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Flue temps with probe vs. surface temp

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by ddahlgren, Jan 23, 2013.

  1. ddahlgren

    ddahlgren Feeling the Heat

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    Using a probe type thermometer vs. a surface mount like rutland and others what temps do you shoot for with the probe type? I have one due here today and will install and need to know logical numbers to shoot for. How low will creosote and how hot is an over fire with a probe?

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  2. Diabel

    Diabel Minister of Fire

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    Every set up will be slightly different. Flue temp on mine will run from high of 500 to low of 350 in the first six hours.
    Stove top temp will sit around 600 during this time.
  3. ddahlgren

    ddahlgren Feeling the Heat

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    That seems logical. I am looking for a do not go under number if you can help to stay away from creosote and a not to go over one on the hight end. I am guessing they are greater than the numbers on the surface mount thermometer.
  4. pen

    pen There are some who call me...mod. Staff Member

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    No need for both, just a quality one or the other depending on your setup.

    After doing a lot of playing around, if you have single wall pipe I suggest magnetic surface (not rutland). If you have double wall, then a probe thermometer.

    pen
  5. Jags

    Jags Moderate Moderator Staff Member

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    I second what Pen is saying. For a real world comparison it is about a 2:1 increase. Surface reads 300 - probe will read about 600. 400/800, etc.

    Edit for clarification: This is only taking the stack into account. By surface, I mean surface of the stack, not stove. Hopefully I did not confuse anyone.
  6. oldspark

    oldspark Guest

    Is that a probe?
  7. Diabel

    Diabel Minister of Fire

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    Yes
  8. oldspark

    oldspark Guest

    Seems low I run those temps on my surface thermometer.
  9. Joful

    Joful Minister of Fire

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    So... what's reasonably hot for a surface probe (or IR gun) on a single wall? 300'ish? I've had mine waaaaaaay over that, in the course of getting my cat stoves warmed up in bypass mode.
  10. Diabel

    Diabel Minister of Fire

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    In bypass mode....different story, if I let it go.... I can clean the clue pretty fast, pegging the thermo!!! In bypass mode never leave the stove unattended !
  11. oldspark

    oldspark Guest

    The safe range on a surface mount thermometer as marked and I consider a good guide line is 250 on the low side and 550 on the high side, I spike way over that at times with no problems.
  12. Jags

    Jags Moderate Moderator Staff Member

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    Don't run over 1100F internal or 550F surface. The stack can handle bursts higher, but those are the numbers for sustained temps. I highly recommend keeping it lower than that for sustained temps (like peak up to 8-900 on start up and then cruise it down lower, what ever that temp might be). Each stove and setup will likely have a different cruise temp on the stack. Mine likes 500-650 when cruising.

    Edit: we posted at the same time, Sparky.;)
  13. madison

    madison Minister of Fire

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    Ditto Pen's suggestion. IMHO a stack thermometer is sorta like having a tachometer in an automatic transmission car -- interesting to watch - but not really necessary.
  14. ddahlgren

    ddahlgren Feeling the Heat

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    I found the rating of the duravent Plus 1000F continuous 1400 for an hour and 3 shots of going to 2100. So my next thought what temperature to try to stay above to avoid creosote?
  15. Jags

    Jags Moderate Moderator Staff Member

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    Water is steam at 212F. Keep it above that. During the out gas stage, I try to keep above 450F (internal/probe). Coaling stage doesn't matter much. Not much nasties left in the wood. This is just my opinion and how I do it. No facts to back up the process, but it has worked for me and keeps a clean stack.
    Mitch Newton likes this.
  16. oldspark

    oldspark Guest

    Oh contrar, good idea to know if flue temps are too low or too high, a lot of people burn questionable wood on here and the best way to do that is keep the stack temps up.
  17. oldspark

    oldspark Guest

    250 to 300 surface, not sure if the thermometer manufactors are erroring on the side of saftey or not.
  18. Trilifter7

    Trilifter7 Feeling the Heat

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    I use my surface temp meter on the flu as my guide for when to close the bypass damper. I typically run the surface temp up to around 500-550 on the flu then close the bypass. It's a good gage as to how intense the fire is in the stove.
    Mitch Newton likes this.
  19. ddahlgren

    ddahlgren Feeling the Heat

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    With the particular Rutland surface temp thermometer I have struggled to get over 320 with a blazing kindling fire going that fills the glass for an hour the reason for the probe type. So much for the Rutland crap..
  20. oldspark

    oldspark Guest

    Well I have a rutland, they are not that accurate but usually are close enough, did you check it with a IR testor?
  21. Joful

    Joful Minister of Fire

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    Yeah... but who's connecting their chimney liner directly to their freestanding stove? Most have a stovepipe, likely most often single-wall, and you can drop more than 100F over the length of that stovepipe.
  22. Trilifter7

    Trilifter7 Feeling the Heat

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    My Condar is typically within 50* of what the IR meter shows. Normally it's around 50* cooler than actually surface temps
  23. Jags

    Jags Moderate Moderator Staff Member

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    I believe those numbers hold true for the stove pipe as well because you are measuring the temp at the stove pipe, not in the liner.
  24. pen

    pen There are some who call me...mod. Staff Member

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    Remember, to prevent creosote, you need to keep those temps over 212 all the way to the sky
    Mitch Newton likes this.
  25. corey21

    corey21 Minister of Fire

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    I have a probe it likes to cruise at around 400.

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