wood stove flue too hot?


I have a wood stove in my basement. I have a thermometer on the pipe where it enters the chimney, and I keep it in the safe range.
After about 5 hours of burning, the chimney / flue gets extremely hot about 12 inches over where the metal pipe goes in. It gets hot on all sides, not just the side where the pipe goes in.
By "hot", I mean I can only hold my hand on it for a fraction of a second.
I am pretty sure the chimney doesn't have a metal liner. I had a chimney sweep guy clean it out in the fall, and he didn't say anything about the liner not being up to the task of handling a wood stove. As I understand it, wood allows a lot more heat to go up the chimney than an oil furnace.
The previous owner used the stove regularly (I just got the house in the summer).
So I guess my question is whether or not it is normal for a chinmey to get this hot...?
Thanks..
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Omissions: 1. Since you have a stovepipe thermometer, we can advise better if we know what it indicates. Hot to the touch is not an adequately precise indicator. 2. You should be aware that, in some jurisdictions (e.g. Ontario, Canada) the fire code is retroactive, i.e. you may be required to upgrade to comply with the current code (more probably by your insurance carrier than by local government.) 3. Modern stove flues ought to be double-walled (as modern fire codes are likely to specify.) These are tested by the standards authority to withstand interior (smoke temperatures) as high as 2000 Fahr. (Some firemen recommend an intentional chimney fire every year or so for cleaning purposes: but they are probably not supposed to say this.) Books about woodstove efficiency recommend the temperature inside the smokestack ought to be above 300 Fahr. -- no problem in a double flue.
You can see for yourself whether the pipe is single- or double-walled by disassembling the stove pipe. If uncertain about this, have the chimney sweep show you how on his next visit.
Do not ask your insurance carrier or agent for advice about wood stove safety. You are not likely to get a coherent answer and you may put the insurer on the road to cancelling your insurance. But it is in your own interest to find out what your local fire code specifies and conform to it if you can.
--
Don Phillipson
Carlsbad Springs
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What do you consider safe range? I usually run my stove so the cast iron top is at least 400 degrees, and a couple of times a day, run it up to about 700F to keep it clean. The stove pipe is easily 400 at any given time. That, IMO, is normal. What does your actually read on the thermometer?
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Thanks for the speedy replies.
I should have specified the pipe temperatures in my original post. The thermometer I use shows the "best combustion" range as 300 - 475 F. Over 475 is labeled "too hot". When it gets up around 500, I shut 'er down to cool off a little.
The stovepipe is defintely single-walled - I have pulled it out of the chimney myself to look at it. It is probably not up to code. I am having a new wood furnace add-on attached to my oil furnace next year, but would like to get through the winter with this stove. But I don't want to crack or otherwise ruin my chimney or burn the house down in the mean time.
And to clarify, it is the brick chimney that I am worried about, not the metal pipe. I have inadvertently let the metal pipe get red hot, so I'm pretty sure it can handle 500 F. I'm just not sure how hot the chimney itself is supposed to get. It is the chimney that gets too hot to touch. (I may have mis-used the word "flue" in my original post.) One friend tells me that the clay liner won't stand the heat of a wood stove, but another friend tells me that he has run his stove 24/7 for the past 3 weeks (he has a clay liner - ie, no metal insert).
Thanks again, I appreciate the help.. Stephanie D.
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If you are meaning the brick chimney with a vitrified clay liner is getting warm on the outside after several hours, I would consider that normal. The tile liner/brick exterior are masonry units in contact with each other. Heat will eventually start to transfer, in certain masonry stoves this is considered a heat sink to hold the heat for future release.
The pipe between the stove and the chimney is normally single wall as it is supposed to be an additional source of heat. The chimney should be either masonry with a clay liner, or a masonry with a stainless steel liner, or a class "A" double wall insulated metal chimney. While masonry chimneys have a problem, especially if they are on an outside wall, of having a lot of creosote and moisture until they slowly heat up, they are very durable. After all the clay liner is kiln baked and heavily glazed with kiln baked coating. Anything your wood stove will do will be less than it survived during manufacture.

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Just let it burn down. That is not a big deal. As I said, I'd heat it up every day to prevent creosote.

Sure,it is. I've never seen multi-walled pipe in an exposed situation. You want that heat in the house, not to force it up the chimney and waste it. If you look at photos from many years ago, the stove would be in the center of the old general store and a long pipe to the chimney to get the most heat from it. Steel takes quite a bit of heat.

Now that sounds too hot. I've never had my brick chiney so hot that I could not lean against it easily. Right at the thimble it may be very hot, but the mass of the chimney itself will usually absorb and diffuse the heat safely. This is hte portion that is in touch withthe rest of the house, like the framing.

Friend no. 1 is an idiot. Clay linings have been fired at much hotter temperatures than your flue will normally see. What you don't want to do is heat and cool rapidly, but they are made to take a LOT of heat. http://www.sandkuhl.com/html/chimney_products.html Clay Flue Liners
A flue liner moves smoke and gases, created by a fire's combustion process, safely and efficiently from a home's fireplace. To do this effectively over the life of a home, the flue liner must be able to withstand excessive heat, chemical attack, thermal cycling and thermal gradients. Sandkuhl Clay Works' flue liners easily endure temperatures in excess of 1500F. They are unaffected by the acids and other chemicals created by the combustion process. Exposure to harsh outdoor conditions at the top of a flue is no problem for Sandkuhl Clay Works' flue liners because the materials are engineered for less than 2% water absorption. This prevents spalling due to freeze-thaw cycles. Many materials cannot with stand temperature differences between inner and outer surfaces (thermal gradients) without failing. Ceramic flue liners are designed specifically with this in mind.
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Edwin Pawlowski wrote:

Good post but...
A properly constructed masonry chimney will not touch any framing. At least not in the few constuction manuals I have read. They specified a 2" clearance minimum. I don't know what code calls for.
Harry K
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snipped-for-privacy@hotmail.com wrote:

Isn't it better that the heat goes into the room rather than up the chimney?
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Thanks everyone for the good information. I feel a lot better about my stove now.
One more question...
In googling around the web for information on wood stoves, I read that wood heat is notorious for sending excessive heat up the chimney.
Is there any sort of device available that you can insert into a standard 7-inch stove pipe that will allow you to recover more heat from the escaping exhaust? I would suspect that such an invention would involve a fan. I can't seem to find anything like that on the Internet.
Perhaps this has been tried but was found to restrict exhaust flow too much?
Maybe a simple fan pointing directly at the pipe would be worth while.
Thanks all.. ..sd
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On 15 Jan 2007 16:22:37 -0800, snipped-for-privacy@hotmail.com wrote:

Fire-places are decorations, not heat sources, but a wood stove should capture anywhere from 50% to 70% of the heat content of the wood, without even trying. I've seen systems that CLAIM up to 85%, but I'm not sure I trust that.
The most common way to extract more heat from a woodstove is to put it as far away from the chimney-stack as possible, and run pipe overhead between the two.
If you really want to go nuts, you could clamp/glue an aluminium or steel fin the length of the pipe. And painting it black might help, if it's not already.
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