I have a newly installed auber temp probe about 6” above my insert. Now that I have had a few fires I am trying to find the sweet spot for closing primary air and not wasting heat up the flu. I realize that my probe is a bit close to the stove, but with it being an insert, that was all the space I had to work with. When starting a fire or on reloads I am having a hard time keeping the flu temps below 850-900 peak temperature. Doesn’t this seem a little too high? Also, as I close the air down to control temps and slow the burn, I oftentimes end up with dirty glass on the lower half of my door. The secondaries are burning vigorously and the primary is shut down enough to not keep the lower part of door clean. Not sure what I need to do? My wood is dry, I can rule that out.
Flue temperature and dirty glass
- Thread starter Slimdusty
- Start date
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Wisco Shepherd
Feeling the Heat
Seems high, maybe you need to start shutting down the air sooner. What kind of temps are you seeing after your fire is in cruise mode?
This is with a Lopi medium flush insert, non cat. Cruise mode temps seems to be around 650, maybe slightly higher and then work their way down as the load of wood diminishes.
I should add, that I can reduce these temps by closing the air down more, but when I do this, the lower half of my glass becomes dirty, in which at that point I feel the fire is starved for air and not ideal combustion. Excellent secondaries and very little flame from below.
Wisco Shepherd
Feeling the Heat
If it comes back down to 650 your flue can handle it. You could try turning down your air a bit sooner. I get the concern for lost heat but a hot flue is a clean flue and a well drafting flue. Are burn times and stove temps good? Chance of an over drafting situation in which a damper could help.
I don't know about your stove, but if i load N/S on the bottom with not very dry wood i can get more blackening on the ceramic glass if the ends facing the glass are very close. The "steam" or off gassing is pushed out the ends of the splits onto the glass and without a nice hot bed of coals the cool zone lets it stick to the glass.
Burn times and stove temps are adequate in my opinion, maybe a bit short on burn time. I insulated my liner over the summer, and now have noticeable more draft, so am relearning my setup. I can turn the air down much sooner and farther now, but also get dirty lower glass when turned down too low, even though my secondaries are healthy. Thats where I am a bit stumped. I can’t imagine I have too much draft, as I have a short exhaust, right at 15’.
I’m almost always loading e/w. I do have splits maybe on the smaller side than others, and softwood. Maybe off gassing too quickly?
Wisco Shepherd
Feeling the Heat
I have a short stack as well but its very exposed and with my easy breather I am looking into a damper.
That sounds ok. The probe is pretty close to the flue outlet so it's going to read a bit higher. Hitting an occasional peak of 800-900 happens sometimes. Try closing down the air earlier in increments as soon as possible without shutting down the fire.
I think the crucial point is increments: shutting down early all at once won't go well (-->dirty windows etc.). Shutting down all at once late not either (high flue temps etc.)
Starting the squeeze earlier, but doing in steps is a bit of trial and error, but that's the way to go. You are going to have to get a feel for how the stove, your wood (which may vary each year...), the draft (flue and weather) behave in concert.
You're going to have bunch of misses, then you'll do it perfect one time and you'll all be happy, only to come crashing down the next time.
Don't give up, try. A mistake here or there happens. That is not the end of the world. The learning curve is to try to avoid making mistakes all the time.
Starting the squeeze earlier, but doing in steps is a bit of trial and error, but that's the way to go. You are going to have to get a feel for how the stove, your wood (which may vary each year...), the draft (flue and weather) behave in concert.
You're going to have bunch of misses, then you'll do it perfect one time and you'll all be happy, only to come crashing down the next time.
Don't give up, try. A mistake here or there happens. That is not the end of the world. The learning curve is to try to avoid making mistakes all the time.
Thanks for the tips, I will keep messing around with it. One thing for certain is that with the insulated liner the stove takes off much quicker and allows the turn down process to be shortened timewise
Yes, the hotter flue will draft stronger. Expect the draft strength to increase more as tempertures drop.
MongoMongoson
Feeling the Heat
A leaking door gasket can cause dirty glass. Have you checked the lower half of your door gasket for leaks? You can search on here for the "dollar bill test". It is a good first thing to check.
That said, the lower corners of my glass get dirty... different stove, though. The PE manual says it can happen with mine so I don't sweat it.
That said, the lower corners of my glass get dirty... different stove, though. The PE manual says it can happen with mine so I don't sweat it.
Yes, I did the dollar bill test and no leaks, all seems good there. My lower corners will get dirty over time as well, I chalk that up to just normal, but my first few fires this season the lower half of my glass was way bad! I’ve got more fine tuning to do
EbS-P
Minister of Fire
What setting is your blower at?
I have a different insert with 23’ of insulated liner and a damper. My glass only gets dirty when I use wood that’s wet. Get a moisture meter. Measure room temp on a fresh split face.
I cruise at 650-850 depending on the outside temperatures and how I pack the stove and how hot it gets in startup/coal bed temps.
I have a different insert with 23’ of insulated liner and a damper. My glass only gets dirty when I use wood that’s wet. Get a moisture meter. Measure room temp on a fresh split face.
I cruise at 650-850 depending on the outside temperatures and how I pack the stove and how hot it gets in startup/coal bed temps.
I continue to see Youtube "experts" moisture testing on end grain. And they get tons of views. Kind of pathetic that they can't even take a minute to learn anything about what they are posing to be expert with.
I have a lopi large flush. I called lopi about temps. My probe is about where yours is. It’s actually a washer probe screwed to the inner liner. Before I could say my temps, lopi said with the probe in that area I would see 1200 on a strong fire. That was exactly what I was seeing. It’s good reassurance. I’ve stopped chasing temps as much and started watching the fire more.
You may feel like you are wasting heat but you don’t know how fast the flue is moving without probing higher. Could see 1000 where you are but 500 at the recommended height if it’s moving slow. Plus you are getting a lot of radiant heat that close.
I know with our short squatty inserts it’s hard to control the secondary fire. I often see flames locking up to the bypass rod hole above the fire blanket. I try to lower it down but can’t always get it without it starting to smother the fire.
Also these wood stoves are tested with a load of dry wood ran at full air for the whole load and then loaded again hot and turned down to the minimum.
Moral of my post, make note of your numbers and how the fire looks. Make your adjustments from that. My flue numbers are always high but we are mounted way closer than it should be.
You may feel like you are wasting heat but you don’t know how fast the flue is moving without probing higher. Could see 1000 where you are but 500 at the recommended height if it’s moving slow. Plus you are getting a lot of radiant heat that close.
I know with our short squatty inserts it’s hard to control the secondary fire. I often see flames locking up to the bypass rod hole above the fire blanket. I try to lower it down but can’t always get it without it starting to smother the fire.
Also these wood stoves are tested with a load of dry wood ran at full air for the whole load and then loaded again hot and turned down to the minimum.
Moral of my post, make note of your numbers and how the fire looks. Make your adjustments from that. My flue numbers are always high but we are mounted way closer than it should be.
I know and have commented on some of them. The response varies from 'thanks' to "I've been burning wood for 50 yrs, and blah blah blah.' I've also seen local wood sellers claiming their firewood is fully seasoned at 10% but they are showing the moisture meter probes in the end grain of the wood sitting on their truck.
On a side note to owning a lopi. They give you a free basic moisture meter. I think it reads lower than what the woods actually is (yes I check at 70* on a freshly split face). I like to place the wood against my cheek and see if it feels warm. If it’s wet it will feel cold. If it’s dry it will feel warm. If it’s in between it will feel in between 
. I still use the lopi one as I’m cheap and don’t want to buy another one but I don’t put too much faith in it.
. I still use the lopi one as I’m cheap and don’t want to buy another one but I don’t put too much faith in it.
Yes, that's the way I tested wood moisture for years. I would also bang two splits together and if they rang like a baseball bat I knew the wood was dry. If instead it was a dull thunk, I would wait on burning that wood or I would bring it indoors for a couple of weeks to speed up drying a bit. This is more practical with softwood and ash than something slower drying like oak or locust.
I vary the blower speed depending on heat needs, usually low to mid speed. I have a moisture meter, haven’t used it in awhile because I am ahead on my wood supply. I also live in an arid climate and am confident in wood dryness. 650-850, is that internal flue temps?
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