Ok, aside from putting in less wood, how do I control temp with secondary burn (Hit 800 last night)

[ecfinn]

Hi everyone,

Had a bit of a scare last night and I'm hoping someone has some tips, suggestions, ideas. I loaded up the stove for the night about 9:45 (7 total splits, 4 smaller, 3 larger). Stove temp was hovering around 300 at the time as it was mostly coals when I loaded it. Let this catch for about 15 minutes with air full open, got stove top temp to around 400, and closed the air to about 1/3. Left it that way for another 10 minutes and temp went to 500. Fully closed primary air control. Within the next 30 minutes the secondary kicked in and my stove temp went to roughly 800ish. Maybe 810. I've got a video posted here to see the secondary burn when it was running about 700. Shortly after the video was made it climbed to 800. I put the blower on high and opened a window. That brought the temp back down to 700 in about 20 minutes. I didn't really want to run the blower last night as it wasn't that cold out.

http://video.yahoo.com/video/play?vid=48f5b4213f11c1908b61215d4e2540db.1521614

So my question is what could I have done differently? I'd prefer to keep my overnight burns around 500 and not flirt with the 800 range on a regular basis. Stove manual states over 800 is over-firing. I know I could put in less wood, but then I wouldn't get the overnight burn either. I literally felt like there was nothing I could do to control the temp. The stove took it from 500 to 800 without me touching it. Should I close the air off sooner?

My middle secondary burn tube was literally glowing bright red. The stove top never really started to glow red so I know I wasn't heating the steel quite to that point, but I felt it was close. I guess I thought I'd have a little more control over the temp of the stove by using the primary air control...

Thoughts, ideas, suggestions?

Eric

 

[elkimmeg]

I would have closed the Bi pass damper all the way down and primary air all the way closed
you did not mention you closed the damper all the way down

 

[ecfinn]

The bypass damper is closed all the time, except when loading. The primary was also closed down fully at 500. Secondary air alone took it to 800 all on its own. That's the concern.

 

[mikenr1c]

I have experienced the same thing with my Jotul 602. If I fill it with dry wood I have to accept the fact it is going to take off for a while. It does not get to 800, if I cut back the air. But it will easily go to 750. I think that it is in the design of the stove. And I have to believe that the Jotul engineers have designed the stove so it can take it.

But I am also a little disappointed that you cannot fill the stove and cut the air so far back that it does not go to these high temperatures.

 

[DiscoInferno]

Isn't it the case, though, that a large fresh load of wood brought up to stove temperatures is going to gassify regardless of air setting, and either the stove burns these gasses and heats up or lets them pass up the chimney (which EPA stoves aren't supposed to do)? That always seemed to me to be the issue with secondary burn, that controlling the burn rate through secondary air control meant increasing pollution and decreasing efficiency (thus why modern stoves don't let you turn down secondary air). So then you are left with trying to control secondary burn through wood packing (tighter burns slower) and wood selection (very dry wood burns faster). I imagine it's also related to firebox size and stove design.

I've crossed 800 on mine, but only when I left the primary open; secondary alone won't keep it up that high, but my firebox isn't that large. My burn tubes are frequently glowing, I think that's got to be expected.

 

[Todd]

In that case you probably should of shut down the air sooner. I've done the same thing with my other stoves I've owned. It takes some trial and error to figure the best way to burn those non cats that have no secondary air control.

 

[Corey]

In my stove, the size of the wood matters alot. Don't know about your situation, but if i threw in 7 splits, I would have a raging fire that would be super hot for a couple of hours, then die. If I put in the same weight of wood, but in 2-3 large logs, I would have a medium fire that would make it through the night easily.

This also goes hand-in-hand with the splitting. If I have a log that is splitting like butter, I bust it up into small splits for those short, hot fires. If I come across a log that won't split worth a cent, I do the minimum work to get it to a size that will fit in the stove and throw it in on some long, cold night when I need heat for a long time.

Corey

 

[precaud]

No offense, but I don't think you have anything to be worried about. It shows you're getting good heat transfer effiency. If I'm not mistaken, the top plate of the Lopi is completely exposed to the flame. So if flames are curling out of the firebox into the secondary chamber above (a condition which is making optimum use of secondary air), the top plate temps SHOULD be in the 700-900 degree range. If they weren't, I'd be concerned.

Corey's suggestion is good. Using larger pieces will help slow the whole thing down. If you have to use smaller pieces, pack them in tightly (less air space).

A couple other thoughts: Does your stove have a small air outlet at the front and center of the firebox?
Does the primary air control actually shut off the air supply completely? You'll have to physically inspect the control to see if it does or not.

 

[BrotherBart]

Yep. It gets scary because you don't know if it is going level out at those temps, or keep climbing. One method I have used to take the edge off a little is loading a half load at a time. Put the first half on the coals and let it get a good bit of the gassification stage out of the way and then load the top layer. Takes a little longer and may not be scientifically the most efficient but it keeps you from getting the crap scared out of you.

One thing you now know from this experience is that your stove probably isn't going feed the fire enough air to climb over eight hundred when it takes off and that should give a little piece of mind. The guy that designed my stove told me that it burns really nice between eight and nine hundred. I will take his word for it. I am kinda fond of 550-650 myself.

 

[JMF1]

I have run into the same situation with my Avalon. If I let the load get going too much I get secondary burn that's a bit out of control when I shut down the air. I've found through suggestions from here that there are a few factors that contribute to this. Shutting it down a little sooner is one, bigger splits and use of the blower to pull heat from the stove all keep things under control for me. I've had no problems since, in fact I can pretty much "dial in" the stove to whatever surface temp I want by making adjustments to any or all of these variables. Since we both have stoves of the same manufacturer (Travis Industries) I thought this may help. Feel free to PM me if you have any questions, I'm by no means an expert, but I will help if I can.

 

[precaud]

The guy that designed my stove told me that it burns really nice between eight and nine hundred. I will take his word for it. I am kinda fond of 550-650 myself.

BB, I'm very glad to hear that a stove designer is actually saying that. I've long been an advocate of the 'hot burn' because that's where the top plate of efficient stoves seem to settle in to, unless there's an air baffle covering it, as on my Morso, in which case I'd join you in the 550-650 camp. But let flames lick against an exposed steel surface and you're gonna get 800 or so. And that's a good thing!

 

[adrpga498]

In my stove, the size of the wood matters alot. Don't know about your situation, but if i threw in 7 splits, I would have a raging fire that would be super hot for a couple of hours, then die. If I put in the same weight of wood, but in 2-3 large logs, I would have a medium fire that would make it through the night easily.

This also goes hand-in-hand with the splitting. If I have a log that is splitting like butter, I bust it up into small splits for those short, hot fires. If I come across a log that won't split worth a cent, I do the minimum work to get it to a size that will fit in the stove and throw it in on some long, cold night when I need heat for a long time.

Corey

Bingo!
Couldn't have said it bettter myself. You nailed it.

 

[heydan]

Are you sure you had the door closed nice and tight? Sometimes a stove door can appear to be closed but if you haven't pushed hard enough on the handle to get some pressure on the gasket then excess air will be sucked in around the edges and can cause the wood to burn faster and hotter than you want.

 

[Roospike]

Lots of good advise about controlling the burn. Something i would like to add is the control of logs and coal.
Logs turned front to back vs east to west will change the way your load will burn. If i load the firebox up with wood and what to keep control of the fire i will rake the coals to the front and when charring wood i will only char the ends of all the logs and then turn it down a "cigar burn" the wood , when charring the whole load and turning it down you can get an out of control stove for a wile before if settles down latter.

On a stove that is normally designed to be loaded front to back you can load east to west and char the front wood/logs and burn your load front to back as well.

With the right mix of wood ( BTU value and split and round sizes ) and how you load the stove and how the load is charred and how log the air damper is left open to char the wood one should have full control of your wood burning needs.

 

[clambdin]

Hey roospike, Do you moniter the griddle temp on your summit ? I run 800+ on mine alot and it seems to be fine !

 

[begreen]

When this topic came up in another thread about a month ago, I decided to figure out how to snuff the Castine in case of a runaway fire. It took some looking, but in the bottom back there is an opening where the OAK connects. I made a mental note and it came in handy during the power outage.

One cold night I was pretty tired and decided to try 4 of the Home Prest-Logs on a dwindling bed of coals. I knew three were dramatic, but controllable and the coal bed seemed pretty low. I've used 4 of these logs in a totally cold stove with good control. But in this case, the stove was still at about 300 degrees. In about an hour I had a conflaguration that was looking mean. With all air shut off, the secondaries were still fiercely burning against the upper front baffle which sits directly in front of the secondary tubes. The baffle was starting to glow and the thermometer was getting ready to peg at 750. Rather than waiting it out and possibly hurting the new stove, I wedged a thin piece of plywood over the bottom heatshield so that it mostly covered the OAK hole. Within a couple minutes the temps began to decend. And fifteen minutes later I could remove the block and resume normal burning. While I fully appreciate the logic behind modern stove design, it seems like adding an emegency cutoff would not be a bad idea. After this experience, I'm considering adding the OAK kit and putting a damper in the pipe so that I can close it off if necessary.

 

[BrotherBart]

The Englander has the three inch OAK intake also. It is in the rear bottom of the stove aimed to the back. I put two 90 elbows on it and a piece of solid three inch pipe so that is comes out right under the front of the stove. Sitting over by the wood rack is a solid plug of rockwool just hanging around in case I need to stuff it in that pipe.

It also keeps the intake from competing with the blower which is mounted in the rear heat shield and draws its air from right behind the stove intake.

 

[heydan]

Yes, I agree an emergency cutoff would be nice to have. I wonder if they're worried that people would use it to burn dirty and/or would risk pushing poisonous gases back into the house?

 

[BrotherBart]

Yes, I agree an emergency cutoff would be nice to have. I wonder if they're worried that people would use it to burn dirty and/or would risk pushing poisonous gases back into the house?

My stove's manufacturer tells me that it is the constraint on them for EPA certification. One of the test points in the certification burn is with the primary air control closed all the way.

 

[Roospike]

Hey roospike, Do you moniter the griddle temp on your summit ? I run 800+ on mine alot and it seems to be fine !

Wow , 800+ on a Summit is one HOT stove putting out a lot of heat. ( u have a summit correct ? ) I have no doubt that the Summit can handle 800° ++ , if anything the inner parts of the stove would warp long before the main steel box would fail.

Here is a thread i posted in with pictures of my stove top temps .

https://www.hearth.com/talk/threads/4854/

 

[clambdin]

Yeah I have a summit classic, I asked PE about this and they said it wont hurt it ..

 

[Gunner]

Are you talking 800 on the steel plate under the trivet or 800 on the outer enameled part of the stove.

Essentially being of double walled construction the "Classic" model PE stoves are a totally different animal than just a straight plate steel stove, IMO they are a true convection heater, with that air space and outer enameled layer. I dare say it they are a steel stove that acts like soapstone. The enameled surface of mine is less than half that with probe stack temps over 1000.