Stretching Burn times.

For the early stages of the burn that is too low for a secondary burn stove. Even "dry" wood still has 15 to 20% moisture that needs to be driven out. For less heat you better shoot for a small, hot fire and let it go out before reloading the stove. For a prolonged burn at low temps you need a cat stove where the cat will take care of the smoke particles.

I was wondering the same thing. I was running my stove the same as you and noticed a little white smoke coming out with secondaries. When it is approaching 40 I don't run my stove like I should. I wasn't sure if this was good practice so this week the stove has not been fed. I let Mr Slim do the job.

I run my Progress Hybrid at its lowest possible air setting all the time, and I see no smoke coming out of the chimney. My definition of burn time has less to do with stove top temp and more to do with room temp. I look at the time duration that my stove can keep my stove room (approx 825 sq ft) above 72* and still reload on a viable coal bed. And during shoulder season and warmer winter months that is often 14+ hours for my stove. At 250 to 300* my soapstone stove is still giving off tons of comfortable heat. During colder weather that run time will decrease, but where I live in Tenn, it has never been less then 9 hours. My home is newer construction with decent insulation and total sq ft of approx. 1500.

my sweep says it's better to have a med size stove burn hot than a large stove burn cool

johnpma said:

my sweep says it's better to have a med size stove burn hot than a large stove burn cool

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I think that is too general a statement. It all depends on the stove. I run my larger cat stove on low often, and my flu and stove interior including the glass remains fairly clean. I only get a small amount of black soot in the corners of my stove glass which quickly burns off when I reload the stove. And the only time I get a small amount of smoke out the chimney is when I start up a fire with the cat bypassed.

johnpma said:

my sweep says it's better to have a med size stove burn hot than a large stove burn cool

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He's right with regards to chimney accumulations and a regular stove. Makes sense since his job is to sweep a chimney.

I like to get mine up to 500 cause thats where the secondaries really kick in. I keep an eye on the stack temp more than anything though. If I can maintain a surface temp over 300 I will let the stove top be a little cooler. If anything go for a big spike in temp to drive out the moisture and then shut it up pretty tight to slow the burn.

It's tough when the lows stay in the 30's. I find myself in the unpopular position of wishing it would just get cold damn it.
I've posted something similar to this and someone suggested it was steam not smoke. I'm still not sure if that is possible. But I have noticed that when it is cold and rainy, sometimes I see what looks like smoke coming from the chimney. In a seemingly identical situation when it isn't raining and (I assume) the humidity is lower, I don't see it. I wonder if the hot air coming out of the chimney causes water in the air to condense and make visible steam?

What is coming out of the chimney even during a "clean" burn is steam, not just hot air. Wood burns into carbon dioxide and water; same as oil and gas. When it is cold and rainy outside it means the relative humidity is high. Hot water vapors will therefore quickly condense in the cold air which will make visible steam.

300 degrees is too low for start up and beginning burning temps. 300 at the end with coaling stage is far different than 300 degrees prior to the coaling stage.
Your burning too low.
Burn smaller loads, hotter and you'll be fine.

VC Encore 2n1: chimney smoke will be faint but visible at 700F cat temp. By 800F there's zero smoke coming out. I can cruise it right there if I want or increase to a hard run at almost 1500F. Stove top temps run approx 1/2 of the cat temp. My cat is staying clean so far. Crossed fingers burning black oak.

You would be better off loading the big stuff in the back and the kindling up towards the door. As Not sure about your stove but most stoves the primary air comes in as air wash for the window of the door. This way the start is getting more air rather being blocked by the bigger stuff up front.

Rake your hot coal forward towards the front and load the back bigger stuff on no coals. For a longer burn time.

DTrain said:

Holy fudge. I'd be a touch unsettled if I had 750 stove top! 600 feels well hot enough! Must be a special kinda smell at 750. I know I can detect that "hot smell" at 600.

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Yeah, my stove likes to cruise at 500F to 550F. At 750F I would be in full blown panic mode.

The BK will not be run at 750 stove top. It is controllable and doesn't need to run that hot to make major mojo. If you need to run your stove higher than 600 on a regular basis then you bought a stove too small for your needs.

Now the non-cat NC30 in my barn. It is too small but there was nothing bigger. I purposely run it past 700 and it seems to like it up there. Wood loads don't last long though.

Highest stove top temp I ever saw was 680F. I typically run CAT temps around 900 and stove top about 500-550.

I think DTrain was taking note of my comment that stove top temps run "approx" 1/2 of CAT temp. I did see 1500 cat a few times but it didn't give me 1500/2 stove top exactly. Yes that's too hot, but not out of limits. Nice thing about the Encore is that all the real hot running components are either ceramic refractory or the Cat element itself - not steel tubing. So it can really soar if you want it to.

I've since reduced the (unregulated) secondary air that feeds directly into the primary combustion. Now the stove regulates down as far as I want - any time I want.

To the OP's point:

Now that I have the Encore slowed down, I also am beginning to think about running too cool. I'm concerned about creosote buildup on the cat and chimney, on the cool-down side of the burn cycle.

What I'm doing is to get the wood all burning well, like 350 stove top (damper open after reload) and waiting 15 min or so before closing the damper and running combustion thru the CAT. The CAT will run right up to 800 easily then I begin to close primary air down in 2 stages. Target CAT temp of about 900-1000. Good clean burn.

But after maybe 3 hours the stove begins to cool down and that's where I have concern. On an overnight burn after about 7 hours the stove top will be about 300 and CAT 500-600. Will this crap things up, or is burning in the coaling stage not likely to build creosote?

Edit: the computer controls aren't on the stove -yet. But soon.

With the tube stove I would focus on shorter burn times in mild weather. I would use half loads, burn hot enough to light off the secondaries, then reload just before all my coals were gone.

Not going to hurt the Cat at anywhere near 1500F, Ceramic subs anyway. I'm trying to degrade a set of 4 @ 2100F at work as i type. 200 hours and counting
Catalyst have come a long way, just the last two years have been game changing in the Automotive industry. Would like to see some of the newer fast/long light off tech make it to stoves someday.

turbojoe said:

Not going to hurt the Cat at anywhere near 1500F, Ceramic subs anyway. I'm trying to degrade a set of 4 @ 2100F at work as i type. 200 hours and counting
Catalyst have come a long way, just the last two years have been game changing in the Automotive industry. Would like to see some of the newer fast/long light off tech make it to stoves someday.

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Yup. Cat's run freaking HOT by design but 2100?! That's higher than I thought they could sustain w/o breakdown.
Thx - interesting indeed!