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Is this Flue Temp Probe Full of "It"?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by pen, Jan 21, 2010.

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  1. pen

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

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    Just opened the box on a new flue temp probe and installed.

    [​IMG]

    Is this sort of results what you guys get? As you can see, my old rutland is very accurate with my infrared thermometer (the low was recorded in the pic as 288, MAX of 315, rutland is reading 300, not bad IMO) But the new probe thermometer is at the top of the safe zone at 900!?!

    The stove has been cruising for about an hour w/ the air turned down. Stove top is about 650.

    Is this normal? I figured since the rutland and the new probe are both 18 inches up, that reading low on the rutland would also read on the low side for the flue probe.

    What sort of readings do you guys get?

    I think the next step is to put the new probe thermometer in the oven to check it's accuracy. I hope that the paint on the face can withstand being IN 500 degrees.

    Thoughts?

    pen

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  2. cmonSTART

    cmonSTART Minister of Fire

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    Your probe thermometer measures the temperature of the gasses inside the flue. Your rutland surface thermometer measures surface temp of the pipe. The surface temperature is just shy of half of the flue temp usually.
  3. pen

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

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    I am well aware of that.

    Point is, they are BOTH flue thermometers. I would have thought that if the external one was reading towards the cool side of the operating temp so shouldn't the probe.

    If I were to get up to 500 on the rutland (which would be safe according to that) I'd be absolutely well above the safe operating specs on the probe thermometer.

    I was expecting more along the lines of the rutland reading 300 and the flue probe 600.

    pen
  4. cmonSTART

    cmonSTART Minister of Fire

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    Ok, I see what you're saying. That does seem a bit fishy, but remember the "safe zones" can be pretty subjective.
  5. ckdeuce

    ckdeuce Feeling the Heat

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    Pen,

    For what it's worth I have the same probe T and I get in the 800-1000 range when my stove is crusing. I would not worry.

    Chris
  6. Battenkiller

    Battenkiller Minister of Fire

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    That may be good advice to not worry since his old Rutland says he's good to go, but I guess I'm thinking what's the point of the probe if it's not accurate. The more accurate external and IR thermos tell you all you need to know.
  7. Todd

    Todd Minister of Fire

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    Single wall pipe right? I brought this up in another thread before, but those Condar probes in my opinion are better for double walled pipe. There is too much heat coming off single wall pipe that boosts the reading compared to double wall pipe. These Condar Probe thermometers are calibrated to read the internal temps and they still have the spring loaded dial on the outside which is effected by the radiant temp of the pipe. DW pipe has a lower outside temp so you will get a lower temp. If you hold a match under the dial or blow on it you will see what I mean. Mine reads similar to yours a 300 external temp is a 700-800 internal on my Condar probe. I now just go with an external pipe temp.
  8. Highbeam

    Highbeam Minister of Fire

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    Is that pipe double wall? If so then you can just ignore whatever the rutland or the IR reads. I really cant tell from the photo.

    If it is single wall then I would expect the rutland to read half of what the condar says. I would also believe that the condar is more accurate than the rutland.

    My condar routinely reads 600-800 when the stove is down around 400. I daily bounce to 1000 for clean outs.
  9. ckdeuce

    ckdeuce Feeling the Heat

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    Yep... And if you question this, pop that probe in the oven and you will see MAJOR temp difference. Like Todd states above, the dial section does not like the heat and will throw it off.
  10. n6crv

    n6crv Feeling the Heat

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    Don't try the oven as it will read WAY high. If you put it in the oven the whole thermometer will heat up and it will be off. Mine read about the same as yours at first. What I did was use a infrared thermometer and a mag mount that read real close. Then loosened up the nut on the Condar probe and turned it back to where it reads 2x the outside temp. Seems to be close to reading correct. It does get off the higher the probe temp goes up. Surface temp of 500 will read about 1200 probe.
  11. pen

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

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    it is single wall pipe.
  12. pen

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

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    Just hate having to manually adjust it that far out of range since it seems like it had a reasonable reading at room temp

    Seems that they should have corrected for the extra radiant heat for this w/ a shield for single wall pipe. Perhaps I'll have to make one out of some flashing and mount it between the magnet and the face to see what happens.

    pen
  13. pen

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

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    Cut a "shield" and placed it between the magnet and probe face to see if it made a difference. Loaded the stove up for bed about an hour ago and ran it just a touch harder (about 675 on stove top) to see the difference.

    In all, I can't see where the shield helped. Perhaps condor is just too conservative (low) with their recommended flue temps? The rutland has tested accurate to what it is reading time and time again.

    view of shield
    [​IMG]

    new readings a little hotter, same result

    [​IMG]

    thoughts?

    pen
  14. Todd

    Todd Minister of Fire

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    That little shield won't help with all that other exposed pipe around. I tried the same thing but used an oversized washer and it didn't help. I wouldn't worry because your external temps are fine.
  15. Battenkiller

    Battenkiller Minister of Fire

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    350º on the external and 1000º on the probe T? What can that possibly that tell you? I was gonna buy one, but that photo made my mind up. I'm gonna order a thermocouple probe for my IR thermo instead.
  16. pen

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

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    I am tending to agree with you. Basically, I know it's safe so I'll just burn the stove as always and just see what that probe has to say about it.

    What a disappointment that it is so terribly off on this single wall pipe. I haven't noticed others post about this before.

    I may also consider plugging this hole and moving it to the other side of the elbow.

    pen
  17. jebatty

    jebatty Minister of Fire

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    I had the Condor probe on single wall pipe and then replaced it with a K-type digital probe. Readings dropped about 125F with the digital probe. I also have a Rutland surface thermometer. On the same flue, simultaneously, the Rutland read about 1/2 of the Condor. I regard both thermometers as giving relative readings and not accurate readings. Another point, the Condor responds quite slowly to temp changes. In other words, on a high burn start, once the Condor probe gets up to the maximum temp, it will drop very slowly even though actual interior flue temp may have dropped a lot.

    On my wood stove, I use the Rutland surface thermometer, about 18" above the top of the stove. My stove purrs at temps of 325-400F surface temp. On my Tarm gasification boiler, I now use the digital probe. The gasifer purrs at 400-475F probe temp, which would be about 200-250F surface temp. The gasifer is rated 4x the btu rating of the stove, and it obviously is much, much more efficient than the wood stove at turning wood into usable heat energy.
  18. pen

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

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    I am consistently reading 3x higher on the condor than on the rutland . Ran things good at warm at start-up this morning. 400 on the rutland was 1200 on the condor.

    I think I am going to move the probe up higher in the flue, to the other side of the elbow.

    pen
  19. Highbeam

    Highbeam Minister of Fire

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    I'm thinking it's time for someone to talk to the condar folks. It is a small american company that prides itself in making accurate instruments. I'm thinking that the above pictures would trouble them and perhaps they can offer advice for adjustment.

    We all know that the single wall pipe's outer shell temp should be "about" half of the internal temp. I would expect that the probe meter be accurate over the normal range and if this means that it's wrong at room temp then so be it.

    Do NOT put any of these in the oven and expect to verify their accuracy. These are not oven thermometers.
  20. pen

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

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    email sent including the pictures.

    I look forward to their response.

    pen
  21. begreen

    begreen Mooderator Staff Member

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    The reading seems wonky. I would expect normal flue gas temp with a probe to be in the 400-600 range. This appears to be confirmed by the Rutland surface thermometer. Flue pipes are not made to be regularly running at above 1000, especially over an extended period of time.
  22. pen

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

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    Agreed, however if that is the case, then they need to change the dimensions of their scale that is printed on the face so that it does provide an accurate reading across its full scale.

    pen
  23. begreen

    begreen Mooderator Staff Member

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    Not agreed. The surface temp is not half the inside temp, at least according to Condar. Condar states that interior temps should be about 50% higher than surface temps. That would mean a 400 °F surface reading would equal about a 600 °F interior temp.

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  24. Diabel

    Diabel Minister of Fire

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    I do not mean to high jack this thread but my situation is related & as intriguing... (sorry for the fuzzy pic) both read pretty much 600*

    btw I just installed the probe to find this out.....For the past five years I used the surface thermo. placed right on the flue & believed that internal temp is double :bug: Many times I almost s..t my pants when temp on that thermo would spike to 750* (I thought I was running at 1500* internal)

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  25. pen

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

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    My mistake in reading. That make much more sense. I have always "heard" the other to be true and make the mistake of assuming it to be correct.

    However, reading it that way makes the problem is even worse! Since a 300 degree exterior stove pipe should only be registering 450 then, and I am getting 1000!

    It's reading looked reasonable when it was at room temp BTW

    pen
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