2023/24 VC Temperature discussion thread

[sargeott]

Oh and also
If I'm dealing with a cold start and still have a warm stove in the am
It's a lot easier to get things up to temp and back into cruise mode for 4-8hr burns.
This stove lives on the cat engaged. I think I only have it in bypass for 20 minutes a day.
And yes I'm burning 24x7 now this time of year. It's my primary heat source because I hate paying my electric bill 😒

 

[AsylumResident]

Had a new level of questioning my life today.

I let the fire burn down to a nice, maybe just a little too small, coal bed. I loaded it up just under fully loaded, had the air 100% open, let the load catch until the flue temps hit 650 (been doing that all week), closed the bypass, and when the cat hit 975 I put the air to 50%. This has been my standard procedure for the past couple weeks that had been going very well. I had the cat hit 1500 twice in the past couple weeks but didn't stay there.

Today I followed that procedure and by an hour and half I hit 1550 on my cat and it just took off. I closed the air to 25% closed, the cat went to 1650. I closed the air to 0%, it hovered between 1650 and 1700 for about 5 minutes and then it kept going up. My flue temp at this point is 950. I opened the air to try and burn off some of the smoke and gasses to lower the cat which it did but that shot my flue to 1100 so I incrementally closed the air down to bring the flue down and hopefully keep the cat down. I spent the next half hour playing with the air and opening the bypass a couple times. In the end I saw my cat hit 1780 and my flue went over 1200 at one point. I ended up taking a few splits out and tossing them in the back yard. I have never had this situation happen.

I'm trying to figure out how it got that out of control. The only thing that I can think of that was different was one of the large splits I put in this load was not a hardwood. It was soft and a little dry rotted. I put that piece on the bottom back of the stove. When I took the three splits out, I got down to that piece and it was one large piece of red hot coals still holding its form, barely. Is it possible that could create this run away burn?

 

[Woodsplitter67]

Had a new level of questioning my life today.

I let the fire burn down to a nice, maybe just a little too small, coal bed. I loaded it up just under fully loaded, had the air 100% open, let the load catch until the flue temps hit 650 (been doing that all week), closed the bypass, and when the cat hit 975 I put the air to 50%. This has been my standard procedure for the past couple weeks that had been going very well. I had the cat hit 1500 twice in the past couple weeks but didn't stay there.

Today I followed that procedure and by an hour and half I hit 1550 on my cat and it just took off. I closed the air to 25% closed, the cat went to 1650. I closed the air to 0%, it hovered between 1650 and 1700 for about 5 minutes and then it kept going up. My flue temp at this point is 950. I opened the air to try and burn off some of the smoke and gasses to lower the cat which it did but that shot my flue to 1100 so I incrementally closed the air down to bring the flue down and hopefully keep the cat down. I spent the next half hour playing with the air and opening the bypass a couple times. In the end I saw my cat hit 1780 and my flue went over 1200 at one point. I ended up taking a few splits out and tossing them in the back yard. I have never had this situation happen.

I'm trying to figure out how it got that out of control. The only thing that I can think of that was different was one of the large splits I put in this load was not a hardwood. It was soft and a little dry rotted. I put that piece on the bottom back of the stove. When I took the three splits out, I got down to that piece and it was one large piece of red hot coals still holding its form, barely. Is it possible that could create this run away burn?

My opinion is this.. and I could be wrong. I avoid putting alot of wood on a small bead of coals. My stove would turn into a hot mess. I avoid having alot of wood catch all at ones. Having alot of wood catch at once means alot of off gassing.. lots of offgassing leads to higher flue temperatures.. aka higher draft.. higher draft leads to a higher burn temperature and the cycle of higher temperatures perpetuates.. it turns into a vicious cycle.

When my stoves low on coals and draft is on the low end. I will pur some medium splits in and get the stove, cat, flue back up to my operating temperature. Then I will fully load the stove, then cut the primary air. I cut my primary air back with a cat temp of 1k wich only take a minute for it to jump back up and the majority of the load hasn't caught fire..

I know this doesn't sound correct. The way I mostly operate my stove in on a minimum. So what I mean is this. My starting flue temps are at a minimum. I will engage my catalyst on the lower end of what it will take to get the catalyst lit off.

Here is something also to add in to the equation. Your starting draft may have been higher then you think. Your used to starting your stove with a 650 degree stack temperature and so that cold front that just went through your area dipped the outside temperatures and now that its colder.. your draft is higher then in the past.

As it gets colder outside your draft will increase, your stove will breathe easier. You may want to see what the lower end of what it takes to get the catalyst engaged.. so you know that more of a shoulder season temperature your stove is good at 650 degrees but if its say 28 degrees maybe your starting temperature is more like 600/575 to keep you catalyst temperatures in line

My setup is a little different then yours as my stack is a little shorter.. but your running 6 inch pipe and im running 8 inch pipe.. when it gets cold.. that 8 inch pipe and pull some air through it..it drafts hard.

The first year I had my auber hooked up it got cold out.. was like 5 degrees.. I kinda did what you did.. I had a cat temp of somsomething like 1650. We've all been in your shoes..

 

[Woodsplitter67]

So this is this mornings burn..

I started at 5am with a cold stove. got the stove up to temperature cat engaged and loaded the stove 2/3s full.. or basically up to the top of the glass.

Primary air is set to about 1/3 open. STT is just under 450, cat temperature.is 1325.. it dropped to 1308 and is sitting at 1456 now.. heres the interesting part.. I have my IR gun on the inside of the double wall and its at 305 degrees.. this temperature was taken when the stove was loaded for this burn

BTW.. at 5am.. im not cleaning my glass.. so this was how the stove looked from yesterday's burn.. 25% full and air of 1/3 open

 

[Woodsplitter67]

so here is where I am in my burn this morning.. lots of offgassing. this is getting to the peak of it.. this load was majority of oak and 1 big split of pine .

Cat temp of 1488 STT of 550. stack at 380. air still at 1/3 open glass is clean and happy..

Ill be dialing it back soon for the long burn

 

[AsylumResident]

My opinion is this.. and I could be wrong. I avoid putting alot of wood on a small bead of coals. My stove would turn into a hot mess. I avoid having alot of wood catch all at ones. Having alot of wood catch at once means alot of off gassing.. lots of offgassing leads to higher flue temperatures.. aka higher draft.. higher draft leads to a higher burn temperature and the cycle of higher temperatures perpetuates.. it turns into a vicious cycle.

When my stoves low on coals and draft is on the low end. I will pur some medium splits in and get the stove, cat, flue back up to my operating temperature. Then I will fully load the stove, then cut the primary air. I cut my primary air back with a cat temp of 1k wich only take a minute for it to jump back up and the majority of the load hasn't caught fire..

I know this doesn't sound correct. The way I mostly operate my stove in on a minimum. So what I mean is this. My starting flue temps are at a minimum. I will engage my catalyst on the lower end of what it will take to get the catalyst lit off.

Here is something also to add in to the equation. Your starting draft may have been higher then you think. Your used to starting your stove with a 650 degree stack temperature and so that cold front that just went through your area dipped the outside temperatures and now that its colder.. your draft is higher then in the past.

As it gets colder outside your draft will increase, your stove will breathe easier. You may want to see what the lower end of what it takes to get the catalyst engaged.. so you know that more of a shoulder season temperature your stove is good at 650 degrees but if its say 28 degrees maybe your starting temperature is more like 600/575 to keep you catalyst temperatures in line

My setup is a little different then yours as my stack is a little shorter.. but your running 6 inch pipe and im running 8 inch pipe.. when it gets cold.. that 8 inch pipe and pull some air through it..it drafts hard.

The first year I had my auber hooked up it got cold out.. was like 5 degrees.. I kinda did what you did.. I had a cat temp of somsomething like 1650. We've all been in your shoes..

What you're saying about the increased draft due to the outside temp drops, I have been anticipating. We had lower temps yesterday morning than we did last night when my stove ran away on me. I figured I would see burns get incrementally hotter as the temps decreased outside. My hope has been (doesn't mean it would become a reality) that if I keep my burns as close to the same as possible, I would see the effects of the outside temps on draft and make changes accordingly. I didn't think it would just pop all of a sudden on me. I also understand there are numerous things that could have come together for a perfect storm last night.

 

[Woodsplitter67]

Here is my burn now.. just past peak.. lots of secondary burns in the box.. when this slows Ill know im past the offgassing and Ill cut the air back all the way for a long day burn

cat temp of 1400, STT of 589, stack at 352..

 

[Woodsplitter67]

What you're saying about the increased draft due to the outside temp drops, I have been anticipating. We had lower temps yesterday morning than we did last night when my stove ran away on me. I figured I would see burns get incrementally hotter as the temps decreased outside. My hope has been (doesn't mean it would become a reality) that if I keep my burns as close to the same as possible, I would see the effects of the outside temps on draft and make changes accordingly. I didn't think it would just pop all of a sudden on me. I also understand there are numerous things that could have come together for a perfect storm last night.

So if I can ask you a question.. why are you using a stack temp of 650

 

[Woodsplitter67]

So now im past the off gassing.. this is my glass.. this is my air all the way back
cat temp at 1108

 

[AsylumResident]

9n

So if I can ask you a question.. why are you using a stack temp of 650

Just to clarify, I have a probe inside the flue, I'm not taking the surface temp of the stove pipe.

I have been using 650 because it has been working well up to this point. Through trial and error I used a few different temps higher than that and it would usually make my cat peak too high. I settled on 650 because it lights my cat off relatively quick and keeps the cat from peaking too high. I did anticipate needing to use a lower the starting flue temp, but again, I figured I would see the burns reflect that as the temps decreased. So the quick answer to your question is trial and error, 650 worked well up to this point.

Also, I did take a quick draft reading just before I pulled wood out of the stove last night because I knew I would want to know. My draft has been pretty consistent at .08-.10 iwc, at its peak temp last night the draft was .15 iwc.

 

[AsylumResident]

So now im past the off gassing.. this is my glass.. this is my air all the way back
cat temp at 1108
View attachment 319423 View attachment 319424 View attachment 319425

So all in all from getting the stove up to temp to cutting the air all the way back, hour and a half?

 

[Woodsplitter67]

9n

Just to clarify, I have a probe inside the flue, I'm not taking the surface temp of the stove pipe.

I have been using 650 because it has been working well up to this point. Through trial and error I used a few different temps higher than that and it would usually make my cat peak too high. I settled on 650 because it lights my cat off relatively quick and keeps the cat from peaking too high. I did anticipate needing to use a lower the starting flue temp, but again, I figured I would see the burns reflect that as the temps decreased. So the quick answer to your question is trial and error, 650 worked well up to this point.

Also, I did take a quick draft reading just before I pulled wood out of the stove last night because I knew I would want to know. My draft has been pretty consistent at .08-.10 iwc, at its peak temp last night the draft was .15 iwc.

Ok.. I didn't know if you had read somewhere that 650 was a recommended temperature for you to use.

Yes I do know that your using a flue probe and your numbers will be higher then mine.

Hot fires like that are of a concern. Im not sure if I've ever asked you this.. is your cat metal or ceramic

 

[Woodsplitter67]

So all in all from getting the stove up to temp to cutting the air all the way back, hour and a half?

From the time the stove was loaded to the time the air was cut back was 1.5 hours.. the stove was lit at 5am.. the damper was closed roughly 5.40.. some splits were added for my coal bed.. the stove was loaded roughly 6.09am for this burn.. when I added the wood for this burn the cat temperature was just about 1k and the stovepipe.. was roughly 300..

What are your thoughts

 

[AsylumResident]

Ok.. I didn't know if you had read somewhere that 650 was a recommended temperature for you to use.

Yes I do know that your using a flue probe and your numbers will be higher then mine.

Hot fires like that are of a concern. Im not sure if I've ever asked you this.. is your cat metal or ceramic

I am using a ceramic cat. I did buy a metal cat to have a back up that's sitting on a shelf.

 

[AsylumResident]

From the time the stove was loaded to the time the air was cut back was 1.5 hours.. the stove was lit at 5am.. the damper was closed roughly 5.40.. some splits were added for my coal bed.. the stove was loaded roughly 6.09am for this burn.. when I added the wood for this burn the cat temperature was just about 1k and the stovepipe.. was roughly 300..

What are your thoughts

Is your stove pipe double wall? I have a double wall stovepipe. I think I'm going to start hitting the stovepipe with the IR gun to see what my outside stovepipe temps are when the internal temp is 550, 600 and 650.

When you add splits to get things up to temp, do you have the bypass open or closed for that process?

 

[Woodsplitter67]

so heres my stove right now.. clean glass cat is 585 stove STT 425 stack is like 280 at 9.15 normally it won't burn down as fast .. but this load had a large pine split..

 

[Woodsplitter67]

Is your stove pipe double wall? I have a double wall stovepipe. I think I'm going to start hitting the stovepipe with the IR gun to see what my outside stovepipe temps are when the internal temp is 550, 600 and 650.

When you add splits to get things up to temp, do you have the bypass open or closed for that process?

yes.. im double wall.. so when I did that I did add the splits a little prior to closing the bypass because the wood that was in the box was used to get things up to temp.. the stove and stovepipe... so I let that wood catch.. closed the bypass and got the catalyst lit.. once up to temp.. I added the wood for this load

 

[arnermd]

Had a new level of questioning my life today.

I let the fire burn down to a nice, maybe just a little too small, coal bed. I loaded it up just under fully loaded, had the air 100% open, let the load catch until the flue temps hit 650 (been doing that all week), closed the bypass, and when the cat hit 975 I put the air to 50%. This has been my standard procedure for the past couple weeks that had been going very well. I had the cat hit 1500 twice in the past couple weeks but didn't stay there.

Today I followed that procedure and by an hour and half I hit 1550 on my cat and it just took off. I closed the air to 25% closed, the cat went to 1650. I closed the air to 0%, it hovered between 1650 and 1700 for about 5 minutes and then it kept going up. My flue temp at this point is 950. I opened the air to try and burn off some of the smoke and gasses to lower the cat which it did but that shot my flue to 1100 so I incrementally closed the air down to bring the flue down and hopefully keep the cat down. I spent the next half hour playing with the air and opening the bypass a couple times. In the end I saw my cat hit 1780 and my flue went over 1200 at one point. I ended up taking a few splits out and tossing them in the back yard. I have never had this situation happen.

I'm trying to figure out how it got that out of control. The only thing that I can think of that was different was one of the large splits I put in this load was not a hardwood. It was soft and a little dry rotted. I put that piece on the bottom back of the stove. When I took the three splits out, I got down to that piece and it was one large piece of red hot coals still holding its form, barely. Is it possible that could create this run away burn?

Welcome to the club.... I been there, done that. It is really aggravating. Half burnt logs have been tossed out my back door too....

I believe as you said, you can get a piece of wood raging right in front of the secondary smoke inlet and it just channels right up into the refractory / cat. All the heat is going into the refractory and away she goes..... Draft will increase with stack temp so the problem snowballs and you get very high draft (as you measured) and it just keeps sucking more air.....

This is one of the reasons I added my key damper and sealed around the outside edge. In this scenario now I will clamp that damper shut and kill the draft, eventually things will cool back down, but it can take a 30 min to an hour.

Another thing you can do is get a plate and a magnet for the secondary inlet. I made a plate that fits up against the secondary air inlet and I use the magnet to hold it in place. This will kill the secondary burn, and if you shut down the primary air too things will cool back down. it is a smoking mess but it does keep it from melting down.

I assume you heard the whoosh? Mine makes a very distinctive, air flow / combustion noise when this happens.

Couple other thoughts:

• I have noticed usually (not always) 650 flue gas temp correlates close to 450 on the STT on my stove. I typically engage cat at 450 on the STT (which is about 650 flue gas temp)
• I do not think you did anything "wrong", I would guess it was just a combination of wood placement, wood quality and coal bed location. For some combination of reasons: there was "light" wood right in front of the secondary smoke inlet and the coal bed / airflow was promoting combustion right there.
• When I load, I always try to leave a 2-3" gap in front of the refractory at the bottom to promotes mixing of smoke, flame and air before it goes up into the refractory channels.
• Another solution might be to rake coals toward the front, (or at least away from the secondary inlet) but this will slow down the cat light off if you have a colder stove.....

 

[Woodsplitter67]

Welcome to the club.... I been there, done that. It is really aggravating. Half burnt logs have been tossed out my back door too....

I believe as you said, you can get a piece of wood raging right in front of the secondary smoke inlet and it just channels right up into the refractory / cat. All the heat is going into the refractory and away she goes..... Draft will increase with stack temp so the problem snowballs and you get very high draft (as you measured) and it just keeps sucking more air.....

This is one of the reasons I added my key damper and sealed around the outside edge. In this scenario now I will clamp that damper shut and kill the draft, eventually things will cool back down, but it can take a 30 min to an hour.

Another thing you can do is get a plate and a magnet for the secondary inlet. I made a plate that fits up against the secondary air inlet and I use the magnet to hold it in place. This will kill the secondary burn, and if you shut down the primary air too things will cool back down. it is a smoking mess but it does keep it from melting down.

I assume you heard the whoosh? Mine makes a very distinctive, air flow / combustion noise when this happens.

Couple other thoughts:

• I have noticed usually (not always) 650 flue gas temp correlates close to 450 on the STT on my stove. I typically engage cat at 450 on the STT (which is about 650 flue gas temp)
• I do not think you did anything "wrong", I would guess it was just a combination of wood placement, wood quality and coal bed location. For some combination of reasons: there was "light" wood right in front of the secondary smoke inlet and the coal bed / airflow was promoting combustion right there.
• When I load, I always try to leave a 2-3" gap in front of the refractory at the bottom to promotes mixing of smoke, flame and air before it goes up into the refractory channels.
• Another solution might be to rake coals toward the front, (or at least away from the secondary inlet) but this will slow down the cat light off if you have a colder stove.....

whats your opinion on the burn above

 

[Woodsplitter67]

so at 1.15 this is what the stove looked like

 

[Woodsplitter67]

sorry about the picture above.. lots of glare..

I just restarted the stove.. here is what the coals looked like

put some small and medium splits on it and got the stove up to temp .. 552..and colsed the damper cat went to 900.. cut the air back to a little more then half way
draft was low..so around 900 will where it will be. stack temp probably around 300

 

[AsylumResident]

sorry about the picture above.. lots of glare..

I just restarted the stove.. here is what the coals looked like

put some small and medium splits on it and got the stove up to temp .. 552..and colsed the damper cat went to 900.. cut the air back to a little more then half way
draft was low..so around 900 will where it will be. stack temp probably around 300

View attachment 319447 View attachment 319448 View attachment 319449 View attachment 319450 View attachment 319451

So you have a bed of coals. You put a couple/few medium splits on the coals, which would burn bright and hot to get the stt back up to temp, correct? When those smaller splits get the stovetop up to temp you engage the cat to get the cat up to temp, correct? Once the cat is up to temp, you open the bypass back up, load up the stove, close the bypass and set the air where you want it?

 

[AsylumResident]

@arnermd I told you last week I haven't had any back puffing happen that I'm aware of. Today it's been happening somewhat regularly. I have a brand new stove to learn based on last night's run away and today's back puffing. Good. I was getting bored.

 

[Woodsplitter67]

So you have a bed of coals. You put a couple/few medium splits on the coals, which would burn bright and hot to get the stt back up to temp, correct? When those smaller splits get the stovetop up to temp you engage the cat to get the cat up to temp, correct? Once the cat is up to temp, you open the bypass back up, load up the stove, close the bypass and set the air where you want it?

yes.. to all of the questions.. you got it

is this any different then how your doing things..

 

[arnermd]

yes.. to all of the questions.. you got it

is this any different then how your doing things..

Ohhh.... you actually open the bypass when the cat is hot and then load up? This is something I did not understand before.... I thought you let it burn down to coals and then loaded up....

When is the cat hot enough where you will open it and load up?

I am going to try that tonight....

@AsylumResident : you should never be bored with this stove..... Happy, sad, frustrated, angry, warm.... but never bored.