2023/24 VC Temperature discussion thread

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This is where @arnermd theory of secondary air infiltrating into the primary combustion comes into play with our bigger Defiants. To me it seems a little bit dangerous. If there is no way to really ‘choke’ down the fire in a run away situation, because we have no control of the secondary air, how could we be liable for an over fire situation? Honestly, if I wasn’t in this forum, I defiantly would have over fired this stove countless times by now. I’m sure my cat would be destoryed.
This is exactly why I am convinced I don't have a thermostat to operate my secondary air inlet (or maybe my secondary has never worked). The only way my cat stays running is if there is fuel in the box and my primary air lever is open more that 60%. If I choke down the Primary to 50% the stove will just glow very very dull and stays about 300degress on the STT until the wood is gone.
 
By design on the VC's all the way closed on the air setting g does not nessasarily mean the primary air is 100% closed. Usually there is still a gap in the primary intake at the "closed" setting. This is an attempt to keep the stove from stalling. The secondary air intake is a secondary attempt at this as well. Usually as you close the primary it we'll open the secondary at some point. The different VC models have different ways of doing this. The Intrepid flexburn that I have now, the secondary intake is way different than the Encore I had about 4 years ago. In the Intrepid the secondary bypasses the combustion chamber all together and goes strait to the flue exit when it opened up in an attempt to maintain a draft in the chimney as the primary is closed down. There's no specific diagram available to show specific secondary air routing on the VC stoves hence the big mysteries and confusion generated. Maybe this is proprietary? One link change in the connecting chain to the flaps can probably make a big difference in the operation. Maybe this explains the different ways the same stove seems to operate for different folks.
 
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By design on the VC's all the way closed on the air setting g does not nessasarily mean the primary air is 100% closed. Usually there is still a gap in the primary intake at the "closed" setting. This is an attempt to keep the stove from stalling. The secondary air intake is a secondary attempt at this as well. Usually as you close the primary it we'll open the secondary at some point. The different VC models have different ways of doing this. The Intrepid flexburn that I have now, the secondary intake is way different than the Encore I had about 4 years ago. In the Intrepid the secondary bypasses the combustion chamber all together and goes strait to the flue exit when it opened up in an attempt to maintain a draft in the chimney as the primary is closed down. There's no specific diagram available to show specific secondary air routing on the VC stoves hence the big mysteries and confusion generated. Maybe this is proprietary? One link change in the connecting chain to the flaps can probably make a big difference in the operation. Maybe this explains the different ways the same stove seems to operate for different folks.
I can only speak to the Defiant / Encore 2n1 designs as that is what I know. I have no clue how similar (or dissimilar) these are to the Dauntless / Intrepid.

For the Defiant / Encore 2n1 designs:
The primary flapper is pretty much closed when the air lever is all the way back. My manual says to adjust it so that on a cold stove the primary are flapper is just closed with the lever all the way to the rear.

That being said, these stoves do have another primary inlet path (we call it the EPA hole). So even when the flapper is full closed there is still a primary air path, albeit a pretty small one.....

I did a schematic last year here:
https://www.hearth.com/talk/threads/2022-23-vc-owner-thread.193685/page-44#post-2650369

And some pictures so you can see how the air flows through internal porting:
https://www.hearth.com/talk/threads/2022-23-vc-owner-thread.193685/page-25#post-2640453

Not sure how helpful these are to you. Different stoves....
 
Its wild hearing all of your guy's challenges, discoveries and tests. My Dauntless is so different than the bigger stoves like the Encore and Vig.
I am 100% convinced the Cat on mine is only there for EPA reasons. Last year I experimented with running it a few days without the cat installed. Lots more smoke out of the chimney and absolutly no increas OR decrease in heat emitted. I keep a spare Cat on stand by because I don't monitor my temps like many of you do. For me, it just helps keep my chimney clean and the air a little cleaner for our kids
 
I can't help myself.... I have to comment on this, this is a fun topic and comes up a couple times a year.... hahaha
  • If you see smoke without the catalyst and no smoke with the catalyst that means the catalyst is giving you more complete combustion, and additional heat that otherwise would go up the stack without a cat..... I think there is no other explanation....;)
  • That being said.... having burned with and without the cat myself I suspect the additional heat output is overstated by stove manufacturers in general.
  • My cat is only really working during the first 30-50% of the burn. On a full load I can get 8-12 hours on a full load with medium air settings, the cat falls off (<1000F) 3-4 hours into the burn. So for much of the burn time it is not really doing much.
  • The cat also enables us to burn with really low air settings without gumming up the stack. Burning with low air settings is more efficient (assuming you get complete combustion) because the stack temps are lower (less heat going up the stack) and fewer open windows in the house... hahaha
But I am with you.... I use a cat primarily to keep the stack cleaner. The low air extended burn is really nice too, if I can ever master the technique....

Waiting on the comments from @Woodsplitter67 ..... he loves this topic. ;lol
 
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I can't help myself.... I have to comment on this, this is a fun topic and comes up a couple times a year.... hahaha
  • If you see smoke without the catalyst and no smoke with the catalyst that means the catalyst is giving you more complete combustion, and additional heat that otherwise would go up the stack without a cat..... I think there is no other explanation....;)
  • That being said.... having burned with and without the cat myself I suspect the additional heat output is overstated by stove manufacturers in general.
  • My cat is only really working during the first 30-50% of the burn. On a full load I can get 8-12 hours on a full load with medium air settings, the cat falls off (<1000F) 3-4 hours into the burn. So for much of the burn time it is not really doing much.
  • The cat also enables us to burn with really low air settings without gumming up the stack. Burning with low air settings is more efficient (assuming you get complete combustion) because the stack temps are lower (less heat going up the stack) and fewer open windows in the house... hahaha
But I am with you.... I use a cat primarily to keep the stack cleaner. The low air extended burn is really nice too, if I can ever master the technique....

Waiting on the comments from @Woodsplitter67 ..... he loves this topic. ;lol


Nothing much for me.to say here.. you pretty much covered it.. Im in complete agreement.. the low burn is fantastic.. I really only use the cat to keep the stack clean.. and Ill add 1 thing.. keep the stove from stalling..

Iv been enjoying the low burn since I got home from work..
 
When measuring STT…something I’ve noticed is how much build up on the plate can decrease your reading. If I have a water pot on the griddle to help with humidity it makes a “cold spot” that builds up quick and acts as insulation. Just pointing out I have noticed that can affect my numbers.

IR guns…they have their place. I use one if I have too but it’s a last resort. TC cable and a reader is affordable, accurate, and precise. I really wanna drill and tap my STT for bolting TC wire to it but I’m to chicken I’ll royally screw it up.

As far as STT temps climbing after cutting air. In addition to the previous explanation we also have to consider we are measuring the temperature on a 400# chunk of iron, just like it reads cold when when you start a fire it will read hot when it’s going the other way. The heat required to take it to 700 degrees could have already been in the box before you ever cut air.

And finally to the folks with the data loggers…you make me jealous! Thanks for sharing the data though.
 
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These were my burns yesterday. I have been doing just under 1/2 loads for now. It's been in the upper teens, lower 20's for temps here the past couple days. Starting and getting up to temp from a cold start has been much more of a struggle. 11-28-23 pm run.jpeg

The small burn I started at 8:00pm really dropped out by 12:00am. At about 9:00pm I move the air from 2/3 open to 1/3 open. At 6:00am this morning I still had a decent amount of coals in the box. I would have expected none but there was was probably 3-4 handfuls of the coals sitting there waiting for me.
 
I can't help myself.... I have to comment on this, this is a fun topic and comes up a couple times a year.... hahaha
  • If you see smoke without the catalyst and no smoke with the catalyst that means the catalyst is giving you more complete combustion, and additional heat that otherwise would go up the stack without a cat..... I think there is no other explanation....;)
  • That being said.... having burned with and without the cat myself I suspect the additional heat output is overstated by stove manufacturers in general.
  • My cat is only really working during the first 30-50% of the burn. On a full load I can get 8-12 hours on a full load with medium air settings, the cat falls off (<1000F) 3-4 hours into the burn. So for much of the burn time it is not really doing much.
  • The cat also enables us to burn with really low air settings without gumming up the stack. Burning with low air settings is more efficient (assuming you get complete combustion) because the stack temps are lower (less heat going up the stack) and fewer open windows in the house... hahaha
But I am with you.... I use a cat primarily to keep the stack cleaner. The low air extended burn is really nice too, if I can ever master the technique....

Waiting on the comments from @Woodsplitter67 ..... he loves this topic. ;lol
What's interesting is with the cat temps in the >1000* range the room temps don't jump up, if anything the slow burn with high cat temps the stove temps stay pretty low. The temp has to go somewhere, but it's not really in the room. I can run people out of the stove room burning without the cat especially when I had SW pipe on the stove.
 
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^
Yup,
I stand solid that the cat doesn't add any additional heat in the room. I also agree it can help keep the stove from stalling as easily.
 
^
Yup,
I stand solid that the cat doesn't add any additional heat in the room. I also agree it can help keep the stove from stalling as easily.

life is good with the super low burn this time of year when its not super cold out.. this is when the cat stoves are at its best
 
What's interesting is with the cat temps in the >1000* range the room temps don't jump up, if anything the slow burn with high cat temps the stove temps stay pretty low. The temp has to go somewhere, but it's not really in the room. I can run people out of the stove room burning without the cat especially when I had SW pipe on the stove.

I think its supposed to warm up some in your area..what do you do.. just a fire here and there..
 
I hadn't burned at all until this week. Had a new heat pump package unit with NG backup put in a year or so ago and my heating costs are low. It's not been below freezing until now and mostly 60's-70 during the days so no need for wood heat. I have kept it burning for the last couple of days continuous as highs were 40's to 50. Supposed to warm up and rain the end of the week so I'll go from there.
 
^
Yup,
I stand solid that the cat doesn't add any additional heat in the room. I also agree it can help keep the stove from stalling as easily.
Clarify the stalling. The cat stalling is one of the biggest problems along with the cat going to overheat. The firebox doesn't stall unless it's green wood.
 
^
To Clarify my statement. If the stove itself and the flew are brought up to solid operating temp (my temps may vary from others) with a solid coal base and I reload with a full box, shut the bypass & engage the cat.... The cat keeps the chimney warmer longer keeping the draft strong.
This allows me to burn at a lower primary inlet air setting, thus allowing the burn to sustain longer than if the cat was not installed. If I had to give it a value % I would say the cat being installed gives me about 25-30% longer burn at lower inlet air settings.
Conversly, if the cat was not installed in my case, at the same primary air setting the fire would go out sooner leaving more unburned wood in the box. I believe this is because that cat is buring the unspent gases created from low primary air settings.
Now, keep in mind this is with my Dauntless stove.
The cats will always stall out at somepoint during the burn process.
Things that attribute to this are:
Stove differences
How dry your wood is
Where during the burn process you engage the cat
How hot the stove is
how hot the flew is
Draft strength
How old the cat is
How much coal base is in your stove and where the coals sit in relationship to the refractery.

Am I missing anything else guys?
 
@sargeott Have you ever burned for a few days without the cat? My fire doesn't "go out" leaving unburned wood. I left the house today, didn't reload as it warmed up, and turned the air down. I came home about 5 hrs. later and there was a nice red bed of coals and no wood left. I also don't see the flue hotter with the cat engaged, without it engaged I have to be carful not to get the flue too hot if I don't turn the air down.
 
Woooo, just witnessed my first backpuff. I had started a fire around lunch time with kindling and small splits to get the stove warmed up for the catalyst. On reload I dropped in two NIELs compressed logs as I wanted to see how low I could go in an effort to increase the burn time. I had let them burn for a while after switching over the the catalyst, but as is usually the case with these logs they didn't approach 1000 degrees on the secondary burn. I had turned them down at that point, but after a minute or so the flame went out. So I switched them back to primary burn and set a timer to go and check on them in 10 minutes. A minute or so before my timer went off I heard my wife close the bypass. I wandered downstairs and asked if she had switched it over and she said, yes the STT was at 660. While I'm standing there I see the flames go out...and then woomph, big puff of smoke lifts towards the ceiling. I thanked her for introducing me to backpuffs as I hadn't seen one yet, and while doing that woomph - again! I threw open the bypass and noticed that the air was all the way down. She'd initially dropped the air to try to affect the STT, but when that didn't work and closed the bypass.

I smell campfire :)
 
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Woooo, just witnessed my first backpuff. I had started a fire around lunch time with kindling and small splits to get the stove warmed up for the catalyst. On reload I dropped in two NIELs compressed logs as I wanted to see how low I could go in an effort to increase the burn time. I had let them burn for a while after switching over the the catalyst, but as is usually the case with these logs they didn't approach 1000 degrees on the secondary burn. I had turned them down at that point, but after a minute or so the flame went out. So I switched them back to primary burn and set a timer to go and check on them in 10 minutes. A minute or so before my timer went off I heard my wife close the bypass. I wandered downstairs and asked if she had switched it over and she said, yes the STT was at 660. While I'm standing there I see the flames go out...and then woomph, big puff of smoke lifts towards the ceiling. I thanked her for introducing me to backpuffs as I hadn't seen one yet, and while doing that woomph - again! I threw open the bypass and noticed that the air was all the way down. She'd initially dropped the air to try to affect the STT, but when that didn't work and closed the bypass.

I smell campfire :)
welcome to the club!
 
@Eman85
I have. When I first got the stove I had to wait for the cat to arrive and again after I found this forum
Not sure what stove you have since it's not in your signature, but my results without a cat trying to burn low and slow leaves unburnt fuel inside the box.
 
It's at the bottom of my posts VC 0028 Encore. Yours is one of the flexburn stoves, not sure how they work. From VC description it looks like it's supposed to have some type of secondary burn even without the cat. My stove when I burn not using the cat I just don't move the damper so the smoke goes straight out. I'm guessing with your stove when you say not burning with the cat you are closing the damper for the flexburn or 2 stage burn as they call it in the brochure.
 
Woooo, just witnessed my first backpuff. I had started a fire around lunch time with kindling and small splits to get the stove warmed up for the catalyst. On reload I dropped in two NIELs compressed logs as I wanted to see how low I could go in an effort to increase the burn time. I had let them burn for a while after switching over the the catalyst, but as is usually the case with these logs they didn't approach 1000 degrees on the secondary burn. I had turned them down at that point, but after a minute or so the flame went out. So I switched them back to primary burn and set a timer to go and check on them in 10 minutes. A minute or so before my timer went off I heard my wife close the bypass. I wandered downstairs and asked if she had switched it over and she said, yes the STT was at 660. While I'm standing there I see the flames go out...and then woomph, big puff of smoke lifts towards the ceiling. I thanked her for introducing me to backpuffs as I hadn't seen one yet, and while doing that woomph - again! I threw open the bypass and noticed that the air was all the way down. She'd initially dropped the air to try to affect the STT, but when that didn't work and closed the bypass.

I smell campfire :)
660 STT on your big stove must have been throwing off some major heat. If mine stays above 600 for any period of time I've pretty much created a sauna.
 
Woooo, just witnessed my first backpuff. I had started a fire around lunch time with kindling and small splits to get the stove warmed up for the catalyst. On reload I dropped in two NIELs compressed logs as I wanted to see how low I could go in an effort to increase the burn time. I had let them burn for a while after switching over the the catalyst, but as is usually the case with these logs they didn't approach 1000 degrees on the secondary burn. I had turned them down at that point, but after a minute or so the flame went out. So I switched them back to primary burn and set a timer to go and check on them in 10 minutes. A minute or so before my timer went off I heard my wife close the bypass. I wandered downstairs and asked if she had switched it over and she said, yes the STT was at 660. While I'm standing there I see the flames go out...and then woomph, big puff of smoke lifts towards the ceiling. I thanked her for introducing me to backpuffs as I hadn't seen one yet, and while doing that woomph - again! I threw open the bypass and noticed that the air was all the way down. She'd initially dropped the air to try to affect the STT, but when that didn't work and closed the bypass.

I smell campfire :)
Just the first of more to come.
 
It's at the bottom of my posts VC 0028 Encore. Yours is one of the flexburn stoves, not sure how they work. From VC description it looks like it's supposed to have some type of secondary burn even without the cat. My stove when I burn not using the cat I just don't move the damper so the smoke goes straight out. I'm guessing with your stove when you say not burning with the cat you are closing the damper for the flexburn or 2 stage burn as they call it in the brochure.
I see that now on my PC. My mobile app gives me limited viewing.
When I say I tried burning without the cat in the past, I should clarify I tried things with the cat physical not inside the stove. The only time I burn ever with the damper/bypass open is when I first start the stove from cold, If im reloading a warm stove, or if I need to open any of the doors/lid.
My dauntless pretty much lives with the damper/ bypass closed and cat inline. If I run my stove with the damper open for any length of time, I loose tons of heat up the flew, the fire is really hard to control and I need to make large primary air swing changes to keep from over firing or it chokes out. It's way easier to control with the damper engaged.
 
It's at the bottom of my posts VC 0028 Encore. Yours is one of the flexburn stoves, not sure how they work. From VC description it looks like it's supposed to have some type of secondary burn even without the cat. My stove when I burn not using the cat I just don't move the damper so the smoke goes straight out. I'm guessing with your stove when you say not burning with the cat you are closing the damper for the flexburn or 2 stage burn as they call it in the brochure.
Here is what I believe to be true...... I welcome opposing viewpoints.
  • The stove is designed for secondary combustion even without the catalyst.
  • The catalyst lights off the secondary combustion at a lower temp
  • As I recall even the old, old Defiants (long before catalyst was used) were designed to have secondary combustion by introducing sperate air into the secondary chamber via a small hole in the side of the stove.
  • As best I recall.... I was able to achieve secondary temps (with no catalyst installed) > 1000F. But it takes a while to get there.
  • So if this is all true..., the catalyst really only helps to get the secondary burn going on a fresh load and maybe sustains it for a little longer on the back end
  • When folks claim the cat adds no additional heat, I can see how that might be almost true.... If you are running hot and can get the secondary temps up with no catalyst then there is only a marginal heat gain with a cat at the beginning and end of burn.
What I believe to be indisputable is:
  • Running with a cat will keep your stack cleaner under "normal" operating conditions.
    • If you run without a cat and get the secondary temps up quickly and run with more air you might be able to keep the stack pretty clean too, but it will never be cleaner than a stack with a properly running cat.
  • Running with the cat allows for lower air settings by keeping the secondary combustion temps high.
    • I suppose if you could keep the secondary temps hot without a catalyst and with low airflow settings then this point might not be correct, but I am pretty sure it would not be possible.
    • Anybody ever try running low air flows with no catalyst? Where you able to maintain secondary temps > 1000F?
 
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