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Stove and Flu temps

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Jags, Sep 28, 2006.

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  1. Jags

    Jags Moderate Moderator Staff Member

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    I am a strong advocate of using the 2 thermometer method for my stove. One on the surface and one for flu temps. When running my stove at the high side of its intended output I try to maintain no higher than 700-750 degree flu temps (although is has snuck over that a time or three) and stove temps will run around 600-650. Are these common numbers for "most" stoves? I am running a Quadrafire Isle Royale. Its a pretty good size stove with a 3 cubic foot box, but there is nothing that I can find anywhere on this. I have searched for several years and am quite simply going by my dealers verbal info. It seems to work well because my chimney sweep gets mad at me because he can only charge me for a house visit. Says he wouldn't fill a shot glass with what a sweep would create. I would like to know what you guys use for "target" temps.

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  2. wtyamamoto

    wtyamamoto New Member

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    That's interesting. I have a new to me Buck Model 26 stove. I only had the chance to really run it once with a half load, but at the time, the stove top near the exit ran over 600 at low and the pipe about 3 inches up registered about 350. So I had the reverse of what you had with the flue temp higher than the stove top temp.

    Wayne
  3. Dave_1

    Dave_1 New Member

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    Wayne,

    I'm curious, what manufacture's thermometer were you using?

    Thanks,

    Dave
  4. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    I am sitting here right now watching the little Jotul in my office burn. The stove top temp is 520 and the stack three feet straight up is 250. The laser thermo and the two Rutland mechanical thermos on the stove all agree.

    That is the way it always is with the little EPA stove. With the Sierra pre-EPA a 550 degree firebox kicks around a 700 - 750 flue temp just about the stove.
  5. wtyamamoto

    wtyamamoto New Member

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    I used a Rutland on the stove, and used a Raytek infrared therm with laser indicator to both confirm what the Rutland was saying on the top and to measure what was happening in the pipe. The Raytek confirmed the Rutland on the top of the stove was accurate. On the stove top, the Rutland was right at the base of the step (the Model 26 is a steptop design), in line with the exit - just a few inches away it was down to about 550 or so (i don't remember the specifics as it was a couple of weeks ago).

    I also tried moving the Rutland to the pipe and it registered the same 350ish that I was seeing with the Raytek.

    Wayne
  6. MountainStoveGuy

    MountainStoveGuy New Member

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    Efficiency play a part of low flue temps? lets say you have a 23,000 btu fire and only 25% of that is lost for chimney heat, that would explain low flue temps. Wouldnt a 80,000 btu stove thats loosing the same percentage be hotter? and a old stove that lost up tp 50% be even hotter yet? I would say the hotter the stove, and the lower the flue temps are a direct result of how efficient the stove is working.
  7. MountainStoveGuy

    MountainStoveGuy New Member

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    How tall is your chimney? i would guess its tall and you are overdrafting the stove. You could be wasting alot of heat if you are getting temps that high. A damper would help.
  8. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Yeah I know. But the Sierra keeps the neighborhood so nice and warm.
  9. wtyamamoto

    wtyamamoto New Member

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    I would definitely agree. I never used a thermo with the old stove, so I'm not sure what the temp variation with it was. It was a pre-EPA monster, whereas the Buck is EPA with a little more about a 2.5ish cf box. What was throwing me off though was that I was assuming the Quadrafire Jags was referring to was EPA. If it is, what would explain the reverse situation with his temps?
  10. MountainStoveGuy

    MountainStoveGuy New Member

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    Overdrafting, 20' chimney or something with no damper. The pipe sucks the flue gas out of the stove before it ever gets a chance to combust, lowering stove temps and raising flue temps
  11. begreen

    begreen Mooderator Staff Member

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    I couldn't get the stove temps BB is seeing out of his 3CB without a draft damper. Otherwise I'd be seeing the flue temps Jags is seeing with the Isle Royale. Now I have to find a good double wall thermometer for the new install.

    BTW, good to have you aboard Jags. I want to here/see more about the Isle Royale this winter. You should add the stove to your signature.
  12. elkimmeg

    elkimmeg Guest

    My personal take is, if you are seeing these temps on the vent connector, you are seriously overfiring that stove.
    I would not be publically bragging about due to lack of cresote. Safety is an issue you are running that stove far beyond
    safe usage. I bet your manual does not suggest stack temps anyway near what you are reporting. Go ahead s hate and shoot the messenger, I telling you this is well beyond safe opperating range.
  13. begreen

    begreen Mooderator Staff Member

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    It seems pretty rare for a stove manufacturer to post recommended stack temps. Most of the manuals I've read only mention stove top temps. That's why Jags is asking the forum their thoughts. I don't think he is seriously overfiring the stove, but based on observations, it appears that a lot of waste heat is heading up the stack.
  14. elkimmeg

    elkimmeg Guest

    BEgreen I overstated my concerns to emphisise Jags to opperate his stove in a safe mannor. Stack temps are hundred degrees less than stove top temps
  15. Roospike

    Roospike New Member

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    I can see it now ........ feet up on the desk , screen save running and poping the top of a cool one sitting there with lazer thermo in hand checking different temps of the stove. AWE..........GET BACK TO WORK . ;-P
  16. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Roospike:

    "I can see it now ........ feet up on the desk , screen save running and poping the top of a cool one sitting there with lazer thermo in hand checking different temps of the stove. AWE..........GET BACK TO WORK . "

    Whoops! I am so busted.
  17. Jags

    Jags Moderate Moderator Staff Member

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    Begreen, Elk and the rest. Yes, this is why I am asking the questions. This stove is an EPA approved with very low emissions. I have scoured the manual, the web site and anywhere else that I can find for info on stack temps that are acceptable to my stove and pipe config to no avail.

    To clarify, the stack temp is being taken with a thermometer located around 2.5- 3 feet above the stove and protruding into the stack to approx center of stack. I am not sure if you guys are using this type of therm or if it is a surface mount. Please let me know.

    My pipe, from stove to tip would measure 20ft MAX. Probably more around 17 feet. Elk, I totally respect your opionion on overfireing, but after several years of opperation, the stove shows no signs of overfiring what so ever. And the pipe appears to be in perfect condition. I am in no way saying that this is an indication of proper operation, mearly that I do consider all equipment to be up to par and in good working condition.

    These temps are typical of my first heatup of the day. As time goes on, say into the second loading of the day the temps settle down and are more even from stove to stack. Around 500-600 degrees for both.

    Now, if I have read the responses earlier and understood correctly, with an EPA certified stove, TYPICALLY one should expect stove temp (surface) to be higher the stack temp (internal).

    Info is why I am asking guys.
  18. elkimmeg

    elkimmeg Guest

    Jags my appology I assumed you were using a surface mount thermo Disregard the rest of my post
  19. MountainStoveGuy

    MountainStoveGuy New Member

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    Your just wasting some heat up that tall flue, do you have a damper installed? Your chimney hight explains the high flue temps and the relativly low stove temps
  20. begreen

    begreen Mooderator Staff Member

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    Ah, I too had assumed that you were talking surface temps. As noted, it sounds like you are doing fine. Once I get a probe thermometer and a draft damper installed I'll be able to give you more meaningful feedback about regulating the stack temps. Your stove's behavior sounds very similar to the way our 3CB ran. If so, the good news is that adding the stack damper did not increase creosote accumulation at all. Teaspoons is the way I would describe ours, year after year.
  21. velvetfoot

    velvetfoot Minister of Fire

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    That temp probe might be useful to check the stack temps of a fossil fuel unit as well, thereby further justifying its purchase!
    However, not applicable for an insert though, I guess. :(
  22. Jags

    Jags Moderate Moderator Staff Member

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    Whew!!!!! Thanks for clarifying guys, I thought that I had been doing "everything right" for the last five years and with the flurry of responses I became real nervous - real fast. I am glad it was a misunderstanding on my part (and probably because I didn't give the whole picture with the internal probe therm).

    Does anybody else run a probe therm on the stack with a surface temp on the stove? I would be interested in YOUR typical operating temps.

    I am taking note of the flu damper, but truthfully would like to stay away from breaking the integrity of the pipe unless it is determined to really be the right thing to do.

    My sweep is coming over tomorrow for the inspection and I do plan on quizzing him as well. This guy is a very well respected sweep with about 30 years experience. I have on other occasions, explained my typical stove operation to him, and in all occasions he has concurred that what I was doing was a "best practice" scenario.

    I have only been burning wood for about 15 years, so one of these days, I will get it down yet. (thats a joke for any of you that may not be awake yet, or has a broken funnybone)

    Oh, and thanks for the welcome begreen - I have been an active member of hearth.com for a short time, but have been lurking in the shadows for quite awhile. This is really the only question I have never had answered about my stove (officially). So I thought "what the heck" I will bring it up.
  23. MountainStoveGuy

    MountainStoveGuy New Member

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    If you are using interior double wall, there is a small section of pipe that comes with a damper installed.
  24. begreen

    begreen Mooderator Staff Member

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    I will have my new stove setup with surface and stack probe thermometer now that I have double-wall pipe. What brand/model stack thermometer are you using? With the 19 ft. stack I have no qualms about adding a damper. Even with the shorter stack on the 3CB it made a noticeable difference.

    PS: post some shots of that beauty in the picture section when you get a chance Jags.
  25. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    The temps are on the F100 BG. The F3 is the lady in waiting at the moment. I haven't slid (lugged) her in place yet. I had a long adventure with a parts replacement.

    I think the tee up top on the pipe turning to the horizontal into the thimble slows the draft down enough to not need a damper at this point. It appears pretty balanced so far. Now when it is 20 degrees outside it might be a whole nother situation.
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