Is a 500 degree stack too hot?

[Razo]

Hi guys,

I just started burning some shoulder fires over the last few days to get acclimated to my stove. I have an all nighter mid mo with front draft controls and a key damper in the my flue. This is the first wood stove I've ever owned or operated.

I am getting the hang of it pretty good, getting the air turned down to get a fairly steady burn while keeping it a clean fire. So far so good. I got 2 magnetic thermometers, one for the stove, one for the stack and I double check it with my infra-red thermometer.

What I noticed is, the stove temp gets going good, up in the 500 degree range, and sometimes up in the 600 degree range, the stack however, gets hot much faster. I have found myself having to control the amount of air entering the stove not because my stove was getting too hot, but because my stack was getting too hot.

The stove is built like a tank, I have no fear that it will over heat, and if it did for a short period of time, I would have no doubt it could handle it. The 24ga seamed stove pipe gives me some worry though. My Condar stack thermometer claims that 225 degrees to 475 degrees is the ideal temp for the flue.





My stove top thermometer claims that 400 to 650 is an idea stove temp. I'd like to run at the top end of that, around 600 or 650 to maximize heat output. The problem is, if I try to build the stove temp to 600, my flue temp wants to creep up around 500. I have the key damper set to about half closed but it still occurs, and have the air down enough to keep it controlled, but open enough to try and build the stove temp.



Another thing I noticed, does the paint on the stove pipe have to cure over the course of a few fires just like stove paint? The stove is well cured since it is used but I noticed a faint paint smell and a little smoke off the stove pipe when I had my first fire. Also, when I got the stack to 500 degrees, I noticed the paint on the stove pipe looks duller now, almost like flat black instead of semi gloss. Is this a normal process? I have since kept my stove around 500 degrees which keeps the stove pipe much more happy, around 400 degrees. Once I see that stove pipe temp climbing it really bothers me since its just thin sheet metal with a snap seam.

I know I was long winded but I guess what I'm asking is if you guys experience the same thing, having to adjust the fire based more off of flue temp than the stove temp. I find myself just watching the flue temp, and having to deal with whatever temp the stove happens to be to keep the flue temp happy. Is a 500 degree flue temp nothing to really be worried about or should I really try to keep it at 450 max?

Here is a pic of my setup:

 

[fbelec]

other than your stove your brick work looks like my setup. i'm not a all nighter expert but sounds as if your doing all right. keep your stove happy and running like it should and you should be ok in the chimney dept. as long as you don't have a creosote problem 500 will keep it good but if you have buildup and pop the pipe temp up you might touch off a creosote fire in the chimney. after 2 weeks of burning check out your chimney and pipe. if nothing looks like shiny tar you doing fine. just keep a eye on your chimney until you get the hang of it so nothing gets bad. once you get to know your setup you can make adjustments

frank

 

[Osagebndr]

Sounds good to me also. There's another thread in the newer wood stove forum on this, it may put your mind at ease. Do your flue temps stay at 500 for long periods or does it fall after your stove settles in. I notice I'll run at 350-500 for short period of time until my stove settles down and stay at 250-350 for a while during the better part of my burn cycle. Takes a min to figure out the air and every fire is different

 

[coaly]

Stove pipe temperature depends on chimney flue size, height and insulation. (inside / outside chimney) The object is to prevent condensation of water vapor and creosote accumulation all the way up. 250* f. is condensing temperature to stay above. (all the way up) More than that is waste. So 350 may be optimal with an insulated interior chimney the same size as flue outlet (which it should be) and double wall pipe allows even less waste keeping flue temp higher where it enters chimney. A larger oversize flue requires much more heat (and fuel) to create the same amount of draft. So your question relates more to the heat required for your chimney, more than stove make or model. Heat output required (stove temperature) should be adjusted for heating need.
Paint will dull. White is getting hot, but not uncommon.
If you can see any part of stove or pipe glow, it is over fired.

Here's a normal color, due for paint..... ;


Once you have optimal chimney, for the stove as made, you have an idea of stove efficiency. Stove temp vs. flue temp. As the stove is made more efficient, (interior baffle / damper setting) a pipe temperature 1/2 of the stove top is achievable. (with the stoves I've tested and modified)

Most of the Fisher Forum can pertain to your stove as well. Check out the baffle thread which was what was used in double door stoves and I adapted to the single door stoves to prevent excess heat going up the stack and radiates heat forward.
https://www.hearth.com/talk/threads...d-fisher-more-heat-less-smoke-under-25.74710/

 

[Razo]

Thanks guys!

 

[begreen]

Sounds pretty normal for an older stove. Is the sloped face the hottest location of the stove top? Have you tried other locations like the flat lower portion of the stove top, just before the sloped face?

 

[Razo]

Have you tried other locations like the flat lower portion of the stove top, just before the sloped face?

You know what I'm not sure, it certainly would be a good idea to test with the other 2 flat faces to see if they are in fact hotter than the sloped face. I'll cross reference it with my IR thermo too so I can even take readings on all 3 areas during the same fire.

Over the weekend I was able to get the stove working almost exactly how I would want it to. The key for me was getting a nice roaring fire going, flue pipe up to almost 500 while the stove was still a bit cooler, then close my key damper practically the entire way, turn the air inlets to about half closed and let her cruise. At that point, the flue would gradually come back down to around 300-400 but the stove would climb up to that 600-650 area I like. Once those settings were achieved, they would hold pretty much hold steady there for about 3-4 hours. This was using soft maple and pine. I plan on mimicking this technique once I tap into my harder woods like white ash and black birch throughout the winter. I'm guessing I'll be able to maintain that "cruising zone" slightly longer using the same techniques but harder woods.

 

[begreen]

Just a guess but it wouldn't surprise me if the lower flat was a bit hotter. Your technique sounds just right. I used to close the key damper off on the Jotul once the fire was strong. Even with it all the way closed it is still passing a portion of the flue gases.

 

[Razo]

I checked last night at various stages of the fire.

Both the sloped area where I have the thermometer and the flat area in front of it alternated as the hottest area of the stove. The upper flat area was always cooler than the other 2 locations. For now I'm going to keep it on the sloped area since its easier for me to see at a glance but I'm going to keep in mind that the front flat area could be up to 100 degrees hotter at any given moment. Seemed when the fire was active, the sloped area was hotter but once I got down to charcoal, the flat area was hotter.