2023/24 VC Temperature discussion thread

[AsylumResident]

This is my favorite weather to run this stove. Mid 30s outside. Snow coming in. Half load of wood, 50% air and just let it cruise. Cat at 1080, STT 375. House at 70°. It'll burn on a half load like this for 3-4 hours. Rinse repeat all day

I'm loving it right now. I could not run a full load when the temps were around 0. There was no combination I could run that wouldn't overheat the cat.

 

[Eman85]

Stove's been cold so I wanted to do a little cleaning and maintenance. This cat was new at the beginning of last season. This is what I found, no ash and the catalyst looks fine. I pulled the door with the cracked glass and replaced the glass and put new gaskets on. You could see where it was sucking some air at the glass gasket and the door gasket.

 

[Woodsplitter67]

Stove's been cold so I wanted to do a little cleaning and maintenance. This cat was new at the beginning of last season. This is what I found, no ash and the catalyst looks fine. I pulled the door with the cracked glass and replaced the glass and put new gaskets on. You could see where it was sucking some air at the glass gasket and the door gasket.
View attachment 324013View attachment 324014

id put that in the category of super mega ultra nuclear...

 

[AsylumResident]

Stove's been cold so I wanted to do a little cleaning and maintenance. This cat was new at the beginning of last season. This is what I found, no ash and the catalyst looks fine. I pulled the door with the cracked glass and replaced the glass and put new gaskets on. You could see where it was sucking some air at the glass gasket and the door gasket.
View attachment 324013View attachment 324014

So it looks like you decided to use it for target practice. Did it take a 9mm at that top corner?

 

[NewGuy132]

2200 wow.... I think that's a record.... Was that at the cat?

My cat was about 1850. I never hit 2200, thats the temp that cast iron will start to melt.

 

[Eman85]

The cast iron melting at 2200 doesn't matter as much as the temp the sheet metal they wrap the cat in distorts as you can tell by my pics. I've never seen temps past 1600 and rarely but that one side sure didn't like it. That is just how the cat sits so it's the upper edge that distorted. It's back in probably have a fire tonight and test it. Had a small fire last night just to cure the gasket cement.

 

[arnermd]

The cast iron melting at 2200 doesn't matter as much as the temp the sheet metal they wrap the cat in distorts as you can tell by my pics. I've never seen temps past 1600 and rarely but that one side sure didn't like it. That is just how the cat sits so it's the upper edge that distorted. It's back in probably have a fire tonight and test it. Had a small fire last night just to cure the gasket cement.

All things considered.... I would say it looks pretty good. Obviously had some issue on the left side there, but the ceramic looks real good. My ceramic cat frames come out all twisted and warped. Not so with the metal cat, it stays pretty straight.

 

[Eman85]

I've still got an old cat that was in for years and it isn't distorted at all and isn't cracked in the ceramic. I'm going to put it in sometime this season.

 

[AsylumResident]

I've still got an old cat that was in for years and it isn't distorted at all and isn't cracked in the ceramic. I'm going to put it in sometime this season.

I, unfortunately, got about two cords of wood through my ceramic cat. Not entirely sure why. I had some high cat temps here and there and one event that touched just shy of 1800. It cracked and a piece about the size of a silver dollar fell out of it. I mourned my loss of losing my first and hope the second lasts longer. I now have a metal cat.

 

[Woodsplitter67]

I, unfortunately, got about two cords of wood through my ceramic cat. Not entirely sure why. I had some high cat temps here and there and one event that touched just shy of 1800. It cracked and a piece about the size of a silver dollar fell out of it. I mourned my loss of losing my first and hope the second lasts longer. I now have a metal cat.

so whats your opinion of the steel cat.. just curious..

 

[arnermd]

I, unfortunately, got about two cords of wood through my ceramic cat. Not entirely sure why. I had some high cat temps here and there and one event that touched just shy of 1800. It cracked and a piece about the size of a silver dollar fell out of it. I mourned my loss of losing my first and hope the second lasts longer. I now have a metal cat.

Just FYI... I have run ceramic cats with "holes" in them for months, one time I even took pieces from a previous one and stacked it on top of the holes. Seemed to work just fine and got me a few more months of use before it completely fell apart...

I have about 6 cords on a steel cat and still going. Did a couple vinegar soaks on it this year, seemed to perk it up a bit but hard to tell....

I usually get about 6 cords out of a ceramic cat, failure mode is always ceramic substrate crumbling.

 

[AsylumResident]

so whats your opinion of the steel cat.. just curious..

The challenge is I don't have apples to apples. With the ceramic cat I was running during warmer weather and all locust. After my first load of full ash when it got very cold here is when I cracked that cat. So I was running the metal cat during very cold weather and burning ash. As it warms up here to get back to a similar situation I'll be able to give a better comparison. So far it as been holding hotter, longer than the ceramic cat.

 

[Woodsplitter67]

The challenge is I don't have apples to apples. With the ceramic cat I was running during warmer weather and all locust. After my first load of full ash when it got very cold here is when I cracked that cat. So I was running the metal cat during very cold weather and burning ash. As it warms up here to get back to a similar situation I'll be able to give a better comparison. So far it as been holding hotter, longer than the ceramic cat.

are you seeing high temperatures like the ceramic.. or do you see lower cat temperatures in general

 

[Sticker]

Do you think this happened because you did a full load on a large coal bed? Maybe since the stove and cat is already hot a full load can be too much fuel for the cat especially if the air is set too low and sending lots of smoke into that secondary burn chamber?

I think just about any stove has a better chance of overfiring with a large coal bed or hot reloads. I try and keep my coal bed to a minimum when I’m on a 8 or 12 hour reload schedule. Sometimes I’ll rake the coals and open the air full for awhile til it’s down to where I like it. Other times when it’s really cold out I don’t worry about the coal bed and just load a half load and burn a little hotter and load more often like you stated.

Think you nailed it on the hot coal off gassing part. I had been trying to "stretch" my burn time by shutting the primary air as closed as possible when reloading on a hot bed and engaging the cat within a couple minutes of reload. I was able to keep my flue gas temp reasonable and stove top in the 450-500 range. The negative effects of this though was a back puff when the fire ran out of oxygen to support combustion and would rhythmically "puff" sending small amounts of smoke into living area.

So I experimented by opening the primary air. To my surprise, at about 25% open the fire no longer puffed back, the glass stayed clean, and the temperature of the CAT actually dropped, leaving a cooler flue but slightly warmer stove top. So on a hot stove with Cat engaged, I'm thinking you are going to burn the off gassing fuel either inside the fire box near the wood, or at the CAT. Small splits means rapid off gassing and rapid rise in CAT temperature even with primary are mostly closed. Large splits give me far better control and are a real pleasure to burn as I get to choose what speed they off gas at by adjusting primary air.

I know this has been stated many times on here, but as I am just getting an understanding of it I will restate the obvious. Once the fire is too hot with much wood remaining, closing the primary air means burning less gas in the firebox, and more gas in the CAT. CAT rises rapidly, and ten minutes or so later logs slow in offgassing and CAT starts to cool. Not sure why it took me a full season to get this cycle through my head, guess I counter intuitively thought closing air would lower both offgassing and CAT. which eventually does happen, but not until things get pretty dicey with CAT temperature.

 

[Sticker]

More details please..... when do you engage the cat? At what temps? What temp are you triggering off of.

I do not have an actual temp probe reading degrees of heat at CAT. I am using the physical bimetal that points to time to engage CAT. I try to keep stove as cool as possible as this the stove is way too large for our house when running close to capacity.

 

[arnermd]

Sounds consistent with my experience and thinking. Except for this part:

CAT rises rapidly, and ten minutes or so later logs slow in offgassing and CAT starts to cool. Not sure why it took me a full season to get this cycle through my head, guess I counter intuitively thought closing air would lower both offgassing and CAT. which eventually does happen, but not until things get pretty dicey with CAT temperature.

Sometimes closing the primary air does reduce cat temps, sometime it don't (until it runs out of wood).
But I think you have captured how things are "Supposed" to work.....

I was not asking about your cat temps, I was asking when do you engage the cat and what are you using as your signal? Griddle temp, flue temp, something else?

 

[Sticker]

Sounds consistent with my experience and thinking. Except for this part:


Sometimes closing the primary air does reduce cat temps, sometime it don't (until it runs out of wood).
But I think you have captured how things are "Supposed" to work.....

I was not asking about your cat temps, I was asking when do you engage the cat and what are you using as your signal? Griddle temp, flue temp, something else?

I have been checking base of flue pipe. When it hits 475 I engage the CAT. That is the way I do it on the start from cold, from warm with decent coal bed, I simply get fire going good and reengage CAT leaving air minimum of 25% open. Has been working beautifully, especially with larger splits of >4 inches.

 

[AsylumResident]

are you seeing high temperatures like the ceramic.. or do you see lower cat temperatures in general

I am seeing higher average cat temps with the metal cat.

 

[arnermd]

Been having some very nice burns the last couple weeks, mostly burning overnight and then just nursing it during the day to keep some coals active. Then I started getting the alarm at night about 2 hours in to a full load. Why? Ash.....

Both ash burns had air set around 30%.
Mixed ash with some oak and that seemed to help last night, also was smaller load.

 

[Eman85]

@arnermd That's some high flue temps!, and on the last 2 burns that's very high STT for having the cat engaged. I do my best not to have the cat run like that to max temps, that anxiety when it crosses 1400 wears on me, I like to see it peak in 1200's to 1300 on the first rise. Then it seems to max out under 1500 on the second rise.

 

[arnermd]

yep, it was hot.... flue and STT way above normal.
Thats ash for ya....

Forgot to mention I did a moisture check on some fresh spits of oak and ash from the same row. 13-15% mc for both. So that rules out the ash being drier as the cause....

And.... there was no bark on the ash. In fact last week I had a big pile (about a 5 gal bucket full) of bark in the woodshed. I threw it on a hot bed of coals and it burned fine for a couple hours.

 

[AsylumResident]

yep, it was hot.... flue and STT way above normal.
Thats ash for ya....

Forgot to mention I did a moisture check on some fresh spits of oak and ash from the same row. 13-15% mc for both. So that rules out the ash being drier as the cause....

And.... there was no bark on the ash. In fact last week I had a big pile (about a 5 gal bucket full) of bark in the woodshed. I threw it on a hot bed of coals and it burned fine for a couple hours.

I would have definitly smelled those burns on 2/8 and 2/9. Would have filled the room with that hot metal smell with flue that high.

I have been burning smaller loads, closer to half loads for the last few weeks. All ash and yes it does burn hotter but has been manageable with the smaller loads.

 

[Eman85]

I would have definitly smelled those burns on 2/8 and 2/9. Would have filled the room with that hot metal smell with flue that high.

My stove is the same. DW pipe and if the flue temps get high I can smell it. If I load the stove and let it burn to get temps up and get distracted the smell lets me know I screwed up.
Makes you wonder if the paint on the pipes is tested for toxics released when it gets hot.

 

[arnermd]

I got the smell the first time but none after that...... Guess I cured the paint. I also think house dust is part of the smell, once you burn it off you get no smell for a while, till the dust reaccumulates. Those with hot water baseboard heat know what I am refering to. That first time in the fall when the baseboards get hot you can smell it, and then it goes away. Not that I use my boiler anymore, been years.

 

[AsylumResident]

I have been burning all weekend just during the days. All day Friday, all day Saturday and barely was able to break 900 at the cat. STT pretty much 450-550 the whole time. Then this afternoon (Sunday) I reloaded and now I'm humming along at 1350 cat.

Based on the air settings, STT, and flue gas temp, I assumed my lack of temperature at the cat was due to lack of draft. Everything today was basically the same as the last two days including outside Temps. Why all of a sudden do I decent cat temps?