Cook Stove Creosote Buildup

[Reynolds215]

We have an Amish cook stove in a new 1000 sf lofted addition with above code north country windows and insulation almost air tight. We have a 7" Selkirk Ultra flue system. Single wall from stove 7' to a box in the ceiling , then double wall stainless 4' thru attic and 8' double wall on roof w/ all supports & all inspected. We run the stove at surface temps from 400- 500 degrees average. We seemed to have less control this month and took inside stovepipe off and were shocked to find creosote build up from stove connection all the way to cap from 1/4" thick up to 1/2" near cap looking up. The chimney was cleaned in November and we have run it approx. 75 days 24/7. In our first shortened season last winter 50 days use we found minimal stage 1 creosote bottom to top easily brushed off, Our flue temperature at exit of stove 3' up single wall pipe averages about 140 degrees w/ surface temp of stove at 400 degrees, when outside temps go below 10 degrees flue much colder . We have always thought that this was too cold. We are using accurate digital lasers to measure . We have asked our dealer and others with each giving varied results. We have quit using stove and want to put in an Osburn 2000 woodstove after flue total stage 3 cleaning. Before we do this again could we get some advice from this forum Thanks.

 

[bholler]

We have an Amish cook stove in a new 1000 sf lofted addition with above code north country windows and insulation almost air tight. We have a 7" Selkirk Ultra flue system. Single wall from stove 7' to a box in the ceiling , then double wall stainless 4' thru attic and 8' double wall on roof w/ all supports & all inspected. We run the stove at surface temps from 400- 500 degrees average. We seemed to have less control this month and took inside stovepipe off and were shocked to find creosote build up from stove connection all the way to cap from 1/4" thick up to 1/2" near cap looking up. The chimney was cleaned in November and we have run it approx. 75 days 24/7. In our first shortened season last winter 50 days use we found minimal stage 1 creosote bottom to top easily brushed off, Our flue temperature at exit of stove 3' up single wall pipe averages about 140 degrees w/ surface temp of stove at 400 degrees, when outside temps go below 10 degrees flue much colder . We have always thought that this was too cold. We are using accurate digital lasers to measure . We have asked our dealer and others with each giving varied results. We have quit using stove and want to put in an Osburn 2000 woodstove after flue total stage 3 cleaning. Before we do this again could we get some advice from this forum Thanks.

With 140 degree pipe surface temps you are going to get lots of buildup it needs to be about 250. Possibly a bit higher with a cook stove they typically are not very clean burning. The 7" flue will probably be ok for a 6" stove because you have decent height but not ideal

 

[Reynolds215]

With 140 degree pipe surface temps you are going to get lots of buildup it needs to be about 250. Possibly a bit higher with a cook stove they typically are not very clean burning. The 7" flue will probably be ok for a 6" stove because you have decent height but not ideal

bholler Thank you so much for real, actionable advice. We feel like we are sitting on a flamethrower. We are certainly not locked in to the new stove. Any other manufacturer/model ideas would be great. The heating area is approx. 1000-1500 ft and we want the safest burn technology available We will certainly add to flue height and temp. in new install.

 

[jetsam]

The two keys to not getting creosote buildup are:

1) Don't let the stack get below 250°F at the coldest point (usually the top). Creosote won't condense above 250°. This may mean an insulated flue, changing burning practices (burn hotter), fixing your setup (take out the barometric damper/leaky cleanouts), and using better fuel (get ahead on your wood and only burn dry wood).

2) Don't send VOCs up the chimney in the first place. On pre-EPA stoves you can't do much except burn every load as hot as possible (and even then it's not as good as a regular stove; get a new stove). Newer stoves can go lower and still reburn the VOCs that the "main" fire puts out via secondary combustion. Also, burn dry wood. Don't cool then firebox and flue with a ton of water that didn't need to be in there, and your secondary combustion will fare much better.

 

[bholler]

bholler Thank you so much for real, actionable advice. We feel like we are sitting on a flamethrower. We are certainly not locked in to the new stove. Any other manufacturer/model ideas would be great. The heating area is approx. 1000-1500 ft and we want the safest burn technology available We will certainly add to flue height and temp. in new install.

You don't need to add height and you have a 7" chimney there really isn't any modern stove that uses 7".

 

[Reynolds215]

The two keys to not getting creosote buildup are:

1) Don't let the stack get below 250°F at the coldest point (usually the top). Creosote won't condense above 250°. This may mean an insulated flue, changing burning practices (burn hotter), fixing your setup (take out the barometric damper/leaky cleanouts), and using better fuel (get ahead on your wood and only burn dry wood).

2) Don't send VOCs up the chimney in the first place. On pre-EPA stoves you can't do much except burn every load as hot as possible (and even then it's not as good as a regular stove; get a new stove). Newer stoves can go lower and still reburn the VOCs that the "main" fire puts out via secondary combustion. Also, burn dry wood. Don't cool then firebox and flue with a ton of water that didn't need to be in there, and your secondary combustion will fare much better.

jetsam, We get both points. We are changing stoves and set-up. We are so far from a hot enough flue, we do not even have 250 near the stove. We much appreciate your input and time reynolds215

 

[Nigel459]

Woodstock keystone has a 7” flue and might do the trick

You don't need to add height and you have a 7" chimney there really isn't any modern stove that uses 7".

 

[stoveliker]

I would also measure (along the grain on a freshly split surface of a split that was left in the home for at least 24 hrs) with a moisture meter. Buying firewood often does not get you properly seasoned wood. The more moisture is in there, the higher the probability you are producing creosote. Get your wood below 20% to eliminate this potential issue.

A moisture meter costs $35 or so. Cheap easy check to do. The tool will give peace of mind for years to come for this specific variable.

 

[Reynolds215]

I would also measure (along the grain on a freshly split surface of a split that was left in the home for at least 24 hrs) with a moisture meter. Buying firewood often does not get you properly seasoned wood. The more moisture is in there, the higher the probability you are producing creosote. Get your wood below 20% to eliminate this potential issue.

A moisture meter costs $35 or so. Cheap easy check to do. The tool will give peace of mind for years to come for this specific variable.

Thanks to the 3 of you. Our wood is all indoors and dried in wooden barn w/ ventilation. Black cherry, both maples and beech 11-16% now. Do you think after cleaning flue we could either reduce current 7" flue to 6" at new stove 6" collar? or could we use a liner to achieve 6" flue? Will check out Woodstock keystone. Really appreciate the help

 

[SpaceBus]

What cookstove do you have?

We need to know what wood you are burning, when it was cut, and when it was split. Then we need to know your burning habits and loading routines. I burn in a very modern wood burning cookstove and only find wispy fly ash and a bit of creosote in the pipe. I run my flue a bit cooler than most would, but I do get the surface temp at the flue outlet (my stove vents almost directly into double wall class A chimney) above 200F for at least a brief period at the peak of the burn. At 200df surface temp on my flue collar is at least 400df inside temperature, probably a bit higher.

I generally don't try to get long slow burns, that's not what a cookstove is meant for. When we were still using the steel cook top I would easily get the peak temperature to 700df, but with the glass top the temperature is even higher due to the different thermal properties. We can heat our 1200 sqft saltbox with only our cookstove, but only on mild days. When it gets into the 20's or less the cookstove has to burn around the clock to keep the house warm, but my Morso 2b Classic can keep the whole house at 70df+ when the weather is in the teens and 20's no problem. The cookstove is designed to heat the cook top and the oven, not really your house.

Some of the bigger Amish stoves could be capable of heating your entire home, but using more wood than a freestanding stove. This is why I like having both stoves. Many folks thought I was crazy, but this setup works very well for us.

 

[Reynolds215]

What cookstove do you have?

We need to know what wood you are burning, when it was cut, and when it was split. Then we need to know your burning habits and loading routines. I burn in a very modern wood burning cookstove and only find wispy fly ash and a bit of creosote in the pipe. I run my flue a bit cooler than most would, but I do get the surface temp at the flue outlet (my stove vents almost directly into double wall class A chimney) above 200F for at least a brief period at the peak of the burn. At 200df surface temp on my flue collar is at least 400df inside temperature, probably a bit higher.

I generally don't try to get long slow burns, that's not what a cookstove is meant for. When we were still using the steel cook top I would easily get the peak temperature to 700df, but with the glass top the temperature is even higher due to the different thermal properties. We can heat our 1200 sqft saltbox with only our cookstove, but only on mild days. When it gets into the 20's or less the cookstove has to burn around the clock to keep the house warm, but my Morso 2b Classic can keep the whole house at 70df+ when the weather is in the teens and 20's no problem. The cookstove is designed to heat the cook top and the oven, not really your house.

Some of the bigger Amish stoves could be capable of heating your entire home, but using more wood than a freestanding stove. This is why I like having both stoves. Many folks thought I was crazy, but this setup works very well for us.

Spacebus The stove is 2 yr. old Kitchen Queen 480. Wood all fine and checked by many. No creosote in firebox , some on cold wall of stove. 90% in flue, exponential increase in last month, no change in wood, loading, etc, flue has always been cold unless we run surface temp at 500 D steady. As stove slows down during night we are not willing to heat that hot. am sure creosote builds up then and in morning measured flue temp 3 ft. up flue from stove is 115Df with cookstove top surface temp at 300 Thanks for your input

 

[MissMac]

Thanks to the 3 of you. Our wood is all indoors and dried in wooden barn w/ ventilation. Black cherry, both maples and beech 11-16% now. Do you think after cleaning flue we could either reduce current 7" flue to 6" at new stove 6" collar? or could we use a liner to achieve 6" flue? Will check out Woodstock keystone. Really appreciate the help

11%MC, unless you're storing it right in front of the fire place doesn't sound right. You need to bring a few of your splits inside your home for 48 hours to let them warm up. Then, split them open and use a moisture metre to check the MC on the fresh face of the split (key is at room temp). I suspect you're taking those 11% readings either on the outside of the piece, or outside where it's too cold and will produce a false low reading.

 

[Bad LP]

Why the single wall pipe for the first 7 feet? I get it that you don't need a double wall for that area but in this case wouldn't it help with your stack temps?
Just spit balling.

 

[begreen]

Just to clarify. It sounds like you reading the surface temperature on single-wall pipe at 3ft above the stove with an IR Thermometer. If the surface reading is 140º then the flue gas temp is more like 280º inside the pipe. I would switch out the single-wall to double-wall stovepipe and get a probe thermometer for it. That will help keep the flue gases hotter and reduce creosote buildup.
Note that when the fire is in the coaling stage it is no longer producing creosote. So a 115º stove pipe temp in the morning is not a big deal. If you want less heat from the stove, either load less fuel or load it earlier and let the fire go out or open the bypass before going to bed to raise the flue temp and lower the stove body temp.

And yes, retest the wood for interior moisture as MissMac suggests. Wood with 14% exterior reading can have a 28% interior reading.

 

[Reynolds215]

Just to clarify. It sounds like you reading the surface temperature on single-wall pipe at 3ft above the stove with an IR Thermometer. If the surface reading is 140º then the flue gas temp is more like 280º inside the pipe. I would switch out the single-wall to double-wall stovepipe and get a probe thermometer for it. That will help keep the flue gases hotter and reduce creosote buildup.
Note that when the fire is in the coaling stage it is no longer producing creosote. So a 115º stove pipe temp in the morning is not a big deal. If you want less heat from the stove, either load less fuel or load it earlier and let the fire go out or open the bypass before going to bed to raise the flue temp and lower the stove body temp.

And yes, retest the wood for interior moisture as MissMac suggests. Wood with 14% exterior reading can have a 28% interior reading.

Thank both of you. We have a 2-3 day supply of dried interior temp. approx. 70f splits in a hallway off our designated 8x12 wood storage area in the rear of our new insulated garage. The wood temps are accurate. Your double wall pipe idea and all advice on temps /coaling/ flue ideas totally well received Thanks again for new info.

 

[begreen]

Resplit some of the thicker splits that have sat indoors for a day or two. Then press the contact pins of the moisture meter firmly into the center of the freshly exposed face of the wood. That should give an accurate read on the wood moisture. For reference, most of our firewood falls in the 17-18% range.

 

[Reynolds215]

Resplit some of the thicker splits that have sat indoors for a day or two. Then press the contact pins of the moisture meter firmly into the center of the freshly exposed face of the wood. That should give an accurate read on the wood moisture. For reference, most of our firewood falls in the 17-18% range.

Thanks again will do

 

[MissMac]

Resplit some of the thicker splits that have sat indoors for a day or two. Then press the contact pins of the moisture meter firmly into the center of the freshly exposed face of the wood. That should give an accurate read on the wood moisture. For reference, most of our firewood falls in the 17-18% range.

Yup - unless it was kiln dried, it's not 11%MC - that just doesn't happen (unless you live in a desert?).

 

[Reynolds215]

Yup - unless it was kiln dried, it's not 11%MC - that just doesn't happen (unless you live in a desert?).

begreen thankyou for your help, we lived in Arizona 6 months of the year for 18 years and we currently own a small tree and fish farm near Montreal. It seems we have a lot to learn about lumber.

 

[Bad LP]

begreen thankyou for your help, we lived in Arizona 6 months of the year for 18 years and we currently own a small tree and fish farm near Montreal. It seems we have a lot to learn about lumber.

Oh ya you do. Good luck. Sounds like you need some fine tuning to your old habits.

 

[Hoytman]

In a 1000 sq ft home that 480 will likely burn you out of there depending on how well insulated.

Smaller version of that stove will also allow for hotter burning and therefore hotter flue temps. Go to double wall pipe first and see if that helps, then trade in for smaller cookstove and you should be fine.

400 degrees off of the 480 is a lot more heat being thrown into the home than same 400 degree temperature coming off of smaller model, so you’ll have to burn the smaller stove slightly hotter to maintain similar indoor temps and similar outdoor temps than when using the 480.

Hope that wasn’t too confusing.

Your 480 at 400 degrees will throw more heat into the home than a 400 degree 380 will. So if your big stove is getting too warm in the house burning a smaller stove will help. All things being equal larger mass at any given temperature will throw more heat than identical design smaller stove.

 

[SpaceBus]

Indeed, the 480 is a fairly large stove. Ours is much smaller and I run it pretty hot every time.

 

[Tractordude]

I am considering the 550. How is your 480 performing for you?