Creosote - Does temp trump all?

[rudysmallfry]

Hi all. I was in Miami all last week sweating my butt off. I really don't get the snowbird thing. I'm so happy to be back sitting in front of my woodstove again. I see I missed some good stuff while I was away, particularly the run away stove thread. Had what I thought was a chimney fire once. I shut to air off, and then discharged a fire extinguisher into the firebox. It was out in 3 seconds.

Anyway, as I sit here burning my very quick burning but also very hot burning Poplar, I'm wondering about creosote. Poplar takes a long time to dry. I'm almost out of splits, so I've started burning the small rounds. They're definitely seasoned to the point where they don't hiss and ignite almost immediately. At the same time, it's a new wood to me and it makes me wonder if it's building up creosote at a faster rate than Maple would.

I guess the basic question, type of wood and degree of seasoning aside, does temperature beat all? As long as I'm burning above 270 degrees, am I producing no creosote?

This Poplar burns wicked hot, so keeping it in the safe range is easy. It also seems to actually benefit my particular stove and style of burning. I can get the stove nice and hot, leave for work knowing the fire's down to safe glowing embers and the soapstone will be holding the heat for another 4 hours or so. I'm actually starting to like this stuff.

 

[Highbeam]

My mom loved the cottonwood I cut for her. She siad it was easy to carry, easy to light, burned hot, and didn't pop sparks onto her rug. Perfect for her lifestyle and she took as much as I could get her.

From what I've read creosote condenses out of wood smoke at 250 degrees. If the stove itself is 270 but the gas leaving the top of the chimney is 200 then it would be safe to say that somewhere in that chimney the temps are low enough to allow the creosote to form on the walls.

Even seasoned wood has 20% or less moisture which makes a lot of steam and such for creosote.

I would say that a stove burnt so as to never exceed 270 will have a chimney of creososte. At the very least I would check for it more frequently than I would if you kept the stove at 500 degrees 24/7.

 

[rudysmallfry]

I never get near 500. I'm more in the 350 to 400 range. My wood burns to ashes far too quickly to keep the stack up to 500. Maybe next year when I have some real hardwoods in there. I try to hang well above the 300 mark. I've just read in the past that 270 is the minimum temp to prevent creosote buildup.

 

[rdrcr56]

Is your 350-400 degree temp with a probe type or surface thermometer. The condair instructions for my probe type says surface temp would be half of what the probe reads. Flue gas would be 700 and surface would read 350.

 

[rudysmallfry]

I've got two surface type. One is 18" up on the single wall pipe, the other on the stove itself. The one on the stack is the one I keep at 350-400. The soapstone runs about the same range, but obviously cools down more slowly than the stack.

 

[rdrcr56]

So than your flue gas temp according to the instructions for the condair probe thermometer is 700-800, anything 400 and above is ok ( operating efficiently).

 

[Andre B.]

I guess the basic question, type of wood and degree of seasoning aside, does temperature beat all? As long as I'm burning above 270 degrees, am I producing no creosote?

No, temperature does not beat all.
High temperatures can ensure that the creosote does not condense out on the chimney wall, but you can still be producing creosote that condenses out in the air and falls to the ground or gets washed out with the next rain etc.. Not a problem in low population areas but if you have a lot of people burning in a small closed valley the air can get thick.

The only thing that can ensure no creosote is 100% complete combustion.

This Poplar burns wicked hot, so keeping it in the safe range is easy. It also seems to actually benefit my particular stove and style of burning. I can get the stove nice and hot, leave for work knowing the fire's down to safe glowing embers and the soapstone will be holding the heat for another 4 hours or so. I'm actually starting to like this stuff.

I like to have some around also, I find it useful even in colder weather. Like when you want to warm the house up a bit more but it is just 2 hours before bedtime at which time you want the firebox hot and empty so you can fill it with hardwood for the night. A few sticks of poplar will put out a good deal of heat and be gone.

 

[rudysmallfry]

If what you're saying about the condair probe thermometer is true, that you essentially double the surface temp to get the inside temp, I am overfiring my stove. I don't remember reading anything about translating the temperature when I bought my thermometers. I assumed that what it says it what it is. At times my thermometer reaches 500, which by those calculations means that it's 1000 inside the pipe. That puppy would be glowing a famous shade of orange, would it not? Anyone else have the surface type?

 

[pistonslap]

My understanding is with the surface guage you divide the temperature in half and add that to your surface temp for inside temp.

 

[BrotherBart]

If what you're saying about the condair probe thermometer is true, that you essentially double the surface temp to get the inside temp, I am overfiring my stove. I don't remember reading anything about translating the temperature when I bought my thermometers. I assumed that what it says it what it is. At times my thermometer reaches 500, which by those calculations means that it's 1000 inside the pipe. That puppy would be glowing a famous shade of orange, would it not? Anyone else have the surface type?

From Condar's website:

"Note that Flue gas readings are approximately 50% higher than surface temperature readings"

From the directions for surface mounts:

"Less than 230°F: Temperature too low. Incomplete combustion, causing smoke, soot and hazardous creosote. Open draft and/or add dry fuel.

230°F to 475°F: Safe operating temperature. Complete combustion and best efficiency.

Greater than 475°F: Wasting energy, possibly overheating. While this temperature will often be reached on initial firing, not advised for normal operation."

 

[slofr8]

If what you’re saying about the condair probe thermometer is true, that you essentially double the surface temp to get the inside temp, I am overfiring my stove. I don’t remember reading anything about translating the temperature when I bought my thermometers. I assumed that what it says it what it is. At times my thermometer reaches 500

rudy,
I have a Hearthstone Heritage and the manufacturer says the max temp as measured on the stove top should be 300 to 400 degrees F. I would think your fine.
My chimney seems to be an over achiever and on nights below 0 F. my stove will hit 600 + with air control at its lowest setting. I'm fiddling with the air intake and seem to have hit the sweet spot but I'll install a key damper next if this doesn't work.
Dan.

 

[rudysmallfry]

Dan, I've noticed in this cold snap that my chimney seems to be over achieving too. Last night with the air completely shut, I was still getting small healthy flames. I find the colder it is, the less air I have to supply.

Just out of curiosity, what type of wood are you burning in your Heritage? How much burn time are you getting on a 75% full load from loading to glowing embers? I just want to dream of next near a little when the poplar will be gone and I'll be burning real wood.

 

[drbond]

Rudy,
I have the Heritage too, and like you have a good supply of yellow poplar and with stove loaded at night, have to get up at least one time through the night to reload stove, I would say average burn time is 4 hours. Don't quote me on that, as I never really timed it. So I have been adding some oak that I have around here with the poplar and it burns much longer. My temps are the same as yours with the poplar. When burning oak, I can keep a very steady 400 - 500 stove top with same type of probe as you. I haven't notice the difference with the cold and burrning that you mentioned, as we have been around 0 at night and teens during the day here too. I just discovered that when lighting I used to open the side door to help the fire, but now I just open the ash door and it works much better and prevents any chance of smoke from exiting the stove too. I have been cutting my poplar splits much bigger than any other hard wood I have to help with the burn time too.

 

[Roospike]

If what you're saying about the condair probe thermometer is true, that you essentially double the surface temp to get the inside temp, I am overfiring my stove. I don't remember reading anything about translating the temperature when I bought my thermometers. I assumed that what it says it what it is. At times my thermometer reaches 500, which by those calculations means that it's 1000 inside the pipe. That puppy would be glowing a famous shade of orange, would it not? Anyone else have the surface type?

From Condar's website:

"Note that Flue gas readings are approximately 50% higher than surface temperature readings"

From the directions for surface mounts:

"Less than 230°F: Temperature too low. Incomplete combustion, causing smoke, soot and hazardous creosote. Open draft and/or add dry fuel.

230°F to 475°F: Safe operating temperature. Complete combustion and best efficiency.

Greater than 475°F: Wasting energy, possibly overheating. While this temperature will often be reached on initial firing, not advised for normal operation."

I cant put a surface mount one on my double wall so questions ................

#1 What are the differences between the stove top temp and the single wall pipe temp at the same fire as per the ° ?

#2 So there saying anything over 475° on the "single wall chimney pipe" temp is wastion energy or on the stove top temp ?

 

[BrotherBart]

All of Condar's references are to stove pipe temps.

 

[Roospike]

All of Condar's references are to stove pipe temps.

So what the difference from stove pipe temp to stove top temp on the same fire ? stove top higher ? how much if so ?

 

[DriftWood]

Just out of curiosity, what type of wood are you burning in your Heritage? How much burn time are you getting on a 75% full load from loading to glowing embers? I just want to dream of next near a little when the poplar will be gone and I'll be burning real wood.

I had a 7 1/2 hour burn last night 2/08/2007 in my New Heritage. At midnight room temp. was 72ºF. I loaded 1 huge split of 2yr seasoned oak and a 4/4 oak dunage piece to fill the fire box on 1/4 box full of hot hard wood coals. The surface temp was 400º F at reload.

I used full air., doors closed, until a secondary top down burn started, them only secondary air all night. At 7:30 AM room temp 64ºF outside temp 10º F all night, the stove surface temp was 275º F and a large bed of hot coals to help start the next load.

 

[slofr8]

Just out of curiosity, what type of wood are you burning in your Heritage? How much burn time are you getting on a 75% full load from loading to glowing embers? I just want to dream of next near a little when the poplar will be gone and I’ll be burning real wood.

Rudy,
I burn mostly beech and maple. Last night was about -5F and I filled up about 10:30 with 74 inside temp and a 400 degree stove top. I could not get a full load in because the size and shape of them would have had them leaning on the glass. Maybe 75 percent. At 6 am I had very little red coals but raked them up and with two small sticks of kindling got a split to start to burn down the charcoal. Stove top was about 200 - 250 I think. Inside temp. was 69.
Dan.

 

[rudysmallfry]

Bummer, you all have me beat on the burn time, but then all I have is the Poplar. My new loads are reduced to coals in an hour. Maybe I'm letting it burn off too much at a full flame before shutting down the air. I've got it in my head somehow that I need to allow for some initial burnoff of newly added wood before relying on the secondary burn. Guess not from what I'm reading here. I'm glad I left the Maple for next year in really big chunks. Larger pieces definitely go further.

Do any of you Heritage guys have the blower by the way? Is that puppy loud? Does it have different speeds, or is it just on or off? Despite playing with fans in all different areas of the room, I cannot get enough of the heat in the area of the staircase where I want it. I think I'm at the blower stage now.

 

[Todd]

All of Condar's references are to stove pipe temps.

So what the difference from stove pipe temp to stove top temp on the same fire ? stove top higher ? how much if so ?

It depends on how much air you give the stove, but on a medium to low burn the stove top should be higher than pipe temp, otherwise your just wasting heat up the chimney. For example, when my stove top is chugging along at 550 my pipe temp is somewhere around 250-300. When I have the bypass damper open the pipe temps can soar over 600 in no time.

 

[rudysmallfry]

Yeah, that sounds about right. With the air shut down, my pipe is around 300 while the soapstone is in the 450 to 500 range. I'll try an all secondary burn load tonight and see how far I get.