How to burn slow without melting my stove?

How do I get these fabled 12 hour burns on the Ideal Steel without melting down my cat?

Background: I installed a new Woodstock IS this winter, started burning sometime in February. I installed an Auber flue probe right away, probe is at 18" above the stove top. During the colder weeks I was trying to run hot and do 8 hour reloads. I could get that with air settings 1-2 notches above the first big notch. That would give me flue temps 450-600, STT 350-500.
But if it was a little warmer out and I wanted to do 12 hour reloads that didn't leave me much coals for the restart. Mid-March I bought and installed a condar cat probe thermometer. I've only had a few days of burning now with the cat probe installed.

It's shoulder season now, lows/highs 30's/40's. I want 12 hour burns. So I tried turning the air down after getting the wood charred. The problem is that the cat probe is getting pretty hot.

For example. This morning I loaded 3 splits of ash, a split of mulberry, and a small round (3") of mulberry onto a nice bed of coals. The stove wasn't jam-packed, but I couldn't get another full length piece in it.
I let it set for a while (15-20 minutes) with the air open full and the door open in the notch. Came back, just burning on the bottom, no flames up top, temps all low. Closed the door, that lets the flames up among the wood. Came back later, nice flame box, cat probe showing 650 or so, flue showing 400 something. Turned down the air a bit, engaged cat. Spent maybe 10 minutes turning down the air until I had just a few secondary jets going, a nice black box of wood, and the air set two notches below the first big notch (almost closed).
Watched it a couple more minutes, it seemed stable with the cat at 1200 and the flue about 450.

Went down to check it a couple hours later. Black box, flue 650, STT 500, cat probe wrapped at the top of the scale (1700+)

Opened the air to a couple notches above the first big notch. box bursts into flame, massive secondaries, etc. Flue climbs to 675, stt toward 550, cat slowly falls.

Currently Flue is at 550, STT at 450, and the cat around 1300. But my nice big load of wood will be coals in a couple hours and there won't be a lot left by 8 pm tonight.

The wood was CSS outside uncovered at least a couple years (may have been as long as four years), then moved into a shed in February. There's decent airflow through the shed.

How do I get longer burns without melting the cat? Mix in wood from outside that's been on the uncovered stack?

 

I don't have a cat probe.. I am using STT and flue thermometers, so when you went and opened it up... flue 650 and STT of 500 I would have left it gone to bed or work..
trying to think of who has your setup on IS to give you an answer ... BDF Unhdsm Hollywood should be able to help.. I plan on adding the thermocouples this summer..

 

Without the cat probe I would have left it too. Figured I had it dialed in just right. My flue temp alarm is set at 780 as I had been under the impression nothing too bad happens below that temp.

Maybe it's not a problem. Woodstock doesn't seem to recommend the cat probe after all. But it seems really hot. I can understand how those radiators end up warped out of shape if they spend much time like that.

 

I went to the factory when I bought mine.. I of course had read the above guys posts about cat probes.. I asked if I needed one.. Lauren, said I did not Need it as long as STT was below 700 it was fine... thinking of getting one just to know when to engage cat, and alarms..

 

I'd try playing some Tetris. More wood doesn't have to create hotter stove temps. If you minimize airspace it will burn slower, (more) consistent, and longer. The difference in burn times between 85% full and 95% full is far more than you would think. Look at BrianK's first 24 hour burn and how full that was with square blocks. You may have to use some smaller splits to fill in the gaps.

 

I can try that. I had thought that bigger splits with less surface area would burn slower, but I can try to fit some smaller ones inbetween. It was a lot of wood, but probably not over 85% full. No room for anything over 2" cross section though.

 

This was a 13-14 hour burn for me. On a 0 degree night IIRC. How does it compare to yours?

 

Leave out that E/W piece on top and that should be pretty close to mine. Mine were all E/W, and large so it's hard to compare exact. Maybe tonight I can take some pictures when loading it. I could have fit several 2" pieces in between and on top yet. Just not any room for bigger stuff.

 

I do think that the burn time would have been long enough if I had left the air turned down. It was the high cat temp that bothered me. So I'm not looking for more heat out of the stove, but rather low heat for longer.

 

I'd give it a shot. That e/w split is worth a couple hours.
Also if you have enough draft lose your aversion to closing it down completely.
Make sure you really clean out as much ash as you can. It builds up in back and blocks a lot of space.
I bet you get close to 12 hours. There is no reason to put up with 8 hour burns on the IS.

 

Are you saying to close it down completely? That wouldn't bother me if the cat stays out of the overfire zone. I have a twisting flue with two 45's and two 90's, but then 29.5' of insulated armorflex after that so I've normally got plenty of draft.

I had cleaned out the ash this morning before loading, that wasn't the problem.

 

I got 2 feet coming off top to 90 .. 3 feet to outside tee so another 90 about 21 up.. had draft measured at 60 pascal.. Tom (Woodstock owner) said put in key damper. haven't done it yet this summer..

 

Well your 30ft stack is certainly pulling a lot air through the firebox . That's a catch 22. I'm sure you have a small window where you don't have hyperactive cat or hyperactive secondaries. Play around with the amount of wood and see how that works. If you don't get where you should you may need a stovepipe damper.
I'm not WS or you, but I'm less concerned if the cat temp spikes high then creeps back down.

 

If you left it in that black box state you probably would have hit that 12 hour mark no problem. Once you opened up the air and got secondaries the wood burns up quicker and your total burn time falls.

 

We have very similer setups. Did I know that already?

 

I think we discussed it at WS open house last year.. if you or hollywood ever go north of Burlington PM me ill have a beer and a steak ready for you. Just so I can figure out how to heat the house on 3 cord

 

Oh heck yeah.

We compared notes every day during beta testing
The key is really just two things:

1) dry enough wood
2) maximize the burn cycle

I'm a believer in 12 hour cycles. Once you move away from that things get all screwy. Hollywood uses 24 HR cycles with an even more full firebox and a half cord less than I do. If you have the right sun exposure this also seems to work.

I still want that beer though!

 

tell me the brand! I'll have it. sun exposure is no problem! house faces southwest every room in 5 stories has south facing window!

the front half is good the back half .. well real cold furnace back up..

 

I agree completely. That 1700F cat just freaked me out. Do you think closing the air down completely would have avoided that issue?

 

That is all part of the hybrid; slow the stove down enough so there is little or no flame in the firebox and the cat. runs really hot because the wood is generating a lot of smoke. No way around it that I know of. My own experience is that if I try to turn the stove down even more, eventually the firebox temps. drop so low that the cat. stalls, very little heat is produced and the fuel makes a wet, creosote mess from the firebox to the top of the chimney.

It also makes a huge difference how large the coals bed is when I reload the stove; a thick load of engaged, hot coals and it is almost impossible to stall the stove and yet it can be throttled way down. A small amount of coals and a firebox full of fresh splits takes a while to get everything up to temp. and burning reliably and unfortunately, this is how I tend to run the stove for overnight; burn the coals down and load as much wood in it as possible. But loaded that way, the draft has to be open further than I would like or I run the risk of a stalled cat. and stalled fire.... a bit more draft and the stove really takes off at 3:00 AM and burns far too quickly for a couple of hours (not dangerous, just putting out way more heat than needed at that time).

I think what you mentioned in your first post is the best idea; mix in a little 'less dry' wood in each load to slow things down. I know the mantra is DRY wood and generally that is a good thing but a little moisture that has to be driven out of the splits really does slow the process down and as long as it is not too much, will allow the stove to burn very cleanly and efficiently. Now I am not suggesting splits that are dripping sap but one- year old oak burns pretty well I find and it is great mixed in with 3 year old wood.

Another thing that helps is bigger splits, again mixed in with smaller splits to make an overnight fuel load. A couple of really healthy splits will slow down the entire burn process and even out the burn.

Brian