Flue Temps?

[kraco14]

Hey all!

First off I want to say that this forum has helped me not only with my decisions on purchasing a stove but also my burning practices. There truly is a wealth of knowledge here.

I've been lurking on this site for a few years and haven't quite found the answer to my question, so I have decided to post to receive personalized wisdom from the folks here.

Although I live in a warm state, my house sits in the mountains and often times we see very low temps during the winter. It's suppose to be close to single digits the next few nights.

After building our house, I had installed a "homemade" stove that was built with plans like that of the old Papa Bear stove. It heated the house great, but I had a chimney fire the second year it was in use. I now know it was because of poor wood and even worse burning practices.

The current set up that I have now is an Englander NC30, in the basement. From the stove, single wall runs about 3 feet up, then makes a ninety degree turn through the concrete basement wall. From there it is exterior Class A chimney that runs, give or take, 30 feet up.

So my question, I believe I am running the flue temps a little hot. In order for the stove to be at cruising temps (550-600), my flue temps, on a magnetic thermometer, jump up to around 500 degrees before I have the stove shut down. Once the stove starts cruising, the temp falls down to around 400-450. Everything that I have read on here says to multiply the surface temp on the flue by 2x or 1.5x. Is this too hot? I have tried shutting the stove down earlier to get the flue cooler, but the stove top temp just doesn't get to where it needs to be. I also have a key damper in the single wall, with having such a tall chimney, but it is more for emergency situations than anything.

 

[St. Coemgen]

So my question, I believe I am running the flue temps a little hot.

First, read this:

http://woodheat.org/thermometers.html

 

[Highbeam]

You're right, that's hot. It's the reason you have that damper. Turn it to slow down that crazy tall chimney.

I have single wall above my NC30 and surface temps are just under half of stove top temps. I run my stove at 700 all the time so pretty wasteful and more heat than usual runs up the flue because of it. Still surface temps of 300-350.

 

[Highbeam]

First, read this:

http://woodheat.org/thermometers.html

I read that article. It is asinine. An oversimplified head in the sand approach that supports the ignorance is bliss method. That site has been long associated with bad, outdated, incomplete information so be careful there.

There are obvious temperatures that are too low in the flue and will lead to condensation and creosote, and there are temperatures that are too high and exceed the flue system rating of 1000 degrees. Both are safety issues that could burn your house down. There is a wide temperature range of goodness in between and you'll only know if you're there with a meter.

 

[St. Coemgen]

I read that article. It is asinine.

Meh. Your opinion.

Based against :

http://woodheat.org/staff.html

What is your professional association in this topic? Care to give your list of degrees and expertise?

I am willing to entertain alternative professional opinions and viewpoints. That is healthy and proper for transparency. But not just average Joe "opinions" or "information" from baloney sources.

 

[Highbeam]

Meh. Your opinion.

Based against :

http://woodheat.org/staff.html

What is your professional association in this topic? Care to give your list of degrees and expertise?

I can make up anything I want too. As I said, outdated and partial, be careful there. As you said, I get my opinion.

 

[St. Coemgen]

I can make up anything I want too.

And, indeed you apparently have done exactly that. With everything, and in everything, regarding all your comments.

I need say no more.

I think that the OP can figure things out from here.

 

[kraco14]

You're right, that's hot. It's the reason you have that damper. Turn it to slow down that crazy tall chimney.

I have single wall above my NC30 and surface temps are just under half of stove top temps. I run my stove at 700 all the time so pretty wasteful and more heat than usual runs up the flue because of it. Still surface temps of 300-350.

That's kinda what I figured. The problem that I have with the damper is that there really is no happy medium. In other words, if I start closing it, it chokes down the fire too much and I don't get the stove top temps that I need. If I don't move it at all, I get the stove top temps that I need but my flue is too hot. I just stopped messing with the key damper for this reason but I will start to experiment with it and see if I can find a sweet spot. Thanks for your reply!

 

[bholler]

What is your professional association in this topic? Care to give your list of degrees and expertise?

I am willing to entertain alternative professional opinions and viewpoints. That is healthy and proper for transparency. But not just average Joe "opinions" or "information" from baloney sources.

well i am a professional with lots of experince certifications ect ect and i totally agree with highbeam i feel running a stove without any thermometer is like driving a car without a speedometer. Sure you can do it but it is far from the best way and you can get yourself in trouble easily

 

[kraco14]

well i am a professional with lots of experince certifications ect ect and i totally agree with highbeam i feel running a stove without any thermometer is like driving a car without a speedometer. Sure you can do it but it is far from the best way and you can get yourself in trouble easily

I guess I can add "fuel to the fire" with this conversation. This is why I had a chimney fire my second year with the "homemade" stove. I had no thermometer what so ever. I had no idea how hot the stove was getting or the flue. Before I knew it, I had burning embers coming out of the top of the chimney....

 

[Squisher]

I regularly see hotter single wall connecting pipe temps than most here seem to get. I regularly get up to 500 on a reload during the off gassing. I will cruise for the whole load from around 400 down to nearly 200 at the end. This is monitored with a auberin unit about 12"s above my flue collar of my summit. So maybe a little bit short. It was very consistent with my magnetic condar thermometer which was stuck on just above the auberin thermocouple. The condar is now on my insert.

 

[kraco14]

I regularly see hotter single wall connecting pipe temps than most here seem to get. I regularly get up to 500 on a reload during the off gassing. I will cruise for the whole load from around 400 down to nearly 200 at the end. This is monitored with a auberin unit about 12"s above my flue collar of my summit. So maybe a little bit short. It was very consistent with my magnetic condar thermometer which was stuck on just above the auberin thermocouple. The condar is now on my insert.

That makes me feel somewhat better. I'm scared to death of having another chimney fire but I'm also scared that I am putting unwanted stress on my Class A. That stuff ain't cheap. Especially if you have 30 feet of it.

 

[Squisher]

I try to stay under 500 during the off gassing. But honestly I've seen 650 before from inattention. The thing to remember with those magnet thermos is that they are relatively slow acting, try to anticipate the climb a little and possibly cut air a little bit sooner.

 

[blades]

Have nc 30 about 15ft flue (main floor) Double wall black to ceiling ( ya I know its not the same as op) apx550-600 stove top- flue wall 250-300 with IR gun Just for some sort of reference. NC30 not the most controllable unit as far as combustion air is concerned due to the 4 different intakes, only one is controlled.
So on your single wall I do not think you are really out in never never land temp wise. Only way to really know what temp exhaust gas is at is with a probe in the middle of the stream.

Course if the flue pipe is glowing a bit reddish with lights out that would be a might too warm.

 

[kraco14]

Have nc 30 about 15ft flue (main floor) Double wall black to ceiling ( ya I know its not the same as op) apx550-600 stove top- flue wall 250-300 with IR gun Just for some sort of reference. NC30 not the most controllable unit as far as combustion air is concerned due to the 4 different intakes, only one is controlled.
So on your single wall I do not think you are really out in never never land temp wise. Only way to really know what temp exhaust gas is at is with a probe in the middle of the stream.

Course if the flue pipe is glowing a bit reddish with lights out that would be a might too warm.

Ok, thanks. I think my main problem is the actual chimney height. Even when I am running with those flue temps, the cap of my chimney is pretty dirty after a years worth of burning. I sweep the chimney from the bottom up and get virtually no creosote for the first 2/3 of the chimney. The last ten feet or so, I usually get some creosote. This also makes me hesitate about lowering flue temps. I just don't want to cause unnecessary damage to the chimney.

I guess I just don't have a "perfect" scenario with my setup.

 

[Marshy]

Have you ever measured your draft?

 

[kraco14]

Have you ever measured your draft?

I'll have to plead ignorance on this one. I'm not even sure how you measure draft.

I would think that if I have a draft problem it would be that it is too stout, but I am far from an expert. I have never had smoke come into the house, regardless of outside temps.

 

[kraco14]

Ok, I figured I would do a follow up because I am still not getting an ideal situation....

I started experimenting with the key damper last night. I found that the more I closed the damper, the less I could close the air on the stove. I still had to have high flue temps in order to achieve a 600 degree stove top. I also tried shutting the air down a little sooner but the temps still reached the same outcome, just a little slower. I am burning 3+ year split and stacked oak. I do not have a moisture meter, so I'm not sure what the moisture content of the wood really is.

I am more worried about damaging the Class A chimney with high temp exhaust. Is this possible with these temps? I'm still getting up to 500 degrees on the single wall and then it is falling through the burn cycle. I have never seen the single wall glowing and there are no combustible materials anywhere close. It's all concrete and there are 10' ceilings.

Is this just the nature of the beast, with a high stack?

Does it sound like a wood problem?

Or is it operator error?

Thanks for your help!

 

[Marshy]

I wouldn't bat an eye, sounds like it's the nature of the beast. Just my opinion, I'm not an expert or have any qualifications in this field though.
One has to question though, what should it be? What is the "standard" or ideal situation you are comparing to? What are the variables between the two and is there a valid reason for concern?

 

[kraco14]

I wouldn't bat an eye, sounds like it's the nature of the beast. Just my opinion, I'm not an expert or have any qualifications in this field though.
One has to question though, what should it be? What is the "standard" or ideal situation you are comparing to? What are the variables between the two and is there a valid reason for concern?

Ok good, thanks. From what I have read on this site, the temps that I have been seeing are a lot higher than what most see on their set-ups. I am nervous about two things. One being a chimney fire and the other is damaging the Class A. If I was doing unwanted damage to the chimney, I do not think I would be able to afford replacing it on the drop of a hat. Although the wood stove is a secondary source of heat for us, it plays a huge role in keeping us warm.

I guess I'm looking at it like any other piece of equipment or tool that I own. If you drive it like you stole it, it won't last very long...

 

[Marshy]

Only way I know of to have a chimney fire is if there is creosote in the chimney that catches fire. If you have a hot flue temperature and well seasoned wood then it's unlikely you will have creosote buildup. You can verify your not getting creosote when you clean the chimney. Chimney fire burn at like 2000F. I'm not familiar with the ratings of Class A pipe but it seems reasonable (might want to verify with your manufacture) that they can operate at a sustained 1000F for normal operation. You could call them and ask what they think given your thermometer readings and how much single wall pipe you have beforw entering the class A to see if they have any concerns. I have not read the thread you mentioned with said take your thermometer temp and use a 1.5-2.0 multiplayer for determining the actual flue temp. That seems overly conservative to me though.

 

[OhioBurner©]

Also magnetic thermometers are notoriously inaccurate. Have you tried to compare it to an IR thermometer or a few other magnetics to see how close they read? You can get IRs now for almost as cheap as a decent magnetic...

 

[Marshy]

Also magnetic thermometers are notoriously inaccurate. Have you tried to compare it to an IR thermometer or a few other magnetics to see how close they read? You can get IRs now for almost as cheap as a decent magnetic...

I agree, harbor freight has non-contact IR thermometers for $30. It would be worth the money to try and validate the mag thermometer.

 

[kraco14]

Only way I know of to have a chimney fire is if there is creosote in the chimney that catches fire. If you have a hot flue temperature and well seasoned wood then it's unlikely you will have creosote buildup. You can verify your not getting creosote when you clean the chimney. Chimney fire burn at like 2000F. I'm not familiar with the ratings of Class A pipe but it seems reasonable (might want to verify with your manufacture) that they can operate at a sustained 1000F for normal operation. You could call them and ask what they think given your thermometer readings and how much single wall pipe you have beforw entering the class A to see if they have any concerns. I have not read the thread you mentioned with said take your thermometer temp and use a 1.5-2.0 multiplayer for determining the actual flue temp. That seems overly conservative to me though.

Ok thanks. I just want to make sure I'm not doing anything stupid with running that high. Thanks for your help!

Also magnetic thermometers are notoriously inaccurate. Have you tried to compare it to an IR thermometer or a few other magnetics to see how close they read? You can get IRs now for almost as cheap as a decent magnetic...

Yes I have compared magnetic thermometers and they were fairly close to each other. I'll get an IR thermometer and see where that takes me. Thanks for your help!

 

[edyit]

easy way to test the thermometer, set it in your oven see how close it comes to what you have your oven set at