What is the hottest your chimney has gotten up to?

I was reading the code rule book where it says something like 'no wood touching the chimney, old dry wood can ignite at 200-250 degrees', now this worries me because I have an unlined chimney in an old house and the wood is right against the chimney in many places. The spot I worry about the most is where the chimney goes through the attic floor, this is at least 25' above where the stove pipe goes into the chimney. I always thought that the chimney will be pretty cool burning strictly anthracite, maybe 100 degrees or so, am I wrong?

Your right, unless you have a chimney fire. But you won't have one of those unless you burn wood.

Our chimney goes right thru the center of the house with the framing almost touching it or touching it in spots. Our chimney, if built when the house was (1890) is also unlined.

My inner temperature of my exhaust pipe, when burning really hot is around 220-270 (max) degrees, the outer is much, much cooler. Maybe 100-120 degrees. The bricks are only slightly warm to the touch, but only at the bottom where the exhaust goes into the chimney, it would gradually get cooler as it goes up.

All cases are different, but that was my concern too! Also, my pipe is really close to my ceiling/First floor rafters, I just put a piece of sheet metal with an air gap and it is cool to the touch.

As you can see, I am less than 6" from the rafters, I have some sheet metal and a old road sign to deflect the heat. This was the only place I could hook it up.
http://nepacrossroads.com/files/temperatures_127.jpg

So far been runing for 2 months 24/7.

The temperature within the chimney is one concern, but the larger problem venting the stove into on older, unlined chimney is the possibility of exhaust gases leaking from the chimney through any mortar that may have crumbled and fell out of the joints. This is a very real danger! I hope you have a working CO detector. Since the chimney is enclosed in the structure, inspecting from the outside is difficult. Some chimney specialists have cameras that they can lower into the chimney to check for faults in the mortar, etc. Years ago a relative had to have a liner installed in an old chimney. She had heard thud sounds from the wall where the chimney was located, it turned out to be bricks falling inside the chimney!

he's right, just line it. and dont wait. i wouldnt be able to sleep in that house...

"unlined chimney is the possibility of exhaust gases leaking from the chimney through any mortar that may have crumbled and fell out of the joints"

complete nonsense, extreemly unlilky first that any mortar would "fall out" if your chimney is in halfway decent condition and second, should that happen especially with an interior chimney you will basically, outside of a chimney fire (not possible w/ coal) never have exhaust gasses exiting through that gap. the chimney is under negative pressure untill the last few feet.

I had a friend, long deceased [from natural causes] that had an old house with a very poor chimney. The chimney was in the center of the house, and had some loose mortor joints. I commented on the mortor joint, and he said, that's nothing look at this. He opened a closet next to the chimney and in the dark closet you could see the occasional flame through GAPS in the mortar between bricks in the chimney.

Now, he NEVER had a fire in the place when he went to bed or when the house was unoccupied, but I thought he was crazy. But when we 'discussed' the situation, he asked me: have you ever seen smoke or smelled smoke or fire in the house. I have a sensitive nose, and I had to admit, I had never smelled anything

He said: See, there is a strong draft pulling air into the chimney from the house, that's why you don't ever smell smoke!!. It's all under negative pressure.

He always had old cast iron cook stoves or parlor stoves using this chimney. It wasn't a fireplace, just a chimney.

I ran across a virtual 'steal' on some SS package chimney from a bankrupt woodstove store, so I installed a new chimney in his old place and then he ran a fire around the clock..


Greg L

hehe mine isn't bad, it just doesn't have a liner. Some of the bricks near the roof have a black coating on them, the chimney "expert" said it was creosote that had seeped through the mortar and the chimney is probably plugged solid. Well I took a look in there and I can see brick the whole way up, no creosote at all, none, and rightfully so I talked with the old lady that lived here in the old days and they never had a wood stove or fireplace- ever. The "Creosote" is just moisture that has condensed on the mortar in the attic, I scraped off about 1/32" and it looks like new again. The experts worry that in a case of positive pressure like a plugged chimney the CO will leak through the mortar if it isn't perfect, well I says that in the event of a plugged chimney the house is going to fill with smoke anyway. I do understand that in the event of a chimney fire an unlined chimney is unsafe.

Our chimney has been venting the Hot water tank and furnance for ?? how ever many years. I know it draws good, It can hold a piece of paper on the inlet pipe. I have since disconnected the hotwater vent (electric tank now) and the furnance only runs when the coal stove is off....seems to work.

Yes, I have CO's on every floor and by the heat vent, in case of a cracked heat exchanger from the furnance (old Janitrol convection type) or any CO that might come out.

There is a good possibility of getting exhaust gasses back into the house from an unlined chimney. First, if the chimney is unlined it generally is in a older home, which is not airtight like newer homes. That being said, if there is a wind blowing, creating a negative pressure on the leeward (all those sailing courses paid off) side of the house, it can draw air from the house. Now, if that old chimney has missing mortar joints or missing bricks (both of which I have seen), and given that most coal stoves have a 6" collar (26 sq. in. cross sectional area) being vented into an unlined chimney (a small one having 64 sq.in. cross sectional area, or more). And given that most coal units put very little heat (or lift) into that chimney, then it doesn't take much to get a draft reversal, where the chimney that was venting your stove, now becomes the source for make up air into the home. Other things that can cause that to happen are exhaust fans, dryers, or a strong downdraft.

In the NFPA 211 the old limit for collar size to flue size was no more than three times (ie 30 sq. in. of collar= no more than 90 sq. in. of flue). The new standards are now set at no more than two times the collar sq. in. for the flue sq. in..

I would line it. You can PM me if you want some recommendations on liners, or if you need any advice on how to do it.


Mike

that's all nice, in theory, however, in practice, in interior chimneys it will basically never happen. there is one problem w/ what your theory too, that older homes are more likely to have downdrafts due to "leakyness" this is simply not true, one is much more likely to have a downdraft in a newer home regardless of chimney placement due to it's "tightness".

Berlin,

I would have to respectfully disagree with your opinions. What I stated is backed by local and state building codes, the National Fire Protection Association, and manufacturers. Newer homes are more likely to experience downdrafts from exhaust fans, dryers, etc. But because they are fairly air tight, they are less likely to be affected from winds like an older home. The state of Massachusetts now mandates liners when a new furnace is being connected to an unlined chimney. I would not risk my life, or the life of my family on the premise that something probably won't happen. I bet in the trunk of your car is a spare tire. Chances are you won't get a flat, but you still have that spare.


Mike

I must also disagree. The mortar in a chimney that old is just sand and limestone and it will fall out. I've seen chimneys like that hundreds of times. It should be lined. It is asking for trouble to use such a chimney, especially with coal.

Berlin wrote:that's all nice, in theory, however, in practice, in interior chimneys it will basically never happen. there is one problem w/ what your theory too, that older homes are more likely to have downdrafts due to "leakyness" this is simply not true, one is much more likely to have a downdraft in a newer home regardless of chimney placement due to it's "tightness".

I agree, but you can't get by Complete Heat's signature line...

"better to be safe, than a victim".

Thats why we have fire marshalls and anal retentive insurance inspectors. You can't pay your insurance once your dead.

* rant warning * The reason for code is to limit liability and prevent accidents in every case. I have a problem with "blanket" recommendations. Code says that the chimney for coal must be the same as for wood, which is a fine recommendation for a furnace that can burn both. It doesn't differentiate for anthracite stoker stoves where wood isn't used. Code also says that my wiring is no good, my plumbing no good, my window placement is incorrect, my railing isn't the proper height, my power outlets are improperly spaced, etc... (Thank god for grandfather laws) If a building inspector checks off that a chimney is ok for burning solid fuel then the town or somebody is liable for damages when some jamokie burns pine slabs and used tires and his house burns down. I can verify that my chimney is under negative pressure, I checked it last summer when it was 55 degrees in the basement and 80 degrees outside and it pulled a draft. 8th grade science says that if it is under negative pressure then air will be sucked INTO the chimney through any gaps, not pushed out. But that is a moot point because I repointed it, the mortar is tight. Where I didn't repoint it is because the builders put the plaster walls right up against the chimney effectively sealing it off. Will wind blowing by my house cause a venturi effect sucking air from inside the chimney? It could, but that same wind will suck out all the smoke and CO with it. A large bolt or engine part could fall out of an airplane and plug the chimney just as easily as that happening. An ostrich could lay an egg in there as well. Everything is possible.

My original question was regarding the wood floor joists that touch the brick chimney in the attic and whether the chimney could get hot enough to ignite that when using coal. In the event of a chimney fire those joist could ignite but I'm not burning wood so it won't. I also have smoke detectors and CO detectors on every floor. I'm not ignorant to safety and I don't want to lose my home to save a few dollars, but to fix something that ain't broke just isn't the way I do things. My chimney actually does pass local code because it has been used for coal exclusively and it never had anything else vented into it. I could burn wood in it legally if I wanted to according to the rule book. And if I cleaned it every month and only burned dry hardwood I'm sure it would be completely safe but I'm not going to. I do have a propane furnace but it is direct vented out the wall. Now if the furnace was installed in the chimney and I wanted to switch back to coal then I would be required to line it. Look at who makes recommendations for chimneys, it is interesting. Metal chimney manufacturers and installers are the biggest proponents of lined chimneys. Neither of those people recommend rebuilding existing chimneys with a fresh clay liner because it is too much work for too little profit. If the pencil pushers had their way we'd all have to wear full body condoms before hugging our wives. * end of rant. Seriously though, thanks for caring about my safety. I do appreciate it and have considered everyones input.