Wood stove impossible to maintain adequate burn temp

[bbacharach]

Hello.
I'm dealing with a conundrum, which I may have figured out, but Im not positive. I'm hoping someone on here will
be familiar with my problem.
I have an older King circulator wood stove. I have a two foot 6" stove pipe coming out of the stove into an 8" adaptor. From there the 8" stove pipe travels approximately 12 or 14 feet straight out through the roof. The stove wants to maintain itself around 250 degrees. In order for me to get it up to temperature I have to open up the air vent door on the ash door. Once it receives that extra air, the stove slowly builds into a raging inferno, so then I have to shut it all down. It seems like its either full throttle or I'm slamming on the brakes. I'm guessing the 8" pipe two feet above the stove is just too much flu for this stove. Is this a correct assessment of the problem? I want to be sure before I engage in any unnecessary projects. I appreciate any thoughts or opinions.
-Branden

 

[Jan Pijpelink]

Do you know the moisture content of your wood?

 

[EatenByLimestone]

With an air vent in the ash door, is this a coal stove? Can you post pics of the stove and chimney?

 

[Corey]

Good points above. Moisture content is a big key and Pics and more description would help. You're essentially saying ~16 feet of straight flue, so that should be fairly decent - certainly not the worst set-up we've heard of.

'Air through the ash door' (assuming coming in under the fire) is a very powerful accelerant for the fire and will get it burning very hot. (that is how old coal forges work). Then you say you 'shut it all down' so yes, that would seem like 'hitting the brakes'.

A wood stove will typically take 10-15 minutes to fully react to your air change and fully adopt a new burn rate. So if you are making changes faster than this, you may be causing the issue yourself. Instead of 'shutting it all down', you might try to reduce (or open) air in stages.

Also, a 'fresh' / new fire will be fairly easy to flair up and also fairly easy to snuff out. (assuming lots of kindling and small wood burning here). Once you get a good coal bed and get into bigger logs, the fire will be more stable in how it burns.

 

[Prometeo]

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[bbacharach]

Thanks for all the responses. Sorry I was kind of brief in my description.
The fire wood is a mixture of probably 6 month and 1 year old. Some of it certainly has a higher moister content than desired. I've been burning wood for 12 years with a different stove with similar wood without this problem. We used to have a vermont casting, hence the 8" flu. I had this stove in the garage and was working fine with actually a shorter chimney pipe and more elbows, but we had a baby in the past year and so I moved this stove in because its so much safer with the tin cowling.
There is a tag on the back that says to burn wood only in this stove. The door on the right side opens and there are two doors, one for the burn changer and then one below for the ash pan. The ash pan has a small flap door that opens when the outer door is opened. For super extreme air flow the ash door can be opened, and yes it is a major accelerant. Makes it very easy to start and restart fires.

Maybe I am reacting faster than the stove can react, I'm not sure though. This problem will occur even when there is a large bed of coals with 3 or 4 logs that have been in the stove for at least an hour. Sometimes I can get an over burn by just turning up the air intake, plus it doesn't just get over hot, it audibly roars. So then the thermometer starts climbing. Then I'll turn down the air intake to half way, which then causes the roar to grow even louder and gives every indication its getting worse. If at this point the thermometer is saying something like 700 with a continued roar, I close down both dampers, shut the air intake all the way down, and leave it like that until it calms down. Once its back down to moderate temps I'll open it back up with the one damper 1/3 closed say, the air intake 1/2 or 3/4 open. At this point probably the temp will just continue to drop down to 150 or 250 and just maintain itself there. So then attempting to get it back to 400 or 500 I open it up again and so begins the cycle.
This is the third wood stove I've had in the house. Even a wood stove that I made out of wheel rims for my shop seems to modulate better. I'm quite perplexed. I've wondered if this stove just cant work well with the adaption to an 8" pipe. Might it be better if I do the adaptor up at the ceiling? If necessary I could even run 6" black wall right down the inside of the 8" triple wall, spacing it so it doesnt toutch the insides of the triple wall.

 

[bbacharach]

An additional detail I should add on the behavior of this situation.
When the stove pipe temp is maintaining at 150, opening up the air intake all the way will do nothing to increase the temperature. Much of the time the only way to increase temp is by opening the flap on the ash door. Its kind of like trying to thread a needle with frayed thread to get it to stay around 400.

 

[Prometeo]

I have a jotul 500 ( no cat )
If I open ash door it help me in starting and when recharge, to obtain soon big fire and then i close it.
Even in my case, closing ash door, often the fire goes down, so i have removed 2 screws down the framework of the ash pan, in this way I have always small primary air active and is a good compromise in my case.
I understood that in my stove little primary air is essential for the flame otherwise in some circumstances I risk having secondary air in the upper part but without creating a flame!
cooling the stove only !

 

[appointed EPA deviant]

Is the auto air damper on the front of the stove working properly? When I ran one of these I would open the damper on the ash door just at start up then close it and use the bi metal controlled damper on the front of the stove to feed air to regulate the size of fire.

Also you could try a key damper in the 6" pipe to slow the draft up the chimney.

 

[appointed EPA deviant]

the chain may be disconnected as in this pic

 

[Eman85]

I had a stove like that years back in my shop. As above post check the operation of the air control. I remember it had a chain and a spring on it to help regulate temperature I ran a 6" pipe on mine.

 

[bbacharach]

Since my last post I changed out the 8" stove pipe to 6" pipe, so now I have about a 5 foot run of 6". This has made a radical improvement. to my problem. I'll carry on through the winter with this setup. Come spring or summer, I'm going to run 6" single wall down through the 8" triple wall so all 15 feet will be 6". I'm fairly confident that the stove will run excellent then.
Thank you to everyone for chiming in.
-Branden

 

[bbacharach]

As far as I know my air control is a manual open and close knob. Alteast has always operated as such.
I will check to make sure I'm not missing something there.

 

[Jan Pijpelink]

Since my last post I changed out the 8" stove pipe to 6" pipe, so now I have about a 5 foot run of 6". This has made a radical improvement. to my problem. I'll carry on through the winter with this setup. Come spring or summer, I'm going to run 6" single wall down through the 8" triple wall so all 15 feet will be 6". I'm fairly confident that the stove will run excellent then.
Thank you to everyone for chiming in.
-Branden

I am not an expert, but I think it is not up to code to run a 6-inch stove pipe all the way inside an 8-inch chimney pipe. Somebody, please correct me if I am wrong.

 

[appointed EPA deviant]

I am not an expert, but I think it is not up to code to run a 6-inch stove pipe all the way inside an 8-inch chimney pipe. Somebody, please correct me if I am wrong.

I think the OP likes the shroud design of the stove so maybe a 8" pipe to shroud around the 6 ' is his objective.
As long as the code is maintained where the pipe exits the room,

 

[bholler]

I am not an expert, but I think it is not up to code to run a 6-inch stove pipe all the way inside an 8-inch chimney pipe. Somebody, please correct me if I am wrong.

It absolutely is not. It may be safe but not code compliant

 

[bholler]

I think the OP likes the shroud design of the stove so maybe a 8" pipe to shroud around the 6 ' is his objective.
As long as the code is maintained where the pipe exits the room,

But stove pipe can't run through a chimney. And unless the prefab chimney manufacturer allows it even a stainless liner can't be run through the chimney

 

[bbacharach]

Thats interesting. I usually understand where code is coming from. If it can be safe, why is it against code, or is that just a silly question.

 

[bholler]

Thats interesting. I usually understand where code is coming from. If it can be safe, why is it against code, or is that just a silly question.

Because it hasn't ever been tested in that application. You are dealing with a UL listed chimney system. Because of that you have to follow that manufacturers instructions. If they havnt tested a scenario to verify that it's safe they aren't going to tell you it's ok to do.

 

[bbacharach]

Ah ok that makes sense. I actually acquired the idea from a friend of mine that did this exact thing. For whatever interest it is to anyone, he said it worked fine.

 

[bholler]

Ah ok that makes sense. I actually acquired the idea from a friend of mine that did this exact thing. For whatever interest it is to anyone, he said it worked fine.

As I said I don't nessecarily see a safety issue with it. (As long as the pipe is stainless in the chimney). It's just a matter of testing and certifications

 

[1kzwoman]

I wonder about insurance coverage if using the untested stainless steel system inside a chimney. I would doubt the installation would be underwritten, that would end my interest in such an installation.

 

[coaly]

Hello.
I'm dealing with a conundrum, which I may have figured out, but Im not positive. I'm hoping someone on here will
be familiar with my problem.
I have an older King circulator wood stove. I have a two foot 6" stove pipe coming out of the stove into an 8" adaptor. From there the 8" stove pipe travels approximately 12 or 14 feet straight out through the roof. The stove wants to maintain itself around 250 degrees. In order for me to get it up to temperature I have to open up the air vent door on the ash door. Once it receives that extra air, the stove slowly builds into a raging inferno, so then I have to shut it all down. It seems like its either full throttle or I'm slamming on the brakes. I'm guessing the 8" pipe two feet above the stove is just too much flu for this stove. Is this a correct assessment of the problem? I want to be sure before I engage in any unnecessary projects. I appreciate any thoughts or opinions.
-Branden

When you understand what makes the stove work, you will be able to troubleshoot the problem. The hot rising gases moving up the chimney creates a low pressure area, or vacuum that allows the higher atmospheric air pressure outside of the system to PUSH into the air intake of the stove, feeding the fire oxygen. This low pressure area is measured as draft. The hotter the gases inside the chimney, and the colder the outdoor air becomes, the stronger the draft. When flue gases are allowed to expand into a larger area they cool. From 6 to 8 is almost twice the diameter, dropping the flue gas temperature almost in half. This drop in temperature reduces NET draft. It also allows creosote to form in the cooler chimney flue. By increasing the intake area, you are allowing a larger square inch area for the atmospheric air pressure to push in, feeding the fire more oxygen. By using a 6 inch insulated chimney, less heat is needed to be left up, making the stove more efficient.

If using a flue damper of any type, this slows the velocity of rising gases in chimney decreasing net draft. The more efficient the stove, the more critical chimney sizing becomes.

Homemade, or older stoves that lose a ton of heat up the chimney creates a much stronger draft to overcome insufficient chimney issues.

 

[begreen]

Come spring or summer, I'm going to run 6" single wall down through the 8" triple wall so all 15 feet will be 6". I'm fairly confident that the stove will run excellent then.

Single-wall stovepipe can not be installed inside of chimney pipe.

 

[coaly]

Since my last post I changed out the 8" stove pipe to 6" pipe, so now I have about a 5 foot run of 6". This has made a radical improvement. to my problem. I'll carry on through the winter with this setup. Come spring or summer, I'm going to run 6" single wall down through the 8" triple wall so all 15 feet will be 6". I'm fairly confident that the stove will run excellent then.
Thank you to everyone for chiming in.
-Branden

The single wall inside the larger chimney is still air cooled. That causes excessive temperature drop. Chimney pipe has an insulation wrap around the inner flue that is needed to maintain the correct temperature. The constant wetting of inner pipe from condensing rusts steel pipe away quickly requiring stainless.