Questions about secondary combustion and overnight burns

[abd1]

We just installed our first wood stove 5 days ago, a PE Super Insert, to heat our 2000 sq ft ranch house in Portland, OR. Thanks to a lot of great info from the members on this forum I think we chose a very good stove and have been really happy with it so far. Not having used a wood stove before I am blown away by how much heat it generates. We've run it the last 2 nights and our furnace hasn't turned on once. Granted, its much warmer here than where a lot of you all live. Overnight temps have been in the low 40's all week, but it still is having no problem heating our house.

My questions today are about secondary combustion and overnight burns. I can acheive secondary combustion once I have a good bed of coals and have the air flow control open 1/2 way or more. However, once I turn down the airflow to get a long slow burn for overnight I lose the secondary combustion. One thing that attracted me to a woodstove was the secondary combustion and how clean they can burn when achieving the secondary burn. Should I control the airflow so that I'm always achieving secondary combustion, even in an overnight burn? If I'm not running it hot enough for the secondary combustion should I be concerned about creosete formation? For those of you who use your stove as your primary heat source what % of the time are you achieving secondary combustion? And, can the secondary combustion still be occurring even if I'm not seeing the fire burning on the top of the stove?

Thanks for all the great info.

 

[Pagey]

I can maintain secondary combustion with my primary air closed about 90-95%. If I close it all the way, I lose secondaries after about 2 minutes. Others can shut theirs all the way down and maintain it, but for whatever reason my setup just won't do so.

If you have to leave the control open 50%, I would have to wonder one of two things: is your wood not dry enough or are you not letting the fire box get hot enough before you begin closing the air down? Another thing to keep in mind is that I get much better performance if I close mine down in stages, not all at once in a single adjustment.

My stove will cruise at about 650F on the stove top during the most active part of secondary combustion when the wood is really outgassing strongly. Keep in mind that once you enter the charcoaling stage, all of that light show is done. However, the charcoaling stage is naturally clean burning, so don't worry about creosote during this final stage of the burn cycle.

I find that the charcoaling stage is technically the longest of the burn cycle for me. So, I would have to say that I get strong secondaries for a shorter portion of a burn cycle than the portion without them.

 

[abd1]

I have wondered if my wood is dry enough too. It's only been seasoned about 1 year but got wet in the rain. Its been covered for a few weeks now, but still might be damp. I did buy some seasoned wood at home depot, not sure what species, but its dry as a bone. I mix it with my cord wood to make sure I'm getting a good burn. I think tonight I'll try lowering the airflow in stages like you suggested and just leaving the air flow 1/2 way open. The stove heats our house so much that even if the fire burns out after 3-4 hours it might be ok, plus its not as cold here in Portland as it is in a lot of places.

 

[Pagey]

My burn routine goes something like this (keeping in mind that my stove, though a non-cat, features a bypass damper that when open allows the flue gases to bypass the baffle and go straight up the flue): when the stove top reaches around 275-300F, I open the bypass and the primary air, and then I rake out my coal bed into an even 2" base. Then I load the desired number of splits running N/S, and push to door to but do not latch it. Once the wood has caught up good from the primary air/air wash air, I latch the door (could be 5 minutes, could be 10 minutes, depending on the load size and air spacing, etc.). Once the stove top hits about 400F-500F and I have signs of secondary combustion, I push the bypass damper closed. This will immediately result in what I call "bowels of hell" type secondaries. Looks like you're going to melt the stove and send the house into orbit. I then close my primary air down about 1/3 or 1/2 of the way. I then, over the next 10-20 minutes, make smaller adjustments to the primary air until I have the stove cruising around 600-650F with visible secondaries. On my stove, my sweet spot seems to be this: when I stand over the stove and look down at the ash lip, I can see the last 4 or 5 spaced "springs" on the "spring handle" portion of the primary air control rod. Sounds like a crazy way to measure it, but I've found that to reliably be the sweet spot on my Endeavor. Depending on the load size, I get about 1.5-2 hours of 600+ stove top temps, followed by an hour or so of 500F. Then it will hit the early charcoaling stage and hold 400F for several hours. After 8 hours, I wake up to a stove top of around 250-300F and a pile of coals in the back that will rake into about a 2-3" bed depending on the species, etc.

 

[logger]

Not sure how different your stove is, but mine will hit the secondaries for 30-40 minutes tops, and thats on a good day. Once the gases burn the secondaries stop. Im not sure how a cat stove would burn the secondaries much longer than that, but I never owned a cat so I dont really know. Also, you cant maintain high enough temps all night for secondaries to last unless you're getting up and adding wood.

 

[k3c4forlife]

abd1, I am in the same situation. I just installed my Regency I2100M last weekend. Its Regency's medium sized insert and heats around 1,500 sq.ft. if you burn it right. When I start to drop the air down I lose all secondary burn. It is interesting though. I have found that if I lose secondaries but leave the air down low, they will begin to come back later in the burn cycle as the wood dries out. It is definitely the wood.

Buy a pack of seasoned home depot or gas station wood. Split one piece up into kindling and use the rest to make a fire. See how that burns for an 8 hour burn time with the air dropped down at the staging above. My staging is very similar.

As you continue through the season with the wood you are currently using, remember to burn full open quite a bit in an effort to keep the chimney cleaner. Let us know how tonight goes.

 

[grommal]

Moisture is definitely a big factor. I have remnants of three loads of wood on hand. All of it is reasonably seasoned, but one batch is super-dry and one batch is just seasoned enough. The third load is in between. All of it is mixed hardwoods of the same species, mostly oaks. With the driest stuff, I can keep secondaries for a long time with the air closed as far as it goes. With the in-between wood, it needs to be about 5-10% open. With the just barely seasoned enough batch, it needs to be about 25% open.

 

[prajna101]

What part of Portland are you in? I could drop off some REALLY dry wood if you would like to try that. Anything to keep you from burning home depot bundles. Those things are really expensive. I dont have a ton of wood to share but if you just wanted to try some really dry ceder you are welcome to a few armloads. That cedar give amazing secondaries but doesnt last very long. Its at least fun to watch.

Todd

 

[Bootlegger]

Not sure how different your stove is, but mine will hit the secondaries for 30-40 minutes tops, and thats on a good day. Once the gases burn the secondaries stop. Im not sure how a cat stove would burn the secondaries much longer than that, but I never owned a cat so I dont really know. Also, you cant maintain high enough temps all night for secondaries to last unless you're getting up and adding wood.

+1, the secondary only burns until the main gas/smoke is burned off, then its clean burning coals.

 

[BrotherBart]

Secondary combustion happens throughout the burn cycle with good dry wood. As long as there are some flames coming off the wood and the secondary air is picking off the stray gases up at the top of the firebox you have secondary combustion. I haven't burned a load of wood with the air shut all the way down in three years. Just a nice burn with flame coming up from the wood and little wisps of flame from the tubes and the sucker burns at 550 forever with the primary air open 25%. I kinda don't understand the burning, pun intended, need for incinerating the top of a load of wood from the top down. Leave some combustion space above the load and let that sucker just sit there and roll and keep ya warm.

 

[madrone]

I find that it's harder to get the stove going in warmer temps. Less draft. I have to run wide open for longer before I can shut down to 1/4 open or less. It's pretty warm here for January.

 

[Cire3]

I was having the same issue with my Regency. Had 2 problems.

First off was the wood... These guys shoot for that because just like me, I thought I had dry wood. Dry is dry, not anywhere near rain or moisture. The water will take days to dry off, and if you use it the stove will use all the heat to dry the wood never giving you flame unless you keep the air open. You won't get any heat either.

Second was my pipe. Got the right pipe and extended it for a good draft. I'm not kidding when I say I picked up 100 degrees easy with the right wood and draft.

By the way, with good dry wood I can burn "after 10-15 minutes of a good fire up" with the air closed. Keeps secondary running until coals.

Hope it helps !

 

[Seasoned Oak]

I find that it's harder to get the stove going in warmer temps. Less draft. I have to run wide open for longer before I can shut down to 1/4 open or less. It's pretty warm here for January.

The cold weather increases the draft ,so the colder outside the faster the wood burns,i recently closed up some leaks in around my cleanout and it was amazing how much different my fire burns now,more draft is better with my Tl-300. My secondary burn will go for hours on end with very little activity in the main firebox,almost looks like the fire is out however if you can manage to see between the coals into the Afterburn chamber its lit up like the4th of july ,white hot burning smoke and making heat.