2023/24 VC Temperature discussion thread

[arnermd]

Looks very good to me. 4hrs > 1000F seems about right, 20 min to 650 on a cold start is about what I am seeing too.

When you start from cold do you use a few small splits and let them cook down to coals before you load up? Do you throw the cat in while you are making the coal bed? Or just burn in bypass?

For your amusement here is a burn gone bad from yesterday.....

• Stove was pretty cold, just a few coals left so I raked them to the back and loaded the stove chock full.
• Took a very long time for the load to catch, even with full air and cracking the ash pan door.
• Engaged the cat at flue = 600F, dialed air down to 50% at 1100.
• All seemed fine and then the cat temp launched (20:45) with no input from me. At the same time I heard the whoosh of the combustion noise from the secondary.
• When it hit 1400 I dialed air down to 0% and closed my key damper, killing the draft. Did not seem to do much good.
• When it launched again up to 1600 I opened the damper and increased air to 25% in order to get more primary combustion going...
• Once the primary burn was showing active flame I closed the bypass and all seemed to be fine after that.

I think my error here was not having enough heat in the primary burn initially, waited too long to reload. Maybe should have done a small burn just to build the bed of coals back up? What I ended up with was a smoldering smoky mess in the primary burn zone...

 

[AsylumResident]

Looks very good to me. 4hrs > 1000F seems about right, 20 min to 650 on a cold start is about what I am seeing too.

When you start from cold do you use a few small splits and let them cook down to coals before you load up? Do you throw the cat in while you are making the coal bed? Or just burn in bypass?

For your amusement here is a burn gone bad from yesterday.....

• Stove was pretty cold, just a few coals left so I raked them to the back and loaded the stove chock full.
• Took a very long time for the load to catch, even with full air and cracking the ash pan door.
• Engaged the cat at flue = 600F, dialed air down to 50% at 1100.
• All seemed fine and then the cat temp launched (20:45) with no input from me. At the same time I heard the whoosh of the combustion noise from the secondary.
• When it hit 1400 I dialed air down to 0% and closed my key damper, killing the draft. Did not seem to do much good.
• When it launched again up to 1600 I opened the damper and increased air to 25% in order to get more primary combustion going...
• Once the primary burn was showing active flame I closed the bypass and all seemed to be fine after that.

I think my error here was not having enough heat in the primary burn initially, waited too long to reload. Maybe should have done a small burn just to build the bed of coals back up? What I ended up with was a smoldering smoky mess in the primary burn zone...

View attachment 318741

When I start from cold to build a coal bed I have always done it with the bypass open.

That is interesting to have the cat jump like that with air at 50%. You would hope there is enough primary combustion to reduce, presumably, so much smoking to feed the cat. If there was better primary combustion ideally the cat wouldn't go so high but also your STT would be a little higher, which to me wouldn't be so bad. What would happen if you opened the air to 75% or so around 21:00? Would your cat expode, or maybe do about the same thing it did? Or maybe reduce the cat after an inital quick temp hike since you would hopefully be getting more primary combustion?

I have yet to have the cat go over 1500 with 50% air. I have had the cat hit 1675 at 0% air.

 

[arnermd]

When I start from cold to build a coal bed I have always done it with the bypass open.

That is interesting to have the cat jump like that with air at 50%. You would hope there is enough primary combustion to reduce, presumably, so much smoking to feed the cat. If there was better primary combustion ideally the cat wouldn't go so high but also your STT would be a little higher, which to me wouldn't be so bad. What would happen if you opened the air to 75% or so around 21:00? Would your cat expode, or maybe do about the same thing it did? Or maybe reduce the cat after an inital quick temp hike since you would hopefully be getting more primary combustion?

I have yet to have the cat go over 1500 with 50% air. I have had the cat hit 1675 at 0% air.

All good thoughts and things I have pondered in the past.

I have had some success increasing the air when I get high cat temps. usually it takes a minute or two but all of a sudden the primary burn will flame up hard and cat temps will drop. I leave it like that for a bit to get griddle temp up and then reduce air. Sometimes it works. Sometimes the cats temps just launch even higher. At that point I will usually just give up and open the damper, wait for healthy flames in the primary burn and griddle temp to rise. Then I re-engage the cat and reduce air.

Sometimes things get really bad and Cat temps are high, flue temps are high and griddle temps are 600+.... In this case I lock down my key damper to kill the draft, reduce air to zero and block the secondary air inlet with a plate and magnet. Then I just wait for things to cool off, it takes a while..... That's a really bad day.

I also think part of the problem is if you get an active primary burn right at the secondary inlet (at the back bottom of the stove) it will suck flame right up into the refractory and you can get very active secondary burns. I would prefer having the cat high in the firebox so flame has a chance to burn out or mix with primary air, before hitting the cat.

In my opinion: 1500 is pushing it but OK for short periods of time. 1675 is too high, but I have been there and higher.....

My alarm is set to 1450 right now, but I will let it go to 1500 before I take action.

 

[arnermd]

another debacle last night.....

• Stove was cold, just a few coals, added a few small splits, air full open, no cat, let them burn down to coals, took 1.5 hrs
• Full load of the good dry wood, full air
• Reduced air to 50% at 1000F, left the stove alone and raised my alarm levels
• Cat went to 1600 until I finally said "no mas" and reduced the air to zero
• This time cat temps immediately responded to reduced air, not sure why it worked this time....
• Increased air to 50% before going to bed.

Maybe a full load is just too much..... very frustrating. Time to call the priest again....

 

[Woodsplitter67]

When I start from cold to build a coal bed I have always done it with the bypass open.

That is interesting to have the cat jump like that with air at 50%. You would hope there is enough primary combustion to reduce, presumably, so much smoking to feed the cat. If there was better primary combustion ideally the cat wouldn't go so high but also your STT would be a little higher, which to me wouldn't be so bad. What would happen if you opened the air to 75% or so around 21:00? Would your cat expode, or maybe do about the same thing it did? Or maybe reduce the cat after an inital quick temp hike since you would hopefully be getting more primary combustion?

I have yet to have the cat go over 1500 with 50% air. I have had the cat hit 1675 at 0% air.

I have to say for somebody that is new to their stove and burning you are doing an extremely good job..

 

[AsylumResident]

another debacle last night.....

• Stove was cold, just a few coals, added a few small splits, air full open, no cat, let them burn down to coals, took 1.5 hrs
• Full load of the good dry wood, full air
• Reduced air to 50% at 1000F, left the stove alone and raised my alarm levels
• Cat went to 1600 until I finally said "no mas" and reduced the air to zero
• This time cat temps immediately responded to reduced air, not sure why it worked this time....
• Increased air to 50% before going to bed.

Maybe a full load is just too much..... very frustrating. Time to call the priest again....

View attachment 318778

So far I have done one load that I would considered FULL. When I did that my cat went over 1600 and then as it came down my STT temp inversely went up to over 650. This was about 2 hours into the burn. My stove hasn't typically run over 550 for too long. When it got to 650 I couldn't lower it by reducing the primary air. First time that ever happened to me. I sat there staring at the stove, putting together a plan of what I was going to do if it kept creeping up, questioning my life decisions up to that point. To my relief it plateaued and started coming back down.

I haven't run a full load since that. The temperatures drop this weekend and then keep going down through the weekend of Thanksgiving. I plan to keep a fire going all week. I will be doing at least one more FULL load and seeing how I can attempt consistent burns with a full load. I would like to burn non-stop and in order to do that I will need to get a solid 8+ hours out of a full load due my wife and my work schedules.

 

[AsylumResident]

I have to say for somebody that is new to their stove and burning you are doing an extremely good job..

I appreciate that. You have been very helpful since I started asking questions here. I have spent a lot of time on here reading through different threads and trying to understand the challenges people are having and what they have done to rectify them. I like something new and I like to learn as much as I can about it. Once I saw @arnermd with the graphs I knew I was in the right place. There is a lot of 'feel' associated with this but being able to have the actual data and to see how the data interacts with different variables is a little happy place for me.

 

[GrumpyDad]

Here's my run from last night:
- Cold start
- Once I had a good bed of coals I loaded up about 3/4 full with ash
- Let that catch with air open 100% until flue temp reached 650
- When flue hit 650 I closed the bypass. Took about 20 minutes to reach 650.
- Kept air at 100% open until the cat reached 1000.
- When cat hit 1000 I dialed the air back to 50% and let it burn.

View attachment 318736

I've been able to replicate this burn pretty consistently. I would like to see a little longer burn time with a 3/4 load. I know I don't have the air closed down as far as I could but with this burn my STT peaked at 429 I'm not too interested in a much lower STT.

yea this is pretty spot on to what happens with me, and ash doesnt seem to last long. 50% with ash and I would be getting some good heat out of the stove, probably hovering around 550 STT and if I got 6 hours from 3/4 of a load with my ash that has been down and split for a long time, I would be happy.

 

[arnermd]

So far I have done one load that I would considered FULL. When I did that my cat went over 1600 and then as it came down my STT temp inversely went up to over 650. This was about 2 hours into the burn. My stove hasn't typically run over 550 for too long. When it got to 650 I couldn't lower it by reducing the primary air. First time that ever happened to me. I sat there staring at the stove, putting together a plan of what I was going to do if it kept creeping up, questioning my life decisions up to that point. To my relief it plateaued and started coming back down.

I haven't run a full load since that. The temperatures drop this weekend and then keep going down through the weekend of Thanksgiving. I plan to keep a fire going all week. I will be doing at least one more FULL load and seeing how I can attempt consistent burns with a full load. I would like to burn non-stop and in order to do that I will need to get a solid 8+ hours out of a full load due my wife and my work schedules.

Very interesting.... seems like we are seeing similar results, which is encouraging and discouraging. Misery loves company?
- "Questioning my life decisions".... I been there bro (usually at 1 AM babysitting the stove). You are not alone.
- Griddle temps are slow to react.... fortunately I rarely have that problem... its always the damn cat temps.

Agree with @Woodsplitter67 you are doing exceptionally well with your stove. I am hopeful we can learn something by sharing data.

Draft readings soon?

 

[AsylumResident]

Very interesting.... seems like we are seeing similar results, which is encouraging and discouraging. Misery loves company?
- "Questioning my life decisions".... I been there bro (usually at 1 AM babysitting the stove). You are not alone.
- Griddle temps are slow to react.... fortunately I rarely have that problem... its always the damn cat temps.

Agree with @Woodsplitter67 you are doing exceptionally well with your stove. I am hopeful we can learn something by sharing data.

Draft readings soon?

I'll keep collecting data and sharing it. We will see if we're lucky enough to stumble into some solutions.

Yes, I should have draft readings starting hopefully tomorrow evening. I know I said that last week but I think I finally have what I need to make it work.

 

[gthomas785]

Hey guys I've been mostly lurking but reading through the posts. I seem to have settled into a pretty stable operating routine for my Encore, though now that I'm posting this I'm sure it will start to act up on me.

One thing is certain. Everyone's stove has a sweet spot for primary air to limit the cat temp, and it's not 0%. Probably varies by setup. For Asylumresident it seems to be around 50%, for me with my short chimney it's around 75%. If my cat is going nuclear I have found opening the air 75% causes the cat temp to slowly drop, always. (yes griddle temp and heat output will go up, of course) Closing the air again will bring catalyst temps back up, but usually not as high as the previous spike.

@arnermd ... you're wondering why shutting the air cat temp to drop this time... My feeling is that it's precisely because you waited longer than usual before closing it. More of that initial offgassing consumed by the primary burn, so less fuel/work for the cat to do. Of course the cat temp is a combination of how active the cat is plus how much heat is coming off the primary burn. So keeping the stronger primary burn going long enough will also eventually lead to higher catalyst temps as you saw.

For me, impatience is the killer. If I close the air down too much or too quickly, the cat will take off. I would say the burn in post #179 looks pretty close to ideal, a bit high at the peak, although I'd be curious what would have happened if the air were lowered to say ~25% once the cat got to 1400. Not fully closed, but a bit less than 50%.

Oh one other thing.. opening the damper while your cat is 1600 degrees is a guaranteed way to crack it and possibly the refractory too. I would never do that.

 

[arnermd]

Good observations and I appreciate the thoughts. It all seems plausible so I do not argue with any of it.
Very frustrating.... sometimes less air = higher cat temps, sometimes lower.....

So you would suggest lowering air at 1400 from 50% to ~25%. I did not last night because I expected it would increase cat temps... but who knows. I'll give it a shot.

Excellent point about the damper when hot.... I had not thought of that. Thermal shock..... bad.

With the short stack is your setup prone to back puffing? I am curious because the manual suggests this is caused by low draft and/or reducing air to quickly. But I have had it occur with plenty of draft and no reduction in air..... Not often but it happens.

 

[NewGuy132]

Wow after reading through this thread I no longer feel bad about not starting up my stove yet. I was planning on this weekend, but I guess it is supposed to warm up a little. I'm home most of next week so I'll probably dust the cobwebs off of it then. I did have 1 small fire a couple weeks ago, but that was just to get the chill out of the room and the stove didn't even get hot enough to engage the CAT.

Before I fire it up I might try boiling my CAT in vinegar. I had problems with it all last year and a new one is only like $100 so I might give it a shot.

 

[Woodsplitter67]

Wow after reading through this thread I no longer feel bad about not starting up my stove yet. I was planning on this weekend, but I guess it is supposed to warm up a little. I'm home most of next week so I'll probably dust the cobwebs off of it then. I did have 1 small fire a couple weeks ago, but that was just to get the chill out of the room and the stove didn't even get hot enough to engage the CAT.

Before I fire it up I might try boiling my CAT in vinegar. I had problems with it all last year and a new one is only like $100 so I might give it a shot.

id still order the cat.. boiling it will only make it last so long.. you may get a couple months out of it, but if its not lightning off its getting to the end

Did you sweep your stovepipe already

You may want to look at a steel cat if your not already using it .. Iv found that it lights off easier in my stove and the cat temp doesn't run up on me..

 

[NewGuy132]

id still order the cat.. boiling it will only make it last so long.. you may get a couple months out of it, but if its not lightning off its getting to the end

Did you sweep your stovepipe already

You may want to look at a steel cat if your not already using it .. Iv found that it lights off easier in my stove and the cat temp doesn't run up on me..

It took a little digging to find a CAT for my Intrepid. I had to email customer service at Condar. They said that most people are buying the CAT for the Dauntless and using it in the Intrepid. I took mine out and measured and it sounds like it is the same CAT.

Chimney swept 2 times over summer by me with the sooteater. The reason for 2 times is I have about a 32 or 33 ft chimney and only bought the 26ft Sooteater. Also I picked up a camera and sent it up. There's still some creosote, but I'd say it is 90% clean(only buildup in the ribs of the flexliner).

My CAT from the factor was steel. I never had much luck if any using it, but the first few month I burned I had unseasoned wood and way too low so I'm thinking that the minerals on it or whatever got coated. The replacement would be ceramic.

 

[Woodsplitter67]

It took a little digging to find a CAT for my Intrepid. I had to email customer service at Condar. They said that most people are buying the CAT for the Dauntless and using it in the Intrepid. I took mine out and measured and it sounds like it is the same CAT.

Chimney swept 2 times over summer by me with the sooteater. The reason for 2 times is I have about a 32 or 33 ft chimney and only bought the 26ft Sooteater. Also I picked up a camera and sent it up. There's still some creosote, but I'd say it is 90% clean(only buildup in the ribs of the flexliner).

My CAT from the factor was steel. I never had much luck if any using it, but the first few month I burned I had unseasoned wood and way too low so I'm thinking that the minerals on it or whatever got coated. The replacement would be ceramic.

Unseasoned wood is a killer. secondary combustion will pretty much be nonexistent.. the water that is burning off has a cooling affect and of course your not burning as hot neither...

Try the cat.. there are a few here that can help you through it..

 

[gthomas785]

I had unseasoned wood and way too low so I'm thinking that the minerals on it or whatever got coated.

If your cat is coated in creosote that's not an issue, it will burn off. You'd know right away by looking at it cause it'd be shiny black. Just gotta get a nice hot fire going with dry wood and engage it.. and keep the air open for a while to really heat it up. Do you have a digital catalyst probe?

 

[AsylumResident]

I finally got some draft readings tonight. I did force a fire tonight when it was too warm but, naturally, I couldn't wait to see what draft readings I would get.

I couldn't get the cat over 900. Did a couple rounds of opening the bypass to try and build the fire up but it just wasn't having it tonight. The goal wasn't to have a big fire on this warmer night, just something to see what the draft would be. The cat sat at about 850 for two hours. While it was steady around 850 the draft reading was .08-0.1

Now that I can get draft readings I'll be checking that more often.

 

[Woodsplitter67]

was the point of .. trying to get the cat temperature up.. to see how hard you can get the stove to draft..

 

[arnermd]

Wow.... I think our stoves are in cahoots..... check this out.

• Stove was cold so I did a pre-burn of 3 smaller splits, bypassed cat
• Fire was going really well so I did not wait for it to burn down to coals.
• Loaded on top of the flames, not a full load more like 3/4, engaged the cat, 100% air
• Fell asleep on the couch so I missed 1000 F, reduced air to 50% at 1250.
• Temps crashed, but everything else looked fine so I let it go....

Other than the low cat temps this burn seemed good.... but very confused why such a different result from past two nights.

 

[arnermd]

I finally got some draft readings tonight. I did force a fire tonight when it was too warm but, naturally, I couldn't wait to see what draft readings I would get.

I couldn't get the cat over 900. Did a couple rounds of opening the bypass to try and build the fire up but it just wasn't having it tonight. The goal wasn't to have a big fire on this warmer night, just something to see what the draft would be. The cat sat at about 850 for two hours. While it was steady around 850 the draft reading was .08-0.1

Now that I can get draft readings I'll be checking that more often.

Draft seem pretty typical of what I see. Note your flue gas temp next time.

A thought: I am wondering if a less than full load leaves more room for flames to mix and combust with air in the firebox. I have often suspected that cat overtemp events are a result of flame channeling directly up into the secondary.

With less wood in there it leaves more airspace for flames to completely combust thus less smoke for the cat and lower cat temps?

 

[AsylumResident]

was the point of .. trying to get the cat temperature up.. to see how hard you can get the stove to draft..

I didn't do a very large load but I was hoping to get the cat cruising north of 1000, which is typical, to see what the draft would be. My stove wasn't interested in getting there last night.

 

[AsylumResident]

Draft seem pretty typical of what I see. Note your flue gas temp next time.

A thought: I am wondering if a less than full load leaves more room for flames to mix and combust with air in the firebox. I have often suspected that cat overtemp events are a result of flame channeling directly up into the secondary.

With less wood in there it leaves more airspace for flames to completely combust thus less smoke for the cat and lower cat temps?

It could be. However, I have had burns where I put two big splits in, get it up to temp, engage the cat and then watch the cat slowly climb to 1600. That isn't a typical result but I've had it.

 

[AsylumResident]

This is the burn from last night.
- Three smaller splits, less than 1/2 a load
- Cat never went above 1000
- Eventually put the air down to 50% around 9:00am, probably didn't need too
- In the morning there was a decent piece of charred wood left, unfortunately.



- Before I engaged the cat the flue was 640 and the STT was 440 and the draft was 0.1.
- When it was cruising around 850 the draft was .08-.1 with the flue around 500.

Now that the temps have come down I should be able to burn more normal again. Hope to have a lot of data by the end of next weekend.

 

[AsylumResident]

Wow.... I think our stoves are in cahoots..... check this out.

• Stove was cold so I did a pre-burn of 3 smaller splits, bypassed cat
• Fire was going really well so I did not wait for it to burn down to coals.
• Loaded on top of the flames, not a full load more like 3/4, engaged the cat, 100% air
• Fell asleep on the couch so I missed 1000 F, reduced air to 50% at 1250.
• Temps crashed, but everything else looked fine so I let it go....

Other than the low cat temps this burn seemed good.... but very confused why such a different result from past two nights.

View attachment 318839

This is a situation where I would love to see what would have happened if you didn't touch the air. Would it have eventually plateaued out and come down? Or just go to the moon.