New Fisher Stove Owner

[Todd67]

What makes it more dangerous? The pyrolisis that has happened over the years of that stove being to close. It has been lowering the kindling point slowly for years. I have opened up walls behind stoves many times and it can be very scary. Yes it may be fine for years. But we just don't know. The argument that nothing has happened yet is utter nonsense and has lead to disaster many times in the past.

Good point about pyrolisis! But being unfamiliar with pyrolisis, what temperature and other conditions/factors does pyrolisis occurr?

 

[bholler]

Good point about pyrolisis! But being unfamiliar with pyrolisis, what temperature and other conditions/factors does pyrolisis occurr?

As low as 120

 

[bholler]

His stove installation might be grandfathered in. The stove has been used for an unknown number of years and hasn't burned the house down yet. What makes his clearances any more "dangerous" than they were when the stove was installed? It doesn't appear to have caused any damage to the walls or floor yet.

My clearances are more than code requires. But my firewood racks put my firewood less than 2ft from my stove. Oh crap, you say? That wood never exceeds 110 degrees, even after getting a new load of firewood in the stove up to 500* on the stovepipe thermometer. That rug on the hearth is a whopping 98* with the stovepipe at 500. BUT, I don't maintain a hot burn like many people recommended to me over the years. The only time I concern myself with stove temp is when I get a new load of wood up to 450-500* on the pipe thermometer. As soon as that 450-500* temp is reached, I close the draft caps, the open them a 1/4 turn. In other words, BARELY OPEN. I've been using my stove like this for 7+ years now without any issues. My cats and dog take turns sleeping on the hearth rug and behind the stove.

This pic will no doubt scare some of you...View attachment 250998

Also the house just changed hands so the install is not grandfathered legally. But my concern is not about the legality it is about safety.

 

[Todd67]

Pyrolysis is a science, so I've been researching it since earlier today. There are many wood stoves and wood heating appliances that weren't/aren't installed properly. Pyrolysis is a real issue, but I'm having a hard time finding another source that says it can happen as low as 120*. Other chimney sweep web sites say as low as 200* and could take decades to form. Regardless, it's good to know that it can be an issue.

 

[bholler]

Pyrolysis is a science, so I've been researching it since earlier today. There are many wood stoves and wood heating appliances that weren't/aren't installed properly. Pyrolysis is a real issue, but I'm having a hard time finding another source that says it can happen as low as 120*. Other chimney sweep web sites say as low as 200* and could take decades to form. Regardless, it's good to know that it can be an issue.

Read the white paper on chimney fires from csia. I believe it was also Virginia tech that did an extensive study on pyrolisis and they found that it happens at a much lower temperature that previously thought. That other chimney site you are referencing contains tons of misinformation.

 

[SpaceBus]

I found pyrolysis on plywood where the hot water pipe passes through for my shower faucet installed in 1975 when the house was built. This house was also used as a vacation home from 1986 to 2018. It could happen very easily. Someone posted historical data about house fires and most were caused by hydronic cast iron radiators which are not 200 df.

 

[bholler]

Pyrolysis is a science, so I've been researching it since earlier today. There are many wood stoves and wood heating appliances that weren't/aren't installed properly. Pyrolysis is a real issue, but I'm having a hard time finding another source that says it can happen as low as 120*. Other chimney sweep web sites say as low as 200* and could take decades to form. Regardless, it's good to know that it can be an issue.

There is a reason I push so much for proper clearances on the stove and chimney or for insulated liners. It isn't about legalities. There are very real safety issues that brought about these codes.

 

[av8r]

There are many modern wood stoves that can fit that hearth without modifying anything. They will produce more heat with less wood. There's nothing wrong with the Fisher stove you have, but something to consider when investing money into it. Also, a modern stove will have a glass door with a view of the fire!

@bholler Is it a possibility that a modern stove would be safer and have reduced clearances? Seems like it would be easier to replace the stove than the wall lol. Or are they just more efficient and the clearances remain the same?

 

[bholler]

@bholler Is it a possibility that a modern stove would be safer and have reduced clearances? Seems like it would be easier to replace the stove than the wall lol. Or are they just more efficient and the clearances remain the same?

Reduced clearances absolutely. There is nothing unsafe about old stoves like this. They are just very inefficient compared to the new stuff. And they require massive clearances

 

[Todd67]

Reduced clearances absolutely. There is nothing unsafe about old stoves like this. They are just very inefficient compared to the new stuff. And they require massive clearances

How often do you have to load a new stove, or how long will it hold a fire? I've been able to load my stove every 12 hours and use the coals in my stove to get the next load of wood burning. Is that possible in the new stoves? I've seen various sizes of fire boxes on new stoves at the stores.

 

[bholler]

How often do you have to load a new stove, or how long will it hold a fire? I've been able to load my stove every 12 hours and use the coals in my stove to get the next load of wood burning. Is that possible in the new stoves? I've seen various sizes of fire boxes on new stoves at the stores.

That depends on the stove. And how much heat I need. This time of year the blazeking I am currently running can heat the house to a consistent 72 for 24 hours.
The regency before that easily 10 hours.
If you are talking just about having enough coals to restart from the regency can easily go 18 hours. The bk doesn't hold coals much past the time it puts out heat because the thermostat will open up the air as the stove temp drops. Yes modern stoves will put out much more even heat much longer than old stoves like fishers. And with smaller fireboxes. If you look at stoves as big as many of the fishers you are into the 36 even 48 hour range

 

[Todd67]

That depends on the stove. And how much heat I need. This time of year the blazeking I am currently running can heat the house to a consistent 72 for 24 hours.
The regency before that easily 10 hours.
If you are talking just about having enough coals to restart from the regency can easily go 18 hours. The bk doesn't hold coals much past the time it puts out heat because the thermostat will open up the air as the stove temp drops. Yes modern stoves will put out much more even heat much longer than old stoves like fishers. And with smaller fireboxes. If you look at stoves as big as many of the fishers you are into the 36 even 48 hour range

Thanks for the info!

 

[av8r]

That depends on the stove. And how much heat I need. This time of year the blazeking I am currently running can heat the house to a consistent 72 for 24 hours.
The regency before that easily 10 hours.
If you are talking just about having enough coals to restart from the regency can easily go 18 hours. The bk doesn't hold coals much past the time it puts out heat because the thermostat will open up the air as the stove temp drops. Yes modern stoves will put out much more even heat much longer than old stoves like fishers. And with smaller fireboxes. If you look at stoves as big as many of the fishers you are into the 36 even 48 hour range

Wow that is extremely efficient! I guess I have another option to consider. If you don't mind me asking, how many square feet is that heating for? And is your house an open floor plan?
It sounds like the blazeking is the way to go! I will do some research and see what I can come up with.

 

[bholler]

Wow that is extremely efficient! I guess I have another option to consider. If you don't mind me asking, how many square feet is that heating for? And is your house an open floor plan?
It sounds like the blazeking is the way to go! I will do some research and see what I can come up with.

That is heating a 1970s ranch 1100 sqft on the first floor. Stove in the finished walkout basement about 900 sqft heated. Those times are only for this time of year with temps in the 30s and low 40s. Once they drop into the 20s with wind I would load 3x a day in either of those stoves. The blazeking excells at low slow heat. But once the btu load increases it doesn't have much advantage over non cat stoves like my regency.

It is a blaze king princess and a regency 3100. The blaze King was lent to me by a member here to try I used it last year and I am trying it again this year.

 

[Ctwoodtick]

Read the white paper on chimney fires from csia. I believe it was also Virginia tech that did an extensive study on pyrolisis and they found that it happens at a much lower temperature that previously thought. That other chimney site you are referencing contains tons of misinformation.

I couldn’t find the virginia tech research online. Do you recall what the lowest temp that pyrolysis was said to begin was?

 

[bholler]

I couldn’t find the virginia tech research online. Do you recall what the lowest temp that pyrolysis was said to begin was?

Like I said 130. I will have to look it up it may not have been vt.

 

[Todd67]

Wow that is extremely efficient! I guess I have another option to consider. If you don't mind me asking, how many square feet is that heating for? And is your house an open floor plan?
It sounds like the blazeking is the way to go! I will do some research and see what I can come up with.

You also have to consider the different climates between PA and NH. Here in northern NY we were still burning wood in June this year. Our month long average temp last March was a whopping 9 degrees. My house is drafty and poorly insulated, built in 1930. It would be interesting to see how a new stove would compare to my Fisher in my house.

 

[Todd67]

This quote is from page 1-4 in the CSIA chimney fires white paper...

When wood is exposed to heat over a period of
time, however, it undergoes a gradual change in
its molecular structure through a process called
pyrolysis. The complex organic molecules of
which wood is composed are slowly broken apart,
and much of the original weight and structural
integrity of the wood is lost. As this process
continues, the material left behind is charcoal,
which is also known by the more ominous
sounding and technically correct term pyrophoric
carbon. Pyrophoric carbon is different from wood
and has different properties. First, it has a
significantly lower ignition temperature than that
of the original wood. Various studies have fixed
this temperature at 200 to 250°F, and there are
suggestions that the figure could be even lower.

 

[bholler]

You also have to consider the different climates between PA and NH. Here in northern NY we were still burning wood in June this year. Our month long average temp last March was a whopping 9 degrees. My house is drafty and poorly insulated, built in 1930. It would be interesting to see how a new stove would compare to my Fisher in my house.

It would give you more heat from each price of wood. Where most new stoves do fall short of old basic steel boxes is in peak btu output. But the peak is so short on old stoves it doesn't mean allot. But if you regularly go 10 hours with your Fisher you aren't pushing it hard at all so most large modern stoves would be fine

 

[bholler]

This quote is from page 1-4 in the CSIA chimney fires white paper...

When wood is exposed to heat over a period of
time, however, it undergoes a gradual change in
its molecular structure through a process called
pyrolysis. The complex organic molecules of
which wood is composed are slowly broken apart,
and much of the original weight and structural
integrity of the wood is lost. As this process
continues, the material left behind is charcoal,
which is also known by the more ominous
sounding and technically correct term pyrophoric
carbon. Pyrophoric carbon is different from wood
and has different properties. First, it has a
significantly lower ignition temperature than that
of the original wood. Various studies have fixed
this temperature at 200 to 250°F, and there are
suggestions that the figure could be even lower.

I will find the study that shows it starts lower than 200. I looked a little bit and didn't find it. But I know it's there. The fact is these clearance requirements were not pulled out of thin air. They were determined through testing and actually some of the ul listed fishers show larger than 36" for clearance required. And saying it has been fine for years is not a valid argument because we know pyrolysis happens over time.

 

[Todd67]

It would give you more heat from each price of wood. Where most new stoves do fall short of old basic steel boxes is in peak btu output. But the peak is so short on old stoves it doesn't mean allot. But if you regularly go 10 hours with your Fisher you aren't pushing it hard at all so most large modern stoves would be fine

My Mama Bear is my only heat source. It heats my 1930-built 2-story house all by itself, other than the basement. Even my half-finished attic stays above 40 on the coldest nights. There are countless days every winter when it never gets above 0 for a high, and minus 20 or colder for a low, and that doesn't include the wind chill. I cut down standing dead trees every year for firewood, enough to heat my house 8 months a year. When I split that wood, the moisture content is already below 25%, and sometimes as low as 14%. If I cut down a live tree, I season it for 2 years before I burn it. I'm not picky about the species of tree that I burn in my Fisher. I'm burning pine right now, that I cut down two years ago. In a few days that pine will be gone, and I'll start burning ash and maple. The few times I've ordered firewood, I seem to get junk wood that won't burn as hot or as long as my own trees, so I avoid buying firewood like the plague. Our low tomorrow night will be 7 degrees, and I'll still be burning the last of this pine.

No matter what stove I have or use, modern or old, it will get pushed plenty hard to keep my old, drafty house warm. We take a 3 hour road trip every January 1st (when my disabled wife is up to travelling), and we come home to a warm house 10 to 12 hours later, with plenty of coals left in the Fisher. I'm not saying it will outperform a new stove. I'm only saying that maybe you underestimate the severity of our winters in northern NY. Based on what my friends and neighbors say about their newer modern wood stoves, furnaces and boilers, they aren't burning any less wood than I am, and most of their houses are much newer and better insulated than mine.

 

[bholler]

My Mama Bear is my only heat source. It heats my 1930-built 2-story house all by itself, other than the basement. Even my half-finished attic stays above 40 on the coldest nights. There are countless days every winter when it never gets above 0 for a high, and minus 20 or colder for a low, and that doesn't include the wind chill. I cut down standing dead trees every year for firewood, enough to heat my house 8 months a year. When I split that wood, the moisture content is already below 25%, and sometimes as low as 14%. If I cut down a live tree, I season it for 2 years before I burn it. I'm not picky about the species of tree that I burn in my Fisher. I'm burning pine right now, that I cut down two years ago. In a few days that pine will be gone, and I'll start burning ash and maple. The few times I've ordered firewood, I seem to get junk wood that won't burn as hot or as long as my own trees, so I avoid buying firewood like the plague. Our low tomorrow night will be 7 degrees, and I'll still be burning the last of this pine.

No matter what stove I have or use, modern or old, it will get pushed plenty hard to keep my old, drafty house warm. We take a 3 hour road trip every January 1st (when my disabled wife is up to travelling), and we come home to a warm house 10 to 12 hours later, with plenty of coals left in the Fisher. I'm not saying it will outperform a new stove. I'm only saying that maybe you underestimate the severity of our winters in northern NY. Based on what my friends and neighbors say about their newer modern wood stoves, furnaces and boilers, they aren't burning any less wood than I am, and most of their houses are much newer and better insulated than mine.

I don't know why the severity of your winters in ny would change my experience burning a mama and a papa bear in my house which I also burned a quad and regency in. I never burnt the BK in that house. I am not comparing my experience with one stove to that of others in a different house who may or may not know how to use their stove. I am not saying there is anything wrong with using old stoves or that they can't do the job. I am just saying that in my experience and the experience of most people who have done the same switching to a modern stove leads to lower wood useage and more even heat with a cleaner chimney.

 

[coaly]

His stove installation might be grandfathered in. The stove has been used for an unknown number of years and hasn't burned the house down yet. What makes his clearances any more "dangerous" than they were when the stove was installed? It doesn't appear to have caused any damage to the walls or floor yet.

The 36 inch clearance was required when the stove was built. NFPA came up with 115* f. over ambient temperature as the benchmark maximum surface temperature which is used by UL. So at 70* room temp, combustible materials surface temp cannot exceed 185*. The testing is done with thermocouples mounted on moveable walls. Stove is over fired with oven dried softwood stapled together in bricks called "Firebrands". This is what determines clearances. Not the manufacturer.

What makes it more dangerous is TIME.
When first installed, the moisture content of building materials is high, with high ignition point temperatures. The longer it is dried over time, the lower the ignition point becomes. If you take a piece of wood and continue to dry it under your stove for a period of time, you will find you can light it very easily. Just like charcoal from the rear of the stove that is raked forward. All the moisture has been released, and it will burst into flame very easily when raised to the temperature of the coals.

The only thing I see wrong in your picture is the window trim and sill, possibly less than 36 inches to stove surface.
When burning at your maximum temp, see what temperature the wood is. This will give you an idea how close it comes to the 115* over ambient benchmark. I use an IR thermometer all the time to inspect cases like this. Check the cats and dogs temps too. Amazing how hot stove dwellers can get.

 

[Ctwoodtick]

Like I said 130. I will have to look it up it may not have been vt.

Sorry, I missed this when first reading. That’s interesting bc I have a pellet stove and wood insert that are installed with correct clearances honored and the combustible material just outside that zone gets a bit over the figures you gave at times. For the pellet stove specifically, I had intentionally had installed with a couple extra inches from walls than specified in manual and temps still get around 125-130.

 

[bholler]

Sorry, I missed this when first reading. That’s interesting bc I have a pellet stove and wood insert that are installed with correct clearances honored and the combustible material just outside that zone gets a bit over the figures you gave at times. For the pellet stove specifically, I had intentionally had installed with a couple extra inches from walls than specified in manual and temps still get around 125-130.

130 is the lowest number I have ever seen given. And I am sure at that temp the pyrolisis is very slow and very minor.