Coaling or dancing flames, which should I shoot for?

[czach]

So I've been running this CEMI Concept II insert for about 10 years now and finally found the manual. Oddly enough I've been running it with the top baffle upside down. Go figure. Well, it's in the right way and according to the manual the purpose is to make some of the exhaust circle back around to the front where it's mixed with the incoming air and ignited.

Seems to work; with a nice fire going and the doors closed I can see that hypnotic slow flame clouds in there. Neat. However the question is this:

The insert will spend a lot of time with 50% load (because it has burned the rest) and that will be a super-hot glowing coal pile+black log with coals on it. Is this good? Should I be aiming for clouds of flames all the time, or is this still ok?

Second question is temps. Currently I have my temp sensor mounted above the air baffles, so it can measure the temps above the insert burn box. I try to keep it between 300-450 degrees. Too hot? Too cold? The manual says something about exhaust air temps being 900 degrees. Um, that's a bit hotter. Should I measure temperature at the doors and if so what's a good temp to run at for best combustion?

Keeping nice and warm, just want to be efficient as possible.

Chris

 

[shawneyboy]

So I've been running this CEMI Concept II insert for about 10 years now and finally found the manual. Oddly enough I've been running it with the top baffle upside down. Go figure. Well, it's in the right way and according to the manual the purpose is to make some of the exhaust circle back around to the front where it's mixed with the incoming air and ignited.

Seems to work; with a nice fire going and the doors closed I can see that hypnotic slow flame clouds in there. Neat. However the question is this:

The insert will spend a lot of time with 50% load (because it has burned the rest) and that will be a super-hot glowing coal pile+black log with coals on it. Is this good? Should I be aiming for clouds of flames all the time, or is this still ok?

The secondaries only flame up when the wood is outgassing. When the gas is gone so are the secondaries.

Second question is temps. Currently I have my temp sensor mounted above the air baffles, so it can measure the temps above the insert burn box. I try to keep it between 300-450 degrees. Too hot? Too cold? The manual says something about exhaust air temps being 900 degrees. Um, that's a bit hotter. Should I measure temperature at the doors and if so what's a good temp to run at for best combustion?

I am not familiar with your insert but.... Usually, to my understanding, the insert top and exhaust air temps are not the same. If you wanted to know the exhaust temps you would need a probe thermo. They do make them with a wire that you can run to monitor your flue temps. That being said, most people with inserts, it seems to me, only monitor the insert firebox temps, and not the exhaust gas temps.
Keeping nice and warm, just want to be efficient as possible.

Chris

I am sure others will chime in here.

 

[firefighterjake]

I'm not familiar with your insert . . . heck, not really all that familiar with inserts in general . . . so I can't answer your question all that well about the temps.

About the goal . . . as Shawneyboy mentioned the secondaries occur in the first few stages of burning . . . when the wood is outgassing . . . when you reach the coaling stage there are no more secondaries . . . but it's OK. The goal is to burn cleanly and efficiently . . . and it sounds as though you are . . . seeing the Northern Lights or Bowels of Hell in your stove is typically a good sign as it means the stove is collecting the unburned combustibles in the smoke and having a secondary burn which equals a cleaner and more efficient burn . . . and more heat.

 

[Jags]

What you are witnessing are the stages of the fire. It is completely normal. Trying to maintain the rolling secondaries through the entire cycle is going to be maddening unless you are willing to feed the beast often.

A typical burn should be pretty simple. Load 'er up - get a good char and flame show (bring the stove close to the desired run temp). Tune it down to cruise speed. First you will get the rolling secondaries, then just flame, then the coaling stage. Then reload when heat output drops below the required btu to keep your desired temp. Lather, rinse, repeat.

 

[czach]

Ok, that sounds good. I wanted to make sure that the pollution controls on this thing (such as they are) were working, and it sounds like it's running as expected.

I'll focus on keeping the top temps (above the firebox there is a plate facing the smokebox of the chimney, that's where I measure "above the box) around 300-400 degrees, which equates to a temp of about 600-700 peak on the box right above the doors.

900 seems a bit excessive so I'll stay away from that. It's so nice, and really cuts down the gas therm usage on the house overall.

Chris

 

[velvetfoot]

Does opening the air prolong the flame somewhat?

 

[czach]

Somewhat. Running it with the side vents open will make for a hotter exhaust temp reading and more flames/brighter red coals. I will usually run full open on both sides to start then 50% once the logs catch.

At night I will load, get it burning, then close 80% both sides to let it run cooler and longer. I just don't want to coke to the chimney or pollute if possible.

C

 

[czach]

Well, I will say that I am getting the reburning a lot more now with the top baffle installed in the right direction. It's doing it now, sheets of slow flame hanging in the air. And I can run it with the side vents closed down 50-80% and still get this effect.

Now, should this happen on all wood stoves? I'm curious because my friend's Squire wood stove/insert has a *lot* more capacity than my CEMI but it doesn't have anything like the top baffle. Instead it has two big vents on the bottom that you open and two little ones near the top of the doors.

I wonder if there is a technique to make that sort of stove recombine, maybe by closing down the bottom vents (which make the coals glow white-hot when running) and open the top vents? I wonder what the damper settings should be (it looks to have full open, 60%, 30%, and closed hard).

Chris