals or your splits are not blocking the center shoe brick (with the holes) so the gasses can flow freely.
Once the coal bed is established and you've added more wood, that needs to burn several minutes or more at full air before you close the bypass... only then can you start stepping down the primary air, in a few stages (if the AB does not stall, a load of dry wood can burn with air almost fully shut. Sometimes. my Oakwood would be at 700+ before the AB would be ready to fire without stalling. If it stalled, I would open the bypass and air and try again. How are you setting the primary air contral over the course of the burn?
My stove pipe is 6 inch. The wood was c/s/s this fall. .could there still be too much moisture in it? The fires catches and rages in the normal burn mode, no signs of any issues that I can tell. ..?thanks!
how long are you burning to get the top to 500-550? I can't burn with the damper open over 3-4 minutes, or i hit over 1100 in the flue.
I reload at 400-450 (approx) on stovetop,,hot coals,,, packing it full. Usually, as soon as i get it loaded, i close the bypass (because i load hotter then most people). I set my air in front at notch 3 and almost immediatly the flue temp will start climbing, (afterburner lights as soon as i close bypass) while the stovetop will be cooling down due to all the new wood shielding it from the heat and the air going (downdraft) down the front and back thru the afterburner in back of the stove.
About 45-90 minutes after reload the flue will climb to 1000-1200 degrees unless i shut the front air down to just under the first notch. The flue will stabilize between 700-900 while burning off the gas, (air down) depending on the day and temp outside,,,,then drop down to 400-500 for the rest of the burn cycle. If i shut air off completely,,,before the flue gets high,,,i can hold flue temps down to 600-750 while burning. The stovetop will be gradually raising to 500-600 during this. When the load is done offgassing,,,the flue temp will drop like a rock,,,and i start running the stove by the stovetop,,,,, opening the air more, as needed, to keep the stovetop at 500-600. As soon as the air control cannot hold stovetop over the 400,,, I reload and start again.
If i am leaving,,,I load,,, shut bypass, move air to 1/2 to 3/4 notch open and leave. The stove will burn for 12 hours or so with stovetop getting to 600 and then running about 400 for last 50% of burn cause i am not there to open air. If I leave air over that first notch,,,my digitals will report high temps of 1000-1300 deg in the flue,,,so i dont do that.
your temps will vary,,,just saying what happens at my house on my TL300. I use digital probes in flue.
I reload at 400-450 (approx) on stovetop,,hot coals,,, packing it full. Usually, as soon as i get it loaded, i close the bypass (because i load hotter then most people). I set my air in front at notch 3 and almost immediatly the flue temp will start climbing, (afterburner lights as soon as i close bypass) while the stovetop will be cooling down due to all the new wood shielding it from the heat and the air going (downdraft) down the front and back thru the afterburner in back of the stove.
About 45-90 minutes after reload the flue will climb to 1000-1200 degrees unless i shut the front air down to just under the first notch. The flue will stabilize between 700-900 while burning off the gas, (air down) depending on the day and temp outside,,,,then drop down to 400-500 for the rest of the burn cycle. If i shut air off completely,,,before the flue gets high,,,i can hold flue temps down to 600-750 while burning. The stovetop will be gradually raising to 500-600 during this. When the load is done offgassing,,,the flue temp will drop like a rock,,,and i start running the stove by the stovetop,,,,, opening the air more, as needed, to keep the stovetop at 500-600. As soon as the air control cannot hold stovetop over the 400,,, I reload and start again.
If i am leaving,,,I load,,, shut bypass, move air to 1/2 to 3/4 notch open and leave. The stove will burn for 12 hours or so with stovetop getting to 600 and then running about 400 for last 50% of burn cause i am not there to open air. If I leave air over that first notch,,,my digitals will report high temps of 1000-1300 deg in the flue,,,so i dont do that.
your temps will vary,,,just saying what happens at my house on my TL300. I use digital probes in flue.
Seems a bit early for the afterburner to need cleaning, but may be worth a try. Proceed with care.
It will take me a couple of hrs of solid feending of smaller sized stuff to be able to get in the 500 s stove top temp. I don't have a flu thermometer. Is that a better indicator of when to engage rather than the stove top temp?
Yes, I think flue temps are more important. Again, where are you setting the air?
My stove may be a bit different, but w/ air and bypass both open, yes, fire will rage and do so even with subpar wood. With no damper or bypass to slow the draft, the stove can really take off in that mode. Many times, w/ a good load of dry wood from a cold start, I would have to close the primary air down before the coal bed was deep enough to engage the bypass, just to keep the stove and flue from overheating. Once I thought INSIDE the stove was hot enough to get secondary combustion, I would open the air back up for a minute or two, and THEN close the bypass.
You may just need to find the right timing, technique and settings by trying a few different things. Keep experimenting. But inability to reach temp after such a long time makes me think wood is still damp. I burn a lot of standing dead, but usually cut/split/stack spring and summer so it has all fall to really dry out. Then I cover it, or bring it in to the barn, in mid/late fall before the rains.
If you are feeding it for hours to get 500f, something sounds strange. (How small is "small stuff" and how full are you filling the stove?) Is the bypass damper is open the whole time? My Oakwood would reach excessive temps, both stove top (800+) and flue (1200+) if I left the bypass open for hours (unless I shut primary air all the way).
From a cold stove, depending on wood, should take 30-60 minutes and only 5-15 minutes on a reload w/ deep coals before bypass can be engaged without stalling. You don't always hear the AB kick in with a loud whoosh, but check your stack outside: if you see smoke, you know it stalled..
mellow
Resident Stove Connoisseur
Wood is still too wet, these downdraft stoves love dry wood, ie wood that has been c/s/s for a minimum of a year in a windy spot.
I leave the air intake wide open for the vast majority of the "coal bed building time". Then I move it to the left to the very middle notch, and there are 3 more notches farther left depending on how much you want it chocked down. Once I engage it I give it and few minutes and I try one of the bottom three notches. Nothing seems to work. The smaller pieces I use in the being stages are probably 3" ,maybe 4"x16 or 18"
Should I try and get a moisture meter for that wood? The stuff practically splits one handed .sure seems dry but maybe not enough?
If you have single wall pipe, try to get a reading on your flue... I bet it's getting pretty hot. Not sure how the cast iron top of my stove differs from yours, or where and how you are measuring temps, but a few hours of wide open air and open bypass should be getting that stove well over 500f, unless you have some sort of draft problem (in a basement?) or that wood never dried out... as I said, when I am getting a coal bed going I have to close my air right down sometimes to keep stove/flue from getting TOO hot before the coals are formed.
If you shut the air down to different stages early in the burn, w/ bypass open, does the fire still rage? What are stove temps then, with little or no primary air? (Another thing to consider with air wide open is you are pushing a lot of heat up the flue.)
Itsdouble wall pipe. I'll have to get one of the probe types to get a good reading I think. If I close the air down with bypass open, I notice instantly the flames aren't dancing as much and can tell a lack of air.
mellow
Resident Stove Connoisseur
Absolutely, even softwoods won't season in that short of time. What wood are you burning?
I cut with a guy this last fall who is an avid wood burner, who has a new efficient stove and said this stuff was premo, ready to burn. No I didn't buy it we split the stuff up, so he wasn't trying to smooze me.. I ll get a meter as soon as I can. This thing is driving me mad!
That is the term for the burn technology of these stoves, in which closing the damper forces the combustion gasses "down" and into the rear chamber, where they are (hopefully) re-burned in the secondary combustion at very high temps.
Most stoves have "burn tube" technology, where heated air enters the top of the firebox (via many small holes, sometimes in steel "tubes" but sometimes in a steel manifold without tubes). In these stoves, the secondary combustion then occurs right at the top of the firebox, rather than in the hidden rear chamber, so you can actually SEE the re-burn occurring, rather than just hearing or hoping.
Then there are catalytic stoves, where smoke is re-burned via the combustor but at a much lower ignition temperature than is required by the other two stove types.
The downdraft type is the trickiest type to operate, as it requires ideal draft, wood and user technique... and often comes with higher maintenance and greater heat loss through the flue.
Not sure the best moisture meter to get, but you could also try getting some kiln-dried firewood or even lumber scraps to run a few loads through the stove and see how results differ.
It takes me approx 1/2-3/4 hour to build small coal bed,,then i burn a small load to get that coal bed deeper,,,then i burn 24hrs a day until it hits above 40 deg,,,then i give it up to the geothermal. I probly only build 3-4 fires a year. The first fire sucks in these stoves. Sounds like you take way to long to get it going. You will love a digital pipe probe, and be surprised at the high temps it will show. I have noticed my afterburner will start better with less air sometimes,,,but if your wood is wet,,,you will fight it the whole time
MishMouse
Minister of Fire
I think your wood is to wet, what is happening is the outside of the wood is dry causing it to catch fire, but as the inside heats up and lets off the moisture it is stalling your AB. Try splitting your wood into smaller pieces and running your air higher once you engage. With dry wood and a good draft it will work really well, with wet wood it is a real pain and requires more babying to get it to burn properly. Because first the wood needs to dry in order for it to burn properly. Which is why a good bed of coals really helps the situation.
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