Is it possible for too much air to cause a fire to burn poorly

[clancey]

Wonderful explaining and me being not very experienced here only about five or six fires without a cat and it seems to me in the first stages the same as yours for it takes quite awhile to even get my blower going and it needs to be at least 375 or 400 in temperature and this takes awhile to get hot enough..I start mine on the left (my stove installer did that so I just repeat that but I notice that if I start a fire on the left and one in the middle too it burns faster and hotter and my window does not get dirty and I try to keep it further from the glass to the back of the stove---just experimenting here with each new stove burning and trying to note the differences...I do notice that if I use pine it it seems to have a lot more smoke to it although I believe it burns faster. The pine was 18 with the moisture meter after I drilled four holes and hammered the four prongs into it to get the reading..--sucky way to do this in reality it is a mixed wood not kiln dried..The temperature outside at burning was 31 degrees when I started using "fat wood" and "quick survive" starters--two of them...But it sure sounds exactly how your fire is going..Now when I use my kiln dried oak 18 inch split pieces which measures 10-12 on the moisture meter it burns hotter and cleaner with a lot less smoke appearing in my stove window as well as my outside stove stack...So just by gathering my wits with your posting I believe it is the wood that you are burning....But I am not experienced and "just saying" because I live in about the same altitude that you are burning at and this I believe makes a difference..I guess your about 7-8000 feet above sea level...I took pictures of my stove and my stove does not have a cat...its a Sirius JA Roby..Thank you for the dedicated and knowledgeable posting of your burning with your cat stove...old mrs clancey

 

[RockyMtnGriz]

I've been fiddling with a similar situation with one of my secondary wood stoves for about a decade (since I bought the house). My problem stove has 2 stories plus of 6" masonry flue above it, so height should be similar to yours. It's not short, anyway. I've made a lot of progress, and luckily, I've been under no pressure to get it fixed, or it would have driven me crazy too. I recognize a lot of what I've dealt with in your problem, so I'm going to throw out what worked for me. Hopefully something will help you.

I'm at 7,000 feet FWIW, so I also have an appreciation how altitude screws with about EVERYTHING! Depending on the design of the stove, it's likely possible to overfuel the secondary combustion. At 9,500' there's about 30% less air pressure to push secondary air to the cat, so I would expect to see that the secondary would be able to burn about 70% of the fuel that it would be able to at sea level. Most stoves primary air is pretty unrestricted compared to the route that the secondary air has to take. Our soft and resinous woods compound that by being very flashy - off gassing very readily. I seem to be able to overpower both my cat stove, and my tube style Kuuma furnace, if I create the right conditions. Lots of smaller splits, too much pitch, or a combination of the two can create smoke outside, and worse performance inside. Reducing the pilot primary air on the Kuuma by about 25% helped, similar to how you get better results from reducing your primary air setting. You might see if you increase the size of the split, combined with some larger round pieces that off gas more slowly, if that helps.

On the stove, also, I'd make sure the secondary air passages are not restricted. The cat can't properly burn smoke without an adequate air supply to the cat. It's a long shot, but worth checking. On mine, I can see how one largeish dead spider could really foul things up.

You're on a steep hillside and in the videos you posted the wind was blowing toward the downhill direction. If that's the prevailing wind, does the stove work better when you have the opposite wind direction? Mine worked great on the odd days when the wind was blowing uphill, and badly most of the time when the prevailing wind was coming from behind my hill and down the slope. Two things helped me: I made a cap that has about twice the opening toward the downhill compared to the uphill direction. I also got very serious about sealing any leak where air could get into the pipe or chimney in order to improve the draft.

You have an interior masonry chimney as I do. You've noticed the same thing I have in that the stove works best with a slow warm up that gives a chance for the masonry to absorb more heat. When the bypass is closed, after a while you can run into problems. I have that issue, and I've attributed it to the chimney cooling with the lower flow rate of gasses when the cat is engaged and the primary draft is reduced. When I first started fiddling with mine, I couldn't reduce the primary below wide open, or I was guaranteed to have smoking inside and out, and backpuffing - unless I had a strong reverse wind that induced more draft. If I opened the bypass and reheated the chimney, it helped some, for a while. My stove also always worked better after the first day when run continuously, which was uncomfortable to do with its cantankerous nature. But once the chimney was good and warm, it was somewhat better.

The thing that made the big difference, besides the uncontrollable wind, is running the blower. Running the blower pulls too much heat from the flue gasses for my marginal chimney situation. I've learned not to run mine at all. I realize that this is going to be a problem with your insert, but some careful experimentation here might be in order. Perhaps restricting airflow or adjusting thermostat settings to leave more heat to create draft might help.

If doing things to improve the draft helps, but not enough, it might make somebody mad, but probably the best answer is not to have a masonry chimney. Since changing to Class A probably isn't an option, maybe an insulated liner is? I'd do it if I could, but the 6" square flue is a problem for me.

You mentioned that life was good for 6 fires or so after you changed the cat. I don't have experience but I read about new cats being "hyperactive" for a while when new. That might be what you're seeing. More complete combustion from the new cat might be giving the flue temps a little boost. I just changed my cat this summer (had to try that too!), and things seem to be working a little better. My old one was also OK I think, based on comparison to the new. Since winter is 3 months late this year, I only have a couple of fires on that stove, and it's too early to tell if there's a lasting improvement.

My stove has gone from utterly unworkable to pretty good from all the work I've done to counter the wind, poor draft, and low flue temps. I wish I could get to "reliable", where I could just put a fire in it and trust it to behave unsupervised, but it's probably not there yet, and I doubt it will get there on its chimney. Thankfully it's not the primary stove, or it would have been gone a long time ago.

Hopefully there's something here that turns out to be enough to rectify your situation and you can get on with life (in under 10 years)!

 

[vdavidoff]

@ABMax24 - I believe all those seals are good, but I will check them the next time the stove is cool enough.

Andy

 

[vdavidoff]

@RockyMtnGriz - It's quite a relief to find someone else experiencing what seems like the same issues I am. All the stuff you're describing sounds dead on with my experience, which in and of itself is very helpful to know.

The winds have a tendency to change direction but usually they are coming downhill towards me. The more wind there is, in any direction far as I can tell, the better the fire seems to run. I guess I can thank the vacu-stack cap for that, as I understand it. Which is good since I often get very high speed winds. I haven't tried to modify the cap and at the moment I don't plan to, but that's something to keep in the back of my mind if I ever think it'll help.

You're right that not running the blower would be an issue for me, primarily because the space I heat with the stove is quite large. I have played with turning it down to keep the stove hotter, though I could play with that more. I will keep that in mind too.

I am still trying to get details on my install from my installer, but I'll find out of there's anything I can do to better insulate the stove pipe from the masonry. I hadn't considered an additional liner besides the stove pipe. Though for all I know, there may be one in there already. I hope to hear back from my installer soon.

Thanks again for your detailed reply - like I say, even just knowing you've experienced the same helps, at least in terms of sanity. At this point even when things are running really well, I am getting so much smoke prior to engaging the cat that I think that's gotta be the wood. The first winter with this stove I burned pine and don't recall having this issue, but maybe I just got very lucky in terms of the condition of that wood, that year, and pine is just gonna be a bit of a struggle.

Andy

 

[John B]

I recently replaced my Sequoia due to similar issues. Probably not what you want to hear, but I could never get a consistent burn out of that stove. And the cats seemed to not last long either I always figured it was due too having to much draft. I just think the stove is too free flowing, and alot of smoke bypasses the cat even when its glowing. I tried alot of different things to fix including adding a damper, having Kuma make a new grill for in front of the cat, restricting the intake, but nothing seemed to work. I finally got fed up and took it out.

Couple weeks ago I put a Woodstock ideal steel in the same spot (reused the same liner) and the difference is night and day. I can easily turn it down and make big heat. Never see any smoke from the stack other than steam which is normal.

 

[Dave_in_ABQ]

That was my next question - if there were stoves that worked better at altitude (or didnt)

 

[ABMax24]

@ABMax24 - I believe all those seals are good, but I will check them the next time the stove is cool enough.

Andy

That would be my thought too since your sweep checked those. But at this point seems best to check everything again in the hopes something was missed.

 

[vdavidoff]

That was my next question - if there were stoves that worked better at altitude (or didnt)

Just to be clear, I don't think there's anything wrong with this stove per-se or for my specific situation, so I'm way off from considering a different stove, but it's certainly possible that at some point this could be something to investigate. I am however optimistic that I'll be able to incrementally keep making improvements here.

Andy

 

[vdavidoff]

A bit of a follow up here. Not really too much to tell, but this is where I'm at with it.

Jason at Kuma has been incredibly kind, attentive, and helpful. We've exchanged many emails and kicked around a number of ideas. He's gone way out of his way to help me. Where I'm at now is still more theory than solution, but I feel pretty good about it. High level takeaways:

* My draft readings are sometimes on the low side of normal, but they are normal / don't seem to be a concern in and of themselves
* After a lot of thought about my 6" liner, we came to the conclusion that it should be fine / moving to an 8" liner shouldn't make any positive difference
* When it's windy and my draft shoots way up, the fire performs the way I think it always should
* Having too much fuel burning at once, even if the stove is very very hot, always causes a ton of smoke out of the chimney and smoke puffing back into the house

The theory at the moment is that the lower level of o2 in the air due to my altitude causes issues with combustion, which generates a ton of smoke that never ignites, and overpowers what my cat can burn off. The increased draft when it's quite windy compensates by sucking in so much more air that o2 levels rise enough for more proper combustion.

At the moment I am researching chimney top draft boosters, and beyond that, I am just using the wood burning methods I have determined work best for my particular situation, but those still aren't great - I think I'm not getting nearly as efficient or hot a burn as I could be with more optimal conditions.

Andy

 

[RockyMtnGriz]

I'm very curious, did your conversations with Kuma ever explore increasing the secondary air supply for the cat? I have no idea how your stove is constructed, so I don't know if it's possible. I do think that it might help at altitude if the secondary supply is restrictive.

Secondary air usually goes over the river, and through the woods to get as hot as possible before it gets to Grandma's house. It's an unproven theory of mine that with 20-30+% less air pressure to get that done, combined with the fact that the combustion reaction is taking place at 20-30% lower pressure, makes it a lot easier to have smoke problems up here in the clouds, that wouldn't happen at the elevations our stoves are tuned at (just like all these CARB/EPA fixed-jet-carburetor small engines that are such the pain).

I've been fiddling with the cat stove that is similar to yours in behavior, as I posted earlier. Putting a new cat in it last summer has definitely helped it, a lot. Unfortunately, I still don't have enough burn time to be certain that I'm past the break-in of the new cat, so I don't know how it's going to hold up over time. I could take a drill bit to the hole that meters the secondary air in this stove, to attempt to prove my theory above, but wanting to see how it does with the new cat, and the absolute PITA project of welding a plate to put the original hole back if it doesn't work, has kept me from doing that so far.

Just had what might be a "special" thought... I could drill out that metering hole, and I could also thread a hole from the outside of the stove to accept a bolt that could encroach on that hole, thus providing adjustable secondary air - hmmm, I'm going to have to explore that idea in the spring!​

Right now, I am having a similar experience with the burn rate and smoke, even with the brand new cat. I just reloaded the stove a couple of hours ago, and with the primary cranked probably 3/4 closed, it was white smoking outside with the cat at around 1,200 - 1,300. I turned it down to about 90% closed, and the smoking stopped in about 10 minutes, the cat dropped to 1,000 but the pipe is also about 50 degrees cooler than what this thing seems to run reliably at. I'm still learning about the stove with the new cat, so we'll see... Big difference now, is that I can actually reduce the primary way down, without the thing immediately going sideways on me and smoking up the house, at least so far.

Update- It's been about an hour working on this post and doing other things. I check the stove and the cat is back to 1,200, the pipe is about where it likes to be, but it's smoking outside a little again. So, I reduce the primary to about 95% closed.​

​

15 minutes later, cat is about 1,1,00, pipe is 75 degrees colder, still a little visible smoke at the cap, AND, I'm starting to smell the stove in the house (ugh!)- so I'm also killing the draft. So, I opened back up to about 90% closed, because a little smoke outside is better than any smoke inside.​

Similar thing the other day, threw a couple of little chunks of really pitchy doug fir - one was a little bigger than a 4x4, and the other was about a 2x4, about 14-16 inches long, into my Kuuma furnace on a healthy bed of hot coals. I regretted doing that. It was rolling coal for at least half an hour - and the Kuumas pretty much don't smoke. Even though I've reduced the pilot air supply by about 25%, I still think there was just too much fuel to the secondary combustion chamber for the amount of secondary air available. I wish that I'd had the opportunity while that was going on to chop the pilot air down more to see if it helped, but I didn't.

It's good to hear that you're making progress with your situation.

 

[vdavidoff]

We didn't discuss increasing secondary air. I asked some questions around it here and there but they were never addressed head on. This is just my speculation because I haven't read the law but I imagine modifying the stove in that way is against EPA regs and that when manufacturers get questions like that, they just don't even acknowledge them.

In my case, I am not sure that'd really help, anyway. Based on my understanding of how the stove is behaving (which to be clear is mostly gut-based, with some actual data sprinkled in, like draft readings), I suspect if I was able to increase the size of the secondary intake (or the primary for that matter), I still wouldn't have enough draft to pull through the volume of air I need to get the o2 I need. Yeah, if I do something like crack the door, I can get the fire to rage, but I think it's still not burning efficiently / smoking too much even in that case. So basically, I think I need more draft than you normally would, to pull the volume of air to get a suitable amount of o2, and that the fire alone isn't going to make up the draft I'm short. If that makes any sense...

Andy

 

[begreen]

At 9500' the air is thin. Have you considered extending the flue a few feet to increase draft? Is this an option?

 

[bigealta]

Could you use a small fan and "funnel" it into the secondary air inlet for a bit of a boost? A simple test like that could help figure out if a Drill modification could even help.

 

[vdavidoff]

At 9500' the air is thin. Have you considered extending the flue a few feet to increase draft? Is this an option?

My installer hasn't mentioned it, and I think I probably can't safely go any higher given the winds I get, but it's something I will ask my installer about.

Could you use a small fan and "funnel" it into the secondary air inlet for a bit of a boost? A simple test like that could help figure out if a Drill modification could even help.

I did have this thought, basically a small supercharger for the stove, but a bit of quick research seemed to indicate doing that full time would be really dangerous since you could potentially overfeed the fire and have a runaway condition. So I scraped that idea quick. When I had the idea I figured it was either fairly smart or outrageously stupid.

As a test like you're describing, I think it suffers from the fact that I'd be forcing the air in, the fire wouldn't be pulling it. I could be wrong but I'd think if the intake being too restrictive was the problem, I'd see much higher draft readings than I normally do. When I've got the fire running well (as well as I can get it to run) with the cat engaged my draft is around .07-.08. I have seen it as high as .11-.12 before engaging the cat, even on a calm day (I get way more draft when I have wind).

If I get what are relatively mild winds for out here, say 5mph 10-minute average with pretty consistent ~10mph gusts, it'll pull .11-.12 with the cat engaged, and burn way more like how I think it should. I have seen up to ~.19 with ~25mph gusts. Basically the more wind I get the more draft I get and the better the stove runs.

Andy

 

[begreen]

Basically the more wind I get the more draft I get and the better the stove runs.

Adding a few feet to the flue will achieve this too. The chimney can and should be braced.

 

[RockyMtnGriz]

We didn't discuss increasing secondary air. I asked some questions around it here and theere but they were never addressed head on.

I suspect if I was able to increase the size of the secondary intake (or the primary for that matter), I still wouldn't have enough draft to pull through the volume of air I need to get the o2 I need.

Andy

Thanks for the answer. I get the reluctance to change the calibration of the stove thing - they can't. Unfortunately, that's the same thinking (though, yes, required by law), gets me a snowblower that runs so rich at this altitude, I can't use it without getting ill on a calm day. It also gets me a (insert modern 2 stroke powered item here) that won't work until I find some way to remove the screw limiters, and lean it out.

Andy - I'm sure this doesn't help you, but since it's related, and sometimes somebody shows me where my thinking is wrong, here goes(!):

I'm going to jump into theory - at least as I've come to understand it: In a cat stove, there's two combustion chambers. The same is true on a tube stove, really. With a cat, theres's the firebox, and the cat. With a tube stove, there's the lower section with the wood and coals, and the upper section with the air tubes, under the insulation.

It's pretty easily seen on a tube stove with a window. You can increase the primary air under some circumstances, and the lower fire perks up, while the fire along the top dies out. The fuel is being consumed on the lower level. Conversely, if the air supply is reduced, under certain circumstances, the lower fire loses visible flame, but the top of the stove lights off. The fuel is allowed to exist long enough to get to the top by the limited air on the bottom, and combined with adequate air at the top, it ignites.

The cat stoves I've seen, aren't designed for efficient combustion in the firebox. The firebox provides smoke for the cat to burn. If the door is opened, an unusual quantity of air is provided to the firebox, and if conditions are right, that's going to improve firebox combustion and reduce the amount of smoke the cat has to deal with. That's why they are typically supposed to start up with the door open, it's a cleaner burn that way if the cat is too cold to work, and it helps to heat the chimney. Once the stove is running in its normal mode, with the door closed, the primary air becomes a smoke feeder control for the cat. More primary air, more smoke to burn, less air, less smoke.

Within reasonable limits for the size of the cat, as long as there's enough air available for the cat (or tubes - in a tube stove) to burn the smoke provided to it, things go well. Not enough air to combine with the amount of smoke provided, and some will go up the chimney unburned as smoke. Same with the snowblower. Big, fixed, sea level, carb jet, not enough air available to mix with the fuel provided, and a lot of CO and other issues result.

So, here's why I went through that step by step: My cat stove that's been burning all day, is still smoking some outside. Sometimes it doesn't, but today it is (low draft day). The cat is at 1,200, and it probably doesn't have 10 day-long burns on it. I left the primary at 90% shut on the last reload, and I just reduced it to say 92% shut (since it's still smoking outside), which is a quarter turn each on the air control knobs (a "smidge"). Earlier today, I did a half turn, and it lost enough draft to start smelling in the house. -- The big difference between the snowblower and the stove, is the snowblower has a positive displacement engine. Every revolution pulls in a set volume of air. If it doesn't burn to its potential, I get less power, and more emissions, but it keeps running. The stove is not positive displacement. If it doesn't burn to its potential, you either get more smoke by using the primary air to keep it pumping (which was my only solution for years), with the primary open enough that there's enough hot gas flow up a masonry chimney to sustain the draft, though there's not enough secondary air to burn all of the fuel that the primary is providing - so it runs but smokes. The other alternative is to reduce the primary to the amount of fuel the secondary is able to burn, but then there's not enough energy in the form of a volume of heated products of combustion to keep the chimney hot to sustain the draft, starting a cascade that ends with the smoke in the house, and the fire dying out. Yes, there may be a happy medium, but it's an incredibly fine line to walk, especially when it changes with stage of the burn cycle, wind, temperature, and whatever else.

30 minutes later - After adjusting the primary knobs 1/4 turn closed, the cat is at about 1,100, and the smoking has stopped, If I had nothing better to do than to look at the chimney, and adjust the stove a "smidge" every half hour, this would be a solution.

So, that's my current theory. My stove is limited by the amount of fuel it can burn based on the secondary combustion air available at this altitude. Unfortunately, it's often too little for the masonry chimney to stay hot enough. If I run enough gasses up the chimney to keep it drawing adequately, the cat can't burn it all, resulting in smoke.

i'm going to get in trouble with somebody, but I don't actually care about the smoke. It'll be fertilizer stuck to a snowflake before it gets the chance to bother anybody else. I would like to burn it for heat, though. I'd also really, really, like it if it burned in the stove instead of creating crud I have to clean out of the chimney!

So, I'm really liking the idea of trying the increased and adjustable secondary air idea I posted above. I think it might just widen the workable combustion range of my stove to get it to work reasonably with my chimney setup.

 

[SurfPine]

Unfortunately, that's the same thinking (though, yes, required by law), gets me a snowblower that runs so rich at this altitude, I can't use it without getting ill on a calm day. It also gets me a (insert modern 2 stroke powered item here) that won't work until I find some way to remove the screw limiters, and lean it out.

I've been following this thread, not because I have a Kuma, but I've found the information in this thread interesting and I also live at 8000' in CO.

I don't want to sidetrack here but something keeps crossing my mind about available air. Yes, it is no joke that the air is thin, it is one reason why I prefer to have my car and truck with forced induction. My wife's car, naturally aspirated, does feel down on power. I also ride a Grizzly 700 ATV on back-country trails up to 13k feet. That is fuel injected but is definitely down on power when compared to much lower elevations, however, I do run an air/fuel ration wideband meter and can see the AFR richen as I go up in altitude.

When I go boondocking at 9500 feet and need to run a generator, it produces much less output power, thus less amps being produced. Unfortunately my generator does not have altitude jets available for the carb. The manufacturer recommends drilling holes in the airbox lid to help aide in available input airflow, which I have done. The generator does seem to start and run a bit better but probably no where near as good as if there were replaceable jets on the carb.

So this leads me to wondering how air tight your housing structures are or do you have a separate, outside inlet air feeding your stoves? I am new to wood stoves but have read the instructions on my wood stove that suggests a separate outside pipe that feeds the stove in the event the housing structure can't adequately feed the fire. My hydronic boiler does have an outside 6" pipe that provides air to it so the boiler can run efficiently.

I do apologize if this is way off base as again, I'm new to wood stoves but do have a fair amount of high altitude experience in other areas concerning combustion.

 

[begreen]

The draft is the engine of the stove. It's what pulls the air through the secondaries. As a test, on a calm day, remove the chimney cal and stick a 3 or 4' length of cheap warm air duct, crimp down into the chimney pipe. This will act as a temporary test extension. Run a fire and see if this makes a notable difference. If so, make it permanent by adding more chimney pipe and bracing it properly.

 

[mar13]

Blaze King's manuals, for example page 17, of their Ashford 30, has a table showing recommended flue heights from 0-1000ft (15ft), etc up to 7000-8000ft (18.5ft) for no elbows. I always remember this being an interesting table.

I have a friend who lives at 9000ft on a mountain with a Lopi (non-cat). I can ask him his experience if anyone cares.

 

[bigealta]

The draft is the engine of the stove. It's what pulls the air through the secondaries. As a test, on a calm day, remove the chimney cal and stick a 3 or 4' length of cheap warm air duct, crimp down into the chimney pipe. This will act as a temporary test extension. Run a fire and see if this makes a notable difference. If so, make it permanent by adding more chimney pipe and bracing it properly.

Yes do that. And also possibly just removing the cap as another test, may elicit some change in draft.

 

[vdavidoff]

Thanks for the answer. I get the reluctance to change the calibration of the stove thing - they can't. Unfortunately, that's the same thinking (though, yes, required by law), gets me a snowblower that runs so rich at this altitude, I can't use it without getting ill on a calm day. It also gets me a (insert modern 2 stroke powered item here) that won't work until I find some way to remove the screw limiters, and lean it out.

Yeah, I have re-jetted my generator and I got an EFI snow thrower specifically so that I'd not have to screw with a carb on it. And my Polaris ATV is EFI.

Andy - I'm sure this doesn't help you, but since it's related, and sometimes somebody shows me where my thinking is wrong, here goes(!):

The way I interpret your theory, I think you're essentially at the same conclusion I am at, but with more specificity regarding the secondary air possibly being the critical piece. It still makes sense to me that to fix it I'd (or, we'd, maybe) need stronger draft (not say, forced induction), a la:

The draft is the engine of the stove. It's what pulls the air through the secondaries.

I think a forced induction setup would result in a similar situation to what happens when you give the stove too much primary, even if you were feeding the secondary intake. However that's based on some playing with my stove, and probably depends significantly on how the secondary vs. primary intakes are constructed in a specific stove, I'd think.

So this leads me to wondering how air tight your housing structures are or do you have a separate, outside inlet air feeding your stoves? I am new to wood stoves but have read the instructions on my wood stove that suggests a separate outside pipe that feeds the stove in the event the housing structure can't adequately feed the fire. My hydronic boiler does have an outside 6" pipe that provides air to it so the boiler can run efficiently.

It's a good thought - this is one of the first things I looked into. I don't have an outside air kit or any kind of supplemental air kit, but I think there's no way this house is too tight for that to be a factor. Part of my testing here involved opening doors and windows near the stove.

The draft is the engine of the stove. It's what pulls the air through the secondaries. As a test, on a calm day, remove the chimney cal and stick a 3 or 4' length of cheap warm air duct, crimp down into the chimney pipe. This will act as a temporary test extension. Run a fire and see if this makes a notable difference. If so, make it permanent by adding more chimney pipe and bracing it properly.

I hadn't even considered a temporary extension on the pipe, that's a great idea. I guess I'll have to pick some up so I can test this out as soon as conditions permit. Thanks for the idea.

Andy

 

[vdavidoff]

I have a friend who lives at 9000ft on a mountain with a Lopi (non-cat). I can ask him his experience if anyone cares.

I'm all ears, if it's not a hassle. Even with a non-cat stove I would be they know stuff that'd be useful to either learn, or confirm some of what I think I already know.

Andy

 

[RockyMtnGriz]

I've been following this thread, not because I have a Kuma, but I've found the information in this thread interesting and I also live at 8000' in CO.

I don't want to sidetrack here but something keeps crossing my mind about available air. Yes, it is no joke that the air is thin, it is one reason why I prefer to have my car and truck with forced induction. 5 My wife's car, naturally aspirated, does feel down on power. I also ride a Grizzly 700 ATV on back-country trails up to 13k feet. That is fuel injected but is definitely down on power when compared to much lower elevations, however, I do run an air/fuel ration wideband meter and can see the AFR richen as I go up in altitude.

Since you have a lot of altitude experience, you probably know all of this, but there's probably others reading along, so:

Even with the perfect mixture from fuel injection, physics dictate you're going to lose about 3% off your max power output every 1,000 ft. increase in elevation - unless it's forced induction. Don't forget to derate generators, pumps, gas furnaces, etc. for altitude accordingly.

The last vehicle I purchased, I counted the turbo as a plus (and I'm hoping it lasts!). I do prefer the better compression braking of a larger, old-school engine when I'm going back down the hill though.

ATVs, small engines, etc. tend to use a crude speed-density injection system (without O2 sensor feedback), so they don't adapt as well as automotive systems.

When I go boondocking at 9500 feet and need to run a generator, it produces much less output power, thus less amps being produced. Unfortunately my generator does not have altitude jets available for the carb. The manufacturer recommends drilling holes in the airbox lid to help aide in available input airflow, which I have done. The generator does seem to start and run a bit better but probably no where near as good as if there were replaceable jets on the carb.

I believe fixed jet carbs are of the devil, but in the case of fixed jets, some benefit can usually be gained by lowering the float level in the carb, though it can be a more difficult, trial and error filled approach compared to simply changing jets. A proper air box shouldn't be restrictive, so the recommendation to drill it seems a bit odd, but if it works...

For generators and such, Honda and Briggs usually show jets for altitude, and Yamaha jets can be identified by calling Yamaha of North America and being persistent, though the first jet I got for my Yamaha generator from their semi-secret chart was one step too lean.

So this leads me to wondering how air tight your housing structures are or do you have a separate, outside inlet air feeding your stoves? I am new to wood stoves but have read the instructions on my wood stove that suggests a separate outside pipe that feeds the stove in the event the housing structure can't adequately feed the fire. My hydronic boiler does have an outside 6" pipe that provides air to it so the boiler can run efficiently.

I do apologize if this is way off base as again, I'm new to wood stoves but do have a fair amount of high altitude experience in other areas concerning combustion.

The boiler system is likely a sealed combustion+ intake and exhaust system that isolates it from inside house pressure. My LP furnace is like that. A good system, but I'm not aware of any wood stoves that achieve that.

I wish my house was tight enough to need a fresh air intake. I had an exhaust vent for a water heater that functioned as such because I don't use it in the winter, but sealing it improved my home heating situation, and didn't impact the stoves. Unless your home is uncommonly tightly sealed, I wouldn't expect that you would need an outside air intake for your stove. If the stove works fine, you don't.

Some folks also think it's more efficient to use outside combustion air, but if you ponder the physics, it makes no difference. If there's a draft of incoming air bothering you, it might make you more comfortable, but it won't use any less fuel, everything else being equal. And, if everything works fine, more changes of the air I'm breathing sounds good to me.

 

[mar13]

I'm all ears, if it's not a hassle. Even with a non-cat stove I would be they know stuff that'd be useful to either learn, or confirm some of what I think I already know.

Andy

My friend who lives at 9000 ft up a ski resort's mountain says he has no problem with his Lopi non-cat (circa 2019) stove. He lives on the top floor of a 3-floor condo (what floor is your stove your house - that could cause draft issues) and his stack is designed to be higher to keep it above the snow on the roof. He uses a lot of kindling to get it going, but overall a clean burn. He burns a lot of bark-beetle killed pine.

So a good burn can be done at that altitude.

 

[begreen]

So a good burn can be done at that altitude.

Indeed they can, but with some more confounding factors depending on the stove design. Some breathe easier than others. One of the original mods here was burning in CO near that altitude. I think he had a Mansfield at the time.