Input needed; Your technique when burning your non-cat stove?

[Woody Stover]

I'm trying to get a handle on burning a secondary stove as cleanly as possible through all stages of the burn, and I welcome advice from PE owners, and those who run other non-cat stoves. We just put in an Alderlea T5 at my SIL's house.
A couple nights ago I started a top-down fire with five splits and some Pine kindling. As the top splits started to catch, the plume got clean very quickly so I started cutting air. I tried to sustain the clean burn by not cutting it too fast, but the plume got a bit dirtier. I saw a couple of small water spots on the end of two splits but nothing I thought was a problem at all...no bubbling.
The stove top slowly went 200..300..400 and the stack slowly moved to 350. I never saw appreciable secondary burning and the plume stayed somewhat smoky. Maybe I saw the clean plume early because not that much wood was involved yet, just the kindling. I think the plume may have eventually cleared up when the stove went over 500, but it got dark out and I couldn't see it anymore.
Some questions I have are:
--How do you start out your non-cat loads to burn as clean as possible? Do you need to maintain a certain stove top or stack temp in order to get a totally clean plume?
I'm guessing yes, I need to have the top of the box and the baffle above some temp to get good secondaries.
--Do you burn pretty hard when starting a new load, to get the stove up to temp fast and get the secondary burn going?
I think that in the above burn, I just cut too much air too early, and even though I had some flame in the box, the secondary just never really got going.
--How much control do you have over heat output? Between what stove top temps can you run, while still burning clean?
If I fire the new load pretty hard and get a lot of wood burning, sure I'm burning clean with good secondaries but there's no dialing the stove top temp back down...it's just going to keep dumping secondary flame around the front of the baffle and the stove top is going to stay at about 700, no way I can turn it down, and it seems like it will burn up a sizeable load of wood pretty quickly, compared to what I'm used to with cat stoves. I haven't yet monitored the heat life of a load at her house in cold weather, but I'd certainly like at least some control over the output of the stove, and how long I can stretch the burn time of a load. With the stove top at 700, the surface magnet meter on the flue about 13" up is around 500...goodbye, heat. Maybe I will have to experiment with a second flue damper when it gets cold out, and draft gets even stronger than it is now at 40* outside. I'm thinking that with more control over the draft, I'll be able to burn hard at the beginning to get the plume clean, then cut the draft and slow the burn rate of the load, while still keeping the plume clean.
--Are you able to burn clean, early in the load, even if you don't see a lot of secondary flames? I'm thinking that if one has cut the burn rate lower, less wood gassing, that these stoves may still be able to burn the smoke even if you don't see a lot of flame off the secondary...?
Thanks in advance for your input!

 

[Highbeam]

If I fire the new load pretty hard and get a lot of wood burning, sure I'm burning clean with good secondaries but there's no dialing the stove top temp back down...it's just going to keep dumping secondary flame around the front of the baffle and the stove top is going to stay at about 700, no way I can turn it down, and it seems like it will burn up a sizeable load of wood pretty quickly, compared to what I'm used to with cat stoves.

This should not surprise you. Cat stoves are known to offer a much larger “turndown” than noncats. If you want to burn clean in a noncat, and you should, then you will need to run hotter than you are used to with the cat stove.

You also failed to specify if you are measuring flue temps on the surface or internal with a probe. On my noncat, anything under 250 on the flue surface is a Smokey stinky mess.

In my experience, the best way to regulate output from a noncat is time between reloads. Not by trying to reduce intake and try to run a cold fire. In a cat stove it’s the opposite.

 

[Woody Stover]

This should not surprise you. Cat stoves are known to offer a much larger “turndown” than noncats. If you want to burn clean in a noncat, and you should, then you will need to run hotter than you are used to with the cat stove.
You also failed to specify if you are measuring flue temps on the surface or internal with a probe. On my noncat, anything under 250 on the flue surface is a Smokey stinky mess.
In my experience, the best way to regulate output from a noncat is time between reloads. Not by trying to reduce intake and try to run a cold fire. In a cat stove it’s the opposite.

With the stove top at 700, the surface magnet meter on the flue about 13" up is around 500...goodbye, heat.

It doesn't surprise me that I can't turn down as low as a cat, but I was hoping for at least some adjustment range. I would be thrilled to run under 350 surface flue temp, with the stove top at 600-700. Seems that I have read that non-cat users can run in this flue-temp range. I mean, this single-wall heats up the wall when blazing at 500.
And my SIL doesn't always have the luxury of timing reloads. Sometimes she is gone all day and some degree of turn-down would stretch the load, and give the stove more time to capture the heat instead of sending it outside.
I was hoping that this, from the manual, was an over-statement of what I have to do to burn clean. "Two or three logs at a time" isn't gonna heat all day unless those logs are some real whoppers. I know that you guys are loading full, and assume that you are burning clean and long. I realize that I'm toward the beginning of the learning curve...I'm just hoping to shorten it a bit with some advice from more "seasoned" burners. I know that part of the problem is that my splits aren't huge. I've been splitting bigger for her, on the wood I've gotten recently. I'm hoping to find upper branches on some dead Oaks I have lying out there, that are low enough in moisture to where I can split big, or leave in rounds, and still have burnable wood for her this fall.
You can see some old wood left over on the bottom, from what we were running in her previous cat stove...too small for the non-cat.


1. Highest smoke densities and emissions occur when a large amount of wood
is added to a bed of hot coals and the air inlet is closed. The heated wood
generates smoke, but without ample air, the smoke cannot burn. Smoke-free,
clean burning requires small fuel loads, two or three logs at a time or 1/4 to 1/2
of fuel load and leaving the air inlet relatively wide open, especially during the
first 10 to 30 minutes after each loading, when most of the smoke generating
reactions are occurring. After 30 minutes or so, the air inlet can be turned down
substantially without excessive smoke generation. Wood coals create very little
creosote-producing smoke.

 

[Highbeam]

Without this becoming a cat vs. noncat thread, your description of operation is why I switched to a cat stove for my constantly heated house but am pretty happy with a noncat for the intermittently heated shop.

I will say that I am very able to keep my noncat’s flue skin temperatures easily in the 250-350 range with clear exhaust and 500-700 degree stove top temps using full loads of dry softwood fuel. None of this 500 degree flue skin stuff! That is wasted energy.

 

[illini81]

I have a noncat that is about 2.5 cuft in size, so similar to the T5 I think.

After 2 years full years of 24/7 burning (8-9 total cords, 2-3 cords marginal wood) and essentially no buildup in the pipe, I have stopped worrying about how I run the stove significantly impacting the cleanliness of the burn. I am not saying that it would be impossible for me to burn dirty if I tried hard, but as long as my burning practices are reasonable, the pipe seems to be sparkling clean.

So personally, I wouldn't worry as much about a clean burn - not because it's not important, but because I don't think you can really "mess it up" unless you don't at all know what you're doing (e.g. you smolder burn) or you have wet wood.

For me, if I want high, sustained heat, I fully load the stove, and run it with fan on medium and air 30ish% open (I don't run it this way often). This will give me an 6-9ish hr burn (e.g. get heat out as fast as possible)

If I want med/high heat, I fully load the stove, fan on low, air at about 5-10% open. This will give me a 9-11 hr burn

If I want med/low heat, I fully load the stove, fan on low, air all the way closed. This will give me an 11-12.5 hr burn.

If I want low heat, I reduce the size of the load, fan on low or off, air all the way closed. At this point, the length of the burn depends on how full the stove is. Interestingly though, the size of the load isn't linearly related to the length of the burn. I.e. if a full load give me a 12.5 hr burn on low, a half load might give me 8 hrs on low where you might think it would only give 6ish.

 

[SpaceBus]

The PE T5 in question is probably twice the firebox volume or more of my stove, but in principle it is the same. For shoulder season I just bring the house to 75 with a small fire and burn another fire when the house gets uncomfortable. I don't try to stretch out a low long fire like a cat stove. Small hot fires are key. Obviously there is a limit to how small of a fire ýou can have. My cut off seems to be 8lbs of wood. It's not a very long lasting fire of course, but it doesn't matter to the house. This definitely won't work with a poorly insulated house. In for real winter I load the fire box full every time and reload when the house becomes uncomfortable. This is 6-8 hrs for us. You have to think of the "burn time" as time between reloads or perhaps time between matchless reloads. In the shoulder season my stove has a 24 hr burn time between loads because my house is comfortable that whole time. In the middle of winter it's like 6 hrs, sometimes even less if the wind is really whipping. This is just how I do it for my stove at my house. I suspect the T5 to be a much more robust heater (too big thus I didn't research it much) than our small stove. Therefore you should be able to run it the same way but with a scaled up load to match the stove.

Burn times to me are really irrelevant, it's like @Hogwildz said, firebox size matters the most. There's only so much energy you can fit into that firebox, so you have to match that to your heat load. I read in the boiler room how some folks have calculated their heat loss and load their boiler or furnace accordingly. This works all the same for a regular wood stove, cat or non cat.

 

[Woody Stover]

if I want high, sustained heat, I fully load the stove, and run it with fan on medium and air 30ish% open (I don't run it this way often). This will give me an 6-9ish hr burn (e.g. get heat out as fast as possible)
If I want med/high heat, I fully load the stove, fan on low, air at about 5-10% open. This will give me a 9-11 hr burn
If I want med/low heat, I fully load the stove, fan on low, air all the way closed. This will give me an 11-12.5 hr burn.
If I want low heat, I reduce the size of the load, fan on low or off, air all the way closed. At this point, the length of the burn depends on how full the stove is. Interestingly though, the size of the load isn't linearly related to the length of the burn. I.e. if a full load give me a 12.5 hr burn on low, a half load might give me 8 hrs on low where you might think it would only give 6ish.

We didn't order the blower yet. I thought we would give it a try without it first. But that would certainly help in getting more heat into the room and less up the stack, so we'll definitely add it.
As for the burn time, full load vs. half, I guess it is possible that you are getting a higher percentage of heat into the room with the smaller load, and don't need to reload in half the time to maintain room temp? Or are these times both at "X" stove top temp, regardless of room temp.
I hope I'm not confusing you, because I've certainly confused myself.

The plume is always clean. Only smoke I really see is when it's really cold outside.

What you are seeing there could be steam, which I also see from my cat stove, especially early in the load. It has a lighter color, and looks lighter in weight, more "wispy" as it is moved by a slight breeze.

 

[ColdNorCal]

Clean burn happens at 375-425 STT on our non-cat. Many times on a cold startup I have walked outside and watched the chimney cap to see when it goes smokeless. 400 degrees is where the ST thermometer says the "Best Burn" non-creosote starts and it seems to be consistently true. Also, we reload when STT is about 350 and reload only 1/3-1/2 of a 2.5 firebox. Granted our outdoor temps are mild compared to most on this forum. On the initial startup burn it seems best to get the STT 550-700+. This range increases the house temp a few degrees quickly, quickly by wood stove standards , making it comfortable. Then on reloads we burn slower @ 400-550. Also, using the fan is well worth the noise intrusion. It makes a huge difference in heat output and heating a very open floor plan. Lastly, we burn seasoned Oak limbs/branches (some stuff that many probably burn outside in the burn pile), small splits, med splits and small rounds. Depending on what we load will dictate burn times.

 

[bholler]

Don't pay attention to stt at all. Run it wide open until the pipe surface temp is 350 to 400 depending on wood and chimney height. You need to figure out what temp to start shutting back for your setup. Then shut it back. Again your setup will determine how much you shut back at a time. My old house I could shut it all the way all at once. This house takes 2 or 3 steps depending upon outside temps. If you can't get the pipe surface temp down to 250 or 300 you have to much draft and need a damper.

 

[edyit]

--How do you start out your non-cat loads to burn as clean as possible? Do you need to maintain a certain stove top or stack temp in order to get a totally clean plume?

If going from a cold start I'll throw in a few sticks of kindling and let that burn to coals before I fill it with full sized splits. The hot coals get it going better than top downs or other methods I've tried. Granted I also don't have that many cold starts.

--Do you burn pretty hard when starting a new load, to get the stove up to temp fast and get the secondary burn going?

Depends on what you mean by hard. Air wide open till flue temps on the outside magnetic hit 300-350. Then closing the air in stages, or if I'm busy using the AAS.

--I think that in the above burn, I just cut too much air too early, and even though I had some flame in the box, the secondary just never really got going.

Yes this can happen if I cut the air back too aggressively for the draft. On colder days I can close it faster than on milder days.

--How much control do you have over heat output? Between what stove top temps can you run, while still burning clean?

Heat output is determined by load size. Less wood in = less heat out. Usually never less than half a load so it'll still burn clean. Soft woods help here too. Pine is great for when you want a quick hot fire. I go by the flue temp more than stove temp but when it's up and cruising it ranges between 450F-700F depending how cold it is outside and how hard I'm running it.

 

[illini81]

We didn't order the blower yet. I thought we would give it a try without it first. But that would certainly help in getting more heat into the room and less up the stack, so we'll definitely add it.
As for the burn time, full load vs. half, I guess it is possible that you are getting a higher percentage of heat into the room with the smaller load, and don't need to reload in half the time to maintain room temp? Or are these times both at "X" stove top temp, regardless of room temp.
I hope I'm not confusing you, because I've certainly confused myself.

I'm confused

 

[Woody Stover]

I am able to keep my noncat’s flue skin temperatures easily in the 250-350 range with clear exhaust and 500-700 degree stove top temps...None of this 500 degree flue skin stuff! That is wasted energy.

I'm wondering whether the high flue temp is partially a function of the T5 design. This pic shows the bottom of the secondary baffle. There is a line of holes back to front, and a row of holes across the front bottom. Then there is also another line of holes right around the corner on the forward-facing short wall on the front of the secondary box. When the secondaries are cranking, some flame is coming from the front-to-back holes, but more is coming off the two lines at the front of the baffle, and that is when the flue temp soars. Seems like a larger proportion of the reburn heat is made closer to the flue exit, compared to a tube stove where more of the holes are further back in the firebox, on the rear tubes. I've never seen a tuber run, though...maybe it's mainly the front tube that does most of the burning..?

Seems that I remember begreen saying he was running 300-400 flue temps, and I think he's got a probe in double-wall connector. That's a lot lower than the 500 surface temp that I'm seeing. Could be that his larger, older-generation T6 handles the reburn differently or that the bigger box can grab more of the heat.
Then again, the times I was able to get the stove top to level off around 600, flue temp was lower as well. I just have to figure out how to do that consistently. I'm thinking it will be easier to control when I have more big splits and rounds to feed it.

I'm confused

Yeah. I didn't word it too good, either.

Or are these times both at "X" stove top temp, regardless of room temp.

I should have said "Do you reload both the half-load and full load when the stove top drops to "X" temp, say 300, or do you reload when room temp drops below a certain point?"
Whatever the reason for what you're seeing, if I can get 2/3 the burn time out of half the wood, I'm gonna like that.

 

[illini81]

Yeah. I didn't word it too good, either.
I should have said "Do you reload both the half-load and full load when the stove top drops to "X" temp, say 300, or do you reload when room temp drops below a certain point?"
Whatever the reason for what you're seeing, if I can get 2/3 the burn time out of half the wood, I'm gonna like that.

Usually with a small load, I am trying to stretch out the burn, and am reloading when it appears that I just have enough coals to restart without kindling. With a large load, I could be taking the same approach if I am on a 2x12hr loading cycle, or if its colder out, then I'm reloading based on room temp.

Overall though, my schedule is really what drives when I load, and then I adjust the load and final air setting based on factors such as when I will be loading next, room temp, outside temp, etc.

 

[begreen]

I'm wondering whether the high flue temp is partially a function of the T5 design.

No, it isn't. After the air has been turned down our -probe- flue temps settle in around 100º less than stove top temp. Our neighbor's Spectrum runs roughly the same. We both burn larger 6-8" splits.

 

[Woody Stover]

After the air has been turned down our -probe- flue temps settle in around 100º less than stove top

So at 700 stove top, I should expect 600 probe temp, 300 surface flue temp? That's a long way from the 500 I'm now seeing...

 

[bholler]

So at 700 stove top, I should expect 600 probe temp, 300 surface flue temp? That's a long way from the 500 I'm now seeing...

Where do you have the air set at? How tall is the chimney?

 

[SpaceBus]

Where do you have the air set at? How tall is the chimney?

Sounds like a high draft situation.

 

[Woody Stover]

Where do you have the air set at? How tall is the chimney?

Sounds like a high draft situation.

The air is cut all the way, and I can't dial it back if I overshoot my intended burn rate. It's only 15' of stack, and it was in the low 40s outside. I can light a fire in the stove when it's 50 out, with no smoke roll-out when the door is wide open. That could be a lot of draft, or a good stove design.
There's a flue damper, but this time I didn't remember it right away; I have kept the stove top at 600 before, but I think it should be a little easier to turn it down if required, shouldn't have to hover over it to get a little lower burn, rather than pushing redline every time if I overshoot. I mean, my splits aren't kindling, most have been decent size, like 5" half or whole logs and such, as you can see in the load pics. I am working on getting bigger stuff.
I might install another flue damper if the draft goes nutz, like I think it will when temps are in the low 20s.

my noncat’s flue skin temperatures easily in the 250-350 range with clear exhaust and 500-700 degree stove top

How far above the stove top is your meter? Mine is about 13" IIRC.
Can you cut the air if you get too much wood burning? Did you have to tweak the stock air intake to get control?

 

[SpaceBus]

Eh, I don't think 40-50 degrees of temperature difference matters when you are talking about 500f flue gas temp. The higher outside temps matter more for cold starts. Once it's all hot, I don't think it matters. My tiny Morso attached to an oversized 25' clay liner drafts amazing. If I'm slow to cut, the STT will scream up over 600 quick. I've never seen it over 800, but I guess it's possible. I think EPA non cat stoves just like to be hot. I think if you saw 700+ for several hours it could be an issue, maybe not even then. My manual doesn't even specify what STT should be, just flue temp ranges.

Right where the exhaust starts exiting the fire box and hitting the stove top on my stove it sees 700+ regularly. A few inches away though in the center of the stove top and it's an 80-100 degree difference with a 250-300f flue surface temp at peak. When I l put a 6" liner in my 8" clay tile liner it should get my flue temps to stay a bit higher, but I'm getting much creosote when I sweep as it is. I suspect if this were an exterior masonry chimney rather than interior it would be a different story. Perhaps the Morso heat exchanger is just too efficient.

 

[begreen]

How far above the stove top is your meter? Mine is about 13" IIRC.

Try it at about eye level, around 18-24" above the stove top. If you have another thermometer on the Keystone, maybe swap to check for the thermometer accuracy?

 

[Highbeam]

Tuesday

How far above the stove top is your meter? Mine is about 13" IIRC.
Can you cut the air if you get too much wood burning? Did you have to tweak the stock air intake to get control?

18” above the stove. The pipe gets a lot hotter as you get closer to the stove. You should move your meter up to the normal 18” height for a test.

Unlike my previous epa noncat stoves I have very good control to snuff out the fire in all cases, however, if you snuff the fire you get a soldering Smokey mess. Trying to toe the line of barely clean burning is tough. I go for a hot clean fire and just space out reloads to reduce heat. My intake is not modified and it feeds a 19 feet vertical flue with no damper.

 

[SpaceBus]

Tuesday


18” above the stove. The pipe gets a lot hotter as you get closer to the stove. You should move your meter up to the normal 18” height for a test.

Unlike my previous epa noncat stoves I have very good control to snuff out the fire in all cases, however, if you snuff the fire you get a soldering Smokey mess. Trying to toe the line of barely clean burning is tough. I go for a hot clean fire and just space out reloads to reduce heat. My intake is not modified and it feeds a 19 feet vertical flue with no damper.

Oddly enough my flue is actually hottest 8" above the flue collar. The collar itself is usually 5-10f hotter than 8" above. The IR thermometer was super fun.


@Woody Stover Now that I know what every temp on the stove will be for whatever load I put in, I rarely even check anything anymore. I don't sit close enough to hit the flue with a laser or see the surface thermometer, it might as well be unknown anyway. Really though, if the stove has secondaries going, then it's a safe bet your flue is hot. On most non cats if your load is too small, you will know because there is never any secondary burn. This will be obvious because your chimney will have smoke and smell like smoke, rather than nothing or steam. My stove can also be snuffed out if I close primary air all the way. It might take a bit, but it will die before the load is burned. The secondary air supply isn't quite enough air to sustain the fire on its own. For a while I really wanted to be able to adjust the secondary air, but I learned to work around it. The stove also has a shaker grate, but there is a gap around where the rod passes through the stove body. So this results in a tiny, tiny bit of air "leaking" into the ash chamber which means under fire air. I like to think of it as a non adjustable "boost air".

Side note: Allegedly my stove is a "multi fuel" stove in Europe and has an adjustable draft cap on the ash pan door, in the US this is not adjustable (but I've seen people make it adjustable). This allows the use of anthracite coal/smokeless briquettes.

Of course every stove is different, but to me all non cats pretty much work the same.

 

[EbS-P]

I have found that if I overload the first cold start load the warmup is slow and secondaries May lightoff but die back one the kindling is consumed. Air flow is key. I try to alternate EW then NS with everything above my first splits and use lots of kindling . I consider my first load not a real heating load. I want to get some coals and the stove up to temp. Just my two cents.
Evan

 

[Woody Stover]

18” above the stove...feeds a 19 feet vertical flue with no damper.
I have very good control to snuff out the fire in all cases, however, trying to toe the line of barely clean burning is tough.

She's not going to be as attentive to the burn as I would, so it would be good to have the level of control you do, in case she gets too much wood burning on a new load. No, we are not going to try to "toe the line" but being able to bring it down to 600 would be nice, and I think that will still burn clean. When it's pushing over 700 stove top, I start thinking it's time to swing open the tops and cool it off a bit. Like Space Bus said though, that's the hottest area, just in front of the flue exit. I guess it just seems really hot to me compared to my cat stove which is usually 550 or less, if I'm not cranking it. Like I said, though I have the clearances, the radiation off the single-wall is getting the wall pretty warm..

Try it at about eye level, around 18-24" above the stove top.
check for the thermometer accuracy?

The thermometer is pretty accurate, according to the IR gun, and flue temp did drop some when moving up the pipe. Can't remember exactly how much, but thinking 75* at least? You're probably right, I shouldn't be too concerned with some additional heat loss. It's a bigger stove, after all. There's going to be more heat going up the stack, as well as coming off the box.
Condar says "Eye level, but no closer than 12" to the top of the stove." 18" is eye level...if I'm kneeling.

My stove can also be snuffed out if I close primary air all the way. It might take a bit, but it will die before the load is burned.

And that's on 25' (though oversized a bit.) It's incredible how easy this stove breathes, at just 15'.

The stove also has a shaker grate, but there is a gap around where the rod passes through the stove body. So this results in a tiny, tiny bit of air "leaking" into the ash chamber which means under fire air. I like to think of it as a non adjustable "boost air".

The T5 has boost air, an unregulated ~7/16" tube feeding in air from the ash pan area.
It just seems that they have made an concerted effort to "smolder-proof" this stove. I don't think I need that much "help" to figure out how to burn clean.

I have found that if I overload the first cold start load the warmup is slow and secondaries May lightoff but die back one the kindling is consumed.

I think that's what happened to me the other day; Plume was clean when the kindling was burning, then I cut the air too low and the splits didn't get flaming enough, resulting in some smoke from the stack until I opened the air up a bit.
In your case, I think the Castine wants more draft than a lot of other stoves...opposite of the T5. Depending on your chimney height and setup, this could be the reason you have to work harder to get a fire established. Of course, how dry your wood is also has an impact.
You might try a top-down start, and be able to load full at the beginning. Put bigger splits in the bottom, then a couple smaller splits and kindling on the top/front of the load. The kindling and small splits will heat the flue and reburn section of the stove more quickly, and you might be able to dispense, if desired, with the extra step of making a coal bed first.
A top-down start will also burn cleaner at the beginning. I've only burned a few times in this stove so far, but it's been all top-down, with these cold starts.
When it gets colder and we have a coal bed to load on, I'll experiment with different coal configurations to get the right amount of wood burning on the reload.

 

[SpaceBus]

I probably should have included something for scale, but it's a tiny gap. I can just sometimes see cinders float up from the grate area.