2023/24 VC Temperature discussion thread

[AsylumResident]

I will be flush with Ash for years. And then I have a ton of maple on the property.

 

[arnermd]

I will be flush with Ash for years. And then I have a ton of maple on the property.

You got that ash borer beetle out there?

Those damn bugs killed every ash tree on my property..... been dropping 3-4, 70 footers every year.

 

[AsylumResident]

Yes we do. We have a lot of low lands and we dozens of trees affected. Definitely over 100 trees just on our property.

 

[Woodsplitter67]

I was burning ash and I did check the primary flapper which was sitting completely closed. It wasn’t the best feeling when I’m fully closed and couldn’t lower the STT temp as quickly as I would like.

1500 is on the warm side for sure. At 1500 I would start to show some concern. At 1580+.. im feeling I have a problem. A short spike of that temperature I wouldn't think twice

700 is a high stove temp and if you kept it there for an extended period of time you may start to warp something.. 750+ is when Id start to be concerned for extended periods of time. My stove has been at 700 and the sun rose the next day I my wife still loves me. Nothing to panic over if its not extended time..

 

[Woodsplitter67]

I didn’t struggle too much with the Cat temps. It got high Saturday night but stayed south of 1600.

Why is there so much flame activity and STT pushing 700 with air at 0%?

Id say maybe you had something not fully closed.. Id double check the stove and do a small test fire.. You should have some wood in the stove and be able to colse the air all the way and see the fire die down or out.. no need to close the bypass when you do this.. this will confirm 2 things.. 1 no air leaks.. 2.. you should hear the primary air flap close.. do not do this gradually.. let the stove rip with the air wide open then close it filly and with in 30 seconds or so.. you should see a big reduction in fire activity..

 

[AsylumResident]

Id say maybe you had something not fully closed.. Id double check the stove and do a small test fire.. You should have some wood in the stove and be able to colse the air all the way and see the fire die down or out.. no need to close the bypass when you do this.. this will confirm 2 things.. 1 no air leaks.. 2.. you should hear the primary air flap close.. do not do this gradually.. let the stove rip with the air wide open then close it filly and with in 30 seconds or so.. you should see a big reduction in fire activity..

I’ll do exactly this tomorrow. I’ll report back the result.

 

[AsylumResident]

Id say maybe you had something not fully closed.. Id double check the stove and do a small test fire.. You should have some wood in the stove and be able to colse the air all the way and see the fire die down or out.. no need to close the bypass when you do this.. this will confirm 2 things.. 1 no air leaks.. 2.. you should hear the primary air flap close.. do not do this gradually.. let the stove rip with the air wide open then close it filly and with in 30 seconds or so.. you should see a big reduction in fire activity..

On a reload I kept the by pass open, let the wood catch decently and then shut the primary all the way down. The flames diminished almost entirely, gave it about a minute and then full open on air and flames filled the box. Based on that I'd say the primary flapper is working as it should. I also checked it, all good. I would think that reaction would also rule out another direct leak into the main combustion (could be wrong).

That reload was three decent splits (less than half a load of ash) hit the bypass, let the cat get to 1000 and then started cutting the air back. By 1100 I had the air down to 10%. Cat kept climbing slowly and got to 1660. At 1660 it started flashing over like crazy, lowered quickly to 1630, stop flashing over back up to 1650, more flashing overs and back down. It did this for about 10 minutes. Then it was non-stop flash overs with a quick temp drop from 1650 to 1400. From there the cat slowly continued to drop over the next hour. During all the flash overs STT was around 450. Once the cat started dropping quick, the STT started rising quick. Cat dropped to 1050 and STT went from 450 to 650. Air stayed at 10% the entire time.

Based on that, two things would make sense to me. 1) my draft is too low, not pulling enough through on the down draft causing a build up of smoke and gasses causing an excess of flash over with the cat getting very high (lack of secondary air intake from lack of draft?).
2) once the temps get high enough there is an increase if secondary air quenching the cat but also overflowing into primary combustion as per @arnermd which would lower cat temp and cause the flash overs and increasing the STT. Possible reason?

If it's number 1 I increase my draft. If it's number 2...damnit.

Long post, I apologize, but man is this fascinating.

 

[sargeott]

Great stuff guys. New information for me:
This morning I finally was able to properly seal up the 6in-8in flange at the base of my chimney from stove adapter. This drastically increased the draft pressure and showed me I have leaks in my stove.
With the bypass engaged, cat firing and primary air at 4 clicks to full closed it was sucking air that I could hear but couldn't figure out from where.
I lit some sage brush in my hand and let it fall down to a smoke, ran it around the front of the stove and saw the smoke being sucked toward the glass seals on both doors. Wth?! This stove is only a year old and I suspect this has been part of my issue since day one.
I let the stove cool down, pulled both glass panels and ran a bead of Rutland furnace cement caulk around the glass sealing flanges.
Let it dry for an hour and fired this girl back up.
Normal start up, small bits down to coals, increased to larger splits down to coals and air control at 5 clicks in from full throttle with bypass open to build a nice bead of 2 in coals.
Loaded it up to the top with fresh fir and oak mix. Wide open air primary for another 20 minutes to a real hot roaring fire. 1 hour total time from cold start.
Stt to 500 at and engaged bypass and cat, dropped the primary down to 6 clicks in from open and I can hear the cat breathing strong and healthy.
It's been running this way for 4 hours tonight. Zero smoke out of the chimney, stt holding at 500 solid for 4 hours, single wall chimney flange surface temp at 300 and the cat is just cruising making a nice constant breath. This has been my view for 4 hours solid.

 

[newguyjoe]

Great stuff guys. New information for me:
This morning I finally was able to properly seal up the 6in-8in flange at the base of my chimney from stove adapter. This drastically increased the draft pressure and showed me I have leaks in my stove.
With the bypass engaged, cat firing and primary air at 4 clicks to full closed it was sucking air that I could hear but couldn't figure out from where.
I lit some sage brush in my hand and let it fall down to a smoke, ran it around the front of the stove and saw the smoke being sucked toward the glass seals on both doors. Wth?! This stove is only a year old and I suspect this has been part of my issue since day one.
I let the stove cool down, pulled both glass panels and ran a bead of Rutland furnace cement caulk around the glass sealing flanges.
Let it dry for an hour and fired this girl back up.
Normal start up, small bits down to coals, increased to larger splits down to coals and air control at 5 clicks in from full throttle with bypass open to build a nice bead of 2 in coals.
Loaded it up to the top with fresh fir and oak mix. Wide open air primary for another 20 minutes to a real hot roaring fire. 1 hour total time from cold start.
Stt to 500 at and engaged bypass and cat, dropped the primary down to 6 clicks in from open and I can hear the cat breathing strong and healthy.
It's been running this way for 4 hours tonight. Zero smoke out of the chimney, stt holding at 500 solid for 4 hours, single wall chimney flange surface temp at 300 and the cat is just cruising making a nice constant breath. This has been my view for 4 hours solid.

View attachment 317731

I replaced my glass gaskets about 2 weeks ago. WHAT A DIFFERENCE! i am able to control this stove a lot better now. unreal. i even put the catalyst back in and everything is working great for the first time in 4 seasons! also i put in the Auber temp monitor. its great too.

 

[arnermd]

Glass gaskets are a common leak point, periodically check them. I often use a lighter flame to isolate a leak.

@AsylumResident : All sounds very familiar, welcome to the club..... was this another hot reload? Did you try raking coals to either front or back? Another thing to try is leave the air open a bit more so you get a cleaner primary burn, problem is you end up with too much heat... open a window. Sometimes I can thread the needle....

My guess is you have too much heat (coals) in the firebox when you reload and it is trying to combust all the fresh softwood, then you close down the air and it all smolders making lots of smoke for the cat. Try letting the coal bed cook down a bit more....

My burn last night.... 3/4 load of some bigger splits.... took a while to get the secondary going. May have closed air down to early.....

 

[Todd]

I’ve never burned a VC but have plenty of experience with other cat stoves. I haven’t seen much talk from you guys about monitoring flue temps and was wondering if doing that would help? In previous cat stoves I liked to monitor the flue temp during reloads because when the bypass was open it could really run away from you if you just let her rip waiting for the cat temp to come up. I would start off with full air til it gets going then cut back to maybe half or a little less air once the internal temp reached about 400 then keep it in the good zone til the cat temp was in the engage zone. My thinking is if the flue gets too hot the draft can be ripping hard and when you engage the cat it can really take off on you.

 

[gthomas785]

I’ve never burned a VC but have plenty of experience with other cat stoves. I haven’t seen much talk from you guys about monitoring flue temps and was wondering if doing that would help? In previous cat stoves I liked to monitor the flue temp during reloads because when the bypass was open it could really run away from you if you just let her rip waiting for the cat temp to come up. I would start off with full air til it gets going then cut back to maybe half or a little less air once the internal temp reached about 400 then keep it in the good zone til the cat temp was in the engage zone. My thinking is if the flue gets too hot the draft can be ripping hard and when you engage the cat it can really take off on you.

Well with a VC stove the cat temp doesn't mean anything unless the bypass is closed... So yes you need to monitor something else. If you wait until the cat is at 500 before engaging you will be waiting all winter.

 

[arnermd]

I will watch flue temps when I am heating up, before engaging the cat, to try and keep the draft under control. Once the cat is engaged I do not do anything with flue temps, I monitor and adjust based on cat temps. Although sometimes I feel like the air lever is just a placebo.... stove does what it wants.

 

[Woodsplitter67]

I will watch flue temps when I am heating up, before engaging the cat, to try and keep the draft under control. Once the cat is engaged I do not do anything with flue temps, I monitor and adjust based on cat temps. Although sometimes I feel like the air lever is just a placebo.... stove does what it wants.

I totally agree with this.. I only look at the stovepipe temperature to see if iv established enough draft to light the cat off.. once it going flue temps to me don't mean that much

 

[AsylumResident]

I totally agree with this.. I only look at the stovepipe temperature to see if iv established enough draft to light the cat off.. once it going flue temps to me don't mean that much

At what flue temp do you engage the cat?

 

[AsylumResident]

Glass gaskets are a common leak point, periodically check them. I often use a lighter flame to isolate a leak.

@AsylumResident : All sounds very familiar, welcome to the club..... was this another hot reload? Did you try raking coals to either front or back? Another thing to try is leave the air open a bit more so you get a cleaner primary burn, problem is you end up with too much heat... open a window. Sometimes I can thread the needle....

My guess is you have too much heat (coals) in the firebox when you reload and it is trying to combust all the fresh softwood, then you close down the air and it all smolders making lots of smoke for the cat. Try letting the coal bed cook down a bit more....

My burn last night.... 3/4 load of some bigger splits.... took a while to get the secondary going. May have closed air down to early.....
View attachment 317732

It was a hot reload and I pushed the coals to back. There was a decent amount of coals in the firebox, I should have let it burn down some more.

 

[gthomas785]

I'll shut the bypass at a flue temp (internal) of anywhere from 600-800 depending on other factors like how big a coal bed I'm loading on. Keep in mind I have a short chimney with marginal draft to begin with. If the previous load was pretty well burned down then I'll usually wait longer and let things get heated up a bit more up to 800. If it's still a very hot bed of coals and the load is catching quickly then I'll close the bypass when the flue is more like 650.

 

[Woodsplitter67]

It was a hot reload and I pushed the coals to back. There was a decent amount of coals in the firebox, I should have let it burn down some more.

Normally.. pushing the coals back is not a good idea with this size stove when hot reloading. You should have plenty of coals.. Only push the coals back when you feel the cats not going to light off. like when its really burned down.. the stovepipe is on the cooler side and the catalyst is at a borderline temperature..

If your stove was already running and pretty much up to temperature.. drop the wood in and close the bypass.. dont let the box turn into a flaming mess.. waiting for everything to catch creates a lot of off gassing.. and high temperatures

 

[Woodsplitter67]

At what flue temp do you engage the cat?

when the thermometer reads about 300

 

[arnermd]

Just want to remind everyone that in my setup the flue temp is gas temp, not skin temp. I have a probe inserted into the stove pipe, so my readings will be higher and faster to react than a skin temp.

 

[Todd]

So what kind of flue temps are you guys seeing once you’re up and running in cruise mode? How does it relate with your stove top temps?

 

[arnermd]

So what kind of flue temps are you guys seeing once you’re up and running in cruise mode? How does it relate with your stove top temps?

See my plots above..... Flue is exhaust gas temp, Orange is a thermocouple in the center of the griddle.

 

[Anthony09]

On a reload I kept the by pass open, let the wood catch decently and then shut the primary all the way down. The flames diminished almost entirely, gave it about a minute and then full open on air and flames filled the box. Based on that I'd say the primary flapper is working as it should. I also checked it, all good. I would think that reaction would also rule out another direct leak into the main combustion (could be wrong).

That reload was three decent splits (less than half a load of ash) hit the bypass, let the cat get to 1000 and then started cutting the air back. By 1100 I had the air down to 10%. Cat kept climbing slowly and got to 1660. At 1660 it started flashing over like crazy, lowered quickly to 1630, stop flashing over back up to 1650, more flashing overs and back down. It did this for about 10 minutes. Then it was non-stop flash overs with a quick temp drop from 1650 to 1400. From there the cat slowly continued to drop over the next hour. During all the flash overs STT was around 450. Once the cat started dropping quick, the STT started rising quick. Cat dropped to 1050 and STT went from 450 to 650. Air stayed at 10% the entire time.

Based on that, two things would make sense to me. 1) my draft is too low, not pulling enough through on the down draft causing a build up of smoke and gasses causing an excess of flash over with the cat getting very high (lack of secondary air intake from lack of draft?).
2) once the temps get high enough there is an increase if secondary air quenching the cat but also overflowing into primary combustion as per @arnermd which would lower cat temp and cause the flash overs and increasing the STT. Possible reason?

If it's number 1 I increase my draft. If it's number 2...damnit.

Long post, I apologize, but man is this fascinating.

My stove operates like yours. I run it all last season. I pretty much just don’t go over half load cause with my setup it seems unsafe. Those 700-750 stove tops n 15-1700 cat temps don’t last too long when half load or so. I don’t think there’s a way for me to get my setup to not do this. Which is ok I can still have a hot stove from 9 pm to 4-5 am when I get up, just frustrating. I often wondered if I don’t have enough draft too when that happens.

 

[AsylumResident]

My stove operates like yours. I run it all last season. I pretty much just don’t go over half load cause with my setup it seems unsafe. Those 700-750 stove tops n 15-1700 cat temps don’t last too long when half load or so. I don’t think there’s a way for me to get my setup to not do this. Which is ok I can still have a hot stove from 9 pm to 4-5 am when I get up, just frustrating. I often wondered if I don’t have enough draft too when that happens.

What stove do you have? How long is your chimney and what size?

 

[Anthony09]

What stove do you have? How long is your chimney and what size?

Encore
6 in probably 22-23 ft but got a pretty good horizontal run straight out of back of stove