Flue temp

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BrownT10

Member
Jun 1, 2021
136
Massachusetts
I know there have been some threads on flue temps, but wanted to try to get some info. I am running the Osburn 3300 and am running a surface temp reading of about 400° to 450° on the Rutland burn indicator. The pipe is single wall 22 gauge so imagine the actual flue temp roughly 1.7 or 2.0 times that? I actually put in a key damper and have damped it down about 2/3 closed. The stove top temp is cruising at about 625° with the air fully closed and the secondaries doing pretty well. I have a half load of oak cutoffs in the stove now. Do these stove pipe temps seems reasonable or too high? Not sure how I could get them any lower, but definitely higher than what I got on the old Defiant. The pipe isn't crackling or popping or anything. Thoughts?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,867
central pa
I know there have been some threads on flue temps, but wanted to try to get some info. I am running the Osburn 3300 and am running a surface temp reading of about 400° to 450° on the Rutland burn indicator. The pipe is single wall 22 gauge so imagine the actual flue temp roughly 1.7 or 2.0 times that? I actually put in a key damper and have damped it down about 2/3 closed. The stove top temp is cruising at about 625° with the air fully closed and the secondaries doing pretty well. I have a half load of oak cutoffs in the stove now. Do these stove pipe temps seems reasonable or too high? Not sure how I could get them any lower, but definitely higher than what I got on the old Defiant. The pipe isn't crackling or popping or anything. Thoughts?
That is definitely on the high side. Not an over fire yet but right on the edge. Can you tell us about the chimney setup and how you are operating the stove? What size are your "cutoffs"?
 
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BrownT10

Member
Jun 1, 2021
136
Massachusetts
I have about 4' of stove pipe into a class A tee that dumps into a 8x12 masonry chimney about 25' from stove pipe to top of chimney. After I posted the temps started to drop to about 350° reading the gauge. I am wondering if the thermometer is off, but don't really have something to check against at the moment.

The oak cutoffs are basically end pieces from all or the pieces I needed to recut to fit into the stove. They are cutoffs from 3"-6" splits basically
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,867
central pa
I should also mentioned that the stove pipe is 22 gauge solid pipe if that matters
It doesn't matter. At what temp did you start shutting the air back?
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
Didn't start until it was 450° or a touch higher. The flue definitely heats quick with a top down fire and the stove top takes some time. I kept the door open for a few minutes and it was running pretty good before shutting the door and still keeping the flames stable. Maybe I should turn the air down sooner even though firebox is slow to catch up. I will try turning down sooner in small increments and that will increase the firebox temp. What temp do you recommend turning air down? How do you operate yours?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,867
central pa
Didn't start until it was 450° or a touch higher. The flue definitely heats quick with a top down fire and the stove top takes some time. I kept the door open for a few minutes and it was running pretty good before shutting the door and still keeping the flames stable. Maybe I should turn the air down sooner even though firebox is slow to catch up. I will try turning down sooner in small increments and that will increase the firebox temp. What temp do you recommend turning air down? How do you operate yours?
Start shutting back a lot sooner. Don't pay attention to the stove top temp it is much slower to respond.
 

begreen

Mooderator
Staff member
Nov 18, 2005
91,319
South Puget Sound, WA
Try shutting down the air a quickly as possible without shutting down the flame.
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
Just loaded up stove this morning and pipe temp is steady at 450° with pipe damper pretty much closed, except for the holes that still allow flow. I loaded up the firebox and the air was shut down and secondaries are strong and stove top is cruising at 700°. Not sure why these pipe temps are this high bit probably need to verify with an IR gun.

Also, I have flames and secondaries going at the top of the firebox and no flames near the bottom. I assume this is ok? See pic

16355105583791022724183549743935.jpg 16355105849282676991841613549122.jpg
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
Also, reading on the flue this morning was 250° with just a bunch of coals. Doesn't seem like that reading could be maintain with reloading the stove?
 

clancey

Minister of Fire
Feb 26, 2021
2,033
Colorado
BrownT10 in post 9---I am going to try out my newly gained knowledge about the flames in your stove---I could be very wrong not very knowledgeable with stoves as of yet just a old woman who lite one for the first time yesterday--lol Those flames are up top in the picture because of the tubes.. Now if I am wrong I sure hope someone corrects me and i just bet that you have one of those window cleaners when the hot air comes around and keeps your glass clean--could be wrong just guessing here.....old mrs clancey
 

Highbeam

Minister of Fire
Dec 28, 2006
19,529
Mt. Rainier Foothills, WA
If that flue meter is accurate, it's too hot. Try swapping the stove top meter with the flue meter and see if they read the same.

To avoid this issue of inaccurate and slow to respond magnetic surface meters and also the lack of precision measuring internal flue temperatures on the surface, I purchased an auber electronic probe meter for my single wall chimney in the shop. I still have the old surface magnetic meter so I can see how much slower and variable the surface temp reading is compared to the actual probe meter readings.

I recommend being much more aggressive on slamming that key damper fully closed and keeping your surface meter readings under 400. Not much to be gained over 400.
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
I think I have a couple of things going on here. First really strong chimney draft which I believe the key damper can handle. Last night I noticed that with the key damper closed and the air intake closed down all of the flames seems to be feed from the front and head right out through the stove pipe this driving those temps up. When this happens the secondary burn isn't stable like I would anticipate. I think it is because there is too much air being sucked into the stove. Even with the air closed down, there is a decent, maybe quarter sized hole in the plate and another half moon opening. I am thinking of puttinga piece of foil tape over the larger hole and monitor it.

I did read another post about an SBI user experiencing this but not sure that the solution was. Anyone here have experience with too much air being pulled in with a strong drafting chimney? I also plan on checking the door gasket and that the door is tight enough creating a good seal. Boy, my old VC Defiant sitting there in the corner is killing my.
 

greengiant

New Member
Oct 18, 2021
2
Northern Vermont
I believe you are simply putting to much wood in your stove for this time of year. I would try to keep a small fire using no more than three sticks of wood burning. I don't like a damper in stovepipe, best to control fire by closing off air intake or building smaller fire. Just my thoughts !
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
That was my other thought too. I was going to try building smaller fires as you say and try to master it so to speak. These conditions are not the best for burning anyway and maybe that is some of the issue. Just concerned that draft will be even stronger and I will have more of an issue in cold weather. Raining and 60 today so will clean stove out and check door gasket and wait until colder weather. Ideally I would rather avoid a key damper, makes it simpler to operate if not needed.
 

Woodcutter Tom

Burning Hunk
Apr 28, 2019
179
Northern Illinois
I have discussed excessive draft with SBI. I was getting extreme temperatures in my flue. (1000 - 1100 degrees). I purchased a manometer and learned my draft was at times around .2 inches of water column. The ideal measurement is .02 - .05 inches. I was way over that. The result was high flue temps and low stove temps. All the heat was rushing up the chimney. At the end of last season I experimented with different damper set ups.
I decided to start this season with one damper assembly in my double wall stove pipe. I was going to try to restrict the secondary air with a sliding plate over it's air intake. I have made a 1/2 dozen fires and am realizing that the way to slow draft is dampers. It has been 50 degrees here and I have to have the damper closed all the way to reduce the draft to the appropriate level. I have been getting lower flue temps and higher stove top temps. These fires have not been full loads.
Closing the secondary air intake does not reduce draft; it just reduces the air flow into the secondary tubes. Air will still be sucked into the stove; thru the primary air intake since that is never fully closed. Mine has a nickel sized hole that opens as the intake lever is moved to the fully closed position.
I experimented with two key dampers in a single wall stove pipe last spring. At that time it was about 30 degrees when I started my fires. It was difficult to control the draft even with that high outside temp.
It is looking like I will purchase a new solid piece of double wall pipe and install two key dampers in it. I also will buy a new 12-18 inch telescoping section and install my damper assembly between it and the ceiling adapter. Thus three dampers. I believe this will help with the different outside temperatures.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,867
central pa
That was my other thought too. I was going to try building smaller fires as you say and try to master it so to speak. These conditions are not the best for burning anyway and maybe that is some of the issue. Just concerned that draft will be even stronger and I will have more of an issue in cold weather. Raining and 60 today so will clean stove out and check door gasket and wait until colder weather. Ideally I would rather avoid a key damper, makes it simpler to operate if not needed.
I would recommend taking some more time to learn the stove and setup before changing anything. Your temps are on the high side but not dangerous by any means. I think with larger pieces of wood shutting down sooner etc you can probably get it working better. If not then try a second damper or restricting the intake.
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
Thanks for the info. I certainly intend to learn the stove before doing too much. The thought of multiple key dampers sounds like a PITA. I would rather learn the stove and limit fuel load to start. I mainly burn red oak right now and some of the splits are on the bigger side, but less than 20% MC and catch fire pretty quick. I will keep at it
 

clancey

Minister of Fire
Feb 26, 2021
2,033
Colorado
I still need to bake my bread and test my temperature gauge...Because my first lite new stove took off during the burn and went up to 800 degrees and then it seemed to calm down as it burned could this be because of the surrounding temperature outside about that time 70 degrees and my stove person put in to start about 6 split pieces of wood oak kiln dried 16 inches and stack it up sideways on top of other pieces then he lite it . Could it be because of the temperature outside and all that wood to burn at that time? Just wondering here and still need to test my gauge in the oven and see if they are about the same for my stove is pretty darn good and exact. old clancey
 

Highbeam

Minister of Fire
Dec 28, 2006
19,529
Mt. Rainier Foothills, WA
I still need to bake my bread and test my temperature gauge...Because my first lite new stove took off during the burn and went up to 800 degrees and then it seemed to calm down as it burned could this be because of the surrounding temperature outside about that time 70 degrees and my stove person put in to start about 6 split pieces of wood oak kiln dried 16 inches and stack it up sideways on top of other pieces then he lite it . Could it be because of the temperature outside and all that wood to burn at that time? Just wondering here and still need to test my gauge in the oven and see if they are about the same for my stove is pretty darn good and exact. old clancey
Testing your gauge that way is false. The gauge was designed to read the surface temperature when it is on top of a stove in room air. Not dunked in boiling water or in an oven.

The common way to test the surface meter is with a known accurate meter or an IR point and shoot temperature gun.
 
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Highbeam

Minister of Fire
Dec 28, 2006
19,529
Mt. Rainier Foothills, WA
Can you recommend a few for me to check out? Would have to order these online...thanks highbeam..clancey

The IR guns are lots of fun. I have a ryobi brand one from the Home Depot but I believe there are many brands including something from harbor freight. Be careful to make sure the meter reads high enough, mine only goes to 600 but I like to run my noncat much hotter.

You can also use it for everything from identifying hot breakers in your electric panel to looking for a dead cylinder on your truck engine.

Or use the laser to play with a cat.
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
After spending some time learning the stove and believing I have really strong draft, I need some guidance on what phase of the loading/initial burn to start to close the flue damper? I never had to ise on on my old stove, but probably should have. I can hear the draft ripping through the class A section of pipe before heading into the masonry line flue. When I close the damper there is a considerable amount of draft trimmed.

I had a fire ripping pretty good and cannot achieve lazy flames. I qIuld love to avoid using the key damper but sometime get these somewhat runway fires.

I had a bunch of coals that I burned down some but tried raking everything to the center and put a split on either side n/s and them 4 e/w on that and it took off pretty quick. The flue temps jumps quick and wondering if I should partially close key damper before hitting a certain flue temp before it jumps?

Maybe, I should try packing the load tightly to avoid excess air working through the load and causing it all to off gas at once?

Anyone using a key damper on a non cat stove with excessive draft? What are your general procedures?
 

BrownT10

Member
Jun 1, 2021
136
Massachusetts
I should mention that I have had pretty good success pretty good temps, but this one definitely got away a bit. The secondaries are raging and can't seem to really get the lazy flames I read about on here.