White sky - smoke! Failing cat?

[jharkin]

I added some reading material to the 2in1 thread that you might find interesting...

http://www.woodstovecombustors.com/maintenance.html
http://www.chc-hpba.org/images/Renewable Heat Symposium.pdf
http://www.woodstove.com/pages/pdffiles/Catalytic Combustor Tips.pdf
http://www.blazeking.com/PDF/posters/Wood Stove 10 Questions.pdf

 

[clemsonfor]

So we have come full circle, as what I see is what I described in my initial post above. I see smoke at temps if 500 - 800F, but according to all the cat combustir literature, a ceramic cat should ignite at 500F, and a SteelCat even lower than this.

Like you, I also often run the cat up to 1000-1500F, but this involves leaving the stove in bypass a little longer after loading so the stovetop exceeds 500F before closing the bypass damper. The literature suggests life should be good, if you get the cat to 500F.

Correct my cat and manual says the same thing, once you hit 500F you can close bypass.... And the cat probe from condor puts the active range from like 500-1800F for active. But what im saying is all 500F is not the same. If i have started a cold stove once the probe says 500F i am fine to engage the cat. If i have a coaled stove the metal alone is 400F degrees up there or so and the rest is the hot air coming through the exhaust, but with new wood on there there is still to much moisture i guess in the smoke to allow full light off?

All i know is what i see and how i have come to learn to run mine.

The way i run my stove is a combination of what i have read on this site, the owners manual, and personal experience with this stove over the past 3-4 seasons.

 

[jharkin]

Interesting, my Condar digital display has printed on it:

• Below 500 - Cool
• 500-1000 - Engage Catalyst
• 1000-1700 - Normal operating range
• Over 1700 - Too hot

Chelmsfor, like you I have learned the best ways to operate via trial and error and lots of advice here. One thing I can say for sure is that simple seeing a probe temp over 500 is not a guarantee of activation. the real tell tale is the rapid temperate increase.

 

[Ashful]

Cool. What this tells me is that I was running the stove properly this fall, but backed off too much in recent weeks. Back in the fall, I was typically running stovetop up to 550F from a cool stove, engaging, and seeing the catalyst shoot up to something over 700F. After that, it would climb further to maybe 1200F over the next ten minutes, and then hang there for a long time. I had more back-puffing trouble when I would then try to throttle down with the cat over 1000F, and I had eliminated those issues by just not letting the cat get that hot on this stove, but then I have smoke out the chimney.

It's interesting so many see 500 - 1000F on their cat probe before even engaging. Mine never reads much over 100F when it's time to engage... I suppose that's unique of the down-draft design.

 

[clemsonfor]

W

Interesting, my Condar digital display has printed on it:

• Below 500 - Cool
• 500-1000 - Engage Catalyst
• 1000-1700 - Normal operating range
• Over 1700 - Too hot

Chelmsfor, like you I have learned the best ways to operate via trial and error and lots of advice here. One thing I can say for sure is that simple seeing a probe temp over 500 is not a guarantee of activation. the real tell tale is the rapid temperate increase.

well what i said may not be true, Im at work and cant see but that is what i remembered but i think your correct as to what mine actually says?

 

[clemsonfor]

Joful, id say that recently you have either not had the cat engaged or not fully engaged.

Backpuffing i noticed is worse the warner it is, i never see it when it is cool outside. but when i try and throttle way back a warm stove cause its say 84F in the room is when i get backpuffs and this is when its warmer outside say 50F or warmer.

Also my stove probe i think reads 200F at the coolest then it just falls below that. to get to 200f i have to have a load from the previous night go out and then the next afternoon it just reads 200f. This may be a little exadurated but easily my night load say 9pm load would still read 200 on the probe at least through lunch to early afternoon the next day

 

[Ashful]

Yeah, I meant more from a cool stove. If I'm reloading a warm stove, my cat also stays warmer than 100F. When my stove is cool, I typically see 500F - 550F on the top load door and 100F on the cat, when it's time to engage. If I engage at 450F - 500F stove top, I will usually see the cat go up to 500'ish and stop. If I engage at 550F - 600F stovetop, the cat will shoot right to 1000F. I rarely want to run this big honkin stove as high as 600F, unless I'm trying to warm up a cold room.

 

[clemsonfor]

I think my rutland thermometer is brolken, I never see that stove therm warmer than 350 at that temp you cant hold your hand off the stove for more than a few seconds, if you touch it its an instant burn. The sides of the bay window are even cooler?

 

[Ashful]

So, how do you guys choose when to close the bypass damper? I've been going by stovetop temperature, but it sounds like one of you is going by cat probe temp (useless, in my case), and the other is going by the visual of seeing that all the wood is charred.

 

[jharkin]

You'll slap me if I say "I know it when I see it"

In reality it is somewhat. Its a feel thing. First off, I always wait for the griddle to hit ~ 500F. Then its a judgement call. If It took a good 20+ minutes to hit that temp then I know I'm usually good to go and just go on bypass. Sometimes however, especially on cold days when Im reloading more frequently and the stove was already pretty hot before reloading it might only takea couple minutes to hit that temp... so I might wait it out a bit. I also tend to aim for higher griddle temps on bigger loads (for 2-3 splits sometimes I can get away with a light off as low as 450 griddle, for full loads 550-600 is more common).

Once I do close the bypass I keep an eye on the cat thermometer for 5 minutes. Even if it was reading cold to begin with, on a good light off it will almost immediately read 500 and then quickly climb to 1000+. If I dont see 1000+ within 5 minutes I go back on bypass, wait 10 minutes and try again.

If you find it useful I can try to take a video of the probe readout next time to show you what I mean by quick rise to 1000....

 

[WoodpileOCD]

I go strictly by what the cat thermometer reads. There is a similar thread on this subject that is active right now as well. https://www.hearth.com/talk/threads...unning-advice-tricks-and-tips-welcome.100464/ and here are some comments I made there (rather than rethinking the whole thing)

"First off let me say that I don't wait for the cat probe to read 7-800 before I engage it. I engage at about 4-500 regularly and it takes off from there. If it is a cold start, it probably takes about 45 min to get the cat to 1000 but if I reload on a hot coal bed with the cat reading 4-500 still, I open the door, load it up, close it and immediately engage the cat again even if it's around 400. I open the air full blast (including the doghouse). I let er rip until the cat is at about 1000 (about 10-15 min) then shut it down 1/2 way or maybe a little more. Once the cat gets to 1500 I shut it down to just a crack past closed and then a few minutes later close it all the way down. It will then run at 1500 to 1700 for a couple hours, depending on the size of the load, and start down from there. If I load it up about 1/2 to 3/4 with good oak, I get about 8 hours of usable heat and if I load it to the gills I can get 12-14. When the cat is in the 1500 range my stove temp thermometer on the front just like yours is in the 600 range. I don't think we can compare stove top temps with what a lot of people talk about here because of the air sheathing around and above it which keeps the temp of the metal lower than one without a blower."

 

[jharkin]

Woodpile, If I used the procedures you quoted, my stove would smoke out the entire neighborhood and somebody would call the FD on me. I think something is definitely not right if it takes 45 minutes for the cat to go from 400 to 1000.

 

[clemsonfor]

I go strictly by what the cat thermometer reads. There is a similar thread on this subject that is active right now as well. https://www.hearth.com/talk/threads...unning-advice-tricks-and-tips-welcome.100464/ and here are some comments I made there (rather than rethinking the whole thing)

"First off let me say that I don't wait for the cat probe to read 7-800 before I engage it. I engage at about 4-500 regularly and it takes off from there. If it is a cold start, it probably takes about 45 min to get the cat to 1000 but if I reload on a hot coal bed with the cat reading 4-500 still, I open the door, load it up, close it and immediately engage the cat again even if it's around 400. I open the air full blast (including the doghouse). I let er rip until the cat is at about 1000 (about 10-15 min) then shut it down 1/2 way or maybe a little more. Once the cat gets to 1500 I shut it down to just a crack past closed and then a few minutes later close it all the way down. It will then run at 1500 to 1700 for a couple hours, depending on the size of the load, and start down from there. If I load it up about 1/2 to 3/4 with good oak, I get about 8 hours of usable heat and if I load it to the gills I can get 12-14. When the cat is in the 1500 range my stove temp thermometer on the front just like yours is in the 600 range. I don't think we can compare stove top temps with what a lot of people talk about here because of the air sheathing around and above it which keeps the temp of the metal lower than one without a blower."

Like Harkin if i did this it would not work to well. This just proves each stove has its own rituals.

 

[clemsonfor]

So, how do you guys choose when to close the bypass damper? I've been going by stovetop temperature, but it sounds like one of you is going by cat probe temp (useless, in my case), and the other is going by the visual of seeing that all the wood is charred.

I go by temp and looks.

From a COLD start i strickly go by the temp probe and anout of wood i have in the stove. IE, if i have a kindeling fire that is fully consumed and my probe say 600f i will not engage, i will put more wood in and wait for a bit of char. But if i have a kindling fire that i fed with more wood when the probe was say 300f and at 600f is full engulfed i will close it at the 600f.

A reload i will almost always be over 400f at least when i put more wood in, usually in the 600 to 700f range (all thats left is coals at this point and not a ton but enough to easily start splits back burning. THIS is the point where i kind of look at the probe to confirm its in the 800F range and that i have decent char on the ends of logs. Then i engage.

We cant really compare our stoves though, there different brands, designs, sizes etc. Now my stove and some of the appilachain and like a buck 91 are all similar enough that i could about compare procedure with those but still is gonna be different.

 

[jharkin]

I go by temp and looks.

We cant really compare our stoves though, there different brands, designs, sizes etc. Now my stove and some of the appilachain and like a buck 91 are all similar enough that i could about compare procedure with those but still is gonna be different.

Exactly. Just like what works for a fireview wont work for me.

There is probably more similarity between my stove and Joful than the bucks. Both my stove and Joful's Jotul (say that 5 times fast ) are downdraft designs.

 

[Ashful]

Yep... of all the methods listed, jharkin's seems most applicable to my downdraft stove.

Thanks, guys!

 

[jharkin]

Ok I timed a start up tonight. I shot a video but its too dark to see.

Starting from stone cold with a few splits and kindling

7:05pm - light stove
7:06 - close door
7:15 add a couple more splits
7:25 fire is raging and griddle temp reads 500F. Catalytic probe reads "cool"
cut air back to 75%
7:30 griddle at 550F
close bypass

30 seconds - catalytic changes from "cool" to 500​

45 seconds - 1000F​

50 seconds 1100F​

60 seconds 1250F​

​

I start cutting back the air and it settled in at 1400F in under 5 minutes.


That's what I mean when I say on a good light off the cat temp climbs fast... really seriously fast. So anytime it just lingers under 1000 I know I have trouble

 

[jharkin]

I should add, outdoor temp is 20, very strong draft. Right now at 30% air its sitting at 500 griddle 1400 cat.

 

[clemsonfor]

wow mine don't climb that fast!! But that sounds normal and like its working fine.

Also I don't cut air until I close the bypass.

 

[jharkin]

That's probably the best I've seen, but its about perfect conditions. I also adjusted the secondary air thermostat last week, opened it up ever so slightly.

Even so if I don't get a stall it rarely takes more than a couple minutes to 1000.

 

[Ashful]

Wow... thanks Jeremy! I can get near that climb rate on the new stove, with the 27 foot chimney, but on the old stove with only 15'ish feet of chimney, things are much slower. That one will usually hit 750 within the first minute, but then takes several more minutes to climb above 1000F. If I don't see above 750 within the first minute, I go back to bypass, 'cause I know it's going to stall there.

 

[Ashful]

So here's what just happened on the older F12 / short chimney...

Burned down my evening load until stovetop was at 350'ish. Larger bed of coals than I usually load on was left, but not so much that I couldn't rake them forward enough to get one log in behind. My firebox is not deep, really only room for two splits in the bottom, E/W. Loaded 7 medium splits, four high in the back, and three high in the front.

Stove went pretty quickly 300 to 500F, but most of the wood was not yet touched by flame, and there wasn't real strong flame activity (just the splits on the bottom were flaming). So, I turned air to 50%, and let it go another 5 - 10 minutes (while I read hearth.com). Went back and found stove top at 650F - 700F, and although load was not yet fully engulfed, I decided I better engage cat before it got any hotter on the stove top.

Cat temp shot up fast to low 600's, then slowly fell to 585F. Hung there, and I headed back to my home office to start typing this.

After a few minutes of typing, just went back out and checked again, stove top has come down from near 700F to a mere 600F, and cat has climbed close to 700F.

The new stove with the taller chimney was loaded with the same wood, in the same way, at the same time, on a slightly smaller coal bed. It climbed to 550F, the wood looked well-engulfed, so I threw the lever and the cat shot up to 915F. This new stove seems to cruise endlessly with the cat right around 1000F, and the stovetop whatever temp I want. Much less exciting... almost boring.

 

[clemsonfor]

wow I guess my cats are toast!! it talks me what seems to be 5 minuets to get to say 1200f. Im about to load it now so I will try and pay attention to the time and temps.

 

[jharkin]

That is interesting behavior. I tend to find that below 1/3 open or so the air control effects how hot the cat gets rather than stove top. I have to really crank to cruise over 600 stove top, and this place is small enough not to need that unless its a real cold day.

Interesting since I'm watching it closely. I put the second load in at 9. Stove still hot, packed it full of old dense oak, some of these splits are 7 or 8 in wedges 3 yr old wood. Packed to the top. In 10 min it was at 450. Cut the air back so the load would char good without overheating flue. At 15 min the griddle is 500 but the cat is at 900. I see this sometimes on big loads, I think a split leans against the cat hood forcing some flames in there even on bypass preheating it. Close the bypass and it rose to 1100. Slowly close down and in 15 min cruising at 450/1200. Shut the air completely and an hour later its settled down to 350/1250. This is where it will probably run most of the night.

 

[jharkin]

wow I guess my cats are toast!! it talks me what seems to be 5 minuets to get to say 1200f. Im about to load it now so I will try and pay attention to the time and temps.

I think that's fine. On big loads mine can take a while.. And mine is only 3 years old... Condar steel cat.


It was the 45 minutes to 1000 story that I thought sounded bad.