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Condar Temp Probe vs. The Thermocouple...

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by WES999, Feb 1, 2010.

  1. Peter B.

    Peter B. Feeling the Heat

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    Incidentally, I thought I might explain how/why I ended up with so many thermometers...

    Originally, I ordered a new FlueGard and the 2" cat probe - the former to replace the 20 year old probe, the latter to monitor catalyst temp continuously... which I'd never done before.

    I discovered the wide temperature discrepancy between the new FlueGard and the old probe right away, wrote Condar and asked for an exchange, which they agreed to, and I requested two of the 4" cat probes so I might AT LEAST have two identical thermometers that actually agreed.

    The two cat probes more or less agreed with one another... and the new FlueGard. But the 2" cat probe came close to agreeing with the old probe, so I really didn't know what to think. The range of difference (in actual use) between the two groups of probes was on the order of 100*-300* at differing stove temperatures.

    In any event, I never got around to returning any of them... so I'm a bit 'overstocked' with thermometers of questionable accuracy.

    Peter B.

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  2. pen

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

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    That questionable accuracy is what discourages me. From everything I have done (and you and wes as well) we seem to be finding that these are very consistent. However, I am afraid that they only accurate in a special set of circumstances.

    I trust that the probe I sent Tim truly did respond as he stated in his furnace. I have no doubts that under certain conditions that his probe would read accurately.

    My point is this:

    1. Installed as the directions on the package state, this thermometer does not perform as stated and will not read accurately for single wall pipe.
    2. I think more testing by condar needs to be done using real wood stoves, and not a furnace.
    3. I think that the package information / directions need to be changed to reflect the differences we have all noted here so that the product can be used as a true gauge of a user's burn quality.
  3. Peter B.

    Peter B. Feeling the Heat

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    A few more comparative observations...

    As mentioned, I've used the 'same old' Condar probe now for twenty years. I learned early on that the flue probe - located about 18 linear inches above the internal catalyst - must read a _solid_ 400* or more before the catalyst will light off. I've used the same guideline successfully for all those years.

    Most literature suggests that catalyst light off occurs at about 600* (stove internal temp, measured at the catalyst 'intake' point).

    My cat slides forward and back to achieve bypass. Using 400* flue temp on the old probe as my most reliable guide, the new 4" cat probe placed in the exhaust flow (at the point where the catalyst sits in the 'on' position), must read 1000* or better before the catalyst will light off. This corresponds to 400* or better on the flue probe.

    If the cat actually lights at 600*, that means the new cat probe is off by a full 400*.

    And if I trusted the cat probe only, I might be trying to engage the cat at a nominal 600* thermometer temp... some 300*-400* below that actually required for light off.

    The new FlueGard (in place of the old probe) would have to read 550*-600* at 18" ABOVE the catalyst to achieve reliable cat light off.

    I don't know what Condar has changed in their probe manufacturing 'recipe' in twenty years, but as near as I can tell they made a rock solid reliable thermometer 'back when'... and they're not doing so now.

    Peter B.

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  4. pen

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

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    If your old one is the 3-19, here is what I was told by Tim:

    seems odd doesn't it?

    pen
  5. Peter B.

    Peter B. Feeling the Heat

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    I'm pretty sure my old one is a 3-19... but something else MUST have changed.

    It's very easy to document the difference between the two directly.

    Leaving out ALL other considerations, the two thermometers read between 150*-250* apart switched back and forth between the same locations and left for several (15) minutes to stabilize... this on a fairly constant fire.

    I specifically requested another 3-19 when I wrote to Condar for an exchange. They said the 3-39 had replaced it.

    I wonder if BeGreen would sell me his old 3-19? Maybe then I could make some useful relative comparisons of stove internal and flue temps.

    Peter B.

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  6. begreen

    begreen Mooderator Staff Member

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    Right. Out of my cold dead hands... :coolgrin:

    I would consider sending it to Wes999 for a thermocouple test. The older 3-19 seems to read a lot lower. It would be nice to see where it falls in a side by side test next to the 3-39.
  7. Peter B.

    Peter B. Feeling the Heat

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    Have it your way... I'm hopping the next freight to come and pick it up.

    And I'll bring a pry bar.

    Peter B.

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  8. imacheezhead

    imacheezhead Member

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    I’d send it back and get a new one. It shouldn’t read 350 at room temp and you don’t know if your adjustment is accurate. I do believe my adjustment is accurate. The meat thermometer is accurate to within 2 deg. according to my highly scientific boiling water test. What is the highest cat temperature I can expect? Right now I seem to be topping out at 1200 deg. burning oak. My cat seems to be in good shape yet and it's only in its 2nd heating season.

    Jim
  9. woodjack

    woodjack Minister of Fire

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    This has been a fascinating thread (Parts I and II). Pen, and everyone else that contributed, thanks much.

    However, the final analysis left me a baffled.
    Pen, considering all the erroneous temperature readings, I'm surprised that you believe the Condor probe thermometer would work properly for a double-walled flue ("In the end, my opinion is that this probe will work fine for double wall as per instructions."). It almost seems to have your endorsement. Am I misinterpreting your conclusion?
  10. pen

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

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    Good question. After running this again this season, and after all the testing last season I'll say this: For the right or for the wrong, it's a consistent thermometer.

    That means, it may read consistently high, but I do trust that it's always giving me the same "value" for a equivalent burn. What I think is junk is the numbers and indicator recommendations. I really wish they just sold a blank one and i'd mark it myself w/ high burn / low burn.

    For me, I couldn't get these burn sections (too cool, normal, too hot) to be even close to being correct until I moved the thermometer almost 30 inches above the stove.

    I think that part of the problem is that the thermometer is taking on a ton of radiant heat from the single walled pipe. It still reads consistently, just not accurately.

    I think that w/ the protection of a double wall stove pipe, It has a better chance at being accurate and precise (consistent) at the recommended 18 inches above the stove.

    However, on single wall pipe, I simply believe them recommending it to be only 18 inches up the pipe is giving readings that are still consistent, but not accurate, and I worry that people are burning their stove too cool as a result.

    Tim tested my thermometer and WES did. I believe that Wes's test was most accurate to a "real world" or "field" setting. I firmly believe that Tim wouldn't lie to me and when he retested my thermometer in his special furnace, that it did test to within spec. My argument is that his thermocycler doesn't duplicate "in the home" conditions and that they should change their testing back to something more like what Wes did.

    pen
  11. Jamison

    Jamison Member

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    Condar confusion!

    Thanks to everyone for doing all this extensive testing! As a newbie, this is why I love this forum, it is always a learning experience based on good solid field-tested results from generous people who care about the "art of the stove."

    That said, I am so thoroughly confused, now, and a bit concerned. As someone new to wood burning, I thought that buying a probe thermometer for my one month old Lennox Canyon ST310 would be a fairly accurate way to see if I am safely burning. I now see that this is not the case.

    When anyone purchases a product, we expect to get what we pay for; what I'm finding from this extensive thread is, this is not always so.

    In my DW pipe, at 18" up ( as Condair recommends) I get a read from 400 to 600 when I'm in a fairly heavy-duty burn cycle. I've posted in this forum about my chimney cap being totally grunged up at only 4 weeks of burning seasoned hardwoods, and now I'm thinking that I've been burning too low because the thermometer is way off. I have a 6" DW pipe ,and I don't think the thermometer is in the center, even though I folowed Condar's drilling guidelines.

    I don't want to burn too low since what I've read is, this is a potentially dangerous creosote situation. So what is the resolution on the Condar? Should I scrape it and get a Rutland for stove top only? I'm now gun shy and rather concerned. Thanks much!
  12. pen

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

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    Most are finding that they read too high which is the opposite of what you are seeing.

    The biggest problem is with the probe thermometers on single wall pipe. Double wall pipe has much lower surface temperatures and therefore I believe it will have a more accurate reading. As such, on a fresh load you should be seeing 800 on that probe no problem.

    More results will come in this week as BeGreen is sending me a vintage condar probe to use as comparison to my new probe since I already have 2 holes in my flue for probe placement.

    pen
  13. Jamison

    Jamison Member

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    Getting 800 on fresh load of splits is something I have not seen yet. Do I have a defective Condar or is the probe not "centered" in a 6" pipe...should I pull it out a bit?
  14. pen

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

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    if it were defective when at room temp the needle would be reading some value that wouldn't look right.

    pen
  15. begreen

    begreen Mooderator Staff Member

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    There could be other reasons for creosote build up. Can you describe the complete flue setup from stove to cap including elbows and tees? A stove top thermometer can be helpful. I like both, but would opt for the stove top first if there was only one option.
  16. Todd

    Todd Minister of Fire

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    Well since this thread popped up again I might as well tell anyone that may be interested, I went out and purchased an SBI probe that is similar to the Condar. I almost drilled another hole in my pipe to get a side by side comparison for you all but decided against it. The SBI is cruising at 600-700 internal with an external of 250-300. My Condar is reading about 50-100 higher in that same external range. The Condar also seems quicker to run away on a fresh reload once temps get up over 800. Not a huge difference and I'm sure these flue temps would be less in a double wall pipe than my single wall. SBI instructions state this thermometer is for double wall pipe unlike Condar who says it's good for both.

    Attached Files:

  17. Jamison

    Jamison Member

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    Hi BeGreen,

    My set up is pretty simple:

    1. Lennox Country ST310
    2. Six inch 4 ft double wall pipe/ top vented into
    3. cathedral ceiling support box, then piping thru my roof and
    4. eight feet Temp Guard chimney piping with cap

    It's a straight shot, no elbows.

    I'm using seasoned hardwoods, start with a small hot fire, then load maybe 6 splits or so, giving them full air flow for about 15 minutes, then will slowly cut back on air.

    What am I doing that I can't get higher temps on the Condar probe? I've got 6" double pipe, and it does not seem to be sitting flush to the pipe...should I cut it? And why the creosote? Thanks much!
  18. woodjack

    woodjack Minister of Fire

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    Todd, I'm confused. Do you think the thermometers are accurate or not? I was going to get a probe thermometer for my double wall pipe, but this thread put a damper on things.

    What's the bottom line on probe thermometers and which brand is best?
  19. 3fordasho

    3fordasho Feeling the Heat

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    Just to add to the Condor confusion- my experience was the opposite, instead of reading too high, my condor probe thermometer seldom got above 200-300F. I concluded it was due to my installation in a telescoping section of double wall connector pipe. Mine was installed in the "overlap" section of telescoping connector pipe there is actually 4 layers of sheet metal... leading to a extremely low reading. I've since moved to Tel-tru probe thermometers that have a reading range of 200-1000F. The coiled element is in the flow of flue gasses (inside the stainless probe tip). I've found these to be accurate and reliable as long as I don't exceed the 1000F limit. These have a quick reaction time, at least compared to what I saw with the condor probe. I use one of their replacements for the thermometer in a "big green egg", can be had for ~$20.
    http://www.teltru.com/s-136-big-green-egg-grill-dome-kamado-replacement-thermometer.aspx
  20. Todd

    Todd Minister of Fire

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    I don't think probe thermometers are accurate "number" wise according to Wes999's tests with his thermocouple, but in my opinion they are close enough and consistant enough to be used as a valuable tool. I also think they are better designed for double wall because the radiant heat off single wall effects the temps.

    Personally I like this SBI probe better. The color of the face plate makes it easier to see from a distance and it seems to read a bit lower than the Condar and not run away at higher temps in the beginning of the burn cycle.
  21. woodjack

    woodjack Minister of Fire

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    Todd, thanks for your reply. And again, thanks for all the info, testing, and analysis. This has been one of the most interesting threads in the entire forum.
  22. begreen

    begreen Mooderator Staff Member

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    Looks like I am one of the lucky ones that gets pretty consistent and usable readings from the flue probe thermometer on double-wall pipe. It might just be the flue design. Straight-up piping may be a stronger influence on readings here than realized. FWIW, I like the smaller, more discrete style thermometer. I only look at them when close to the stove. From a distance I let the fire and ecofan be my guide.

    Todd is there any indication of country of origin for the Condar or SBI products? They look remarkably similar except for the dial paint.
  23. Todd

    Todd Minister of Fire

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    SBI probe is Made in China, but SBI is out of Quebec. I think they build Osburn and Drolet stoves?

    Condar says built in the USA.
  24. begreen

    begreen Mooderator Staff Member

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    I just had a nice chat with Tel-Tru. They are looking at the stove market. I asked if they were considering making thermometers with a higher temperature range, more appropriate for flues. The response was that they don't make any bi-metal thermometers for high temp ranges because the spring gets too brittle, affecting its accuracy. "All thermometers with a bi-metal sensor including the surface type thermometer need to be limited to temperatures under 800F because the high heat will harden the coil and it will become less accurate and eventually stop working."

    Perhaps this relates to the inaccuracy seen at the high end with these units?
  25. pen

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

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    Hmm, that is interesting. With these tel-tru units, is the bimetallic coil visible on the back?

    pen

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