Concerns about clearances to combustables with a Hearthstone Heritage woodstove

[JoeC]

I was recently in a stove shop and saw some very attractive cast iron panels that might be designed to go in a fireplace....so about 30 inches wide, about 30 inches tall.
They had different impressions in the iron, so one had flowers, one had a wolf head, etcetera.

You may want to think about putting one of those between the stove and the wall.
It should not touch either the wall nor the stove, just get one with a stand.

I just looked it up.
It's named a cast iron "firebacks"

Plow and hearth has a few nice ones, there are many more to choose from when looking on google...

Good Idea... I just might take a look at these!!.. Thanks for the idea!

 

[STIHLY DAN]

Table of Hot Water Scalding Temperatures & Times Water Temperature Setting
Exposure Time Effects of Exposure to Hot water at These Temperatures

Water at 120 degF 5 minutes 2nd & 3rd degree burns on adult skin
Water at 130 degF 30 seconds 2nd & 3rd degree burns on adult skin
Water at 140 degF 5 seconds 2nd & 3rd degree burns on adult skin
Water at 150 degF 1 1/2 seconds 2nd & 3rd degree burns on adult skin
Water at 160 degF 1/2 second 2nd & 3rd degree burns on adult skin

This chart is a load of crap. Most showers baths are 128* Anti scold. My tank is at 130 and the wife and teenagers can be in there for an hour. How hot is a hot tub? 130* or so

 

[Rob From Wisconsin]

Water can be dangerous because it has an incredible "heat content" - more so than even metals.
When you make contact with it, a lot of cooler mass is required to bring it down in temp significantly.

 

[JoeC]

If you can hold your hand on it - it ain't too hot. Installed per manual - you should be good to go. If you see readings with your IR thermo reaching 160F - I would revisit the question. South of that should not be an issue.

Ok so right now tonight I have my stove heat at around 400F to 430F and the wall temp in a small location is around 170 to 175F...!! I can put my hand on it without burning but it's pretty hot! I'm going to call Hearthstone company tomorrow and see what they tell me... I called them a few days ago and the technician said to me it's the ambient temp + 117F ... not Ambient temp and 90F like someone else here was saying... anyway, I'll keep you all posted on what I find out tomorrow.. later!

 

[begreen]

It appears I erred a bit on the conservative side. I should have checked instead of relying on my addled memory. This is from Craig's article:
The benchmark temperature, which determines safe clearances, is typically 115 degrees F over the ambient room temperature. In other words, if the ambient room temperature is 70F, the benchmark wall temperature cannot exceed 185F.

https://www.hearth.com/econtent/index.php/articles/stove_wall_clear

 

[JoeC]

It appears I erred a bit on the conservative side. I should have checked instead of relying on my addled memory. This is from Craig's article:
The benchmark temperature, which determines safe clearances, is typically 115 degrees F over the ambient room temperature. In other words, if the ambient room temperature is 70F, the benchmark wall temperature cannot exceed 185F.

https://www.hearth.com/econtent/index.php/articles/stove_wall_clear

Thanks for that article!...and all the help!...... Actually right now with the stove running an even rate... around 350 to 365F.. the wall temps are around 130 to 148F....(And these temperature are in a very narrow area.. once outside this small radius the temperature drops pretty significantly..).

 

[akbear]

it's a shame there still hasn't been any definitive or real world research on this (observing matchsticks and small chunks of wood hardly replicates a stud in the wall). I was reading another thread on here of the same subject and someone had linked to a paper on low temp pyrophoric ignition which claimed AN incident of supposedly viable ignition from long term 170 degree exposure (though the photographic proof after the fire looked to me as though the hot water pipe went through OSB, which is likely more glue than it is wood). There are just so many variables, such as humidity of a location, are there compounds on or in the wood that might vary it's ignition point, surface contaminants that might easily ignite (dust, pet hair, etc, remember those tricks for stating campfires? and we certainly know how dust can build up in choke spots where there is a convective flow) just as three different variables.

But think about this, have you ever taken the IR gun outdoors on a summer day and taken a reading on the side of your home or other objects? You'd be surprised at how hot something can get in the sun (a black roof can easily get to 160-195 degrees), yet how many houses do we notice spontaneously combusting in the summer? Are there laws against painting houses dark colours due to safety concerns (yet even the 10 degree difference between yellow and white are enough to have the school bus industry rethink what colour to paint a school bus roof these days)

So unfortunately it all comes down to, nobody really knows, do your best to avoid it, don't tempt fate and if it worries you, take some steps that will help radiate some of the heat elsewhere for your own peace of mind as it can only improve the situation (and in your case where it's just a specific area, maybe full fledged wall protection isn't necessary and you could get away with a strip of decorative stamped metal or grill, maybe some metal artsy piece that could radiate it away from the spot, an eco fan sitting on the corner that could direct just enough heat in another direction, perhaps even a mirror or mirrored finished stainless steel or some hanging decorative metal tiles could bounce back enough of the radiated heat to satisfy the concern. But if it's full scale wall protection that would make you feel better, that's what you should do rather than to rely upon a polling of opinion.)

 

[Rob From Wisconsin]

Is it my imagination.....but have "R" ratings for hearths/floors been trumped-up for stoves in general over
the last several years?? Our recently installed Homestead required a rediculously high floor insulation
rating (2.5), and even with a hot fire over an exented period of time, it has one of the coolest to-the-touch floor temps
of any of the previous stove we've owned.....I'm confused!

 

[akbear]

I think a lot has to do with reducing liability much in the same way children now play on playgrounds that are a cushion of rubber when we might have played on asphalt or concrete, nearly any object has to have a child warning label on it, and even hot dogs come with warnings. If they can prevent or weasel out of a lawsuit, so much the better, and hey! if three inches are safe, then 6 are doubly safe.

Of course I'm not advocating going against sound, tried and trusted advice, but in many ways our society has become obsessed with the if it saves just one it's worth it mantra and in some cases all the protections have caused more injury or recklessness.

 

[begreen]

It comes down to setting a limit on the lowest common denominator. As noted, no one is going to be able to determine the variables that will be found in the individual stove location. In this case it is certainly prudent to err on the side of caution.

Here is a shot of pyrolysis from hot water pipes in contact with wood timbers. This is from long term exposure to 180-190

http://www.doctorfire.com/low_temp_wood1.pdf‎

As for sun heat, well vinyl sure doesn't like it. When reflected off of neighboring low-E glass it can be close to ignition temps.

 

[akbear]

it's also interesting to note that the pipes in that picture are wrapped with insulation (except perhaps for the portion that went through the floor) which might concentrate the unwrapped portion (if it was so) as the only viable transfer point for heat to radiate off them. The Tees right above and below the floor could also have added to the issue as fluids tend to resist a redirection (which can be a source of heat as well) and can form unique flow patterns at junctures that can possibly add their own restriction. I'm sure there could be many explanations of what could have happened (including what types of floor covering that might have come in contact with the pipes), or what might have occurred that pushed things beyond limits, but what I find most interesting in the studies that have been conducted, is that they all seem to centre on two conditions happening, an anaerobic environment that leads to charcoalling of the wood, and then an aerobic environment that allows the wood to ignite.

If there were any easy answers, we'd have them without question by now, but let's face it, there's no way to duplicate all the possible conditions or substances any installation might encounter even in using the exact same plans and materials, so I'd say consensus is to do your best to minimise any conditions that seem to be problematic or could develop into a problem. The cooler you keep that wall, the better your peace of mind will be no matter if it could become an issue or not.

In my own situation I have a portion of my tiled wall that I feel is warmer than it should, even though it hasn't hit any magic danger number for temperature, I fully intend to install some sort of solution (perhaps a backsplash for my cooktop) that redirects more of the heat forward so that I don't feel that I must routinely check the wall and ponder if I'll have a future problem or not.

 

[JoeC]

it's a shame there still hasn't been any definitive or real world research on this (observing matchsticks and small chunks of wood hardly replicates a stud in the wall). I was reading another thread on here of the same subject and someone had linked to a paper on low temp pyrophoric ignition which claimed AN incident of supposedly viable ignition from long term 170 degree exposure (though the photographic proof after the fire looked to me as though the hot water pipe went through OSB, which is likely more glue than it is wood). There are just so many variables, such as humidity of a location, are there compounds on or in the wood that might vary it's ignition point, surface contaminants that might easily ignite (dust, pet hair, etc, remember those tricks for stating campfires? and we certainly know how dust can build up in choke spots where there is a convective flow) just as three different variables.

But think about this, have you ever taken the IR gun outdoors on a summer day and taken a reading on the side of your home or other objects? You'd be surprised at how hot something can get in the sun (a black roof can easily get to 160-195 degrees), yet how many houses do we notice spontaneously combusting in the summer? Are there laws against painting houses dark colours due to safety concerns (yet even the 10 degree difference between yellow and white are enough to have the school bus industry rethink what colour to paint a school bus roof these days)

So unfortunately it all comes down to, nobody really knows, do your best to avoid it, don't tempt fate and if it worries you, take some steps that will help radiate some of the heat elsewhere for your own peace of mind as it can only improve the situation (and in your case where it's just a specific area, maybe full fledged wall protection isn't necessary and you could get away with a strip of decorative stamped metal or grill, maybe some metal artsy piece that could radiate it away from the spot, an eco fan sitting on the corner that could direct just enough heat in another direction, perhaps even a mirror or mirrored finished stainless steel or some hanging decorative metal tiles could bounce back enough of the radiated heat to satisfy the concern. But if it's full scale wall protection that would make you feel better, that's what you should do rather than to rely upon a polling of opinion.)

Very good thoughts, observations and suggestions...I would've never thought about the siding on the house or roof temps on a hot summer day.. It puts a lot of things in perspective to what I'm trying to learn about.. thanks for your post!

 

[JoeC]

It comes down to setting a limit on the lowest common denominator. As noted, no one is going to be able to determine the variables that will be found in the individual stove location. In this case it is certainly prudent to err on the side of caution.

Here is a shot of pyrolysis from hot water pipes in contact with wood timbers. This is from long term exposure to 180-190
View attachment 115457
http://www.doctorfire.com/low_temp_wood1.pdf‎

As for sun heat, well vinyl sure doesn't like it. When reflected off of neighboring low-E glass it can be close to ignition temps.
View attachment 115458

Now if I remember correctly from what I read.. long term exposure at 180-190F.. would have to be continuously at those high temps in order for pyrolysis to happened? Correct me if I'm wrong..

 

[JoeC]

it's also interesting to note that the pipes in that picture are wrapped with insulation (except perhaps for the portion that went through the floor) which might concentrate the unwrapped portion (if it was so) as the only viable transfer point for heat to radiate off them. The Tees right above and below the floor could also have added to the issue as fluids tend to resist a redirection (which can be a source of heat as well) and can form unique flow patterns at junctures that can possibly add their own restriction. I'm sure there could be many explanations of what could have happened (including what types of floor covering that might have come in contact with the pipes), or what might have occurred that pushed things beyond limits, but what I find most interesting in the studies that have been conducted, is that they all seem to centre on two conditions happening, an anaerobic environment that leads to charcoalling of the wood, and then an aerobic environment that allows the wood to ignite.

If there were any easy answers, we'd have them without question by now, but let's face it, there's no way to duplicate all the possible conditions or substances any installation might encounter even in using the exact same plans and materials, so I'd say consensus is to do your best to minimise any conditions that seem to be problematic or could develop into a problem. The cooler you keep that wall, the better your peace of mind will be no matter if it could become an issue or not.

In my own situation I have a portion of my tiled wall that I feel is warmer than it should, even though it hasn't hit any magic danger number for temperature, I fully intend to install some sort of solution (perhaps a backsplash for my cooktop) that redirects more of the heat forward so that I don't feel that I must routinely check the wall and ponder if I'll have a future problem or not.

Good point... and I might consider doing some sort of shielding of my walls too...Just for piece of mine like you have suggested...

 

[begreen]

It varies. Pyrolysis could be happening if the surface is continuously or repeatedly exposed to high temps for extended periods of time. If you are anxious, add some wall shielding or move the stove further away from the corner.

 

[Highbeam]

How hot is a hot tub? 130* or so

Hot tub is at 100-105. I like a nice 103 and plan to enjoy it tonight. At 105 it is safe but you won't be able to stay in for more than about 10 minutes and your submerged skin will be temporarily pink from bloodflow.

 

[Seriesnuns]

The walls near my stove get to 160 sometimes.

I also have steam radiators heat at my house. (I rarely use now).

My steam pipes run inside the walls next to joists and studs and my radiator are next to the walls surrounded by wood enclosures.

I never checked the temp but the iron gets so hot I can't touch. And I checked steam happens at 212 degrees.

Food for thought.